# underground piping



## 2.beans (Mar 22, 2008)

whats the best for the buck? i need to replace mine. thanks


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## adamant (Mar 22, 2008)

i uset thermo pex at 10.95 per ft..
what do you have now?


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## 2.beans (Mar 22, 2008)

i used fred setons method with corigated pipe , pex inside then insulate over the top. worked last year , but this year im having a problem with ground water and it melts snow. at its worst id loose 15 degrees in 240'. i saw some new stuff on ebay , its similar to maxx but it comes in a roll not in 8' pieces.didnt know if any has tried this. i need to change my pipe asap . im burning oil now because its using to much wood, seems like a waste to heat the earth.


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## heaterman (Mar 22, 2008)

2.beans, We use bare pex and hire an insulating contractor to spray foam it in the trench. Cost is usually about $6-10 / ft depending on the tube size, how much product they use, travel time etc. It works great for us. I don't use anything else now but I have had good results with InsulSeal in the past. Don't get sucked in by the corrugated stuff with the pex inside wrapped in a couple layers of bubble foil. My nephew is growing green grass above his as we speak. He loses about 9* from his OWB to his house in only 80'.


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## 2.beans (Mar 23, 2008)

the stuff on ebay wasnt  the bubble wrap. the pex is inside 1/2" rubber tube with foam oxygen barrier. is the spray foam dense enough to not absorb water? can break/crack and allow water in?


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## trehugr (Mar 23, 2008)

Heaterman, with there being so many kinds of PEX, what specific brand would you use for the system your using ?


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## trailhound68 (Mar 23, 2008)

I have 1" pex about 75' underground each way. The tube is in insulation, that is in 4" electrical conduit, glue joint.
Supply and return are seperate. Each in its own insul and conduit. 
I thought this was a darn good installation, yet I have a 10 deg loss if all stats are accurate. it will also melt the snow if its a thin layer. 
Most of my tubing is 24" plus below grade with no water issues.
I'm wondering if my pump speed is too slow?


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## SciGuy (Mar 23, 2008)

Yikes

If you're pumping 5 gallons per minute with a 10 degree F. delta T that works out to ~  25,000 BTUs per hour loss.  Pumping faster will actually *increase* the loss a bit due to greater delta T that will occur.   The loss will be proportionally more or less if you're pumping a a higher or lower gallonage/minute.

I would double check the temps.

Hugh


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## henfruit (Mar 23, 2008)

2 beans what are you useing for a heating unit? also what part of nh are you in. i am in effingham.


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## heaterman (Mar 23, 2008)

trehugr said:
			
		

> Heaterman, with there being so many kinds of PEX, what specific brand would you use for the system your using ?



I use Viega and Rehau pex just about exclusively. I've had excellent results with both and to me it's not worth risking an installation on something I can save a dime a foot on. I know a lot of contractors have good luck with Wirsbo/Uponor but I've heard issues with customer service since they changed names and got rid of a bunch of the folks that grew the company to where it is today.


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## 2.beans (Mar 23, 2008)

henfruit, i have a seton w130 or w200, whatever one you want to call it. the boiler is in my shop which is 240' away.i live in hillsboro


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## 2.beans (Mar 24, 2008)

heaterman when you spray foam the ditch is the pex in pipe or do spray a layer down lay the pipe then spray over it? on the insulseal  how rugged is the outside insulation?  thanks


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## henfruit (Mar 24, 2008)

2. beans do you know a ray leblanc in that area?


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## EForest (Mar 24, 2008)

trailhound68 said:
			
		

> I have 1" pex about 75' underground each way. The tube is in insulation, that is in 4" electrical conduit, glue joint.
> Most of my tubing is 24" plus below grade with no water issues.



two problems here. Every person I have spoken to on this subject will agree.
1.should have been below frost line at minimum 42" in CT
2.Glue joints are too risky. every one has a chance of failure.
Are you certain that water hasn't filled the pipe?
What size/brand splitter you selling and how much $?


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## 2.beans (Mar 24, 2008)

henfruit ,the name is familiar.what town does he live in?


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## henfruit (Mar 25, 2008)

2 beans some where in that area. he used to own a fruit and produce company.


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## heaterman (Mar 25, 2008)

2.beans said:
			
		

> heaterman when you spray foam the ditch is the pex in pipe or do spray a layer down lay the pipe then spray over it? on the insulseal  how rugged is the outside insulation?  thanks



We have the Pex in the trench when the guys come to spray it. As the guy with the gun moves down the length of the trench, he'll lift the pex with his foot and spray 3-4" underneath it. The product they use blows and hardens in a matter of seconds, at which point he'll drop the tube on the foam and proceed to spray the sides and top. The only disadvantage of this that I can see is if for some unknown reason you would ever want to pull the tube like you could in the InsulSeal type system. We typically go one size bigger on our tube just in case an additional load pops up in the future. Going to 1 1/4" vs 1" tube greatly reduces the flow resistance (head) on any run over 75 or so feet or that requires more than 6-8 gallons per minute. It makes the difference between having to run an 0011 vs a 007 Taco for example. Substantial savings in long term electrical costs between those two circs.

The foam on the outside of the InsulSeal is pretty rugged. Nothing that you would want to cover with rocks mind you but it will certainly hold up under normal backfilling.


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## Donl (Mar 25, 2008)

heaterman said:
			
		

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## 2.beans (Mar 26, 2008)

heaterman i asked a local spray foam guy for a price and he told 2600.00. thought that was enough. i can buy pipe for that but not 1 1/4, which id like. thanks for the help


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## heaterman (Mar 26, 2008)

Don L said:
			
		

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## Scotty2 (Apr 5, 2008)

I'm having problems getting a large slab to heat up using a Seton 300...his biggest I believe?
Running 3/4" line Pex 150' in a 4" flex line that's uninsulated except for 2-4" of rigid over the top...all above groundwater.
At the manifold in the warehouse (uninsulated), I'm tapping into 7/500' 1/2" lines and seem to only be getting 2 to 2-1/2 gallons of flow total.
Temp is around 170 degrees leaving the heat exchanger near the stove and 130 at the end of the 150' run...the return is down around 100 degrees.
2 questions on the 3/4" supply/return lines...
     Should I upsize to 1" or 1-1/4"?
     Should I use insulated PEX (if I upsize), or spray foam (If I retrench)...(has anyone tried those small cans or containers of spray foam?...Is there a special density or ? when purchasing it?
Fred Seton has suggested I install a mixing valve between the heat exchanger and the pump going to the warehouse to keep the return temp up. Does this sound correct?
Regards, Scotty
PS...I'll be posting about my "MAJOR" creosote problems along with some pics that will have you smiling.


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## heaterman (Apr 6, 2008)

Seton stove said:
			
		

> I'm having problems getting a large slab to heat up using a Seton 300...his biggest I believe?
> Running 3/4" line Pex 150' in a 4" flex line that's uninsulated except for 2-4" of rigid over the top...all above groundwater.
> At the manifold in the warehouse (uninsulated), I'm tapping into 7/500' 1/2" lines and seem to only be getting 2 to 2-1/2 gallons of flow total.
> Temp is around 170 degrees leaving the heat exchanger near the stove and 130 at the end of the 150' run...the return is down around 100 degrees.
> ...



Let's start at the beginning. The first question you have to ask in any situation is what is the heat loss of the structure. From there you can determine flow rates required which will tell you tubing size, loop length, and circulator selection. From there you have to look at the type of equipment and heat emitter being used to select the right control set up.

Here's some rules of thumb: rough but generally accepted as safe

The following flow rates will all develop about 6' of head per 100' of the corresponding tubing size.
Using a 20* drop you can figure that each gpm is good for 10,000 BTU of heat transfer.
1/2" = 2 gpm
3/4" = 4 gpm
1"  = 8 gpm
1-1/4"= 15 gpm
1-1/2" = 22gpm
2"  =  45gpm

Note that the 6' of head is PER 100' of tubing length. Taco or Grundfos' website will have specs detailing the performance curve of the circ you're using. 

Loop lengths recommended for good performance without resorting to ultra high head circs in a slab heating application            (IE) 009/0011/26-99

1/2" 300'
5/8" 400'
3/4" 550'
 Each of those will give you about 1-1.3gpm per loop or using the 20* drop, 10,000 - 13,000 btu per loop.

A well insulated cement slab in a building with normal heat loss will require no more than 120* water and usually it will be closer to 100-110*.

Now back to your system............

I'm assuming that your building is about 3,500 sq ft based on the 7-500' loops. 30 btu's / sq ft. (WAG) would equal about 105,000 btu heatloss. This translates to roughly 10-11 gpm flow required.  

From that you can see your main loop out to the building should be 1-1/4". A 007 Taco or a 15-58 Grundfos will provide all the push you need to get the water there and back.

In the shop you have loops that are overly long so the temp drop is going to be higher than you would like due to reduced flow rates. In a warehouse application the excessive temp variation in the loop probably isn't a big deal other than you'll probably have to use a high head circ. (009)

Seeing as you have no storage you'll have to limit flow or temp drop in order to keep water temps up in the boiler above the creosote threshold. Then in the warehouse you could use a straight thermostatic mix vavle to limit the temp going out to the slab .
A cement slab can drain enormous amounts of heat whil coming up to heating temps. Far more than the actual heating load per hour would normally be. Picking up a load like that with no storage or backup means you have to rely totally on the output of the boiler. If the pickup load is greater than the boiler output you'll find that the boiler temp will just plummet and stay there. Hence the need for a mixing device in order to protect the boiler from condensing temps. 


Tell us how you're system is piped exactly. What model circ do you have on the 3/4" lines and what model is running the warehouse floor?

Are you using a thermostatic mix valve to drop the temp going to the slab?


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## Scotty2 (Apr 6, 2008)

What a great amount of information...let me start off by expressing my thanks for your (and every other posters), time helping with this.
Building is 4500 sf, uninsulated Quonset style warehouse. uninsulated slab is 6" on pig wire over compacted sand (I think there was a vapor barrier in there somewhere), with 1/2" lines attached to the pig wire. I recall the lines being approx. 18" apart.
When setting up the loop lengths, diameters, spacing, pumps etc., I relied on the same person who sold me the Stove...thus I didn't insulate under the loops (water table is pretty low), used 1/2" (why pay for 3/4" when you don't need it), 500' loops (experience has shown the old 'limits' to lengths are incorrect), and a Taco 0011 to push the water to the warehouse (again, it's all you need for your circumstances...comments are those of the stove seller).
You mention a Taco 007 and 009. I'm using one Taco 0011 about 3' from the heat exchanger that pumps to the warehouse AND pumps the 3500' of 1/2" in the slab (I was told 1 pump does it all)(I do have a spare Grunsfos 15-58 F4 on the shelf).

So...with some items indelibly fixed, here's what I can change...
I can insulated the walls of the warehouse...probably take a season or two to get it done however.
I can upsize the supply lines to 1-1/4 (Ouch)...at least I can use the existing 3/4" stuff for future expansion to a      greenhouse, kiln, or mobile home.
I can upsize the pump.
I can put in a storage device...with propane backup?
You mention using a straight thermostatic mix valve (in the warehouse), to limit the temp going out to the slab...I was recently told to install a mixing valve between the exchanger and the 007, not out at the warehouse...do these provide the same result e.g. keeping the water temp at the stove up?

When it comes to storage/backup heat...Easiest around here would probably be a propane fired - water heater. Any thoughts on this? (I can possibly do this quicker than insulating the warehouse as it's full of stuff and will be hard to access other that a bit at a time).
Next, I'll get to working on the pics of the creosote problems.
Regards, Scotty


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## Bob Rohr (Apr 6, 2008)

Ouch is right.  4500 square feet of un-insuated space will be a tough go.  It's more like a snowmelt system with a metal roof over it 

With 1/2 tube, 500 foot lengths and 18" on center you have the deck heavily stacked against you.

Building insulation would be the first place to start.  Spray foam works well in that type of building.  You could add additional lines from the stove.  Maybe another set of 1" lines, manifold them together to get your flow up.  Then you can move all the heat the boiler is capable of producing.

Without under slab insulation start up may take days.  edge insulation would be a huge help.

Run a load calc as the building stands, and one with an R-19 insulation.  50 BTUs per square foot, for example would require 225,000 BTU per hour.  Divide that by the amount of loops you have to distribute it.  doubtful that 1/2" tube will ever move that much load, even with a 5 HP pump 

Run the load calcs, maybe we can tune around what you have.

 hr


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## Scotty2 (Apr 6, 2008)

Your analogy of a 'snow melt' under a metal roof made me laugh...that's about what I have at best of times.
As to spray foam...I did a bit of checking on this, and it appears I've got to be careful about the fire hazard (and I'd probably have to empty it out for a couple of days),...so I'm thinking of firring it out with horizontal 2x4 2' o/c then attach 1-2" rigid with a face of some sort (looks like plastic or vinyl-blue in color)...been told I should fasten 2x from the outside and rigid from the inside.
Load calcs...can you point me to a formula, work sheet, indepth explanation?
Regards, Scotty


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## Bob Rohr (Apr 6, 2008)

This free download from Slant Fin is a fairly easy one.  If it has a half round roof that may be little harder to calc.  "google" area calculators for some help with that square footage.

It pretty much comes down to the amount of wall and window exposed and the delta t between outside temperature and desired indoor. Maybe some wind induced loss (infiltration)  that will need to be a guesstimate.   60F indoor is sometimes plenty for a working shop. 

www.slantfin.com/heat-loss-software-get.html

 hr


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## heaterman (Apr 7, 2008)

Seton stove said:
			
		

> What a great amount of information...let me start off by expressing my thanks for your (and every other posters), time helping with this.
> Building is 4500 sf, uninsulated Quonset style warehouse. uninsulated slab is 6" on pig wire over compacted sand (I think there was a vapor barrier in there somewhere), with 1/2" lines attached to the pig wire. I recall the lines being approx. 18" apart.
> When setting up the loop lengths, diameters, spacing, pumps etc., I relied on the same person who sold me the Stove...thus I didn't insulate under the loops (water table is pretty low), used 1/2" (why pay for 3/4" when you don't need it), 500' loops (experience has shown the old 'limits' to lengths are incorrect), and a Taco 0011 to push the water to the warehouse (again, it's all you need for your circumstances...comments are those of the stove seller).
> You mention a Taco 007 and 009. I'm using one Taco 0011 about 3' from the heat exchanger that pumps to the warehouse AND pumps the 3500' of 1/2" in the slab (I was told 1 pump does it all)(I do have a spare Grunsfos 15-58 F4 on the shelf).
> ...





Scotty.........how can I put this politely..........hmmmm...........your doomed comes to mind........

Seriously, there is no way the system as it stands will ever work. It doesn't matter what size boiler you drive it with or what circulator you put on the shop zone, 500' lengths of 1/2" tube are incapable of carrying that amount of heat. It's a physical impossibility. You can't get enough gpm through 1/2" to satisfy the heat load of the building. The concrete itself won't radiate that much heat unless you drive it to about 100*+. (Guessing that your heat loss is on the far side of 300,000. 60-70 btu's per sq ft @ 50* indoor)  We actually do a lot of systems that are much like that for dairy barns here and we use 5/8" or 3/4" tube, shooting for at least 2gpm per loop, 2.5-3 is better. This means loop lengths of not much over 300 ft even with the big bore tube. 

I guess the first thing I have to ask is does you stove seller have any experience at all in system design? If so, he really screwed up on this one and should take some responsibility for it. It would seem that he has held himself out to be at least somewhat of an expert in this seeing he made recommendations to you regarding tube size, insulation requirements and circulator sizing. I don't know if you have contacted him regarding the lack of performance but I would sure get him in the loop and put him on the hook.

As to the question of mixing valves, you need two or else a single 4-way with an intelligent control driving it. Your system needs two things. Number one is that the boiler needs to be kept at operating temperatures above the condensation point of the flue gas (roughly 300*) or you will have gobs of creosote hanging from everything. The valve would sense the boiler temperature and reduce flow to the heating load while keeping the boiler temp where it needs to be. As MOS stated, the other side of the coin is that you don't want water temps above 140* hitting the slab lest you invite problems with cracking and spalling of the concrete. (Normal water temps for a slab are in the 90-110* range)That would be the function of a manually set thermostatic mixing valve in the shop. (This is assuming that you can actually get 180* water out there in the first place.) 
  In short, the first mix valve protects the boiler from condensation, the second one limits the temp going to the floor to prevent damage to it.

If you were my customer, I would suggest abandoning the in floor approach for now because it will never work unless you can drop your heat load down to less than 10 btu per sq ft. If you can get the building insulated to some extent you could hang a couple hot water fan coils in it to provide heat. Make sure  to oversize them by 40% because they are rated based on 215*steam. Along with that you're going to have to run at least 1-1/4" tube at the minimum, 1-1/2" would be better as you're going to need a lot of flow.

I really do feel badly for you. I see so many systems that are "field engineered" by these OWB guys just looking to turn a quick sale. Either they are just that ignorant or else they just don't care. Bad both ways.


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## Tony H (Apr 8, 2008)

Don L said:
			
		

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## Scotty2 (Apr 8, 2008)

Responding to nolomich...the designer was good ole' Fred Seton himself...He basically said (and more than once), " Don't listen to those guys with their fancy numbers...I've done hundreds of installs over 20 years and what I'm telling you is based on practical experience"...
That advice was...
Don't insulate under the slab if the water table is low...do insulate around the edges. The return on your investment doesn't warrent it.
Use 1/2" pex, 500' runs
A 3/4" feed line will be sufficient...simply put in uninsulated 4" drain pipe and cover with 2-4" rigid (top only).
Fred did actually see the building as he personally delivered the stove.
Same person also said:
Green wood is actually better than dry as it will hold the fire longer...don't split em, if you can lift em in the stove they'll burn.
I recall no mention of a mixing valve being a necessity, nor the importance of keeping the stove water above 100 degrees.

So; I will insulate the building, probably 1-2" rigid with an air space between the metal skin and the rigid foam.
Possibly install additional heat source...I could run a second set of supply lines and divide up the 7/500' runs between the two?
I'll up size the supply line(s) and insulated them properly.
I'll look into a different pump...Fred said one (Taco 0011 is plenty), did I hear someone say 1 pump from exchanger to warehouse and a 2nd at the start of the 7 lines?
I'll also look at a hot water storage backup...will need anyway if we put in a greenhouse.

I should mention in Fred's defense...when the stove was running well, it did keep the warehouse above the dew point, and the temperature above freezing (probably high 30's when it was mid 20's outside-uninsulated remember).
I recall each 500' run was showing around 1/3-1/2 gallon per minute...I do have the option of shutting off 3-4 lines in the back of the warehouse as it houses no freezable stuff...and the flow rate for the remaining 3 lines gets up to 3/4-1 gallon per minute each. I think the gauges on the 1/2" line only go to 1.5 or some such. The floor doesn't actually get warm, however you can tell it's warmer than normal.
Finally, Fred has always been willing to answer questions and offer advice...that was a big selling point when were starting out.
Regards, Scotty
Regards, Scotty


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## 2.beans (Apr 8, 2008)

i also listened to fred. i ran two 3/4' pipes inside 4' pipe, insulated over the top, buried it and then burned wood like crazy. i was losing 15 degrees in my 250' run between my house and boiler. so i got to change my pipe last weekend in the snow and mud. it worked good last year but this year it didnt. although i did have a nice melted path up to my shop. it worked like my heated walkways. i think fred should stick to building boilers , even though he does seem knowledgeable . i wish he could have helped me change my pipe.


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## heaterman (Apr 8, 2008)

Seton stove said:
			
		

> Responding to nolomich...the designer was good ole' Fred Seton himself...He basically said (and more than once), " Don't listen to those guys with their fancy numbers...I've done hundreds of installs over 20 years and what I'm telling you is based on practical experience"...
> That advice was...
> Don't insulate under the slab if the water table is low...do insulate around the edges. The return on your investment doesn't warrent it.
> Use 1/2" pex, 500' runs
> ...



There's nothing "fancy" about the numbers. They are what they are and if I've learned one thing about hydronic heating it's that there are no shortcuts. You either take the time to design a system right or it will come back to bite you. Do I always get it right? I'm human, what do you think?
That being said, I've found that the laws of physics pertaining to heat transfer don't bend. I didn't invent those laws of physics but I have sure learned that I have to follow them no matter how good I think I am. Heat doesn't magically appear where you want it just because you have some tube in a floor or running from one place to another. Boilers don't generate heat or run cleanly unless certain conditions are met. All wood boilers will creosote unless you keep the water temp above 130-140*, doesn't matter who made it. Physics aren't fussy about whose stuff they mess up.  Radiant heat  travels equally in all directions, 360* from the tube, unless you give it a reason not to. Why let it go into the ground?


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## terry (Apr 9, 2008)

Heaterman, were also in the market for pex tubing. Have you ever heard of Microflex pex duo 32mm, 125mm outer jacket?  Looking for GPM flow rate for that diameter tubing as well as the quality of this product.  We found a distribitor on Garn website.  We have a 225 ft. run from barn where the boiler will sit to the house. 450 ft. is a lot of head for selection of pump sizing. Any info is greatly appriciated. Thanks Linkolog


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## heaterman (Apr 9, 2008)

linkolog said:
			
		

> Heaterman, were also in the market for pex tubing. Have you ever heard of Microflex pex duo 32mm, 125mm outer jacket?  Looking for GPM flow rate for that diameter tubing as well as the quality of this product.  We found a distribitor on Garn website.  We have a 225 ft. run from barn where the boiler will sit to the house. 450 ft. is a lot of head for selection of pump sizing. Any info is greatly appriciated. Thanks Linkolog



The first question is ..........How many GPM do you need through that tube? The 32mm is roughly 1-1/4" .  About all you're going to get through that length tube is 7-8GPM using a circ like a 15-58 Grundfos, a bit less witha 007 Taco. Using a high head circ like a 0011 or 26-99 will bump it up to 10-10.5 but you rapidly reach a point where you're adding gobs of head with little resulting gain in GPM. Then you're just wasting electricity. If you go with the metric tube make sure you get the right fittings for the ends.

If you're load is 100,000+ you may have to use something in the 1-1/2" class.  I ran the numbers on My design software and captured a screen shot but the picture is too big to post here. Using 1-1/4" tube, 450' circuit, 2 full port ball valves and 4 elbows I came up with 7.52 GPM with a 15-58 Grundfos, a little over 6 with a 007, 10.8 with a 0011.


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## Tony H (Apr 10, 2008)

heaterman said:
			
		

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Just wondering at what point would it be practical to use two 1" feed and two 1" return lines instead ?


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## Gooserider (Apr 15, 2008)

Dumb question in regard to the OP's problem...  Would it be practical, and / or beneficial to him if he could break into the floor enough to find the middles of those 500' loops and break them up into more smaller loops?  Not sure how difficult it is to break into a floor w/o damaging the pex, but it sounds to me like that would at least give him more potential gpm's through the floor and presumably let him dump more BTU's?

Gooserider


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## terry (Apr 18, 2008)

Heaterman, Linkolog here, sorry I havent been around to respond to you latest reply r/t gpm flow needed to heat the house. Here are the facts.  Our est. load to heat the house is 106,000 btu,  We have two forced air furnaces, one on each end of the house. Air to water coils est. btu range is 75,000-100,000  each. How does one calulate gpm flow rate to each furnace coil if 1 gpm=10,000 btu. Hate to steel from this thread but my issues continue and I believe your the man with the answers. We have on demand hot water two pipe system with circulating pump from furthest fixture from hot water tank back to cold water supply input to on demand tank. Were not sure if we should use a plate to plate heat exchanger on supply side of tank or boiler mate. Were unsure of how to calculate demestic hot water demand load for a family of four, On demand hot water tank has a 180,000 btu/hour max..  Were unsure on  how to calculate gpm flow rate threw plate to plate exchanger or boiler mate from wood boiler secondary piping. Thanks Heater man.


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