H2o heater for radiant floors?

[shinnlinger]

Hello,

I have been building my house for a LLLOOOOOOONNNGG time due to limited funds and time.   I currently have a 75 gallon propane hot water heater I found on the side of the road hooked up to my radiant system which consists of pex coils in the slab and then stapled between my first floor floor joists with arma foil, which is like a cross between aluminum foil and tyvek.

This arrangement has worked relatively well for 2 years now. When I first hooked it up, I cranked it up and it sweated us right out of the joint. I now set the heater itself to a middle range and have the mixing valves on the floor systems turned to their coldest setting, which keeps the house in the mid 60's and fire up the wood stove when we are around to make it more comfortable.   Unitll yesterday, I didn't even have the first floor circulator turned on.

I am wondering though if it would be more efficient to set the water heater on its highest setting to keep the water itself warmer.  Are there any thoughts on this? Since it is colder now, cranking it up some would be appreciated.

I will probably get a direct vent unit at some point but this mickey mouse setup works pretty well for now.

[WmFritz]

I haven't had a tank heater for so long, I don't remember what the temp range is on them. I'm thinking high range is 140°?  Regardless it seems to me it would be more efficient at the lower temps then higher. Your best effeciantcy would be with a modulating on-demand heater, when you get to that stage.

Nothing wrong with junk yard technology though.

[Holmes]

  One of the classes I went to we were told "in theory every 3 degrees you lower the water temperature you get a potential 1% savings in fuel" Right  from Rich Tretheway himself.

[shinnlinger]

Would you recommend turning the heater down and the mixing valves up?   It is now too warm for the misses so I shut the 1st floor loop off

[beenthere]

What are the mixing valves "mixing" ?  Sounds like mixing cold water with hot, to lower the temp?

Not clear to me if this heater is for house heat, domestic hot water, or combination of both.

[Holmes]

 Mid range should be around 120*   This time of year  30 ish temps outside, you may only need 80* water to keep the house warm. I think mine is running at 28C, 82*f now.  My baseboard heat on constant circulation with modulating temperature control is running at 107* and the temp right now is 37* outside the house is 72* and very comfortable
If you need to get cooler temp in the radiant system it sounds like you need to turn the water heater down because you already have the mixing valves at there lowest temp setting.

[bandmiller2]

Radiant floor heat is very uncomfy if too hot, probably best to  turn down the water temp. My system uses an outdoor water tube boiler. The hottest water first goes to heat the domestic hot water, then to baseboard radiation then to radiant floor after it has dumped some heat and on its way back to the boiler. Frank C.

[Don_Papenburg]

I would set the water temp where you are comfy so you don't have to cool off the water that you just heated. 

[r.man]

Losses of heat inside the building aren't really losses but I would say that getting the tank to run as little as possible would be financially beneficial. I would turn the tank down to what I wanted to run through the loops and most people recommend just slightly over room temp I believe. With a dedicated source your mixing valves shouldn't have to mix.

[Ron Wenrich]

I have 2 different types of system in my house.  In the old part, there are the big radiators, and they run hot water.  In cold weather, that might be 180°, but normal is 140°.

In the new section, I put in radiant heat.  It was a German system, and it fit under wooden floor.  They use a temperature sensor that is mounted outside to alter the mixing temperature.  On the coldest of nights, that might bring the mixed water up to 130°, which is well under where the furnace is set.  During warm periods, it might be around 75-80°. 

[Just Me]

Not sure about a water heater but in my last house with infloor heat I did some research and with the SlantFin boiler I was using it was most efficient to leave the boiler at the recommended temp [145]and let the mixing valve take care of the temp in the floor tubing. Bills were extremely cheap so must have worked.

Because I could not afford it when I built the new house I put in forced air with a wood add on. The house is super insulated, but it is still not as "warm" as the house with infloor at the same temp. We miss it....

[Don_Papenburg]

My system is set up to lose about 20* from entering the loop to return . During colder weather  the  water heater will keep inbound water close to 100* . Above 5*F the water will be 110 inbound and above 20*F it will be 120* .  The thermostat keeps the room temps regulated well.  I don't have any tempering valves.