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Discussion Starter · #1 ·
Sorry if this is redundant to previous posts. I tried to replace a true mechanical AC / Electric Heat thermostat (no common wire) with a Honeywell Round with electronics power stealing thermostat.

The AC compressor and fan would operate in Auto; the fan would operate in Manual (fan on); but the Heat and Fan would not work in Auto. If I manually turned the "fan on" first, the Heat would then work, but only if the "fan on" was operating first. Jumpering the 24vac to fan and heat simultaneously worked as did going back to the true mechanical thermostat.

Thought I'd try a battery operated RiteTemp 6022 thinking the battery function would help. Nope. Tried running a common 24vac wire to the Ritetemp 6022. Nope. Went back to the old mechanical thermo.

Investigated the control relays and found the W heat circuit had a N/O fan relay contact in series. So no current path unless the Fan Relay pulls in first. Checked the fan relay and found it has a timer off circuit which draws almost no current from the G wire.

The 24v transformer is 20va. Just found a thread that suggested a 1k resistor from W to common. Have not tried that yet.

Question: Does a programmable thermostat like the Ritetemp 6022 still power steal for W operation even when powered by batteries and 24vac common or is something else preventing the electronic thermostats from working. (See attached for wiring basics on this system).

thanks
 

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Power robbing stats need an isolating relay to work on certain heating systems. Yours is one of them.
 

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Does it work, if you put the old mechanical back on.
 

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Discussion Starter · #4 ·
Does it work, if you put the old mechanical back on.
yes it does work with the old mechanical thermostat. May need to add an isolating relay as HVACLover suggests.

However, still wondering:
Does an electronic thermostat like the Ritetemp 6022 still power steal for W operation even when powered by batteries and 24vac common or is something else preventing the electronic thermostats from working. (See attached for wiring basics on this system).
 

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Don't know. Its not a thermostat I would ever use.

I use Honeywell. Their battery operated don't steal power.
 
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