DIY water heater radiant setup

[Don1357]

I laid down PEX on the slab of my new garage/workshop for radiant heating.

Can somebody point me to a basic setup to run that off a water heater?

 

[Jakemedic]

Try these folks, very helpful and friendly. My budget didn’t allow for in floor heating, but rather a mini split for cooling and a natural gas overhead furnace for heating. Good luck with your project! I was just in Palmer Alaska a year ago. Beautiful place!

https://www.radiantec.com/installat...qiihB5EJlQGNB8Xel20coBC_eBArZeskaAhLaEALw_wcB

 

[Don1357]

So far the price hasn't been that bad. On a 24x36 I ran 3 coils of 300' PEX before the slab got poured. The coils were about $330 and the ancillary stuff (crimper, clamps, etc) probably made it $400. I made the manifolds with copper joints I already had laying around.

I'm looking more for a DIY, off the shelf components. I already built the manifolds and plan on just buying a water heater, probably gas if i get around running a gas line from the house but most likely electric. What I would like to see is a basic diagram of what I need to put in place.

 

[Chris705]

Lots of useful info in this link....
https://www.caleffi.com/usa/en-us/technical-magazine

 

[kabinenroller]

Insulation is the most important part of a hydronic system. My first building had forced air heat, I removed the floor and installed tubing with rigid insulation under the tube and along the foundation. I could not install any insulation on the exterior of the foundation because of a the excavation would have torn up the yard. I used an electric hot water heater for one season, it would heat the building but not recover without running constantly. ( I’m in Wisconsin so we have relatively cold winters) I changed the water heater to a propane unit (no natural gas where I live) it was better but not efficient. My new building was designed for hydronic, super insulated foundation, slab, and the building itself. The hydronic system is conventional except that I use a wall mounted on demand propane hot water heater instead of a tank type. I heat 1,900 sq. Ft. And keep it a 60 degrees all the time. It works perfectly, I very seldom hear the heater run, I have my house on the same propane tank so it is hard to tell how much it costs to heat the shop but between both of them the cost is reasonable.

 

[PWC Repair]

I see you're in Alaska. I hope you super insulated that concrete. Even then, the electric tank unit is not enough BTU to run it. I'm in Arkansas with mild winters. My concrete was 53ish degrees when I finally turned on my system. It ran constantly until it couldn't keep up anymore just to get the floor to 55*. This year I'll try to maintain he floor temp before it drops off cold.

I also setup a hot water fan coil in my shop which I used all last winter and it worked great off the electric tank water heater and did not use much power. Check it out on the last couple pages of my build thread.

 

[yeldogt]

300' is the max for loop length on 1/2 pex .... the delta will be large and you need to check overall head for pump. what is the pipe separation? doing 4 loops would have been better

Are they all about equal?

BTU output is the problem using water heaters --- the burners or resistance coils are designed to heat a small tank of water ... not a building. Also -- they are not designed to run 24/7. Most gas 40g have 26k burners at 80% .. you have to do a heat load to see what the BTU's are for the building.

Setup can be simple --- feed -- air elimination -- expansion tank. Pump ... control

 

[nadogail]

Under Floor Radiant Heating has been used for centuries with various heat sources from Wood Fires, Geo Thermal, even heat pumps drawing heat for decaying piles of manure.

Good Luck in finding something that works in your Matanuska Valley Shop.

 

[glentre]

Conventional water heaters do not have the recovery rate necessary to heat a slab and you will be pumping warm water around. Years ago, I designed a radiant slab system for my father's home in Chino Valley, Arizona and, to save cost, he used two tank type conventional heaters (don't recall what size) instead of gas or electric units designed for that purpose. On cold nights, he couldn't maintain a comfortable temperature and ended up changing out those tank heaters.

Glen

 

[Jackfre]

I would suggest you continue to do the research and speak with a couple of your local supply houses. Upon and Rehau have a lot of good info on their sites. Try to find out the preferred local boiler used in your area. If you get into a jam it is good to have folks who know the products. I suspect one of them will be happy to supply you with the parts you need. Keller Supply and Ferguson would be a good spot to go. Also give Russ at All Alaska Wholesale a call. He is down Homer way. You really don't want to use water heaters.

 

[TurnipTruck]

A former coworker down here in Kenai heated his 28x36 shop with a diesel water heater. He would get about 5 years before the heater was worn out/eroded/cracked.
I have heard of a few locals heating their shops with Takagi? Mini boilers.
My former Quonset shop is heated by a generic nat gas boiler with primary/secondary pumping loops to temper the water to the loops to about 105*F but maintain the return to the boiler to at least 120*.

 

[yeldogt]

A former coworker down here in Kenai heated his 28x36 shop with a diesel water heater. He would get about 5 years before the heater was worn out/eroded/cracked.
I have heard of a few locals heating their shops with Takagi? Mini boilers.
My former Quonset shop is heated by a generic nat gas boiler with primary/secondary pumping loops to temper the water to the loops to about 105*F but maintain the return to the boiler to at least 120*.

If the oil was a typical oil burner -- they put out lots of BTU. I have had many in my time. Seems every weekend house I bought in PA had oil w. oil hot water.

We would shut them off when we left for the week -- on return they were up to temp in about 12min. 30 gallon tanks -- they would produce endless hot water.

 

[Don1357]

Addressing a few of the posts at once:

The slab is insulated with 2" blue foam including under the edge, with an additional 2" going down 24" around the perimeter for a total of 4" perimeter insulation.

I ran 3 coils, all under 300', all pretty near identical lengths.

The shop won't be heated 24/7, I'm going to be running glycol on a close circuit. heck if on a -20f day it can speed up warming up the slab so an above ground heater can bring the work area to a toasty 40f, I'm a happy camper. The next owner is welcome to pump a million BTUs through the slab, I simply don't care for it.

Heck this morning it was mid 50's when I went out and about in shorts and a T-shirt to pick stuff off the lawn. You get used to the chill.

So, I need the manifolds (built them already), the water heater, a pump, an expanding tank, a pressure gauge, two temperature gauges, a relief valve, and what else? I'm just looking for a picture of a setup like this. If the water heater doesn't cut it everything else should still work.

 

[Showkey]

Sounds like your going to do what you want.........in floor heat that is not running 27/7 and warmed with vastly under sized water heater........is going take days to heat the cold slab.

You would be far better of with a torpedo heater or ceiling mounted heater ......both are perfect for “instant heat” for a shop.

In floor is great for gentle constant heat.........not great of on off or large temperature swings.

 

[Don1357]

Sounds like your going to do what you want.........in floor heat that is not running 27/7 and warmed with vastly under sized water heater........is going take days to heat the cold slab.

You would be far better of with a torpedo heater or ceiling mounted heater ......both are perfect for “instant heat” for a shop.

In floor is great for gentle constant heat.........not great of on off or large temperature swings.

Thank you for your permission, most appreciated.


I'm not trying to be difficult but this is not an uncommon setup here. A lot of folks, myself included, are happy heating a work area not far from freezing, turning it on the night before. If you are trying to make it 65 degrees I can see how you'll need a whole lot more BTUs.

 

[kj_mustang]

Then you do the calculations, how many BTUs and how much time are you going to need to raise a slab temperature of 40 F to 60 F while keeping the water supply temp around 125 F. As previously stated, radiant is better to keep a constant temperature, turn the the thermostat up to a temp and leave it on. Add supplemental heat to bring interior temps up quickly.

 

[nadogail]

Don1357,
It has been more than 40 years since I was in the valley, but my memory is not completely shot. When you can think in terms like Delta T, once your slab gets warm it can be kept warm with fewer BTU than it took to warm a cold slab.

Looking at your posts, I did not notice a circulation pump to keep the water moving through your radiating coils. The pump would IMHO be controlled by a differential thermostat.

When the heated water temp returning to the tank rises to an acceptable point the water heater could stop using what ever fuel source was heating the water.

Remembering that Dairy was a big industry in the valley, I wonder how much heat could be taken from a decaying manure pile.

 

[Don1357]

Don1357,
It has been more than 40 years since I was in the valley, but my memory is not completely shot. When you can think in terms like Delta T, once your slab gets warm it can be kept warm with fewer BTU than it took to warm a cold slab.

Looking at your posts, I did not notice a circulation pump to keep the water moving through your radiating coils. The pump would IMHO be controlled by a differential thermostat.

When the heated water temp returning to the tank rises to an acceptable point the water heater could stop using what ever fuel source was heating the water.

Remembering that Dairy was a big industry in the valley, I wonder how much heat could be taken from a decaying manure pile.

I think we are down to one dairy outfit out here. Farming is still alive but as everywhere else in the U.S. diminished. It is strange: cost of everything is higher up here due to transportation costs but apparently not large enough to support a lot of farming; local costs vs. global prices and all that. The skies are every bit as blue as they used to be.

Getting back to my project... I managed to get answers from another forum (that didn't got hung up on the power source without actually answering anything). I got a pretty good idea of what I need and how to put it together, expansion tank, pump, air eliminator valves, shut off valves, temperature and pressure gauges, etc. Looks like I don't need a one way valve as there won't be gravity to push the liquid back, nor a mixing valve as the max temperature gets regulated at the source.

I also got a chance to talk to somebody else that has a similar setup up here that I plan on taking a look at. He says that indeed from cold it takes forever to warm but that if her's going to work on a project he would pump supplemental heat and let it warm up. Once warm it is easy to keep it so for the duration of whatever he may be doing.

I figure eventually the setup can be used with a real heating source so connecting the second hand water heater is not wasting me much time and energy.

 

[nadogail]

Agreed, a BTU is a BTU, IMHO it doesn't matter where the heat comes from. Just South of me in Mexico there are wood burning hot water heaters. Your concrete slab will store heat, just like a battery stores electricity. One the slab comes up to temperature all you will have to do is keep it warm.

 

[nadogail]

Ment to write “once the slab gets to temperature, you can reduce the heating to the point that you are just making up for the losses.”

 

[Showkey]

Setback is one thing ( not simple with hydronic) .......shut down between uses is a whole nother strategy.

https://www.energy.gov/sites/prod/files/2014/06/f16/ba_case_study_hydronic_setback.pdf

 

[yeldogt]

I think we are down to one dairy outfit out here. Farming is still alive but as everywhere else in the U.S. diminished. It is strange: cost of everything is higher up here due to transportation costs but apparently not large enough to support a lot of farming; local costs vs. global prices and all that. The skies are every bit as blue as they used to be.

Getting back to my project... I managed to get answers from another forum (that didn't got hung up on the power source without actually answering anything). I got a pretty good idea of what I need and how to put it together, expansion tank, pump, air eliminator valves, shut off valves, temperature and pressure gauges, etc. Looks like I don't need a one way valve as there won't be gravity to push the liquid back, nor a mixing valve as the max temperature gets regulated at the source.

I also got a chance to talk to somebody else that has a similar setup up here that I plan on taking a look at. He says that indeed from cold it takes forever to warm but that if her's going to work on a project he would pump supplemental heat and let it warm up. Once warm it is easy to keep it so for the duration of whatever he may be doing.

I figure eventually the setup can be used with a real heating source so connecting the second hand water heater is not wasting me much time and energy.

No hang ups .... it's called "help" . W/O knowing the BTU's need for the building and knowing the BTU's of the heat source ... what's the point?

If you need 60k BTU and the water heater puts out 26K ..... will it work?

If I have a one car garage in PA -- 400ft of tubing and using a 40g 26k heater with an old pump .... I can heat the slab and someone may be happy and tell all the neighbors how great it is. That does not = safe and if it will work in AK.

Turning off radiant and trying to bring it bake up over a big delta takes a lot of BTU's .... and can stress a slab

 

[Don1357]

No hang ups .... it's called "help" . W/O knowing the BTU's need for the building and knowing the BTU's of the heat source ... what's the point?

If you need 60k BTU and the water heater puts out 26K ..... will it work?

If I have a one car garage in PA -- 400ft of tubing and using a 40g 26k heater with an old pump .... I can heat the slab and someone may be happy and tell all the neighbors how great it is. That does not = safe and if it will work in AK.

The point is that the actual question I asked was not answered even once, which was about a diagram for the setup. You know, the actual arrangement of expansion tank, pump, air eliminator valves, shut off valves, temperature and pressure gauges, etc. Because no mater what the energizer bunny I connect to it, that's what I'm trying to sort out.

Turning off radiant and trying to bring it bake up over a big delta takes a lot of BTU's .... and can stress a slab

For quick warming the place I have my 80k BTU induction propane heater which I expect can bring the entire building up to speed in under half an hour. After that the radiant heat can just pump enough heat to keep things from freezing. And do keep in mind that my idea of a warm garage space is most people's idea of outside winter weather; maintaining a building in the 40's doesn't take as many BTUs as trying to do 65f. Heck that's when we start opening windows here. I kid you not; every year when we get into the 70's my daughters want me to go out and but an AC...

Why not just rely on the propane heater and call it a day? Because baking the piping into the slab was cheap enough, you are not supposed to run a propane heater when you are not looking at it, and one day when I retire I may want to keep my garage warm all winter long. Heck when retirement happens I may want to put a real boiler there. For now the propane heater and second hand water heater will do just fine.

 

[yeldogt]

The point is that the actual question I asked was not answered even once, which was about a diagram for the setup. You know, the actual arrangement of expansion tank, pump, air eliminator valves, shut off valves, temperature and pressure gauges, etc. Because no mater what the energizer bunny I connect to it, that's what I'm trying to sort out.



For quick warming the place I have my 80k BTU induction propane heater which I expect can bring the entire building up to speed in under half an hour. After that the radiant heat can just pump enough heat to keep things from freezing. And do keep in mind that my idea of a warm garage space is most people's idea of outside winter weather; maintaining a building in the 40's doesn't take as many BTUs as trying to do 65f. Heck that's when we start opening windows here. I kid you not; every year when we get into the 70's my daughters want me to go out and but an AC...

Why not just rely on the propane heater and call it a day? Because baking the piping into the slab was cheap enough, you are not supposed to run a propane heater when you are not looking at it, and one day when I retire I may want to keep my garage warm all winter long. Heck when retirement happens I may want to put a real boiler there. For now the propane heater and second hand water heater will do just fine.

google "pumping away"

 

[like2wheel]

I laid down PEX on the slab of my new garage/workshop for radiant heating.

Can somebody point me to a basic setup to run that off a water heater?

There used to be a thread here something like "pics of your radiant set up".
I cant find it anymore, but I thought it was helpful as a reference. Some were quite simple.

 

[That1Guy]

Sorry, I'm a little late to the party. Here's a couple videos I found while researching my basic slab heat system and I think you might find some useful info here.


This guy made a video of a bare bones system thats been working great for him.
You should be able to get a basic idea of the parts that you"ll need for a minimalist setup.

This is another fella who went the basic route with great results.

OK, one more and I'll stop. Ol Ben here used a mini boiler but he explains things really well. It's not a water heater setup but still worth a view.

Good luck with your setup. Keep us posted as to what works and what doesn't. Your info and results will definitely help any future members trying the same thing as you're doing now.

Be well!

 

[Don1357]

Sorry, I'm a little late to the party. Here's a couple videos I found while researching my basic slab heat system and I think you might find some useful info here.


This guy made a video of a bare bones system thats been working great for him.
You should be able to get a basic idea of the parts that you"ll need for a minimalist setup.

This is another fella who went the basic route with great results.

OK, one more and I'll stop. Ol Ben here used a mini boiler but he explains things really well. It's not a water heater setup but still worth a view.

Good luck with your setup. Keep us posted as to what works and what doesn't. Your info and results will definitely help any future members trying the same thing as you're doing now.

Be well!

Thanks, most appreciated. This year I plan on just freezing my *** off, next year I'll look at attaching something to my system. We don't see -20F that many days during the winter months so it ain't that bad

 

[yeldogt]

Sorry, I'm a little late to the party. Here's a couple videos I found while researching my basic slab heat system and I think you might find some useful info here.


This guy made a video of a bare bones system thats been working great for him.
You should be able to get a basic idea of the parts that you"ll need for a minimalist setup.

This is another fella who went the basic route with great results.

OK, one more and I'll stop. Ol Ben here used a mini boiler but he explains things really well. It's not a water heater setup but still worth a view.

Good luck with your setup. Keep us posted as to what works and what doesn't. Your info and results will definitely help any future members trying the same thing as you're doing now.

Be well!

The water heater will work only if the BTU's it produces are high enough to match the load of the space....

The first guy has an electric water heater -- so he is heating his space with electric. A larger water heater does not = more heat ... it's all about what the electric coil inside can produce. Most 40 and 50 have the same coil ... the pump should be after expansion tank. As long as the coil is making the BTU's for the space -- that's all he needs .... the size of the tank does not matter. I'm not seeing how big the space is or where it's located.

The second guy has 60k BTU available -- that's often plenty for a modest house/garage. My winter vacation home is over 4000sf with that load. Hot water --pumped onto a slab ... will heat the slab. He is correct in his opening line -- he does not know about radiant.

The third guy made up a primary/ secondary loop system w/ manifold .... the primary is to keep the boiler happy and the secondary goes out to the PEX.

The average gas water heater is 26k BTU -- at 80% .... so if the second guy used one of them he may not have had enough heat. He is getting about 48k out of his unit ... a typical 40/50 gas is under 21k and this will fall behind in a poorly insulated double garage.

The piping layouts are easy to figure out -- the pumps are fine on the hot side. The complexity after a few basic parts is about service and control .. and safety. The second guys system is a mess ... it goes to show you how you can do things and still have them operate. Also -- they circulate .. not pump.

Again -- the piping is easy and not complex to get right. I love his hours to fill ... I'm sure there is a bubble at the top of the tank and the circulator location is not helping.

The average gas lawnmower engine was designed for 100 hours --- they figured it was 10 mowings a year for 10 years ... the average lawn taking an hour. Same with a water heater .... the burners are designed for a given duty. maybe two/ three cycles a day. When you start using them for space heating the burner and tank are often running much more ... if really cold -- all the time. They are not designed for that .... how long can they run ? Some people have great luck .. but, it all a question of what they are asked to do. Also -- they tend to hold air and that causes some rust.

 

[Innovate1]

I put together my own system that runs off a gas water heater (130k BTU 90% efficient condensing) for both domestic hot water and floor heat. The floor heat runs through a heat exchanger to keep the floor separate from the drinking water. It's more complicated than you need...

You need a small circulation pump, an expansion tank, air purge valve (probably not absolutely necessary) and two valves for filling and purging air from the system.

There is lots of information online about how to do this. I suggest looking at multiple sites because there are lots of ways to do it and opinions on things. For your case you don't need zone valves or mixing valve.

I do think you will be disappointed at the performance with your average electric water heater as others have said... My 130k btu heater heats my 1000 sq ft garage just fine but when the floor heat kicks in the temp in the heater drops a lot. Enough that I put in a system to turn it off when I want to take a nice hot shower. The tank recovers in a about a minute so that works well.

 

[yeldogt]

130k for a water heater is a lot .... what type of water heater? Also there is some loss with an exchanger.

Bradford White makes a water heater with a coil inside -- they provide the unit with an uprated burner. It's really designed for supplemental heat -- say for a kitchen or bath that you want some radiant. They are designed for constant circulation or almost constant -- this way the tank is not getting hit with very cold water. There is not enough BTU stored in a tank to heat a floor. I think it's 60k burner -- I have used them twice for kitchen and bath renovations w/ radiant floors.

Again -- it's all about the building load. You have to match the BTU's .... and a unit that can keep a slab warm may take days to get one up to temp if it's allowed to cool down -- or never.

Buying a simple book like ...pumping away. Going online and looking at the Viessmann application guide that will show piping layout for various systems. Understanding close couple primary/secondary -- it's not hard to figure out.

All the ones online that I look at are a mess --- many don't even have the circulator oriented correctly.

 

[purplezr2]

The point is that the actual question I asked was not answered even once, which was about a diagram for the setup. You know, the actual arrangement of expansion tank, pump, air eliminator valves, shut off valves, temperature and pressure gauges, etc. Because no mater what the energizer bunny I connect to it, that's what I'm trying to sort out.



For quick warming the place I have my 80k BTU induction propane heater which I expect can bring the entire building up to speed in under half an hour. After that the radiant heat can just pump enough heat to keep things from freezing. And do keep in mind that my idea of a warm garage space is most people's idea of outside winter weather; maintaining a building in the 40's doesn't take as many BTUs as trying to do 65f. Heck that's when we start opening windows here. I kid you not; every year when we get into the 70's my daughters want me to go out and but an AC...

Why not just rely on the propane heater and call it a day? Because baking the piping into the slab was cheap enough, you are not supposed to run a propane heater when you are not looking at it, and one day when I retire I may want to keep my garage warm all winter long. Heck when retirement happens I may want to put a real boiler there. For now the propane heater and second hand water heater will do just fine.

Check out menards website, they have nice pictures of the parts and pieces on a panel.

This is what I did, I haven't assembled the panel yet, but in the process.

 

[yeldogt]

Check out menards website, they have nice pictures of the parts and pieces on a panel.

This is what I did, I haven't assembled the panel yet, but in the process.

Each type of heat source uses a different setup ..... The OP is saying he has an "induction" ??

80k at 80% will heat a decent building ... But -- you can only transfer so much heat to a slab ... this transfer is based on the amount of pipe and the flow through the pipe.

If you want quick heat up you need more pipe and shorter lengths of pipe ... it's math.

Also -- the better condensing boilers need protection -- actually many boilers do except some of the electric.

Here is my new house -- very tight space for equipment. Boiler loop/ indirect loop/ system loop. Three pumps -- there is not much to it (the piping) and it's a 4 manifold 3 type radiant and 4000+sf. I used a low loss header as it's the way to do it with lots of radiant Pex ... but you can use simple close "T" on a small system for a garage. It's propane -- so at 4x natural gas running cost some upfront cost to get it right are well worth in in long term running cost