underground piping

[Bob Rohr]

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.

(broken link removed to http://www.slantfin.com/heat-loss-software-get.html)

hr

 

[heaterman]

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

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.

 

[Tony H]

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.

Heaterman, Where do you get your fittings for the 1-1/4" pex? I have 1-1/4" Rehau's Paupex and having a difficult time finding fitting that will adapt to NPT. I can't afford the tools for Rehau's Everlock fittings. Are there any compression fittings available that will work with this pipe?

Don

Don,
I got 1 1/4 pex and comp fittings from Dave at Cozy Heat. I got pex to 1" copper, pex to 1 1/4 threaded and pex to pex 1"

For buried pipe it is not required to go below the frost line as long as you use continuous pipe. Pipe joints usually fail due to frost heaving.

 

[Scotty2]

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

 

[2.beans]

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.

 

[heaterman]

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

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?

 

[terry]

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

 

[heaterman]

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.

 

[Tony H]

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.

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

 

[Gooserider]

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

 

[terry]

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.