Basement Radiant Floor Heating cools water heater

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Old 01-10-13, 04:48 PM
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Basement Radiant Floor Heating cools water heater

Hi, I bought a house that already had radiant floor heating installed in the basement which is approximately 700-900 square feet. The system has 3 supply/return pipes off of a manifold setup leaving the water heater. The water heater (bradford white 75 US gallon capacity, 68,400 Btu/hr) is a dual design used for both the radiant floor heating in the basement and hot water needs for the rest of the house. In the winter time (I live in Western Canada) when the basement thermostat initiates the floor heating circulation pump the system runs forever never heating the floor to a point where the thermostat cuts the system out. Normally what happens is the water in the whole house becomes cool. For this reason I rarely have the thermostat set high enough to call for heat. When I do a test run and the water through out the house becomes cool I reduce the thermostat to turn off the call for heat -- after doing this the hot water heater eventually returns hot water to the rest of the house. During my first few tests the hot water heater pilot light would actually go out. Is this a result of the hot water heater running too long and shutting off to protect itself from overheating?

I was hoping this might be a common problem with a plan of attack to resolve it. I'm willing to get a plumber to inspect it but would like some input beforehand in case the plumber's recommendation doesn't line up and instead is more costly. I'd appreciate any insight you can provide.

I've attached some pictures of the water heater and floor heating installation for reference.

Thanks, Arden
 
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Old 01-10-13, 05:52 PM
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Wow... that is one pricey pump! ( about $450 ).

You have no way of knowing how far down in the slab the tubing is placed, or whether or not the underside of the slab is properly insulated... that might be part (all?) of the problem. If the tubing is at the bottom of a 4-6 inch slab with no insulation, you are only going to heat the earth... 'micro-global warming' !
 
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Old 01-10-13, 05:53 PM
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What temperature is the water heater set at?

Is there a 'tempering valve' on the hot water to the home?
 
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Old 01-10-13, 06:29 PM
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Thanks for your reply.

Given a previous owner installed the radiant floor heating I don't know if it's properly insulated or at what depth the lines are at. Are there ways to determine that without breaking concrete (tests that I can run that provide some indication)? The house is 12 years old and I know the 2nd owner (who I bought it from) installed the radiant floor heating starting from a concrete floor. Does that imply the tubing isn't at the bottom of a 4-6 inch slab? Also, I forgot to mention in the previous post that when I test the radiant floor heating system in the spring/summer time it does warm up the floor. Does that imply it's not insulated?

I'm not sure the temperature of the water. The water heater just has non-quantitative settings. I've attached a picture. I've tried setting it to hotter settings and it doesn't seem to change the outcome.

I don't believe there is a 'tempering valve' on the hot water to the home. The hot water line leaves the water heater with no other connections/devices.
 
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Old 01-10-13, 08:03 PM
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installed the radiant floor heating starting from a concrete floor. Does that imply the tubing isn't at the bottom of a 4-6 inch slab?
I think that could well be a good sign that it's not too deep. It may be embedded in a 'top coat' of gypcrete. Still might not be any insulation, but it's certainly better than having it at the bottom.

Does that imply it's not insulated?
I think it's a good bet that since the floor did not originally have radiant in it, that there is no insulation at the bottom of the slab. It IS possible that there could be some insulation under the gypcrete though.

I don't believe there is a 'tempering valve' on the hot water to the home.
Be careful then about turning the temp up, don't want to burn anyone!

I've got my thinking cap on...
 
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