For those of you running boilers tied into a central HVAC system via a water to air exchange what's the minimum temp for the water in order for it to feel warm? I'm sure you can get heat out of water that's 120 degrees but does it actually feel like heat?
Minimum water temps to feel warm?
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On my system it depends a lot on what the outside temp is running. If its 40 degrees out running my storage down to 120 will heat the house. If it is 0 out 120 is too low. This time of the year I try to keep my storage more around 160 and up keeps the run time down on the furnace with the heat exchanger in it.
A facility in northern MN that heats a 56,000 sq ft facility with a Garn WHS3200 and WoodGun E500 and has full dining services and sleeping rooms for more than 100 generally targets minimum boiler supply water temp of 130F for its fan coil water/air hx heaters. 120F water is the low borderline, and maximum supply water is about 160F. As I post this outdoor temps are -17F, windchill is -35F, wind is NNW at 8mph. Forecast High today is -2F.
Supply temps on the low side result in much heavier and expensive electricity use by the system circulators and fan coil units due to long and possibly near continuous run times.
Supply temps on the low side result in much heavier and expensive electricity use by the system circulators and fan coil units due to long and possibly near continuous run times.
That’s significantly colder than my design day, we might see one of those every 2 years. Typically we get 6300 +\- dd per year, my design day is 0degf at 143 deg water temp, if it’s windy I’ll bump the curve up a little. I have good solar gain that helps.
Generally temps. between 150-165F are best for forced air applications, this will heat the house up quickly but you should have a thermostatically controlled pump in place so you don't over-heat.
140 is about as low as I can run and be satisfied with the results. That is what I generally do at the edges of winter. One sure burns a lot less wood than at 170. it is in the 30s and 40s here now and with my water temps between 150 and 160 I am getting hvac blower run times similar to if I was using the gas furnace.
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