speaking of thermostats and obsolescence

Grallert

I've never been good at low voltage and thermostats. Thought in obsolescence and I'm stumped. I'm trying to replace an old busted up chronotherm T8085A heating only thermostat. It's operating a Honeywell M644A zone actuator. I'd like to install a modern thermostat maybe a wifi connected TT? Any suggestions? The space it's in is an old gymnasium now used as a meeting space/ performance space. There is an AHU in the ceiling and steam perimeter radiators. The AHU is controlled by a different system I operate at my desk top. So the wall TT will only control the perimeter steam.

ratio

It might be a better idea to integrate the AHU and the radiators together so they can't fight each other, esp. if one of them has internet access (which is often seen as license to fiddle).

That said, this shows that as having standard thermostat wire names (W, R, etc.), so it should be a straight swap, although if a common is lacking you may have to add one.

@Leonard, check out page 4 of the attached PDF, it shows how to set the anticipator.

unclejohn

Do you have any info on the amp. draw of the actuator motor.

ratio

This gives it as 0.7A on page 1.

Also, keep in mind that this is a starting point, it should be adjusted if the system isn't performing adequately.

Solid_Fuel_Man

There are no wifi thermostats that can operate w/o a common wire. If you have 3 conductors you golden, or if you can fish/pipe one to a new location for your wifi thermostat. That may be easy to do.

I would also suggest integrating the AHU and radiation into one control. If you can adjust the AHU with your laptop, it most likely is controlled by some type of BMS (building management system) which would most likely have a spare output to run a radiation valve.

EBEBRATT-Ed

A series 60 honeywell actuator is two position drive open drive closed. This link may help
http://machineryequipmentonline.com/electric-equipment/electric-control-fundamentalsseries-60-two-position-control-circuits/

Grallert

EBEBRATT-Ed said:

A series 60 honeywell actuator is two position drive open drive closed. This link may help
http://machineryequipmentonline.com/electric-equipment/electric-control-fundamentalsseries-60-two-position-control-circuits/

thanks guys. Still struggling at this. Called honeywell and they were very willing but not so helpful unfortunately. I did find the manuals for the actuator but I guess I just don't get the how the thermostat wiring board is connected to the actuator

The actuator has a 24v power source to TT. There is another transformer that powered the clock on the old cronotherm
The green and yellow wires come from a separate transformer to the clock. Any help would be great. This is one of the areas that stumps me.

HVACNUT

Use the diagram in the manual for Series 20 wiring.
The Red wire to R with slider joining Rc.
The White wire to Y.
The Blue wire to W.

The 24v (Green and Yellow) from the secondary transformer cannot be used.

For WiFi you will need a Common (C) to power the thermostat. You can take it from the transformer that's powering T1,T2 on the actuator. I assume T2 is Common but double check.

Solid_Fuel_Man

Exactly what he said. ____/\____

Grallert

Ok just now did this wiring. still a blank screen. As if there is no power to the stat. I have 24 across R and W wire.

Steamhead

Whichever terminal you connected the Common wire to (T1 or T2) try moving it to the other one. Verify which is the correct terminal by checking for voltage between R and T1, and R and T2. You want the combination that gives you 24V.

Grallert

Thanks a bunch fellas. The issue was the wrong location of the improper wire if that makes any sense. I've been forced out of that space for the time being so the students can do exams. So on to the next thing. Thanks again.

HVACNUT

> @Grallert said:
> Thanks a bunch fellas. The issue was the wrong location of the improper wire if that makes any sense.

Nope. I think that's a double negative. When you have time, explain please.

Grallert

it was then that I put the proper wire in the improper location. With one choice left, I put the proper wire in the proper location.