Zoned Electric Forced Air Heating?

Discussion in 'Shop Talk' started by Ken Scharabok, Jan 10, 2007.

  1. Ken Scharabok

    Ken Scharabok In Remembrance

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    Is it possible for an electric forged air heater to work off of two separate thermostats with it responding to the higher setting of either of them?

    I have a single wide trailer with the thermostat in the living room. I would like the option to turn the rest of the trailer down at night and just heat the back bedroom. I figure I could do this with a second thermostat there and then putting a catalog on top of the floor grates in the rest of the trailer so air only comes out of the two floor grates in the back bedroom. In the morning I turn that one down, cover the two there, increase the one in the living room and take off the covers there.

    Feasible?
     
  2. tyusclan

    tyusclan Well-Known Member

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    The only way that I know of to make it work would be with a digital t-stat that has a zone sensor option. You could put the stat in the living room and the zone sensor in the bedroom. There is a switch in the t-stat that tells it to read either the stat or the sensor. You would have to flip the cover off when you wanted to switch from one to the other. You could switch it to read from the stat in the morning, and then switch it back and close off the registers at night. It would then read from the sensor in the bedroom.

    I don't know of any way to make it read from the higher of two stats.
     

  3. Ken Scharabok

    Ken Scharabok In Remembrance

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    What about if only one thermostat was turned on at a time? Rather than turning one up or down you turn it off. Seems that way unit on the furnace would only sense one thermostat. I doubt the living room would go much below 60 degrees at night.

    I have two bedrooms at one end and one large one at the other. The front one is closed off now with the grate covered. The other smaller one is my office. The large one I close off during the day anyway.
     
  4. Ross

    Ross Moderator Staff Member Supporter

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    Two thermostats turning them on and off and covering heat ducts may work. The bigger problem is if you have enough supply and return ducts in both ends of the trailer and you can isolate each end with a door. If you can't isolate the halves the furnace will draw from a cold end at least half the time meaning there will have to be a greater temperature rise to satisfy the one thermostat than the other so it will take more power to actually do the job half of the time. Now it might not add up to enough to matter. You'd also have to see what dampers were used to balance the duct work, one end may be set to get less heated air. Then there is the extra enery needed to brign the used half back up to a comfortable temp. Now with electric it might work, and shouldn't hurt to try, but oil or gas neeed the air flow to keep from going off limit and cracking the heat exchanger.
     
  5. Ken Scharabok

    Ken Scharabok In Remembrance

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    Hummm, there is about a 1 1/2" gap under the back bedroom door. Air being forced into that room should flow out under that gap. That returning area should help keep the living room/kitchen area warmed a bit. Only return air is at the furnish itself. Heat ducts run in a straight line to one side of the center of the trailer.

    Perhaps one way to experiment is to purchase a length of thermostat wire to make the current thermostat portable so to speak.

    I've long felt it wasn't properly located anyway being near the second floor grate which blows heated air up directly at it. To me it should have been placed further away to start with.
     
  6. idahodave

    idahodave Well-Known Member

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    You don't need to add a thermostat.....just turn it down and cover the air outlets.

    With a bit of trial and error you should find a combination of a setting and number of outlets covered to keep the back room warm and the rest of the trailer cool.
     
  7. Ken Scharabok

    Ken Scharabok In Remembrance

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    As I mentioned above, part of my problem may be one of the floor grates is almost directly under the thermostat. Causes the unit to cycle on and off. As an experiment this AM I put a catalog on that vent so the primary one was at the other end of the combo LR & kitchen. Furnace ran longer but seemed to heat the room more evenly. The air return at the furnace would have pulled it across both rooms. This evening I'll play with closing off both of the grates in that room and leave the back bedroom two open.
     
  8. Ross

    Ross Moderator Staff Member Supporter

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    Simplest of all is to just turn down the thermostat and plug in a portable heater in the room/s you want warmer.
     
  9. Ken Scharabok

    Ken Scharabok In Remembrance

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    Yes, but... I am reluctant to use a space heater while sleeping. I do use one in my office room, but turn it off if I leave the room for any length of time.
     
  10. ninny

    ninny Well-Known Member

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    Sure you can, run your t-stat wire to the room where you want the additional t-stat, put a toggle switch at the air handling unit to separate the t-stats so that only one will operate the air handler. I've done it a bunch of times on condominiums that are split level. T-stat upstairs and t-stat downstairs on a single unit. Just flip the toggle switch to the t-stat that you want to operate the unit, whether it be the up or down, in your case the back room or the other room. Need a four pole toggle switch. They're sold at most electrical supply places, and maybe Home Deport or Lowe's. Hardest part is running the t-stat wire to the second t-stat.
     
  11. Jack in VA

    Jack in VA Well-Known Member

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    They do make a wireless T-stat you can carry around with you.Also Lowes is clearing out their heaters. Got an oil filled radiator there yesterday for $13.
     
  12. Runners

    Runners A real Quack!

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    This is probably too expensive, but a zone controller using stats & relays. One relay per stat - hook up the stat to the relay coil, hook up one set of contacts to the furnace, other the set of contacts to automatic dampers to open the air ducts. The air ducts would "fail open" in a powerless condition (in other words, it takes power to "close" them.

    You'd probably want to build an adjustable time delay circuit to cycle the furnace to prevent overheating, short cycling, etc. I did one of these years ago for my brother, 4 zones, and while it seemed expensive to build, the heating cost savings quickly paid for it.

    To sort of automate things, a guy could just install a couple of automatic dampers, put a timer on them, so while one was open, the other closed, depending on what time of day you thought you'd be spending the most time in this or that zone... hook up the timer to different zone stats with the dampers.

    I'd be concerned about moving enough air over the heat exchanger, we wouldn't want to read about you in the newspaper... due to a overheated/cracked/burned out exchanger.
     
  13. Ken Scharabok

    Ken Scharabok In Remembrance

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    The situation has improved noticeably after I put a catalog on the floor grate immediately under the thermostat. System kept cycling and and off. Apparently the area around the themostat would heat up quickly and it would shut off. Then cold air from rest of the kitchen/LR combo would cool that area down, so unit would kick on again. With the air now being vented at the other end of that area of that room it heats up much more consistently. Somewhat the equivalent of moving the thermostat to the other end of that room.

    Found a floor grate in the middle of that room to one side I didn't realize/remember was there. No air comes out of it. Will try shinning a light on a mirror to see if there is a blockage. I've second owner of this trailer and sometimes people do hide things in ducting.
     
  14. Ross

    Ross Moderator Staff Member Supporter

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    Middle of the room? Should be a cold air return shouldn't it? I'm not up on mobile homes and they could be different in the USA.
     
  15. Ken Scharabok

    Ken Scharabok In Remembrance

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    No. My A/C and electric furnace are on the same thermostat, but function differently. The A/C has a large return vent in the floor. The furnace's return air is the top half of the furnace itself.

    The small floor grate at the side of the main room should exhaust air. I said nothing came out of it. With the furnace blowing a very small amount of air comes out of it - a wiff. Definitely not a return.

    Went looking around for a small mirror and realized I don't even have one.
     
  16. hunter63

    hunter63 Well-Known Member

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    If you really wanted to "Zone" the areas, it requires installing dampers in the duct work, along with nessary controls relays sensors etc. Big bucks!

    Sound like you have it under contol with your home made system.

    Mounting the T-Stat in the wrong place is very common, as well as putting a T.V. or other appliance in front of it, sunlight thru the window, etc.
     
  17. Ken Scharabok

    Ken Scharabok In Remembrance

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    All I've done is to even out the heating in the LR/K combo room. I would still like to be able to let the rest of the trailer get cold at night, while keeping the one bedroom at say 65 degrees and then reversing it during the day. The older I get the more I like to be warm.
     
  18. Windy in Kansas

    Windy in Kansas In Remembrance

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    It seems to me that wiring a second thermostat in parallel with the first should allow either thermostat to then trigger the furnace into action. After all a thermostat is really just a switch activated by temperature rather than manually.

    As an example think of it like this---Assume that we run two individual wires from one battery post to post A of both switches. From post B on each of the switches we run a wire to a lamp terminal. Of course the other lamp terminal wire goes back to the remaining post on the battery. Either switch will complete the circuit allowing the lamp to light.

    Go one step further with parallel wired thermostats and use ones with a digital set back mode. Thus one would automatically turn itself down at night while the other turned itself up. Vice versa in the morning.
     
  19. Ken Scharabok

    Ken Scharabok In Remembrance

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    Just closure on this:

    I ran it by a BIL who is in the H&A/C business. He said in theory it would work, but...

    Two thermostats should be the same brand purchased at the same time to be compatible.

    Real problem though would be in airflow restrictions. He said not to limit either discharge or return below 50% of normal capacity. There are eight floor registers and I would only be using two, and at the end of the line as well.

    Return isn't a particular problem but the bedroom door may have to be left open 2-3" for proper return air flow.

    Likely will buy a heater pad for the mattress and see how that works out. I don't like an electric blanket as I am a 'thrasher' when I sleep.
     
  20. fordy

    fordy Well-Known Member

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    If , I'm understanding your situation you want to run the central heat\air blower to heat one room . This would seem to be very inefficient to me . You can buy a passive , oil filled radiator type electric heater at wal-mart for 60 . It has 3 settings , 600 , 900 and 1500 watts and should be more than enough capacity to heat one room . This heater has NO fan nor does it pivot like alot of the other models do it should last several winters . I've been using one in my 5'ver and it works quite well . fordy... :)