New Lennox XC14 + SLP280UHV with Nest

[sedeuce]

Hello HVAC-Talk Community!

I have been reading/learning for the past month - great information here and the knowledge provided by professionals is incredible - thank you!!

New install completed Friday:
- 2 stage variable speed gas furnace (indoor)
- 1 stage a/c condenser (outdoor)

I have been using the Nest with my previous 20+ year old furnace. I have the following wires connected at the Nest:
Y1, W1, G, Rh

This has been working well for me with my previous furnace (single stage only).

Now that I have a new 2 stage variable speed furnace (which I understand the Nest will support 2 stage furnace but does not have direct control over fan speed), did my installer technician cut a corner by only wiring W1 and connecting a jumper to W2?

When heat kicks on I am pretty certain it is only using Heat Stage 2 (I can read the Lennox LED panel and it shows the H2 value and I have never seen it show an H1 value unless the W1/W2 jumper gets removed).

Thanks in advance for your help!
Scott

[RoBoTeq]

This is not a DIY forum, but you would be better off not trying to use that NEST stat with your current system.

[mark beiser]

It could be wired for thermostat control of both stages of heat.

If you want to keep your Nest, you really should have them pull a new wire so that both stages of heat can be connected, as well as the common.
Power robbing type thermostats can sometimes cause odd behavior in equipment with variable speed blowers.

I'd recommend replacing the Nest with a Honeywell Prestige IAQ, or Ecobee Smart thermostat.
You would not need to have a new thermostat wire pulled, both are better comfort controls than the Nest, and are much higher quality.
IMO, unless your house is some kind of modern or Industrial decor, they look better than the Nest too.

[qwerty hvac]

I see he did not use the blue wire. There is your issue. But I would use a different stat to get the most out of your system.


The future isn't what it use to be.

[54regcab]

It could be wired for thermostat control of both stages of heat.

If you want to keep your Nest, you really should have them pull a new wire so that both stages of heat can be connected, as well as the common.
Power robbing type thermostats can sometimes cause odd behavior in equipment with variable speed blowers.

I'd recommend replacing the Nest with a Honeywell Prestige IAQ, or Ecobee Smart thermostat.
You would not need to have a new thermostat wire pulled, both are better comfort controls than the Nest, and are much higher quality.
IMO, unless your house is some kind of modern or Industrial decor, they look better than the Nest too.

+1

[pacnw]

also, I am fairly secure in saying that jumper from Y1 to Y2 is unnecessary.

NEST has been well marketed but real world operations are less than stellar. As has been stated, other thermostats are better at PROPERLY controlling HVAC equipment.

[54regcab]

also, I am fairly secure in saying that jumper from Y1 to Y2 is unnecessary.

NEST has been well marketed but real world operations are less than stellar. As has been stated, other thermostats are better at PROPERLY controlling HVAC equipment.

Nest says in their install instructions specifically NOT to jumper the outputs.

[sedeuce]

also, I am fairly secure in saying that jumper from Y1 to Y2 is unnecessary.

NEST has been well marketed but real world operations are less than stellar. As has been stated, other thermostats are better at PROPERLY controlling HVAC equipment.

Hi pacnw - The HVAC technician wired a jumper from W1 to W2 on the furnace controller. (as per pic).

As a result the furnace runs at stage2 all the time. It has been identified in this thread that this wiring setup will be a problem for running the furnace at stage1.

As you can see from the Nest tstat pic, there are no jumpers on the Nest wiring:


Thank you all for your suggestions on thermostats. We're going to run with the Nest for now and research some better alternatives.

Thanks,
Scott

[sedeuce]

The HVAC tech came back to remove the W1-W2 jumper from the furnace control board and used the existing blue common wire as the W2 line. Connected the same at the tstat and 2 stage heating is confirmed now.

The question then becomes: what do I lose by not having common? I am not using any additional humidifier or aux heat equipment. I am pretty sure the common was NOT wired on the furnace with my previous configuration. I definitely did not use common at the Nest previously.

thanks!
Scott

[martyinlincoln]

Hi pacnw - The HVAC technician wired a jumper from W1 to W2 on the furnace controller. (as per pic).
<img src="http://hvac-talk.com/vbb/attachment.php?attachmentid=456971"/>
As a result the furnace runs at stage2 all the time. It has been identified in this thread that this wiring setup will be a problem for running the furnace at stage1.



Thanks,
Scott

That depends if he set the control board up a single stage thermostat or a two stage. If it set to operate on a single stage thermostat then the control board in the furnace will bring on first stage then bump up after a time.

[sedeuce]

That depends if he set the control board up a single stage thermostat or a two stage. If it set to operate on a single stage thermostat then the control board in the furnace will bring on first stage then bump up after a time.

The installer left the dip switch as default (off), which on the Lennox controller board means that it is configured for 2 stage tstat.

[martyinlincoln]

Call him back then and ask why they're not using that blue wire for w2.

[54regcab]

Keep in mind Nest "stages up" but doesn't stage down. Not sure it's any better than just using the timer built into the furnace.

[pacnw]

Hi pacnw - The HVAC technician wired a jumper from W1 to W2 on the furnace controller. (as per pic).

As a result the furnace runs at stage2 all the time. It has been identified in this thread that this wiring setup will be a problem for running the furnace at stage1.

As you can see from the Nest tstat pic, there are no jumpers on the Nest wiring:


Thank you all for your suggestions on thermostats. We're going to run with the Nest for now and research some better alternatives.

Thanks,
Scott

You may want to reread my post more carefully.

I was referring to the cooling, Y1 and Y2 being jumpered together.

[pacnw]

The question then becomes: what do I lose by not having common?
thanks!
Scott

without a Common wire the stat becomes a power stealing/robbing type. this tends to lead to issues with some stats and definitely leads to issues with the NEST.

again, NEST is something that is MARKETED to accomplish something that really is not necessary and can be accomplished by other products already on the market, most of the time less expensively.