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honeywell t991a temp controller

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[Deleted User]
[Deleted User] Posts: 0
in Thermostats and Controls
Potentiometer. Red is common. R&B for more. R&W for less.

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  • michael siena
    michael siena Member Posts: 53
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    honeywell t991a temp controler

    any info on this controller? in need of schematic help!!!!!!!
  • carol_3
    carol_3 Member Posts: 397
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    Try this website, but IMPORTANTLY, when you get there, immediately scroll down to the very bottom righthand corner. http://customer.honeywell.com. At the very bottom right corner is a little white box. In it enter t991, and click on the arrow to the right of the box. That brings up all the tech lit about the T991. Click on the various pdf's along the left to open up the documents.
  • Empire_2
    Empire_2 Member Posts: 2,343
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    Good call Carol

    I use the HW site all the time. The control asked about, is missing about 4 or 5 numbers. There are a wide variety of controls using this #.....

    Mike T.
  • michael siena
    michael siena Member Posts: 53
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    i am asigned to a jail and we use bulb stats with belemo valves to control reheat coils. It was a "quick" fix because they were having problems with the PLC. Dont ask me i am here 4 mo.s any way i have a packaged unit being used as a makup unit and the controls were riped out and these bulb stats were put in.

    i dont have line voltage at belemo valve. could a seperate transformer be used to power the valve and the stats in the unit on roof be a)powered by a transformer on roof or B)by same transformer as belemo vavles? thanks
  • carol_3
    carol_3 Member Posts: 397
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    Make sure you don't exceed the VA rating of the transformer. For example, if it's 40VA, trying to take more than that will burn out the transformer. The mysterious part is how many VA is your load. Take the amp rating (A) of the load (valve) and multiply by 24V. V x A gives you the VA. The T991 is a switch, so you don't have to worry about a VA rating for it.
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