1F78 to nest

[rojulb]

hello... 

I have below wiring of my old thermostat.

I have 4 wires: Yellow, Green, Red, Blue coming out of the wall, No White wire coming out of the wall but there is a jumper wire between Yellow and White.

How do I wire Yellow, Green, Red, Blue to nest so I can have heat (Y). Thanks.

[HVAC]

What letter slots are your wires in!
Pic doesn’t show. Is there a switch on the back of the your thermostats indicates heat electric or / gas?

you’re colored wires need to be in the same slots on nest & equipment to verify proper 24 volt operation. Good luck 

[rojulb]

pls see my response below thanks

[EdmondB]

Hello rojulb,

Thanks for posting here in the Community. Just to confirm: Are you installing two separate Nest thermostats? There are two different photos of the wiring from the Nest thermostat: the one with the blue sticker on the wires (solid wires) and the one without the sticker (stranded wires).

Thanks for the help, @HVAC.

I look forward to your response.

Best,
Edmond

[rojulb]

Is there a switch on the back of the your thermostats indicates heat electric or / gas? yes... it indicates electric.

heat pump model: whalen V-A-400-1

more pics and diagrams. current setup: only A/C works, no heat since no white wire from wall to nest thermostat i believe.

[HVAC]

The jumper between Y & W is ok on your old stat is ok you probably need to do the same with nest. Also configure it for heat pump the issue is you supposed to have a separate wire for the the reversing valve to make the switch between heat & cooling  that wire goes to o/b on nest then you tell neat to use it it in O mode or in B mode. I have a feeling that’s what your blue wire does so it’s not supposed to go to C on nest problem is can’t really see your old stat letter slots wires are in the way. You still need a 5th common wire so nest has power all the time otherwise it might act up & you have to charge it once a while. I’d Recomend calling Hvac tech to have them replace that low voltage wire to a 5 wire set & have them connect all. Good luck.