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  1. #1
    Join Date
    Jan 2006
    Posts
    32
    Does anybody have an idea how much the Tekmar 062 can modulate boiler temps down from the calculated boiler tempeature based on the heating curve with outdoor reset ? My continuous circ Air handler system runs beautifully on cloudy days and all nights with the current input parameters (115F boiler temp for a 70 deg room temp on a 14F design day). But on sunny days, even though the RTU is in the great room where we have alot of solar load (south facing house with a lot of low-E glass) it seems to not have the range to account for the solar gain and the house overheats.
    I've partially solved this by setting the WWSD to 45F and putting the outdoor sensor on the south facing wall of the house. But on a day like today (32F, cloudy) there is still some solar load and the house is creeping up past it's 70F setpoint. When I turn the RTU air sensor off (so now it's just outdoor reset working) the boiler target temperature goes up 5F, so the RTU is pulling that down 5F. Is that it's limit ?

    EDIT: The RTU is hooked up to a Tekmar 262. I do have a regular heat/cool thermostat for the cooling system that I could use to turn off the boiler demand on the 262. Seems inelegant given the amount of money that I've put into the system.

    [Edited by odcman on 02-16-2006 at 01:02 PM]

  2. #2
    Join Date
    Jul 2005
    Posts
    947
    You answered your own question... Find your ideal WWSD and kill the boiler when you don't need to run it, keep the AHU fan on to utilize the solar gain from the Great Room throughout the house.

  3. #3
    Join Date
    Jan 2006
    Posts
    32
    The AHU fan always runs. It's a 60 W ECM motor pushing 350 cfm. So it does circulate the warm air and I have 4 sq. ft. of returns in the great room and kitchen that have the south facing glass for exactly that purpose.

    I'm doing more or less what you said, but the problem is that on a sunny 23F day I need no heat from 9 am to 4 pm, but on a cloudy 23F day, I do need some heat. On the sunny 23F day, the south facing sensor may indicate 45F, but on a cloudy 23F day it does indicate 23F. However, extending your idea, there probably is also better place to put the RTU so it picks up the heat gain faster from the sun and cuts out the boiler. I'll try that too.

    thanks

    [Edited by odcman on 02-16-2006 at 05:46 PM]

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