WHite-Rogers LR27925 * Type 1F56-306 to Nest Gen 3


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Old 04-19-20, 04:49 PM
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WHite-Rogers LR27925 * Type 1F56-306 to Nest Gen 3

Thanks for choosing to read my post and help out.

The girl wants to replace the old White-Rogers that is pretty shot, with a new friend she and her friend Alexa can talk to
As a novice, I've done a few Nests for guys at work and such, but the wiring, and the labels on this old thermostat have me stumped. I have no idea where the furnace is, in order to investigate it.

1st pic shows wiring after massive dust and cover removal.
2nd is cleaned up to view wire labels. The G-V, Y-C and the RV below those 2 kind of confused me also.
3nd pic and 4th pic just show that the Nest device determines that it's wired correctly. But there is a mistake also. The wire to Y1 (heat/cool) on the Nest, is actually not a yellow that Nests assume, but a white wire.
So in this configuration that Nest thinks is good, the Nest begins in cooling mode. The fan kicks on, but it's not cooling, Unit is not near, so I can't hear a compressor kicking in. But it's not cooling anyway.
Switching A/C breaker on does not function, but the Heat breaker does turn the fan on.
By the way, the red wire on terminal RV, was just wrapped around the screw once, and the rest of the red wire was stripped and run over to the screw at 4-M.

I appreciate any help you guys can give. Lately, in this part of Texas, it's going from 32 degrees to 95. Sometimes in less than 12 hours. Thanks.

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Old 04-19-20, 04:59 PM
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Welcome to the forums.

It's very important to know what type of system you have. If you don't know..... you will need to find out. It sounds like it may be a heat pump system with no back up heat.

You need to be careful guessing as equipment can be damaged.

Your old stat shows 24v going to W in heat mode.
If that is a heat pump it would need to be a Rheem/Ruud system.
 
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Old 04-19-20, 05:20 PM
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Wow, pretty awesome getting a response that quick in this day and age. Thanks a whole lot Pete!

Gotcha. She just moved into the "new" place last night, so I'll snoop around and see what I can find out.
I'll let you know what I find out.
 
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Old 04-19-20, 05:34 PM
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If old thermostat is a 1F56-306 then is supposed to be conventional (non heat pump) thermostat. So white wire would go to W1 on Nest. Old is double labeled. G/F=Fan, Y/C=Cooling, W/H=Heating, R/V=Voltage.
 
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Old 04-19-20, 05:42 PM
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It shows as a standard stat but that jumper from R to 4M looks suspicious.
 
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Old 04-19-20, 06:33 PM
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Sorry, I just realized my jpegs were way too gigantic. I'll resize tomorrow.
Anyway, after moving the White to W1 and leaving the other 3, I have an E77 error, Missing a Y1 wire. But it's getting a bit too warm now, so I'll check some things with the office tomorrow and post whatever I find out. Thanks much fellas for trying to get us up and running with this thing. G'night
 
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Old 04-19-20, 06:59 PM
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4-M is Rh which explains the jumper. They have a cross reference chart: https://climate.emerson.com/document...en-4236322.pdf
 
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Old 04-19-20, 07:17 PM
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E77 is when Nest still thinks it is attached to a heat pump. So still detects a wire in O/B connector. Blue needs to go to Y1.
  • White - W1
  • Blue - Y1
  • Green - G
  • Red - Rc
 
ChronicLogic voted this post useful.
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Old 04-20-20, 11:09 AM
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After you change wiring.... you need to repower the nest.
Take the R wire out for one minute.
When power is restored and the stat is installed it should no longer detect as a heat pump.
 
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Old 04-20-20, 12:46 PM
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Well this morning I followed your advice and did the wiring swap, and the restart.
The device operates both heating/cooling just as expected now!
Well one small glitch I have to sort out.
While the unit operates climate features fine, none of the other features of the device are usable
as the internet connection and firmware updates and such are blocked by a "low battery" warning.
It's been hooked up and working for about 5 hours, so obviously the unit is not charging.
 
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Old 04-20-20, 12:54 PM
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This is what can happen with a power stealing thermostat.
It charges very slowly...... allow it time to charge.

If you had a spare wire you could connect C and eliminate the charge problem.
 
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Old 04-20-20, 04:10 PM
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Well fellas, the Nest is completely operational at this point. I am really grateful for you helping me sort out this frustrating issue. I mean I was only aggravated that I knew I didn't know how to proceed. I did know that there must be somebody knowledgeable and willing to help out, Thanks a billion for the help!
 
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Old 04-20-20, 04:25 PM
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Good job and you're welcome................
 
 

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