Radiant heat question

Hi guys, this is my first winter in my home. I purchased an AHS 260 to heat my house and garage instead of using propane. I have radiant heating in all but 1 room and the rest is radiant including the cellar and garage. I'm having a heck of a time heating the garage. The house and cellar are great but the garage just don't seem to work for crap. I have a 1" pex pipe feeding the garage. Once in the garage it hits a small manifold and goes into the concrete in 4 (1/2") pex pipes. I know I have a bad mixing valve in the cellar and have been regulating the temp with a shutoff valve. I know I shouldn't but I've been pumping 180* water out and the return temp won't go above 80*. It's been running non stop for 2 weeks and the temp won't even register on the thermostat. Last week I had pipes freeze in my apartment above the garage and I really could use any help or suggestions to try. Any help would be greatly appreciated.

ok so the 4 1/2" pipes going into the concrete. whats the concrete thickness/insulation /depth of stone?

whats the surface temp of the garage floor? how big?

What circulator is driving the garage radiant zone?

Im not sure how thick the concrete is. im guessing 4-6" the garage is approx 26x40'. Ive never measured it but its an oversized 3 car garage. I looked at the size of the pump but didn't see any hp rating so I took a pic.
Im sure I will probably have to install a new pipe next year but if there is something i can do to get me through the winter that would be ideal. thanks

You must have no insulation under the slab, and the substrate is wet and drawing the heat out of the slab. That is a huge amount of heat entering the slab, for you to no have a warm slab.

Do you have any idea of the construction of the slab and it's insulation?

If you can't raise the slab temperature, you will be better off hooking the hot water to a MODINE water to air heater and heating the air in the garage to prevent freezing the pipes in the apartment above.

That pump is roughly equivalent to a Taco 007.

Greg L

My opinion is the same... the size of it is just to much and or the underslab layout/insulation not efficient.

sounds like a good idea to "divert" into a modine (radiator type) unit for the apt. protection

So you have put a new pump on? There is a set of flanges that appear to be Taco's and you have a new Grundfoss pump. There are pump problems? Is the pump installed pumping in the right direction. Is the pump actually pumping full flow? Maybe the pump is plugged? That just happened to me. The pump would pump just enough to make the pipe temp hot. If there was enough flow, the return pipe would be almost as hot as the supply. Given the condition of the piping, I wouldn't be suprised that some of the lines were filled with air bubbles. Were the lines bleed properly after the new pipe and new pump were installed?. Go thru the system and eliminate all possible problems.

The fact that the water goes out at 180*, and comes back at 80*, means it is circulating, and shedding it's heat into the slab..

Greg L

LsFarm wrote:The fact that the water goes out at 180*, and comes back at 80*, means it is circulating, and shedding it's heat into the slab.

Maybe, maybe not. I have seen two places where tubing got plugged, or crushed, or something, and the flow was severely restricted. (one place lives with a cool zone, the other put in baseboard) I'd first visually verify flow. Disconnect the pipes, get a garden hose hooked up so you can put water in and have it come out into a five gallon bucket. Is it possible to get to that manifold & check each tube independently? If it takes more than a few minutes to fill the bucket you may have permanent flow issues. Modine time. If the flow is OK, then you probably have not enough pump not enough tubing, and , or, not enough insulation. Then we are back to adding a Modine or baseboard.

<edit> Whoa! Hold the horses! I just noticed..... Is that mixing valve in the picture the one that controls this floor? I have used that exact valve and it does not have good flow for a large zone. That in itself may be your entire problem. Also, you say the mixing valve is bad.... it's OK to use ball valves to control the temp, but if so, you should remove the guts from the mixing valve and valve the cold leg. I'll go look & come back with a better mixing valve.

<edit> Here's a mixing valve. A Hoffman 21H. About $300....but cheaper than a Modine if it is the cure.

LsFarm wrote:The fact that the water goes out at 180*, and comes back at 80*, means it is circulating, and shedding it's heat into the slab..

Greg L

I will agree with Freddy, Return temp of 80 does not mean it's circulating. when a heater core in a car plugs up upper line will be hot and return line will be cool, but no heat going to the core.


On a side note maybe the heat is going into the ground instead of the slab?



Eric

Is the slab insulated under and around it? Is the garage insulated?
Maybe the pump can't flow the correct amount for the amount of tubing you have. Its loosing too much heat in the slab since it's could be circulating too slow. Also, slabs to take a long while to heat up.

a perfect time for a infrared thermometer. shoot the floor where the 180 goes in and then "scan" around to see where the heat is going. confirm flow is a must also. they make a electronic flow detector, used in auto a/c repair, that clamps over the pipes and "listens" for flow. like a mini sonar gimick. its cool but if the ability permits the bucket method gives you a visiual.....


the fACT the pump was changed, the discoloration of all joints, makes me wonder what the pumps impeller looks like...

Where is the other manifold?...
Are the 4 lines to the manifold in the picture with the low temp thermo the return?
More pics and a diagram of the system would help...
as would a wider shot of the pump and pipe system that you already took...

According to one of the books I just finished reading, you may be able to 'mop' the floor and see where the pipes are. If you have a break/leak, that will show up as a circle, I think (I'll re-post tonite after finding that particular passage in the book).

In case you don't have a IR gun.

BTW, check around the perimeter of the garage, if you have flowers blooming, you probably don't have an insulated slab.

kstills wrote:
BTW, check around the perimeter of the garage, if you have flowers blooming, you probably don't have an insulated slab.

oh that's harsh even for me

Can you INCREASE the flow rate so the liquid has far less time to give up its heat energy to the slab as it flows?