How to make sense of the choices? Thread split off.

[beenthere]

PS: The CPU line to R, is so the CPU knows the limit, roll out, etc is open.

[RoBoTeq]

PS: The CPU line to R, is so the CPU knows the limit, roll out, etc is open.

So, if this particular furnace shuts down on limit, power is shut off to the thermostat? I'm sure glad I don't have to put up with that furnace.

And, what keeps the blower and IDB running after the limit opens?

[Mr Bill]

Any Pro here that knows anything about controls, could wire in one of these n/o relays and you would never loose power to the stat, I could have it wired in probably in less than 10 minutes. Or better yet, just wire your "red" to the secondary side of the fuse, if the limit/limits open it still kills power to the CPU.

[beenthere]

So, if this particular furnace shuts down on limit, power is shut off to the thermostat? I'm sure glad I don't have to put up with that furnace.

And, what keeps the blower and IDB running after the limit opens?

The CPU is still powered. It controls the relays and keeps the blower running.

[54regcab]

Any Pro here that knows anything about controls, could wire in one of these n/o relays and you would never loose power to the stat, I could have it wired in probably in less than 10 minutes. Or better yet, just wire your "red" to the secondary side of the fuse, if the limit/limits open it still kills power to the CPU.

I think get using the relay to keep the thermostat power while still allowing the limit to do it's job, tell me if my crude diagram is correct. I don't quite understand the 2nd part of your quote that is in bold.

[beenthere]

Shouldn't post wiring diagrams in the open forums. DIYers could attempt to use them.

[54regcab]

Shouldn't post wiring diagrams in the open forums. DIYers could attempt to use them.

Sorry about that, I don't have access to the closed forums...
How much allowed about wiring diagrams in the open forums?

[beenthere]

About zero.

If someone posts a diagram that is in an install manual that should be left with the customer, thats ok. Posting it after making drawings on it for wiring is not.

[Joehvac25]

Can't you go pro 54?

[54regcab]

Can't you go pro 54?

I was pro, but my account was "revised". In our current project we don't repair or install furnaces or AC units, we just install thermostats and run service calls when they don't operate properly. Started with the project because $14/hr was more than most shops pay starting out. It's relatively easy work for the money. Just got $1 raise, I'm up to $15/hr now. Full health insurance, 10 PTO days per year, and matching 401k included.

[54regcab]

About zero.

If someone posts a diagram that is in an install manual that should be left with the customer, thats ok. Posting it after making drawings on it for wiring is not.

Gotcha, no modified wiring diagrams in open forms...

[Joehvac25]

I was pro, but my account was "revised". In our current project we don't repair or install furnaces or AC units, we just install thermostats and run service calls when they don't operate properly. Started with the project because $14/hr was more than most shops pay starting out. It's relatively easy work for the money. Just got $1 raise, I'm up to $15/hr now. Full health insurance, 10 PTO days per year, and matching 401k included.

Looks like the mans trying to keep you down lol

[RoBoTeq]

The CPU is still powered. It controls the relays and keeps the blower running.

So why would it not also keep the t-stat powered through the R terminal, indicated by the wiring to the R terminal from the CPU?

Do you know for a fact that this model furnace kills the power to the thermostat when the limit switch is open? I'd like to see the circuitry on the back of that board for myself.