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trouble with radiant heat

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Joined: Mar 9 2013

We've been in our Eichler for close to a year now, and with winter coming, we'd really like to get a handle on the radiant heat. It definitely works, but we can't seem to figure out how to adjust it so that it's warm in the mornings and cooler the rest of the day. The heat seems to kick in around noon, just as the sun is heating up the house. We have one thermostat but two places where the pipes are visible (master bed closet and linen/hall closet) - does that mean we can control areas separately?

We'd also like to get a recommendation for a new thermostat (ours looks original, or at least quite old). We tried the Nest but it's not compatible with our voltage.

Any tips, recommendations, guidance, etc would be most appreciated!

Thanks in advance

Joined: Jun 28 2003


My advice is to get a programmable thermostat.  Mine heats up at say 6 am and reduces (or you can shut it off) at 8 am; then comes on 5 am and cuts off at 10 pm; and weekends are different.  

 There are overrides and holds (so if you are gone a for long period, you can hold the thermostat at a set degree ).  

I have a Lux and I love it.


Joined: Nov 18 2012

The in floor radiant is very very slow to change temperature. The concrete slab is a very big mass that wants to stay the same temperature and can take 4 or 5 hours to warm up the house. We found that setting a schedule was making things worse insead of better. We had to turn the heat up at 4am to have the temperaure where we wanted it at 8am and then the house would get very hot because the heater is off but the floor stays hot for a while. Over heating the floor every morning meant that gas usage was often higher than just leaving the temperature constant. I am sure someone more creative than me has figured out a schedule to make this behave somewhat better.

For the thermostat there are line voltage programable models from LUX, Honeywell and others. Thermostats intended for hydronic heat should (might?) have fewer control issues with the slow response of the heating system.

The pipes in the closets are send and return lines for the heater. Some banks will have adjustement valves where you can balance the heat between rooms. In our house the bank in the master bedroom closet and the bank in the heater closet have valves. The only trick is figuring out which valves control which zones. After over a year in our house, ours are still a mystery.

Joined: Apr 19 2007

all of the above are good insights... a few other bits:

• your temp swings should really be no more than 6-8 degrees -- say, 66-72 -- because of the thermal mass mentioned above. you'll find that /keeping/ the slab slightly warm will be far easier (and less taxing ont he system) than /getting/ it warm.

• the zones are controlled (in theory) by the valves mentioned above, however, most folks today suggest leaving them all wide open ( grove in the adjuster point up and down: 12 and 6 oclock) and dealing with it (as the risk of getting a clog in a partially closed valve is high and very unwanted).

• we have this thermo and it's performed wonderfully for 7 (?) years: this is a really simple system: on/off. the more complex the thermo the more complications you'll have -- you discovered this with the nest.

• when you program it, create a simple chart with an X/Y axis: time of day on the bottom // temp up the side. mark points of ideal temps (again within a 6-8 degree range) every two hours. probably 66 during the day; 72 when you're watching TV in the den at night; 70 as you're sleeping and 74 for a short burst right when you wake up so as to not be cold when showering/dressing... now, take that chart and move everything back two hours... i.e.: if you want the heat to transition from 66 to 72 at 8PM, then program the thermo to make that shift two hours earlier.

• one of the reasons the house is heating up at noon is likely due to assive solar and less with the radiant, but knowing the above, you can program for this.

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