Little help with heat plumbing

[nate379]

I am working on my garage heat system. I'm adding a small Modine water to air heater to help with recovery rates in the garage (slab heat).

What I am going to do is T off the zone valve that supplies hot water to the slab.
Also T into the return side.

The Modine heater will have it's own T Stat which will be set lower than the floor heat T Stat. So only if the floor can't keep up will that heater come on.

Do I need to put a check valve on my T so I don't screw up the flow??

 

[Jackfre]

You might want to consider putting it on its own zone valve. As it is now whenever the radiant zone calls the Modine is going to get flow, right? Depending upon the pump location (which you don't show), piping lay-out, you may see more of that zones flow going to the Modine than to the floor. If you try to balance that flow you may not have enough flow to supply the Modine. Do you have this boiler working off an outdoor reset control? Your radiant supply temp may not be enough to make the Modine produce much, so you may want to get the supply ahead of the temp valve or whatever you are using for floor temp control.

 

[nate379]

I have 2 pumps, both are near the boiler, one on the supply and one on the return. I was going to take photos but there is a ton of piping and I think it would confuse anyone unless they could take a look in person.

On the temps that is something I was thinking about as well. My output for the floor heat is around 135*. The heater BTU is listed with water at 160*, so it would reduce the output.

I could probably go before the mixing valve to get full temp water, my water heater is plumbed that way. Would need to put in a zone valve... on that, can I run 2 zone valves off the same circuit?
So when the main garage T Stat calls for heat it would open the floor zone valve and the Modine zone valve?

Thanks for the info, you got me thinking of a better way to do this.

 

[Jackfre]

Two off the same circuit. What are your design flow rates for both the slab and the UH? If it is 3/4" supply, probably, yes. 1/2" i'm going to guess no. Do you have flow indicators on your manifold? Your AH shoulf be rated at flow and delta T. 135 may still do the job, just not as fast. What model Modine is it?

 

[nate379]

I'm not sure what most those abbreviations mean. The heater is modine hc24s01.

The pipes that run for my heat are 1.25" until the zone valves and those are 3/4"

Flow is wide open they are rehau manifolds and they only read to 2 g and it maxes that out.

 

[Jackfre]

Sorry, I meant "air handler" just to shorten and confuse I guess. With 3/4" supply you should be able to carry both.

 

[nate379]

Gotcha.

I think what I'm gonna do is copy the setup the water heater uses and it taps into the primary loop of the boiler (160* ish) water. This is before the mixing valve. Being the heater is so small and it will only run in conjunction with the floor heat I don't think it will be an issue.

I'll just put a zone valve and tie it on the same controller section the other zone valve is on (this is assuming the controller can handle 2 valves on an output?).

I may need a check valve, will figure that out later on.

The house is primarily heated with wood, so the case where the boiler would be running all full power heating every zone at the same time isn't too often. The little heater would just be in use if the slab heat in the garage can't keep up.