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Honeywell Prestige dehumidification

ChrisJ
ChrisJ Member Posts: 11,966
Hi all,

I'm not saying I'm going to do it,but I recall seeing an option to make the newer Prestige thermostat run both the heat and air conditioning to dehumidify.

Is this true and if so, how?

If I wanted, could it fire up my boiler and A/c together? Or could it run an electric heater in the ahu if I had one?

I'm just exploring options, don't actually have a problem. I guess I'm bored again. Wish I had room I for a hot gas reheat setup.
Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

Comments

  • hvacfreak2
    hvacfreak2 Member Posts: 500
    I'm not familiar with that thermostat but I have done this using a new blue screen 8000 , it was in advanced settings and it had the selectable reheat options as " hot gas " or "heating equipment ". This was on a Carrier rooftop unit that had hot gas reheat ( 24 hr fitness center ) , the space was over cooling but it was pouring rain outside so I selected the heating option and it worked great as a temporary measure until I could get up and fix the hgrh.

    I would imagine that using electric heat would work , as in a residential ahu. But I'll bet it could get expensive real quick depending on the setpoint / load. You could do a hot water coil from your boiler but that's not free either. Both of these options violate current energy standards though ( no new energy to be used for dehumidification reheat ) . If your ahu is an ecm type it should have a dehumid feature of some sort ( slows the fan and allows overcooling to some percentage ).
    hvacfreak

    Mechanical Enthusiast

    Burnham MST 396 , 60 oz gauge , Tigerloop , Firomatic Check Valve , Mcdonnell Miller 67 lwco , Danfoss RA2k TRV's

    Easyio FG20 Controller

    ChrisJ
  • ChrisJ
    ChrisJ Member Posts: 11,966
    edited May 2018
    > @hvacfreak2 said:
    > I'm not familiar with that thermostat but I have done this using a new blue screen 8000 , it was in advanced settings and it had the selectable reheat options as " hot gas " or "heating equipment ". This was on a Carrier rooftop unit that had hot gas reheat ( 24 hr fitness center ) , the space was over cooling but it was pouring rain outside so I selected the heating option and it worked great as a temporary measure until I could get up and fix the hgrh.
    >
    > I would imagine that using electric heat would work , as in a residential ahu. But I'll bet it could get expensive real quick depending on the setpoint / load. You could do a hot water coil from your boiler but that's not free either. Both of these options violate current energy standards though ( no new energy to be used for dehumidification reheat ) . If your ahu is an ecm type it should have a dehumid feature of some sort ( slows the fan and allows overcooling to some percentage ).

    Yep it's ecm and slows the fan down to something like 325 cfm per ton in low stage. Oddly enough I've rarely seen it needed as its set to 50%. I'm running the normal 400 per ton otherwise.

    Like I said I'm bored and looking for things to do. ;)

    I wonder if the reason my prestige doesn't show it is because I've got it in residential mode instead of commercial.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 10,218
    Any heat source can be used. Basically on a call for dehumidification you bring on the cooling and run it full tilt. Then the space will usually overcool. The "reheat" or heat source is brought on to raise the space temp to load the space so the cooling can't overcool (when their isn't enough internal heat gain)When the air temp is too cold the dew point of the air drops, the lower it goes the less humidity the ac can take out. So the heat raises the dew point. The more TD between the cooling coil and the air passing through it the more humidity is removed.

    My understanding is in general not supposed to heat or cool the same airstream. Humidity control (cooling &reheat) shouldn't be used at the same time UNLESS it is a lab, or temperature controlled room for a mfg process etc. You can hold a room temp to within 1 degree if you run cooling and heat and let them "fight" each other.
    Cost $$$$ to run and an energy pig
    ChrisJ
  • ratio
    ratio Member Posts: 2,918
    IIRC it's "reheat dehumidification", then you tell it to use either the universal contacts or W1. If the heating coil is after the cooling coil & the boiler is hot, there's no reason not to do it other than the cost of running the boiler & condenser at the same time.
    ChrisJ
  • ChrisJ
    ChrisJ Member Posts: 11,966
    ratio said:

    IIRC it's "reheat dehumidification", then you tell it to use either the universal contacts or W1. If the heating coil is after the cooling coil & the boiler is hot, there's no reason not to do it other than the cost of running the boiler & condenser at the same time.

    Am I right in assuming I need to put the Prestige into commercial mode to make that available?

    Mine is currently in residential.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • ratio
    ratio Member Posts: 2,918
    Possibly. Write down all your settings before you change it though, I think it resets everything to defaults when you change modes. I have to look every time I need to set it to reheat dehum—whatever menu it's under isn't too intuitive if you don't already know what it does. :disappointed: