take a look please at my in-floor heat

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R

rombi

Member
Dec 17, 2007
112
Green Bay Wi
I will start with one question. I have an Aquatherm wood inhaler that does a good job heating my house with a forced air hx. no problem there.
when I turn on the in-floor heat the temp just drops like a rock. from 175 you can watch it run down to 100. With about 5 hours of burning and running the floor straight it might struggle back up to 150 if I am lucky. even when the slab is warm and the pump kicks in by thermostat the return temp is 110 going in temp to the slab is 125. from what I have read that sounds right. I have had the slab running for a week and a half now so it should be stable and the 1000 feet that it is heating is warm and comfortable but I burned about a months worth of wood.
it is insulated under and on sides with 2" pink board. this is the mixing valve, supply on left getting mixed and down to floor and back up to return water which mixes with the return from the house. is this correct?
 

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You have 1000 feet of PEX on one zone?
 
I don't want to sound dumb, but I think it is all one zone. This is in my dog kennel and all 1000 feet is going into about 800 square feet where the dogs are. I have one thermostat that controls the shut off valve and pump.
 
That in-floor piping is connected in such a way that it doesn't restrict the flow thru the entire system, correct?
turn down the in-floor temps to 100 degrees, that'll help the system move less heat into the floor, but run longer (better all around)
when you say the temps drop, generally that's because the stove can't output enough heat to keep the loop up to temp.
some return protection may be in order on your stove loop.
 
when I turn down the temp to the floor to say 100 the return pipe feels really cold. I would think that the return to boiler should be warmer with less heat going into floor but when I turn the floor supply to around 130 to 140 the return to boiler pipe is hot. kind of backwards to my thinking I guess.
 
A radiant slab usually is operated all the time at a set point temperature. That is usually 80-110F. If you are running 175F water into it, this is not good for the wood boiler or the concrete slab.
As Karl said, set your mixing valve to 100F to start.
Whoever installed a radiant system that is 1000 feet long in a single loop made a grave design mistake.
Loops should be 2-300' long.
As long as you can pump it, and it is only for a kennel, it can work. Not as good as a residential system but not too bad. Don't tell the dogs I said that.
 
there is two loops going in and coming out, and I think they were 300 feet each which means I have 600 feet in 800 square feet.
 
I do not run 175 to the floor the mixing valve turns it down to 125 or so. I think that the boiler just cant keep up with the return temps from the floor
 
OK. It sounded like it was different. I would still turn down the floor lower and keep more constant circulation going. The system is a bit undersized, tubing wise. A rule of thumb is a lineal foot of tubing per square foot of floor. Where you are is not real bad for a kennel. If you are turning it on and off in these months, allowing things to cool down, the warm up time will be significant, as you are finding. I would still be at 100-110. Not hotter.
 
Another rule of thumb is that if you want the space to be 70F, the floor surface should be 80F which means the water going to the floor has to be hotter
(usually that 100-110F, this time of year).
 
I am thinking of going with a different way to heat the in-floor water for the kennel besides wood. Propane verses electric I guess are my options.
 
Time-of-Use Savings Rates
$0.05705 per kWh During electric Off-Peak hours
$0.18056 per kWh During electric On-Peak hours
would it make sense to do this with an electric boiler and run it during off peak hours?
 
If you have room for hot water storage all the better for your kennel as the floor if properly designed with perimeter
insulation, moisture barrier and insulation under pex, plastic pex anchor sheets and thermal sand mix concrete all the better.

The other thing is the concrete needs to be vibrated,please do not forget that. AND do not let anyone tell you you do not need to
have a vibrator for the pour!!!!!!

Saying that though, hot water radiators-not baseboards with storage may be much more cost effective and comfortable as long as the
foundation and slab are properly insulated with the proper foam board and moisture barrier.

A dogs feet are very sensitive to heat and if the sheath covering of the paw is torn...............
 
If the off peak rate is 5 cents including delivery, that is equivalent to oil at about $1.66 a gallon. (assuming 85% oil delivery efficiency.
You can store some energy in the slab to bridge over the peak periods. How much temperature the dogs can tolerate is something I am not sure about,
but if the slab is insulated and the space over the slab is insulated, then you might be able to make it work without storage.

OF course, if you need storage, I think I know where you might look....
 
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I think the dogs will be fine. I left pretty wide spacing where they lay down. Our weekends are the busiest and those are always off peak.
anyone know how much an electric boiler would cost? I have an installer
 
There is a Time-of-Use electric savings option to meet your needs and hours of operation. Choose one of the three convenient savings schedules listed below and you'll pay the Time-of-Use Off-Peak rate during those hours.
Option 1 Option 2 Option 3
Summer:
(May-Sept.) 7 p.m. - 9 a.m. 8 p.m. - 10 a.m. 8 p.m. - 9 a.m.
Winter:
(Oct.-April) Noon to 4 p.m.
& 9 p.m. to 8 a.m. Noon to 4 p.m.
& 10 p.m. to 9 a.m. 8 p.m. - 9 a.m.
Remember, Saturdays, Sundays and major holidays are around-the-clock savings days.
Holidays include New Year's Eve, New Year's Day, Good Friday, Memorial Day (Day Observed), Fourth of July, Labor Day, Thanksgiving Day, Friday following Thanksgiving, Christmas Eve, Christmas Day.
If the holiday falls on Sunday, then Monday becomes a savings day. If the holiday falls on Saturday, then there will be no alternate savings day.
 
I have successfully done off peak using just a 4" concrete slab as storage. I did it all manually controlled, 2 years ago when I wouldn't pay $4 for propane. I used an old hot water heater, hooked thru my american solartechnics solar storage tank as the interface with the in-floor. I would turn it on at 8PM, and let it run all night into my 1000 sf floor. turn it off at 8 AM, and coast all day. I've done similar things with other applications.
 
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