Hydronic floor heat DIY

[Blacksheep10]

We put insulation and pex under my dad's wood shop a couple years ago. We've yet to do anything with it, but it is time. It is only 20x20 and most of the kits you look at are made for much larger areas. I'm hoping someone has some experience in this area and can give a simple run down of exactly what parts I need. Every page I find on searching is trying to talk you into doing hydronic/radiant, or trying to get you to buy their stuff. I'm sure there are vids/sites I'm missing, but I glazed over after a couple hours of searching.
Total system volume in the slab, 5-6 gallon. Only 400 ft^2. Just a shop, detached from house. No drinking water and doens't have to be 70 at all times. Decently well insulated, no windows. Very little heat really needed. It is 2 loops of pex, single zone. I can make a manifold etc. The pump seems easy, grundfos 3 speed. Pre or post heater?
More wondering if anyone has experience on where to place the sensor to turn it on and off (floor not ambient?)
What type of heater/boiler. We have about 60 amps or less available. We also have natural gas available and the unit will be on an exterior wall, so venting is easy.
Outlets for component parts that are more reasonable than others?
This is my first dive into this stuff and I don't want to fawk it up.
Also, how the hell do I subscribe to a thread? It was easy at the old place. Perhaps I'm auto sub'd if I start it.

 

[Dethmachinefab]

You need a mixing valve or injection pump set up to get the water in the slab to be around 90. So primary boiler loop with pump, close spaced tees come off that to feed your mixing circuit and pump that sends the warm water into the slab. Do an image search for radiant heat primary secondary loops.

 

[tsm1mt]

Heat Loss Calculator is a start - you need to figure out your "degree heating days" - here in Montana, I used 10,000.

Then fill in the rest, and you'll find out roughly how much of a boiler you need and go from there.

I'm close to hooking mine up - I put R-10 under the slab and a bunch of 1/2" Pex in the floor, R-10 down to 2' on the perimeter, and I'm hoping they foam the walls this week so I can move on to wiring and plumbing the boiler.

I'm going electric - I put 24kw of solar on the roof to offset.

The temperature probe was supposed to go in the floor - you stick an extra chunk of Pex into the slab and you slide the probe down into it.

For something that size, I think you can get by with an electric boiler on 60A service - I was doing the calcs for my mom's woodshed ( I have some left over Pex and insulation) and I found some boilers that would work at a 40A draw.

 

[Blacksheep10]

Total heat loss 8,000 BTU/hr. Small system. The mixing valve ones I've seen are using an instant hot water heater, the boiler ones weren't using a mixing valve.
I was looking at single zone closed system with expansion tank and air skimmer, no mixing valve.
http://www.radiantcompany.com/prices/prices/

 

[cj3a]

Do you have a local plumbing store? Most will do the design for free if you buy the parts from them. My friend did this for me. About 1200 sf under a tile floor. Nothing fancy but works well.

 

[Java230]

If its single zone its REALLY easy. Boiler, pump and a relay to turn shit on and off if the boiler doesn't have pump control.

Make sure you have expansion tank. Pump is generally after boiler. Cj3a posted a pretty typical small set up, heat loop and floor loops. Make sure you have isolation valves at the pump (most of the modern flanges have them built in) also valves after the floor loop return so you can purge the air out of the drain fitting.

EDIT: I have used these in the past for small systems, 1-9KW units. Circulator pump switch incl

http://www.electromn.com/gen/emb.htm

Super basic dwg in here http://www.electromn.com/pdf/BL308.pdf

 

[Blacksheep10]

If its single zone its REALLY easy. Boiler, pump and a relay to turn shit on and off if the boiler doesn't have pump control.

Make sure you have expansion tank. Pump is generally after boiler. Cj3a posted a pretty typical small set up, heat loop and floor loops. Make sure you have isolation valves at the pump (most of the modern flanges have them built in) also valves after the floor loop return so you can purge the air out of the drain fitting.

EDIT: I have used these in the past for small systems, 1-9KW units. Circulator pump switch incl

http://www.electromn.com/gen/emb.htm

Super basic dwg in here http://www.electromn.com/pdf/BL308.pdf

I like that little boiler. Looks like 90-160 temp range, is this too hot, and if so, is this the mixing loop that Deth is talking about? Adjustable so that you can set it at the lowest and let it ride while you pump? The basic drawing doesn't have a mix loop, just a manifold post pump to push through the loops and a manifold to take it back to boiler.

I didn't put a piece of pex in the floor for a temp sensor, can I drill and epoxy one in? Or grout if that conducts better.

 

[kf4zht]

I've been researching into these for a few weeks. Looking at doing a tankless WH setup, probably 4 zone for a 1800sqft house. Its ga so it doesnt get stupid cold, but enough to where a heat pump alone won't work.

The biggest thing I dont completely understand is the controls. Do you have one controller that turns the whole system on and off, or one with a bunch of temp probes? None of the systems seem to use solenoids per loop to need seperate controls per zone.

 

[Java230]

I've been researching into these for a few weeks. Looking at doing a tankless WH setup, probably 4 zone for a 1800sqft house. Its ga so it doesnt get stupid cold, but enough to where a heat pump alone won't work.

The biggest thing I dont completely understand is the controls. Do you have one controller that turns the whole system on and off, or one with a bunch of temp probes? None of the systems seem to use solenoids per loop to need seperate controls per zone.

Get a zoned system with solenoids for the loops. Its impossible to balance the system otherwise.... I like the SBK manifolds. NY thermal makes a great combi boiler. Its DHW and boiler in one unit.

 

[Java230]

I've been researching into these for a few weeks. Looking at doing a tankless WH setup, probably 4 zone for a 1800sqft house. Its ga so it doesnt get stupid cold, but enough to where a heat pump alone won't work.

The biggest thing I dont completely understand is the controls. Do you have one controller that turns the whole system on and off, or one with a bunch of temp probes? None of the systems seem to use solenoids per loop to need seperate controls per zone.

No the boiler will kick on when heat is called for. Run it hot, no need to mix if your not heating DHW with it.

 

[Blacksheep10]

No the boiler will kick on when heat is called for. Run it hot, no need to mix if your not heating DHW with it.

Assuming that was for me, just worried about dumping too hot of water into the loop, thinking I read there was an upper limit the concrete would take.

 

[Java230]

Assuming that was for me, just worried about dumping too hot of water into the loop, thinking I read there was an upper limit the concrete would take.

Pex is rated for ~180 usually. Concrete wont care. Its a rock....

 

[kf4zht]

Get a zoned system with solenoids for the loops. Its impossible to balance the system otherwise.... I like the SBK manifolds. NY thermal makes a great combi boiler. Its DHW and boiler in one unit.

So boiler vs tankless WH. What really is the difference? I'd be running natural gas and ideally vent through PVC (which I have with current TWH).

 

[Java230]

So boiler vs tankless WH. What really is the difference? I'd be running natural gas and ideally vent through PVC (which I have with current TWH).

the combi Boiler does not use the domestic water in heating. It has a separate heat exchanger for the heat circuit. IMO the DHW heaters are not really happy running heat systems, far more demand than normal hot water.

EDIT: they vent thru PVC. some require a little section of sch 80. The boilers are just beefier versions of HWT's basically. But often include the heat loop inside them with a pump.

 

[Blacksheep10]

If its single zone its REALLY easy. Boiler, pump and a relay to turn shit on and off if the boiler doesn't have pump control.

Buying the Electro like you linked. Has relay internal.

Make sure you have expansion tank. Pump is generally after boiler. Cj3a posted a pretty typical small set up, heat loop and floor loops.

Looking at Taco air scoop and air eliminator on top, expansion on bottom.
"Heat loop and floor loop" Most I'm seeing go from the pump into a manifold straight to the floor, then back into a return manifold and into the boiler. Are we saying the same thing?

Make sure you have isolation valves at the pump (most of the modern flanges have them built in) also valves after the floor loop return so you can purge the air out of the drain fitting.

In the drawing linked below, there is a valve between the air elim/expansion tank and pump, Here is another panel you can buy, pic only for plumbing example. It appears to have a valve or 2 right before the pump and some bleed valves?
https://www.northerntool.com/shop/t...Vuf_jBx046w5gEAQYBCABEgKpsvD_BwE&gclsrc=aw.ds

I get the return manifold > drain/bleed valve > isolation valve > tee> up to boiler, over to fill (I think)

EDIT: I have used these in the past for small systems, 1-9KW units. Circulator pump switch incl

http://www.electromn.com/gen/emb.htm

Super basic dwg in here http://www.electromn.com/pdf/BL308.pdf

Boiler sizing, I'm showing 8K btu loss on most calculators. Figured it a couple different ways. The in stock electro is 8500 btu, and 120v. The 3-4 week out 240v 15k btu electro is the one recommended by the company that quoted a full system. We are getting that 8k btu figure from the coldest day calculation, in KS it isn't single digits very often. Almost never. Price is essentially the same, am I better to be right at the line, or get one that is just under double the minimum and let it run less? 2 units considered:

https://www.houseneeds.com/heating/...electro-electric-mini-boiler-hydronic-emb-s-5

https://www.houseneeds.com/heating/...electro-electric-mini-boiler-hydronic-emb-s-2

Thanks for all the help. I'll hopefully have a pic of the manifold we build tonight by tomorrow.

 

[Blacksheep10]

Do you have a local plumbing store? Most will do the design for free if you buy the parts from them. My friend did this for me. About 1200 sf under a tile floor. Nothing fancy but works well.

In the pic, what's below the pump? Mixing/bypass valve of some sort? Assuming lines going down and away to the left go to a heat source.
To the right of the pump, above the return loop bleed valve, pressure relief valve? psi? is there one above the pump as well? same?

 

[Java230]

Don't know how you fancy quoted that shit so here goes.




Originally posted by Java230 View Post
If its single zone its REALLY easy. Boiler, pump and a relay to turn shit on and off if the boiler doesn't have pump control.

Buying the Electro like you linked. Has relay internal.

Make sure you have expansion tank. Pump is generally after boiler. Cj3a posted a pretty typical small set up, heat loop and floor loops.

Looking at Taco air scoop and air eliminator on top, expansion on bottom.
"Heat loop and floor loop" Most I'm seeing go from the pump into a manifold straight to the floor, then back into a return manifold and into the boiler. Are we saying the same thing?
With that boiler you shouldn't need a heat loop. The Taco mount for the expansion tanks are slick and make it easy. IIRC that boiler comes with a air emittance valve for the top of it.... If not you will want one there also. Mount it in a T with the T&P valve.

Make sure you have isolation valves at the pump (most of the modern flanges have them built in) also valves after the floor loop return so you can purge the air out of the drain fitting.

In the drawing linked below, there is a valve between the air elim/expansion tank and pump, Here is another panel you can buy, pic only for plumbing example. It appears to have a valve or 2 right before the pump and some bleed valves?
https://www.northerntool.com/shop/to...E&gclsrc=aw.ds

I get the return manifold > drain/bleed valve > isolation valve > tee> up to boiler, over to fill (I think)
The ones on the nothern tool setup are for their bleed/drain. I am talking for pump replacement in the future, There are flanges for the pumps that have ball valves in them. Way easier to close those, swap pump and belled a little air, vs drain the damn system down.

EDIT: I have used these in the past for small systems, 1-9KW units. Circulator pump switch incl

http://www.electromn.com/gen/emb.htm

Super basic dwg in here http://www.electromn.com/pdf/BL308.pdf
Boiler sizing, I'm showing 8K btu loss on most calculators. Figured it a couple different ways. The in stock electro is 8500 btu, and 120v. The 3-4 week out 240v 15k btu electro is the one recommended by the company that quoted a full system. We are getting that 8k btu figure from the coldest day calculation, in KS it isn't single digits very often. Almost never. Price is essentially the same, am I better to be right at the line, or get one that is just under double the minimum and let it run less? 2 units considered:

https://www.houseneeds.com/heating/h...dronic-emb-s-5

https://www.houseneeds.com/heating/h...dronic-emb-s-2

Thanks for all the help. I'll hopefully have a pic of the manifold we build tonight by tomorrow.

Bigger is better IMO unless you don't care if its marginal on the real cold days, unless 240v is harder to get out of your shop panel.

 

[Blacksheep10]

With that boiler you shouldn't need a heat loop. The Taco mount for the expansion tanks are slick and make it easy. IIRC that boiler comes with a air emittance valve for the top of it.... If not you will want one there also. Mount it in a T with the T&P valve.

Pardon my ignorance, still not sure what a heat loop is, like I said, most pics I see have the heated water going straight from the boiler to the floor after the expansion/air skimmer.

T&P valve?

Bigger is better IMO unless you don't care if its marginal on the real cold days, unless 240v is harder to get out of your shop panel.

Totally get what you mean for pump replacement. Got it. I was thinking functionality thing.

Buying the bigger boiler now. We have the amps. I have another question not answered in the boiler literature. It shows 18.7 amps, is that max draw, or is that what it draws while on, period. Meaning, If you're only asking a boiler capable of 150* to make 90* water, is it just triggering the pump to move more water, or is it drawing less amps and heating at a slower rate of consumption. I guess, is the heating element an on/off switch, or is it variable draw.

 

[Java230]

Totally get what you mean for pump replacement. Got it. I was thinking functionality thing.

Buying the bigger boiler now. We have the amps. I have another question not answered in the boiler literature. It shows 18.7 amps, is that max draw, or is that what it draws while on, period. Meaning, If you're only asking a boiler capable of 150* to make 90* water, is it just triggering the pump to move more water, or is it drawing less amps and heating at a slower rate of consumption. I guess, is the heating element an on/off switch, or is it variable draw.

I believe its just on/off. It keeps boiler temp at desired temp when heat is called for.

EDIT: looked at the manual, its single stage. just on/Off

 

[cj3a]

In the pic, what's below the pump? Mixing/bypass valve of some sort? Assuming lines going down and away to the left go to a heat source.
To the right of the pump, above the return loop bleed valve, pressure relief valve? psi? is there one above the pump as well? same?

Yes it is a mixing valve. The house has hot water baseboard which is design to run at 180f. Radiant heat runs around 80-90f

 

[Muckin_Slusher]

Boilers and tankless heaters? Really? For a 20x20 slab?

Why can't you simply install an old fashioned tank water heater (ng power vent or non-power vent), a circulating pump connected to a wall thermostat?

Stupid simply and bulletproof. You'll also need a tank that is open to atmosphere that you'll have to keep full (either automagically or manually). If manually, put a float in it to kick off the system if the water gets too low.

 

[Blacksheep10]

Yes it is a mixing valve. The house has hot water baseboard which is design to run at 180f. Radiant heat runs around 80-90f

Ok, so stuff I don't need.

I pose the same question again though, To the right of the pump, above the return loop bleed valve, Looks like an air eliminator, as well as above the pump. Just planning on one above the expansion tank on mine right after the pump.

30 psi pretty standard for a pressure relief?

 

[Java230]

Ok, so stuff I don't need.

I pose the same question again though, To the right of the pump, above the return loop bleed valve, Looks like an air eliminator, as well as above the pump. Just planning on one above the expansion tank on mine right after the pump.

30 psi pretty standard for a pressure relief?

You will want one at the top of the boiler as well. Just an air emittance valve is fine there, dont need the bubble trap.

30 psi is plenty. The system shouldn't have much in it at all. Max system pressure is usually 18 IIRC

 

[cj3a]

Yes the system has two air vents