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Wiring to replace a Trol-A-Temp Mastertrol Mark V with Honeywell HZ322

Hi All,
I'm replacing my Trol-A-Temp Mastertrol Mark V with Honeywell HZ322. I have 3 questions.

1- Comp (Y) has 2 wires. Should I do the same in HZ322 and connect both wires to the Comp (Y)?

2- Nothing connected to RH. I do have heat, so I'm guessing it's connected somewhere else with RC. for my HZ322 connection. Should I keep it the same? Not to connect anything to RH on the board?

3- I do see 2 wires connected with a red cap (shown in the picture). Should I leave them the same when I connect it to HZ322?

Thank you all for you help!


  • tamertamer Member Posts: 9
    @ratio Any recommendations?
  • ratioratio Member Posts: 2,614
    Need more details. Follow the wires & tell me where they end up at.
  • tamertamer Member Posts: 9
    edited June 2019
    Thanjkd @ratio - I moved all the wires to the new board with the same layout and colors and worked. Heating and cooling are working .. the only issue I have now is that the blower doesn't stop even after I turned off the thermostat .. Is it possible the limit switch is bad? or because I didn't connect the DATS (C7735A1000) ? Please advise. thanks

  • ratioratio Member Posts: 2,614
    A stuck limit would keep the fan on, but if it wasn't stuck before you changed out the panel, I'd look for other causes first. The green wire going into the furnace is usually the fan call. Unhook it from the TrueZONE panel & see if the fan turns off. The zone thermostats can call for the fan independently from the TrueZONE panel, but I can't recall if the panel will light up the fan indicator for a thermostat, so maybe check them to see if the fan switch is in the on position.

    Also, in the picture you sent, the system is calling for heat, and zones 1 & 2 are open (wanting heat). Was that picture taken during the heating phase of your checkout?

    If you have the DAT, I'd install it, It allows the system to temporarily stop the heat or cool call if the ΔT gets excessive. Plus it's neat to watch it on the screen.

  • tamertamer Member Posts: 9
    edited June 2019
    Hi - I did notice the fan running before the new panel and only with heating. Fan light will be ON with AC, but with heat, the fan runs but no light on the board. Not sure if this is normal.
    Is the black thing in the middle is the limit switch? I don't see any model or number for it.
    How do I check if the switch stuck? Thanks
  • ratioratio Member Posts: 2,614
    In cooling, it's the responsibility of the thermostat to call for fan. In heating, most (all?) furnaces will turn on the fan automagically via a limit switch or timer. It should come on within 20-40 seconds of ignition, & go off 1-2 minutes after the burner shuts off.

    Your description of the panel sounds like it's doing the right thing, but if the fan never ever shuts off then something's not right. Are you sure you didn't just catch it shortly after the burner shut off, when the limit switch would still have the fan on?

    If it really does run continuously, start by unhooking the wire landed on the 'G' terminal in the furnace. If the blower stops (or doesn't start back up, you might have to put the door back on the furnace to get everything powered back up), start following the green wire back towards the zone panel. If the fan still runs, replace the limit. You should be able to get one with just the model & serial of the furnace.

  • HVACNUTHVACNUT Member Posts: 3,576
    Show the diagram of the furnace if it's there. Behind the blower door?
    Remove the green from G on the equipment side of the zone board. If the fan shuts off it's on the low volt side. If the fan stays on its likely the line volt side of the heating circuit is the culprit.
    The black box is the fan/limit control. The fan contacts could be stuck closed. You should have an electrical meter to check where the circuit to the blower motor is closed.
  • tamertamer Member Posts: 9
    Thank you so much, guys! Problem solved. I increased the limit switch from 100 to 110 and now the fan shuts off after a bit. I think because these days are hot days, so 110 made the fan to turn off. Thanks again

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