# NEW IN-FLOOR SETUP IN THE SHOP



## jimdeq (Jan 12, 2012)

I am starting the second phase of my boiler system.  I want to get my shop infloor up and running.  My Tarm and 1140 gallons of pressurized storage are in my home with the storage in the basement.  My heat loads in the house run off a Grundfos Alpha 15-55 which will also push water to a heat exchanger on the back wall of the house where I have 1-1/4" Thermopex.  The Thermopex runs 150' to the shop.   In the shop I have 1200 square feet of heated space.  The Grade Beam slab has 1.5" high density foam underneath and 1" high density around the perimeter.  The walls are also spray foamed and then batted.  Ceiling will be blown in fiberglass.  I installed 6 loops with a average of 275' of Wirsbo Hepex O2 barrier in the floor.  My question is how large of a pump do I need to pump 150' from the house to the shop?  I was thinking I would put the mixing valve in the shop instead of the house so I could still add a high temp unit heater if needed.  Also what size pump would run the infloor and can the same pump supply the high temp unit heater?  I also ran CAT  5 wire in a conduit from the house to the shop for control wiring.  The system will be filled with glycol.  I am looking forward to any suggestions and imput.


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## ewdudley (Jan 12, 2012)

Sounds like you're golden, Jim.  

With radiant heat you can expect nice big deltaT, call it 70 degF.  At 2 gpm that's 70000 btu per hour.  Any small steep curve pump should work for pumping the 300 feet round-trip, a 008, 15-58 for instance.  If you've got a 007 laying around I'd even try it before springing for a new pump.

As a point of reference on the slab pump, I just hooked up a three-speed 15-58 -- because that's what I had laying around -- on a 1000 square feet of radiant flooring an it's doing a nice job on low speed with four 300 ft 1/2" PEX loops pulling through a 3/4" mixing valve.  The mixing valve should definitely go in the shop.

--ewd

[Edit:]

Had another thought on this.  For as much flow as it will take to feed 1200 sq ft, a single circ pulling though a mixer and all the way from storage could do the trick perfectly.  Later another pump in parallel could feed the high temp unit when you're ready for that.  

This would eliminate the problem of balancing the transfer flow with the demand flow and it would guarantee minimum return temperature to storage to prevent mixing of storage.


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## huffdawg (Jan 12, 2012)

I have a 15-58 3 speed for my shop infloor. 900sf. 4 loops of 200ft and I am sending a gal. Per min. down each loop on low speed.1"supply and mixing valve.


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## jebatty (Jan 12, 2012)

> ew: With radiant heat you can expect nice big deltaT, call it 70 degF.  At 2 gpm thatâ€™s 70000 btu per hour.



Is this really correct in a radiant slab application? While the math is right, isn't the btuh calculation based on delta-T between slab supply, slab return, and gpm? The mixing valve is not likely going to be set 70F higher than the slab. For example, I supply the six loops of 1/2"pex (275-300') in my floor at 100F, return is at about 70F, delta-T=30, gpm 2.75 based on the little flowmeters on the manifold, btuh = 41,000.

Of course, if the supply to the shop has a 70F delta-T with the mixing valve in the shop, the extra btu's on the slab return could be used in a unit heater, so 70,000 btu's are available; or the unit heater could have optional plumbing to allow it being supplied first with it's return to the slab and also a bypass to the slab, which I think is the way I would go. That would give immediate high heat boost if needed, and I bet the unit heater return is still high enough (100F+) to adequately supply the slab. In this scheme system delta-T could be 100F+ and > 100,000 btuh.

jimdeq, what's the size of your Tarm? How much extra btu's do you think you have available after heating the house? Your 1200 sq ft shop is a little smaller than mine (1500 sq ft, six loops) and by your description is better insulated than mine. With your location NE WI and mine in northern MN, our weather may not be too different, unless your temps are moderated by Lake Michigan or Lake Superior. Based on last winter, perhaps a little colder than the current "normal," my highest 24 hour heat load in the shop was about 17,000 btuh, more normal average winter heat load was 12-14,000 btuh. I keep the floor temp at 61F and 1F differential. The floor sensor shows a floor temp range 61-64F.


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## jebatty (Jan 12, 2012)

> ... or the unit heater could have optional plumbing to allow it being supplied first with itâ€™s return to the slab and also a bypass to the slab, which I think is the way I would go.



Which is the way I did my plumbing. I have stub-outs in place for a unit heater which I have but have not installed. If installed, unit heater first, slab mixing valve and slab second. With the floor set at 61F, I never have needed an extra heat boost.


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## ewdudley (Jan 12, 2012)

jebatty said:
			
		

> > ew: With radiant heat you can expect nice big deltaT, call it 70 degF.  At 2 gpm thatâ€™s 70000 btu per hour.
> 
> 
> 
> Is this really correct in a radiant slab application?



I think the OP is proposing two pumps, a transfer pump and a slab circ.  The transfer pump would have the advantage of working with a large deltaT, you're right about the slab part.


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## jebatty (Jan 12, 2012)

I missed that, good observation. Might one circ work anyway?


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## ewdudley (Jan 12, 2012)

jebatty said:
			
		

> ... Might one circ work anyway?



You bet, I was editing my original post with this suggestion as you were posting yours.  I think a single pump pulling through a mixing valve and all the way from storage for the slab would be ideal.  Should run the numbers, but I wouldn't be surprised if a single 15-58 would do it, or maybe a pressure controlled ECM Wilo Stratus or Grundfos Alpha, they're getting more and more affordable.


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## woodsmaster (Jan 12, 2012)

jimdeq said:
			
		

> I am starting the second phase of my boiler system.  I want to get my shop infloor up and running.  My Tarm and 1140 gallons of pressurized storage are in my home with the storage in the basement.  My heat loads in the house run off a Grundfos Alpha 15-55 which will also push water to a heat exchanger on the back wall of the house where I have 1-1/4" Thermopex.  The Thermopex runs 150' to the shop.   In the shop I have 1200 square feet of heated space.  The Grade Beam slab has 1.5" high density foam underneath and 1" high density around the perimeter.  The walls are also spray foamed and then batted.  Ceiling will be blown in fiberglass.  I installed 6 loops with a average of 275' of Wirsbo Hepex O2 barrier in the floor.  My question is how large of a pump do I need to pump 150' from the house to the shop?  I was thinking I would put the mixing valve in the shop instead of the house so I could still add a high temp unit heater if needed.  Also what size pump would run the infloor and can the same pump supply the high temp unit heater?  I also ran CAT  5 wire in a conduit from the house to the shop for control wiring.  The system will be filled with glycol.  I am looking forward to any suggestions and imput.



 Don't over look that the water should be pulled threw the valve and not pushed.


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## Hunderliggur (Jan 12, 2012)

Do you really think you need glycol?  It reduces the efficiency significantly.  If you had the backup heater you could fire the slab if temps got too low (say 40F).  You even just circulate the water in the loop if your supply is below the frost line.  With the thermal mass of the slab and the insulated underground pipes I think your freeze risk is very low.  If you are concerned about the above slab piping, build a box around it, insulate well, and add a thermocube controlled heater.


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## ewdudley (Jan 12, 2012)

Hunderliggur said:
			
		

> Do you really think you need glycol?  It reduces the efficiency significantly.  If you had the backup heater you could fire the slab if temps got too low (say 40F).  You even just circulate the water in the loop if your supply is below the frost line.  With the thermal mass of the slab and the insulated underground pipes I think your freeze risk is very low.  If you are concerned about the above slab piping, build a box around it, insulate well, and add a thermocube controlled heater.



+1

If it were a hunting shack used twice a season, that's one thing, but integrated with your house system it would take tiny amounts of heat to keep above freezing, even out in the windswept frontiers.

--ewd


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## goosegunner (Jan 12, 2012)

I live in central Wisconsin. My neighbor lost his garage in floor to freezing his first year. I am not sure of the details but it is heated by a lp boiler. The first winter cold snap it froze near the overhead doors.  He no longer has in floor in his garage. He had other issues with his system so my guess was his installer did something wrong.

Around here it is really tough to find people that are knowledgable about radiant heat. Several people I know that have it complain about their heat bills and ability for house to keep up on temp swings.  I believe that it is usually related to poor installs.

gg


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## DaveBP (Jan 12, 2012)

If you're talking about using glycol throughout the entire system (1200+ gallons) price out a few barrels of glycol before committing yourself to it. 

You could use a heat exchanger for the shop circuit and use glycol only out there. Perhaps that is what you're considering. 

Contrariwise, you could just put one of those freeze alarm thermostats out there and see if it ever gets close to freezing and if it just isn't a problem, ignore it. You could always add glycol if it turns out to be a threat. Gotta think of the power outage scenario, though. If you had no electricity for a few days during a cold snap would you be screwed?


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## DaBackBurner (Jan 12, 2012)

Hunderliggur said:
			
		

> Do you really think you need glycol?  It reduces the efficiency significantly.  If you had the backup heater you could fire the slab if temps got too low (say 40F).  You even just circulate the water in the loop if your supply is below the frost line.  With the thermal mass of the slab and the insulated underground pipes I think your freeze risk is very low.  If you are concerned about the above slab piping, build a box around it, insulate well, and add a thermocube controlled heater.



I would agree that glycol is probably an expense not worth it in this case especially if you have a backup heater. I pondered this when I installed my slab radiant and was a bit 'scared' not to but after researching it seemed logical to me not to because of the constant circulation of the floor circuits. If you do outdoor reset with your floor circuits then you could treat your supply circuit from the home as an injection mixing circuit using a controller such as a Tekmar 356 or equivalent and a standard shallow curve pump like a 007 or 15-42 etc. and get constant circulation of that loop with a high delta T. Your shop is 80sq/ft bigger than mine (I don't know your ceiling height so volume might be different) but I find that for the most part I supply the floor with 75-80deg water with a delta T of 10. Last year I had a much higher delta T (less flow) for the floor circuits and found this to be an inefficient method for slab radiant, because with more flow and a lower delta T you can have a much lower supply temp and get the benefit of that huge emitter being the same temp which also lowers distribution losses. I have 6 loops approx. 250 ft long and they each flow at approx. 1/2 gal/min. for a total of 3 gal/min now. Last year I had 0.2gal/min per circuit and while I didn't have to shovel in front of the garage doors, made for an overall inefficient system in my case. Make sure you get a mixing valve that has the same or as close a Cv as your total flow into your floor circuits for me this was a 3.5Cv mixing valve. And yes always pull through a mixing valve.

Find out your heat loss calculations for your building and you can then find out what size pumps or possibly only one pump you will need. I think if you only go with one pump you will need a high head low flow pump to accomplish this because you will be pulling through the mixing valve with it's psi drop the friction loss of the supply loop and the friction loss of the floor circuits but I could be way off base so now I gotta run the numbers to see, because its snowing like heck here and I don't feel like plowing.


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## DaBackBurner (Jan 12, 2012)

Ok, so one more cup of coffee and I hope my math is correct.

I making some assumptions (therefore its usually ME that is made the one).

25,000 BTU/hr heat loss.
For slab radiant delta T of 10.
275' of 1/2" pex (you didn't state the size but it is pretty standard).
6 loops.
No glycol.
a = 0.055 avg water at 85 deg
c = 0.786 for 1/2pex and 0.01668 for 1-1/4pex

Ft=Q/k x deltaT = 25,000/500 x 10 = 5 gpm
Fl = Loops/Ft = 6/5 = 0.83 gpm/loop

Hloop = (acL)(f)^1.75 = (0.055 x 0.786 x 275loop) (0.83)^1.75 = 11.88825 x 0.72175 = 8.6 ft of head + fittings = 9.5 more realistic.

Hsupply = (0.055 x 0.01668 x 300supply) (5)^1.75 = 0.27522 x 16.72 = 4.6 plus fittings and psi of heat exchanger = 6 more realistic

Htotal = 15-16

So one pump with 5gpm at 15-16 head loss should do it.

Otherwise one loop pump with 5gpm at 9.5head and one supply pump at 5gpm at 6head. Although if you did injection mixing the supply pump calcs would be different because of the higher delta T lower flow and so forth.

Please check my math as I've only had 2 cups of coffee.


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## DaBackBurner (Jan 12, 2012)

For freeze protection and no glycol, constant circulation is the key I believe. Although I do have constant circulation I used a pump exercise add-on board for my pump relay which allows me more piece of mind if the slab sensor or t-stat gets satisfied. If either of those does gets satisfied and the pumps turn off, the add-on board starts a timer and will exercise the pumps up to 4min/hr with no call for heat. Lets me sleep better at night and was very inexpensive insurance.

Time to plow for me.

Good luck and keep us posted with your final design.

I also use a UPS for my shop pump/relay in case of power outages.


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## DaBackBurner (Jan 12, 2012)

If you already have your mind made up about glycol then replace the constant 'a' above with 0.07 for an average water temperature of 85deg, or 0.065 for an average water temperature of 100deg. You'll see that more flow hence higher head pumps will be necessary to extract the same amount of BTU's, but it might also let you sleep at night. 

Another benefit of near-continuous circulation is the ability of the floor panel to redistribute heat within the slab like the interior portions to the areas of higher heat loss like overhead doors, to prevent freezing for many hours or days because of the high mass system. I think where most failures occur, if they don't have glycol, is because of the lack of near-continuous circulation and/or the delta T being too high, therefore too low of flow, so that the whole slab is not acting as one giant radiator with relatively the same temps everywhere. I would think this problem of too high a delta T or on/off circulation for the slab could also be compounded if the hottest water were not directed around the perimeter first or where the highest heat loss is expected like overhead doors for example. To me it just makes sense to add outdoor reset especially in this application to get the added benefits of near-continuous circulation with a lower delta T.

Anyone have any other thoughts? This stuff is interesting as heck.


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## in hot water (Jan 12, 2012)

On shop floor radiant you can get away with a larger âˆ†T t in the loops.  You probably will not be barefoot out there.  Just guessing 

You need to know the pressure drop thru the mixing device as Da mentioned to select the correct pump.  Both the grundfos 15-58 and 26-99 are now 3 speed so you have plenty of adjustability.

Remember on first, cold start up you will have a huge âˆ†T until the slab ramps up in temperature.  The thermal mass of that slab will over power your boiler and probably the temperature in the buffer.Don't try to adjust it away for a day or so.

When we fire large commercial slabs in winter time temperatures it can take 3 days or more for the slab to show a "feel-able" temperature, be patient.

Also be sure you protect the boiler against the cold slab return temperature.  If that return can get to the boiler, maybe your buffer tank will mix it up first.

hr


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## DaBackBurner (Jan 12, 2012)

yes very true not many people go barefoot in their shop. So hr what is a reasonable delta T for shop floors? I know that last year I had delta T of 40-50 and that didn't seem to work very well. This year it's at 10 but that is probably too low especially for shop floors. Don't mean to hijack thread but it seems to fit. I keep my shop relatively warm, 65,  since I'm in there most of the day.
-Bob


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## kuribo (Jan 12, 2012)

DaBackBurner said:
			
		

> Fl = Loops/Ft = 6/5 = 0.83 gpm/loop



Won't flow rates this low result in flow velocities less than 2 fps which are considered the lower limit for moving air, sediment, etc., through the system?

I am trying to size my circulators at the moment and am running into this issue....my flow rates at a 10F delta T and a 35000 heat load into 8 loops of 250' are around 0.875 gpm at the design point. They would be much less than this most of the time....The minimum recommended flow rates through 1/2" pex to keep velocities above 3 fps are around 1.1 gpm......

What am I missing????


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## DaBackBurner (Jan 13, 2012)

Yes they will be lower than 2fps at that flow rate with that size pex. I think that's why it becomes even more important and harder to bleed all the air out of the loops and to make sure you have air/dirt seperators before the loop circuits. The alternative is to increase your loop circuit flows which would decrease your delta T. This is what I did initially to help purge air before dropping flow rates to maintain my delta T of 10. Adjustable flow rate/indicator manifolds really help in this area. If all the circuits are balanced or the same flow rate you would be able to see if there was a restriction in one loop at a glance. It is not 'out-of-the-norm' to have your loop flow rates with that size pex.

When you say your flow rates most of the time...is this for something other than slab radiant like a home-run for panel rads?


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## kuribo (Jan 13, 2012)

Those are the flow rates at the design point heat load of 35,000BTU/hr (-30F day here in Wi). The heat load may be half that or even less on a more typical winter day and thus the flow rates would be way less than 0.875 gpm.....

It seems that the most common in slab pex size is 1/2"....is it common for flow rates to be 0.25-0.5 gpm in these systems?


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## DaBackBurner (Jan 13, 2012)

I wouldn't expect your flow rates in your loops to change Chris, except for warm weather shut down or slab or t-stat satisfaction (off). Your mixing valve should vary the supply temperature either manually or motorized with a controller, based on heat demand. I could see if you had an injection mixing pump that varied the flow rate of an injection loop therefore taking the place of a mixing valve, but I've never seen or heard of variable flows in the slab loops. They are usually supplied by a fixed speed circulator hence only one constant flow rate. But heck, I'm always open to new ideas if there is a better mouse trap I'm all ears. Now you may want to install a 3 speed pump for your floor loops, in case your calcs are off for tweaking purposes, but once that is done you will have one flow, with variable temperature supply. I would say a fairly common flow rate per loop with 1/2" pex that is between 250-300 ft long would be 0.4gpm -1.5gpm, but it really depends on your heat loss.
-Bob


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## jimdeq (Jan 13, 2012)

To answer everyones questions, my tarm is "Solo 60". So far above 25 degrees equals one fire per 24 hrs. Lower than 25 degrees equals one fire every 12 hrs. I have figured out to not let the bottom of storage get below 120 due to termovar function upon restart.   Jebatty, I liked the option you described, because I don't always want my shop at 60 degrees. If I leave for a week or go on vacation I would probably turn it down and let the unit heater due a quick recovery when I'm home. I understand thermal mass but I want to keep it easy for my wife and kids to do the boiler. I want to use gylcol for the shop loop. I already have about 40 gallons from a friend. The heat exchanger I have in my basement has 1- 1/4 supply and return from boiler, but the problem is it has a 3/4 inch restriction where it ties into the 1 -1/4 inch thermopex. It is a stainless tube in shell pool exchanger.

DBB: I don't understand outdoor reset or injection mixing circuit. If you could explain to me what type of mixing valve has a CV close to total flow? I don't understand what all that means? I have a WATTS 3/4 inch mixing valve, but don't know if that is correct. Also, if I go one pump, will I burn more electricity with the high head pump vs. two small pumps?

Thanks for all the imput.  Jim


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## in hot water (Jan 13, 2012)

kuribo said:
			
		

> Those are the flow rates at the design point heat load of 35,000BTU/hr (-30F day here in Wi). The heat load may be half that or even less on a more typical winter day and thus the flow rates would be way less than 0.875 gpm.....
> 
> It seems that the most common in slab pex size is 1/2"....is it common for flow rates to be 0.25-0.5 gpm in these systems?



.6 gpm is what the Radiant Panel Assoc suggests for a 1/2" loop.  300' loops are about right.  

Really the starting point should be the heat loss of the building.  Then, knowing the available "un-encumbered" floor area you build the radiant installation.  Divide out any floor area under tool chests that sit on the slab, cabinets, etc.  Radiant energy, like sunlight needs to "see" the load, line of sight.

Typically 12" on center, 1/2" tube 300' lengths, at .6 gpm will provide about 25 BTU/ square foot output. Flowing .6 gpm of water thru 1/2' 300' loops would have a pressure drop of 3.8 feet of head, very reasonable.

If the load is higher you can decrease tube spacing, increase supply temperature, or increase flow rate.  It's best to make changes to the supply temperature to change floor output.  Once the tube is in the slab, that's hard to change.

 That is what outdoor reset control accomplishes.  Think of it as a "cruise control" for your heating system.  It tries to supply the exact amount of energy (water temperature) to match the ever changing load of the building.  The load being the outdoor temperature, & infiltration.

To have a variable temperature control you need a smart component.  This could be a motorized 3 or 4 way valve, or a variable speed circulator feeding into a manifold.  A 3 way thermostatic valve would not be considered a reset-able  valve, it only reacts to temperature supplied to it, not the outdoor temperature input.

As always how much control and how accurate you want it depends on how much $$ you want to spend.

hr


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## DaBackBurner (Jan 13, 2012)

jimdeq said:
			
		

> To answer everyones questions, my tarm is "Solo 60". So far above 25 degrees equals one fire per 24 hrs. Lower than 25 degrees equals one fire every 12 hrs. I have figured out to not let the bottom of storage get below 120 due to termovar function upon restart.   Jebatty, I liked the option you described, because I don't always want my shop at 60 degrees. If I leave for a week or go on vacation I would probably turn it down and let the unit heater due a quick recovery when I'm home. I understand thermal mass but I want to keep it easy for my wife and kids to do the boiler. I want to use gylcol for the shop loop. I already have about 40 gallons from a friend. The heat exchanger I have in my basement has 1- 1/4 supply and return from boiler, but the problem is it has a 3/4 inch restriction where it ties into the 1 -1/4 inch thermopex. It is a stainless tube in shell pool exchanger.
> 
> DBB: I don't understand outdoor reset or injection mixing circuit. If you could explain to me what type of mixing valve has a CV close to total flow? I don't understand what all that means? I have a WATTS 3/4 inch mixing valve, but don't know if that is correct. Also, if I go one pump, will I burn more electricity with the high head pump vs. two small pumps?
> 
> Thanks for all the imput.  Jim



Cv = Flow coefficient or flow capacity rating of the valve and it is typically chosen close to the total flow of the distribution loop for a 1psi drop which equates to 2.3ft of head that the pump must overcome. So for example if you needed 5gpm flow and had a lower Cv valve say 3, your pump would have to overcome more pressure (psi) or head to flow those same gpm's. Most manufactures list their valves Cv or can be looked up at least, and it is fairly common practice to match a valve's Cv to the total flow which also allows the valve to mix properly. 
I don't actually know your heat loss so I can't give you any suggestions but my guess is that your valve may be just fine, there is after all some 'lee-way'. It's also hard to determine whether or not one pump vs. two will save you electricity without knowing your heat loss. 
You most likely would save electricity by going with, as ew pointed out, a variable speed ECM but probably only involving injection mixing (a whole other animal) because the pump would vary its speed and typically only run at 30-50% rated output hence electricity savings. 
Once your heat loss is known many things can be determined...or at least calculated.

Oh yeah.... GO PACK (forgot that last time, hehe)


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## kuribo (Jan 13, 2012)

Thanks for the info...was looking at injection pump systems....much easier to just vary supply temps...

My tubing is already placed (1/2", about 6" oc). At max output of 35 btu/hr./sq ft, using the standard of .6 gpm from above, I get a supply temp of 125F, a delta t of 14.5F, and a total flow of about 5 gpm on the first floor which is tiled, and a supply temp of 107F in the basement which is bare concrete, a delta t of 14F, and a total flow of 10 gpm. All told, about 100,000 btu/hr. Calculated heat loss on the design day is about 85,000 btu/hr so I have a little extra capacity....Is this roughly what others are seeing?

Now to figure out what type of supply/distribution system to use....


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## jimdeq (Jan 31, 2012)

Sorry for not getting back to this topic for awhile.  We had some health issues in the family.  I want to move forward with the infloor.  Today I ordered materials to get started.  I still havent decided on the one vs two pumps.  I leaning towards two pumps for the simple reason that I dont want to get it done and find out I do not have a big enough pump or my electric bill goes up $25.00 a month.  

DBB, I appreciate all the math you did for me and it was a big help.  I had a contractor do a heat loss and he came up with 20,000 BTU.  I have a very similiar building to Jebatty.  I want to keep things simple and it seems one pump would be much simpler.  Glycol is the other issue as to how it will impact my heat calc.  The variable speed Alpha 15-55 ECM would be awesome if it could handle the 300' transit and the 6 loops.  Then the unit heater?  I would think the 1-1/4" thermopex would keep the head down ,but it is still a long transit.
Any more comments would be appreciated.


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## ewdudley (Jan 31, 2012)

jimdeq said:
			
		

> Sorry for not getting back to this topic for awhile.  We had some health issues in the family.  I want to move forward with the infloor.  Today I ordered materials to get started.  I still havent decided on the one vs two pumps.  I leaning towards two pumps for the simple reason that I dont want to get it done and find out I do not have a big enough pump or my electric bill goes up $25.00 a month.
> 
> DBB, I appreciate all the math you did for me and it was a big help.  I had a contractor do a heat loss and he came up with 20,000 BTU.  I have a very similiar building to Jebatty.  I want to keep things simple and it seems one pump would be much simpler.  Glycol is the other issue as to how it will impact my heat calc.  The variable speed Alpha 15-55 ECM would be awesome if it could handle the 300' transit and the 6 loops.  Then the unit heater?  I would think the 1-1/4" thermopex would keep the head down ,but it is still a long transit.
> Any more comments would be appreciated.



I think DBB's number for the flow rate from house to shop might be off.  He's showing 5gpm, but if heat flow is 20000 btu / hour, and deltaT is conservatively 50 degF, the flow from house to shop would be no more than 1 gpm.  Therefore house to shop headloss would be more like a foot or less.

Bottom line, one small pump, e.g. 15-58 or 008 should have no problem pulling all the way from the house and through a mixing valve.  Keep in mind that the flow from house to shop will be only enough mix the radiant supply up to 120 degF or whatever, and that the return temperature to the house would be that of the return from slab, quite low.

The high temp heater, if implemented, would have its own pump drawing in parallel with the radiant pump.

--ewd


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## woodsmaster (Jan 31, 2012)

I'm not an expert, and in my opinion all those fancy controls are really not nessasary. Sure It's fun to play around with the stuff
but for a shop? I have a single 3 speed circulator and a mixing valve. Works great.
  As far as freezing I've left my circulater off in the shop for 4 days and only droped 10
degrees and thats with cold vehicles going in every day. My power would have to be out for weeks to have somthing freeze.
By the overhead doors I left the pex back a couple of feet from the edge so as to not waste heat to the outside and for no worries about freezing. Have fun with the install.
 My 2 cents.


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## jebatty (Jan 31, 2012)

> Iâ€™m not an expert, and in my opinion all those fancy controls are really not nessasary. Sure Itâ€™s fun to play around with the stuff, but for a shop? I have a single 3 speed circulator and a mixing valve. Works great. As far as freezing ... power would have to be out for [a long time] to have something freeze.



I pretty much agree, even though I am one for fancy controls, monitoring, data logging, etc. My shop has a single speed circulator, mixing valve, set it and forget it on the floor sensor, no reset. A few degrees variation in air temp in the shop just doesn't make any difference for anything I do. As for freezing, I do have antifreeze in the floor pex, use a plate hx, but boiler and storage tank in the shop are water. I have been gone for 2 weeks in some very cold winter (-10 to -35F), no freezing. My backup simply is a 5000W - 240V space heater to keep the air temp about 50F during long absences. I figure that will heat the floor as well as everything else to prevent freezing. Much less expensive than any alternatives, and rarely used. All pex is 12" o.c., except for first three passes around the perimeter.


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## DaBackBurner (Feb 1, 2012)

ewdudley said:
			
		

> I think DBB's number for the flow rate from house to shop might be off.  He's showing 5gpm, but if heat flow is 20000 btu / hour, and deltaT is conservatively 50 degF, the flow from house to shop would be no more than 1 gpm.  Therefore house to shop headloss would be more like a foot or less. --ewd


 :lol: That certainly wouldn't surprise me.

My limited experience with my shop floor (slab on grade with 2" xps perimeter and below slab) is that last year I ran a Î”T of 40-50 for the shop loops. This didn't fair too well for me because I needed a fairly high supply temperature (120-130) because of my lower flow rates in those loops in order to maintain my desired air temperature. Because my loops are 6" OC at the perimeter and 12" OC for the field, with flow around the perimeter of the building first (this made sense as that should be the area of the highest heat loss) I found I was melting snow around the exterior of the building (after-all it is only R-10 we are talking about). This year I increased my flow rates in my loops to maintain a lower Î”T, now 10-20, and find that my supply temperature (80-90) into those loops can be much lower while maintaining my desired air temperature. As a result I have no snow melting around the perimeter of the building this year, which is always a good thing in my eyes because my distribution losses have been minimized. As on old-timer fluid mechanic for iron tailings told me "Flow too low is a big no-no, flow to fast and it just won't last, flow just right lets crack a Miller Light".

I'm really poor at this as well...but let's see some pictures.
Best of luck.


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## ewdudley (Feb 1, 2012)

DaBackBurner said:
			
		

> ewdudley said:
> 
> 
> 
> ...



Not your in-slab numbers, I was talking about unmixed flow from the house to shop mixer, which I think you said would be 5 gpm, whereas I believe it would be less than 1 gpm, your in-slab numbers made good sense.  The amount of unmixed flow to support the 20000 btu per hour heat demand should be tiny.

--ewd


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## DaBackBurner (Feb 1, 2012)

ewdudley said:
			
		

> Not your in-slab numbers, I was talking about unmixed flow from the house to shop mixer, which I think you said would be 5 gpm, whereas I believe it would be less than 1 gpm, your in-slab numbers made good sense.  The amount of unmixed flow to support the 20000 btu per hour heat demand should be tiny.
> 
> --ewd


I totally agree Eliot, the numbers were incorrect for the loop from-to house portion. I didn't know, last year, that my supply manifold adjustable flow rate indicators were not fully open from the factory. I was under the impression that they would have shipped them that way. Silly me. This year I found out differently, what a difference.


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## DaBackBurner (Feb 3, 2012)

I was just splitting some wood this unusually warm morning (crazy winter - no complaints) and went to check on the heat in the workshop and at this point I'm just gum flappin'...
Could he have put a mixing valve and pump in the house? Assuming his existing fossil boiler in the house was adequate to provide the extra BTU's (they are usually oversized anyway), couldn't one use that as the backup source? I'm proposing to do something similar this spring, albeit the other way around. It might be nice to control the heat in the garage from the house as well, not to mention easier to check if all your pumps are working from one location. Like I said, just gum flappin'.


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## jimdeq (Feb 6, 2012)

Sorry for the delay fellas ,but I have been away from home for work.  Here is a picture of my proposed plumbing diagram using the two pump system.  Take a look at it and if anyone could provide imput or suggestions I would appreciate it.  I am very intriged by the single pump concept , but dont understand how to pipe it.  I have a Grundfos Alpha 15-55 and a 15-58 sitting on the shelf. The second picture is the 1 1/4" thermol pex in the basement of the house.


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## DaBackBurner (Feb 6, 2012)

Here's one possible design that may work for the one-pump scenario.


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## nate379 (Feb 7, 2012)

Mine is same way and it sucks in the fact that the snow melt drains toward the door and then freezes the door closed.  Only is a issue when it's cold out -20* though.  I guess prying the door up is better than freezing the pex in the floor though.



			
				woodsmaster said:
			
		

> By the overhead doors I left the pex back a couple of feet from the edge so as to not waste heat to the outside and for no worries about freezing. Have fun with the install.
> My 2 cents.


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## woodsmaster (Feb 7, 2012)

NATE379 said:
			
		

> Mine is same way and it sucks in the fact that the snow melt drains toward the door and then freezes the door closed.  Only is a issue when it's cold out -20* though.  I guess prying the door up is better than freezing the pex in the floor though.
> 
> 
> 
> ...



 It rarely gets that cold here, and my floor slopes away from the door both inside and out.


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## jimdeq (Feb 8, 2012)

Thanks DBB for the drawing.  Seems like a simple plan and easy to pipe.  I am going to show it to my buddy who is helping me with the plumbing. I also like the idea of controling the shop from the house, I hope the blue Cat5 wire you see in the picture will work for controls.  Can you explain the diverter valve, I could not enlarge the picture to read all your comments?


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## DaBackBurner (Feb 8, 2012)

Sorry about the picture. 
Here is a link to one example of a motorized 3-wire control 3-way ball valve. 
http://www.caleffi.us/en_US/Technical_brochures/01131/01131.pdf
When your garage is calling for heat and another mechanism (possibly an aquastat) determines the house supply is not hot enough, it puts the diverter valve in a bypass position, which closes flow off from the house supply, fires the backup heater and flow would progress through it instead. The common 'AB' side would be toward the mixing valve. The 'A' side towards the house and 'B' towards the backup heater (or vice versa).


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## nate379 (Feb 8, 2012)

Not allowed to have a floor drain here cause on septic so it has to slope toward the door for drainage.  I guess could be flat but then it would pool somewhere, cause it's never "flat".  I have about 1.5" slope over the length of the garage, 26'.. just enough.



			
				woodsmaster said:
			
		

> NATE379 said:
> 
> 
> 
> ...


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## DaBackBurner (Feb 8, 2012)

DaBackBurner said:
			
		

> Sorry about the picture.
> Here is a link to one example of a motorized 3-wire control 3-way ball valve.
> http://www.caleffi.us/en_US/Technical_brochures/01131/01131.pdf
> When your garage is calling for heat and another mechanism (possibly an aquastat) determines the house supply is not hot enough, it puts the diverter valve in a bypass position, which closes flow off from the house supply, fires the backup heater and flow would progress through it instead. The common 'AB' side would be toward the mixing valve. The 'A' side towards the house and 'B' towards the backup heater (or vice versa).



You could probably do this 'bypass' loop with two zone valves as well (might be cheaper). One N/O ZV (for the house supply) and one N/C ZV for the backup heater. When the aquastat reaches it's set point it opens the backup heater N/C ZV and when this is fully open triggers the house supply N/O ZV to close. I'm not a controls guy and defer to the other more experienced posters on this forum, but this seems like it may work.


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## jimdeq (Feb 8, 2012)

OK but I dont want the unit heater to be set on anything that automatically turns it on other than me or the thermostat. I want to keep the shop warm ,but not hot.  I understand the benefits of not letting a large thermal mass cool off.  I dont know what temp I will keep it at ,but probably around 50.  The only time I will use the high temp unit heater is when I am home and probably have a fire burning.  Thats why I want the unit heater  on its own stat and controls.  I dont want the unit heater running if know one is home or working in the shop.   I was thinking that when I added the unit heater that would have it's own circ that would kick on in tandem with the primary circ ,but not sure about that either.  I really like the one circ drawing DDB made if that will work for my situation.  I got confused when you added the three way motorized.  Would the  same drawing work without using the diverting valve or does the diverting valve save me from sending hot water back to the house that could go back to the infloor zone.


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## DaBackBurner (Feb 8, 2012)

jimdeq said:
			
		

> OK but I dont want the unit heater to be set on anything that automatically turns it on other than me or the thermostat. I want to keep the shop warm ,but not hot.  I understand the benefits of not letting a large thermal mass cool off.  I dont know what temp I will keep it at ,but probably around 50.  The only time I will use the high temp unit heater is when I am home and probably have a fire burning.  Thats why I want the unit heater  on its own stat and controls.



Sorry about the confusion Jim...then I would suggest using the unit heater as a stand alone circuit possibly connected to a modine or something similar that is a low mass heat emitter then, so you can quickly raise the temperature in your garage at your leisure. Use the slab radiant as a base temp from house supply only. The additional heater would not even be part of that circuit then.


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## jimdeq (Feb 8, 2012)

Exactly DBB.  So if that is the case would you suggest another pipeing diagram.  I know it is alot of work ,but I would appreciate it.  I cant find any diagrams similiar to what I need?


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## DaBackBurner (Feb 8, 2012)

Just remove the 'backup' heater out of my previous drawing along with the diverter valve. Install a slab sensor for your radiant loops that controls the pump, and maintain whatever slab temp you would like, with the mixing valve, as a base air temperature.
The low mass heater is a stand alone unit that has no bearing on the piping diagram anymore. A fossil Modine unit could be used or similar. Something that has a quick enough response to bring your base air temperature up to your desired air temperature while you're out there. That unit would have it's own air temperature T-Stat.


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## ewdudley (Feb 8, 2012)

jimdeq said:
			
		

> diagrams similiar to what I need?



This might do it.


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## jebatty (Feb 8, 2012)

FWIW, this is my setup, which I regard as very simple. Shop is similar size to jimdeq's; similar climate; 6 loops of 1/2" pex @ 275' +/-, 6" o.c. near perimeter and then 12" o.c.; supplied from a 5" x 12" x 30 plate hx with a Taco 009 to the floor loops. Building has 2" foam perimeter insulation down 3', and 2" foam under entire slab. Sensor embedded in the slab about 4' in from perimeter controlled by a Ranco, constant setting 61F, 1F differential. Also a stub out for a unit heater which I have not installed and have not needed. Shop air temperature may hit a low of about 50F at -35F outside temp, typical air temperature 56-63F during winter depending on outside temp. 50% antifreeze in floor loops. 100F+/- supply temp to floor via mixing valve; loop flow based on flow meters on manifold is 2.75 gpm, typical delta-T=30F+/-, typical floor btuH = 40,000+/- when radiant circ is "on"; typical building heat loss 12-14000 btuH, max is about 17,000 btuH. Building has one 12' x 12' residential style, insulated OH door, 1 - 3' steel insulated entrance door on front; 1 - 4' wood access door on rear; 2 - 2' x 4' insulated windows on sunny side of the building. Building dimensions 32' x 48' x 14'. 6" fiberglass in walls R-19; R-39 minimum blown-in fiberglass in the ceiling.

Comments/differences from jimdeq: The unit heater may need to be plumbed between the HX supply/return lines rather than shown, which is more like supply from a primary loop. I plumbed this way because I felt that if I needed the unit heater, the radiant floor circ likely also would be "on", and I also can manually turn "on" the radiant floor circ so that I have the function of a primary loop. But as mentioned, I have not needed to install the unit heater. My Tarm Solo 40 and 1000 gal pressurized storage is in the building; Tarm serves only the building, no other heat load. Tarm functions to load storage. Radiant is supplied separately from storage as required.

The diagram does not include the air separator and expansion tank for the radiant, isolation valves, etc.

I stubbed out for the unit heater before the mixing valve so, if needed, it would be supplied with the hottest water, and then return to the hot water line for use by radiant, which only needs 100F water via the mixing valve. I guestimate unit heater delta-T not greater than 20F and probably less. I also have a 5000w-240v space heater to provide supplemental heat if I am gone for a period when I might be concerned with freezing, as the Tarm and storage are water, only the floor is glycol. Supplemental heat may not be needed if the HX/shop was all glycol and freezing was not a concern.


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## DaBackBurner (Feb 8, 2012)

I should add that I was referring to a non-hydronic low mass modine unit, vented out the side of the wall for instance, since I neglected to even ask what type of unit heater you had.


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## jebatty (Feb 8, 2012)

Need to add that when the Ranco calls for heat, it turns "on" both the radiant circ and the circ that supplies the system side of the HX.


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## jimdeq (Feb 8, 2012)

Thank you Jebatty,DBB,and EW it seems as though you are all on the same page which makes me feel good about proceding.  A couple of quick comments,  I dont think my shop needs to be as warm as yours Jebatty ,so at what point do you hinder the performance of infloor.  In a perfect setup for me the infloor would stay set at the minimum temp required for thermal mass consistency without sending super low return temps back to the boiler via termovar.  Is 50 degrees too low?  What about a Timer set to pump to the shop for 3 hours in the late afternoon when my storage is depleted anyway?

DBB,  Due to having the glycol I was going to use a hydronic unit heater and not use any gas burning appliance.    As I stated with Jebatty then I could just boost the heat up with the unit heater if I am home and there is a fire burning.  

My system is heating the shop ,but also a 2200 square foot home and DHW for 4  (2 teenagers).  I do have 1140 gallons of presurized storage and have been only making one fire per 24 hours, I understand that may change with the shop now but at the 24 hour mark I usually have about 1140 gallons with a temp of 160 on top to 130 on bottom so there is useable BTUs to send to the shop.


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## woodsmaster (Feb 8, 2012)

j said:
			
		

> Thank you Jebatty,DBB,and EW it seems as though you are all on the same page which makes me feel good about proceding. A couple of quick comments, I dont think my shop needs to be as warm as yours Jebatty ,so at what point do you hinder the performance of infloor. In a perfect setup for me the infloor would stay set at the minimum temp required for thermal mass consistency without sending super low return temps back to the boiler via termovar. Is 50 degrees too low? What about a Timer set to pump to the shop for 3 hours in the late afternoon when my storage is depleted anyway?
> 
> DBB, Due to having the glycol I was going to use a hydronic unit heater and not use any gas burning appliance. As I stated with Jebatty then I could just boost the heat up with the unit heater if I am home and there is a fire burning.
> 
> My system is heating the shop ,but also a 2200 square foot home and DHW for 4 (2 teenagers). I do have 1140 gallons of presurized storage and have been only making one fire per 24 hours, I understand that may change with the shop now but at the 24 hour mark I usually have about 1140 gallons with a temp of 160 on top to 130 on bottom so there is useable BTUs to send to the shop.



I cant answer about the termovar as I use a danfoss. Here are some thoughts though. I've been using a timer to heat my
shop for almost two seasons. I ran out of funds for the thermostat when I installed everything and just haven't found it necessary
to get one. I will buy one eventually. First year I kept the shop between 50 and 55 f. Didn't have any trouble keeping it between those temps. The danfoss always kept the return water to boiler 140 or above no matter what the temp of storage. there are 
usable btu's in your storage, but If you start dumping heat into the cool slab it won't take long at all to deplete your storage.
I've been running my timer for the floor when the boiler is going to make the storage last longer. That slab can really use the 
storage up quick especially When you only run the circ. once / day. This year I'm keeping the shop between 55 - 65 depending
on how much im out there. I plane on making a unit heater this year. I will the keep the shop at 50 and use the
unit heater when doing projects out there.


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## jebatty (Feb 8, 2012)

> I dont think my shop needs to be as warm as yours Jebatty ,so at what point do you hinder the performance of infloor.  In a perfect setup for me the infloor would stay set at the minimum temp required for thermal mass consistency without sending super low return temps back to the boiler via termovar.  Is 50 degrees too low?  What about a Timer set to pump to the shop for 3 hours in the late afternoon when my storage is depleted anyway?



Off hand I can't think of a point where infloor is hindered. Keep in mind that it will take hours and lots of btu's to raise the floor to higher point from a lower point. For my floor with the sensor set ON at 61F and OFF at 62F, floor actual ends up at 63F (maybe briefly at 64F) as heat continues to migrate through the concrete. The sensor is set in the middle between two loops. Also, this 1-2F temperature increase takes about 83,000 btu's, which also means that it drops storage temp by about 10F.

I don't think 50F is too low, perhaps something like mine and supply at 90F rather than 100F. Keep in mind that water from the boiler/storage may be anywhere up to 180F or so, or much lower, and will be getting mixed down to 90F, which means the return to the HX may be considerably higher, depending on Side A and Side B flow rates.

A timer may work, at the cost of over-shooting or under-shooting desired floor temp. You can experiment with the timer and find a good middle ground. It might be helpful if you installed or can install a floor sensor to read floor temperature.

Here is an example from data I recorded on Dec 3, 2010, which appears to be near the end of a floor ON cycle and also at a point where storage is nearly depleted. Also, Side A flow rate is with a 007 and is quite high, while Side B flow is with a 009 through the floor with flow of about 2.75 gpm, which explains the low Side A temp drop compared to the high Side B temp drop

AIN = HX SIDE A SUPPLY FROM STORAGE = 105.35
AOUT = HX SIDE A RETURN TO STORAGE = 99.5
BIN = HX SIDE B RADIANT FLOOR RETURN = 72.275
BOUT = HX SIDE B MIX VALVE SUPPLY TO RADIANT FLOOR = 102.2
FL = FLOOR = 64.0625
L1/R1 = TOP OF TANK TEMP = 107 +/-
L4/R4 = BOTTOM OF TANK TEMP = 104+/-
OU = OUTSIDE AIR TEMP = -1.75
IN = INSIDE AIR TEMP = 56.525


```
#     ID#          DATE     TIME        TEMP   SENSOR
521,0000027B7420,"12/3/2010 8:10:06 AM",72.275,BIN
521,00000220F620,"12/3/2010 8:10:06 AM",105.8,L2
521,0000025BBED8,"12/3/2010 8:10:06 AM",102.2,BOUT
521,00000220D3F8,"12/3/2010 8:10:06 AM",106.025,R3
521,0000027B8B34,"12/3/2010 8:10:06 AM",99.5,AOUT
521,0000021E05CC,"12/3/2010 8:10:06 AM",64.0625,FL
521,000002B500FC,"12/3/2010 8:10:06 AM",83.75,SU
521,0000027B8F2E,"12/3/2010 8:10:06 AM",103.8875,L4
521,0000027B71BE,"12/3/2010 8:10:06 AM",104.9,L3
521,000002B53FBE,"12/3/2010 8:10:06 AM",87.4625,RT
521,0000021DEB2D,"12/3/2010 8:10:06 AM",106.1375,L1
521,000002210993,"12/3/2010 8:10:06 AM",105.35,AIN
521,0000027B6CCB,"12/3/2010 8:10:06 AM",107.15,R1
521,0000027CE347,"12/3/2010 8:10:06 AM",56.525,IN
521,00000291CE67,"12/3/2010 8:10:06 AM",104.5625,R2
521,0000021DE117,"12/3/2010 8:10:06 AM",105.6875,R4
521,0000027CD87F,"12/3/2010 8:10:06 AM",-1.75,OU
```


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## jimdeq (Feb 9, 2012)

Thanks for all the great info.  Nothing beats real exprience as you all have.  Great numbers Jebatty.  I hope my system can run as smooth as yours.  I will keep use posted on my progress and maybe some pics.


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## nate379 (Feb 9, 2012)

I have a water to air heater plumbed in on the primary loop on my boiler for the garage.  The floor only gets 130ish* water which wouldn't do a lot on that hanging heater.

I leave the garage floor heat on at 55* and the T Stat for the water to air set to ~50*.  The idea is when I open the door to pull stuff in or out and it cools down the garage, that it helps to recover faster.  Also if I wanted to I could kick it up to 60-65 while I'm in there, but I find 55* just fine when I'm working on stuff.


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