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Bad thermostat or???

I have a Rheem Air handler that is connected to a Rheem A/C Heat pump. There is also a hydronic coil that is mounted in front of the air handler and piped to my boiler. I have a Braeburn 5220 thermostat controlling the system. It works fine for the cooling season but is giving me trouble when in heat mode. The air handler fan will just randomly start for no reason. There is no call for heat at the time. The only way to stop the fan is to turn off the thermostat and turn it back on. This is sometimes successful and other times not. Sometimes I have to pull thermostat off of mount and let it sit to get it to behave again. I spoke with Braeburn tech support and they thought I may have a shorted wire (maybe from mouse damage) that would make this occur. I disconnected the wires at thermostat and air handler and checked with VOHM meter all wires were open - no sorts indicated.
I was wondering if anyone has gone through similar circumstance? I suspect the thermostat is bad but don't want to get fooled into buying new thermostat for no reason.

Thanks for the help!
Andrew

Comments

  • Peter_26
    Peter_26 Member Posts: 127
    I just looked up the user manual and you need to verify that fan control mode is set to AUTO as described below. If it is set to CIRC then you will see the unwanted operation you described in your post. Hope that helps.

    Setting the FAN Control Mode
    The Fan Control has 4 modes of operation – AUTO, ON, CIRC and PROG. The mode can be selected by pressing
    the FAN button to scroll through the different modes.
    NOTE: Depending on how your thermostat was configured, some fan modes may not be available.
    AUTO The system fan will run only when your
    heating or cooling system is running.
    ON The system fan stays on.
    CIRC The system fan will run from time to time
    to help circulate air and provide more
    even temperatures when the heating or
    cooling system is not active.
    PROG The system fan will function in the
    AUTO or ON modes depending on your
    program schedule.
    MikeAmann
  • ajbeckerhead
    ajbeckerhead Member Posts: 5
    HI Peter Thanks for the reply. Yes, it is in the AUTO mode as you describe. It works fine in A/C mode but not in the heat mode. So far this year it has been behaving. It is damn nuisance though when it happens in the middle of the night and blows cold air all over you..brrrr
  • pedmec
    pedmec Member Posts: 711
    Make sure the aquastat is wired correctly on the coil and that your not getting ghost flow in the piping. could be turning on the fan because its getting hot water in the coil during the off cycle. bad flochek at boiler maybe
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,913
    edited October 2022
    If the air handler was not designed for a hydronic coil to provide heat, then the addition of the Hydronic coil was an add on. There is no "standard wiring" for doing that. It takes someone with electrical control design experience. Not every standard HVAC tech or electrician can handle this task. You may be experiencing a situation where there is a strap on aquastat controlling the fan. The conventional logic is when the coil has hot water in it, the fan should operate. When the coil cools off, (and there is no other call for heat or cooling from the heat pump) the fan will stop. This is pretty sound logic until the attic gets hot OR THERE IS GHOST FLOW FROM A HOT BOILER and the water in the coil become hot enough from attic ambient temperature to operate the fan. I have come across this design and this problem from time to time.

    The fix for this is to have both a relay and an aquastat in series to operate the fan. This way the fan will not just operate when the fan relay pulls in and blow cold air while the boiler goes thru the sequence of operation that might include thermostat call for heat to a Zone Valve to end switch to boiler pre-purge to trial for ignition to main burner to water temperature increase to minimum temperature for warm air top be delivered can take up to 4 or 5 minutes of blowing cold air before heat is delivered top the ductwork.

    did you follow that? If not read it 3 more times slowly

    An aquastat only design may cause the problem you are having. So check if you have both an aquastat and a fan relay in your aftermarket control design. I had fan coils in one of my homes and have tested different control strategies for these type systems.

    Mr.Ed


    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • ajbeckerhead
    ajbeckerhead Member Posts: 5
    HI Mr.Ed

    Thanks for the reply. I understood exactly. I KNOW there is no aqua-stat on the hydronic coil. I had asked about it when the fellow installed the A/C and he wasn't very helpful. I should not have used the installer I used but that is history now. I am glad you replied because I was going to seek information here about just that issue. I had spoken to Braeburn a while back and the techs had alluded to possibly a new feature on their thermostats being able to add a Fan delay as a setting. Unfortunately, it wasn't built in. I understand the need of a thermostat on the hydronic supply and was looking into it to add myself. I couldn't find any thermostatic controls that would close on rise of temp and works on low voltage.
    Are you aware of such an item? I would appreciate the help to purchase it. The other issue is if I wire that thermostat between the air handler and the thermostat (yellow wire - fan control) what happens in the A/C season. It would seem I would have to bypass the aqua-stat so the thermostat could send the signal to the air handler fan.

    The actual problem I posted with the fan coming on randomly has so far NOT occurred but once this year. I still think there is an issue with the thermostat but like I said in my post I don't want to throw money at it and not repair the problem. Can you enlighten me to what the control board does inside the air handler? I know there is a setup for adding electric heaters. Is it responsible for setting fan speed?

    Again, thanks for the reply. I do appreciate your comments and knowledge
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,913
    edited October 2022
    I couldn't find any thermostatic controls that would close on rise of temp and works on low voltage.

    This control can strap on to a pipe (i use the return) close to the fan coil. There is a set of NO contacts that will make on temperature rise. You can use it to make and break line voltage or low voltage.
    https://www.supplyhouse.com/Resideo-L6006C1018-High-or-Low-Limit-Circulator-Strap-On-Aquastat-65-200-DegreeF-range-5-30-DegreeF-Adj-Differential?_br_psugg_q=l6006c1018
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
    MikeAmann
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,913
    Can you enlighten me to what the control board does inside the air handler? I know there is a setup for adding electric heaters. Is it responsible for setting fan speed?

    Here is the wiring diagram from a typical Rheem air hander.
    When the control board in the Rheem air handler gets the thermostat signal that closes R to G, the fan will operate. that board may or may not have a short delay on, or, delay off, or, both. The fact of the matter is that the original installer selects the fan speed at the time of commissioning the system.

    In the Red circle the Black wire from the motor is Hi Speed, the Red wire is low speed and the Yellow wire is the 208V speed. The factory default is the black wire. No other speed is connected because the unused wires are placed on blank lug terminals on the board.

    Rheem has several air handlers including one that has a fan coil built in. Unless I know what air handler you have, I can only speculate what is inside it.
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • ajbeckerhead
    ajbeckerhead Member Posts: 5
    Thank you, Mr. Young. I am an idiot because I had seen controls similar but understood them only to be a high limit - in which that was no good to me. I guess I didn't read well enough. I also referred to the yellow wire in my previous writing by mistake. Anyway, this is a big help to me.
    From my previous question: My A/C is also used as a heat pump The thermostat is setup in 2 stage configuration. If I send the green wire from the thermostat to the hydronic control that would be an issue.

    I appreciate you helping me with this. It would be nice to be able to have you to speak with when needed I would be glad to compensate you for your time. I would like to have someone I can speak to when there are things I don't understand or when I have similar issues. I will also soon be embarking on putting in radiant floor heat so having an experienced voice would be very helpful Not sure if you would be interested but let me know if you are.

    thanks very much again for your help!
    Andrew Becker

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,913
    edited January 12
    @ajbeckerhead, I am looking at the Braeburn thermostat manual. and I believe you need to set it up in the Installer setup mode to something a little different that what you might think. On installed setup item 11 select [HE EMER]. and on item 13 select [HE AUX].

    Call me with quetions
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org