Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > HVAC

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 05-17-2010, 10:49 PM   #1
rjp
Newbie
 
Join Date: May 2010
Location: Texas
Posts: 2
Share |
Default

Electronic Thermostat Won't Work, Mechanical Does


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
Attached Thumbnails
Electronic Thermostat Won't Work, Mechanical Does-wiring2.jpg  

rjp is offline   Reply With Quote
Old 05-18-2010, 02:53 AM   #2
Member
 
hvaclover's Avatar
 
Join Date: Oct 2008
Location: Suburbs of Detroit Mi
Posts: 3,704
Default

Electronic Thermostat Won't Work, Mechanical Does


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

__________________
Just slow, not stupid.
hvaclover is offline   Reply With Quote
Old 05-18-2010, 06:02 AM   #3
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 24,506
Default

Electronic Thermostat Won't Work, Mechanical Does


Does it work, if you put the old mechanical back on.
beenthere is offline   Reply With Quote
Old 05-18-2010, 11:07 AM   #4
rjp
Newbie
 
Join Date: May 2010
Location: Texas
Posts: 2
Default

Electronic Thermostat Won't Work, Mechanical Does


Quote:
Originally Posted by beenthere View Post
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).
rjp is offline   Reply With Quote
Old 05-18-2010, 12:42 PM   #5
An old Tradesmen
 
Join Date: Oct 2008
Location: PA
Posts: 24,506
Default

Electronic Thermostat Won't Work, Mechanical Does


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

I use Honeywell. Their battery operated don't steal power.
beenthere is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Carrier Edge Thermostat Installation Issue ptalar HVAC 1 07-13-2010 05:40 PM
Odd Thermostat "Fan On" issue TJ_in_IL HVAC 9 03-30-2010 09:05 PM
handling unsafe work by an electrician wuxingming57 Electrical 1 11-14-2009 07:07 PM
noma electronic thermostat model thm303m rickevin29 HVAC 7 10-22-2006 10:29 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.