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Honeywell T-stat mystery

Right, that stat doesn't have adaptive intelligent recovery. It's normal for a stat without adaptive intelligent recovery to overshoot setpoint. One of the features of AIR is that it can stop right at setpoint.

Comments

  • D107
    D107 Member Posts: 1,777
    'System ON' indicator goes off before temp satisfied

    For main floor, I have a Honeywell magicstat/32 CT3200 programmable, --2-wire I think--at least 10 years old, probably more. I noticed that on returning from 2-degree nighttime setback in the morning, the 'on' indicator will show upon burner/boiler startup, then go off for a little while before target temp --even though as far as I can tell the circ is still running and even sometimes when boiler is still firing--though it could have been firing for the other zone as well which is run by a White Rogers 1F90-51/60 digital Comfort-Set II T-stat.

    The relays for each of the three zones are Honeywell R845A1030(4). Basement zone wasn't on at this time. This is on a 1982 gas-fired Weil Mclain Model CGM-7P1 Series 7.

    --Aquastat Hi Limit: White-Rodgers 11B81-3; Operating Temperature Control, SPST, Auto Recycle, 140-240F Range: 10F
    Subtractive Differential, w/ 3/4" N.P.T.

    I would be concerned if somehow something was mis-wired so that only one zone came on at a time --during return from setback when at least 2 zones should be running since thte boiler is way oversized and I'd be wasting alot of fuel. Both zones do seem to maintain the right target temp so perhaps the digital 'on' indicator is malfunctioning? (I do notice that the room temp on the magicstat goes from 63 to 65 very quickly at one point--I leave the room and come back 10 seconds later and it's reached target temp......)

    Question: Is 'system on' indicator supposed to show when burner is firing with circ pumping or circ is pumping--but no burner fire if water is still warm enough?

    Thanks,

    David
  • Empire_2
    Empire_2 Member Posts: 2,343
    Hi Dave....

    Generally, depending on how it's wired the system on indicator is nothing more than a call for heat which in this case will cycle the pump until any calling stat is satisfied. The burners are controlled by the Aqua stat and comes on and off whenever water temps need to be raised. I'm not sure about the t-stat you are using, but some setbacks have a smart recovery option which can take place up to 2 HRS and cycle the equipment to raise temp a little before start of occupied program.

    Mike T.
  • D107
    D107 Member Posts: 1,777
    thanks mike

    Well your comment on 'call for heat' indicator verifies what I would have thought a T-stat would do. So as long as the room temp is below target temp, it should stay on, which it doesn't seem to do. What I may not have made clear is: day temp starts at 6am and has to make up a 2-degree difference, from 63 to 65.

    'System on' Indicator goes off when it's still at 63. However while I'm fairly sure this t-stat has no intelligent recovery, perhaps the anticipator setting gauges that target temp will soon be reached, which it usually does, but not until after at least one more 'system on' appears. As I mentioned, room temp indicator seems to jump very quickly from 63 to 65. I do notice that generally that on many cycles, target temp is often surpassed by two degrees.

    Thanks,

    David
  • D107
    D107 Member Posts: 1,777
    Anticipator?

    Thanks Carol; I did wonder if you agreed that absent intelligent recovery on this unit, it could be that the anticipator for some reason is turning system off before target temp is reached, with the T-stat turning it on again when temp remains unsatisfied for a certain time.

    Also which of Honeywell’s residential t-stats have AIR?

    Thanks,

    David
  • carol_3
    carol_3 Member Posts: 397


    Ahhh, an electronic stat, which this is, right?, doesn't have an anticipator. That's because the purpose of an old-fashioned anticipator is to set cycle rate. Electronic stats have a cycle rate adjustment instead. If you don't have the instructions anymore to check the cycle rate that it's set at, you could go to the website http://customer.honeywell.com (no www). Once there, scroll to the very bottom right corner and enter the stat number in the little white box. That brings up all the lit about that stat. Look in the installation instructions. If it turns out that the cycle rate is set for 3, that could cause some overshooting. Standard cycle rate is 6 cycles per hour (can come on every 10 minutes during normal operation, but doesn't if there's no call for heat), even for hydronic unless you have cast iron radiators or steam.
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