Lennox G71MPP - How can I tell if it's running in variable mode?

[MNG71MPP]

The installers are coming tomorrow to look at the wiring on my G71MPP and Honeywell IAQ (see earlier post). In anticipation of possible suggestions from the installer, is there a difference in the efficiency between running it in variable capacity mode (requires the addition of the W2 wiring) vs running it in three stage mode (single stage thermostat - no W2 wiring)? Are there reasons why you would not want to run the furnace in variable capacity mode?

[Vettgetsmwet04]

Variable capacity is the main benefit for this unit, otherwise u should have got a g61 if u dont want the variable capacity.

Varible capcity gives u just the right amount of heat that the space needs at a giving time, every cycle the furnace varies up and down according to the load presented. that way u dont get big temp swings and the noise is at a minimum.

the effiecentcy doesnt really change no matter what mode u run the unit in. its a 95% furnace at all capacities.

Essentially in variable capacity mode u have a 60 stage furnace, 40%, 41%, 42%,ect.- all the way up to 100%. so its a no brianer with the honeywell IAQ stat.

[westlaker]

Hi Vettgetsmwet04

My installer will be coming tomorrow to install an IAQ. Do you forsee any issues
with this stat when running a single stage XP15 heat pump/g71mpp furnace.

Where is the best place to install the EIM?

The installer should change the dip switch setting Switch 1 off, Switch 2 On and Switch 3 off, for variable capacity heat on the G71, correct?

[Vettgetsmwet04]

MAKE SURE THEY READ ALL THE INSTRUCTIONS FOR THE FURNACE SETUP, AND STAT WIRING!!!!!!!!!!!!!

Also make sure everything is cycled and checked out, all stages of heat pump heat, gas heat, cooling, humidity if u have a humidifier ect. for everything.

Its unfortunate sometimes with this really high quality equitment so many contractors have very little ability to install correctly because of lack of experience or training.

The honeywell iaq will be perfect for your system.

Good luck

[westlaker]

I'm hoping my installer will know all the important setup features of the IAQ and my duel fuel setup.

Thanks.

[ChicagoJim]

I'm hoping my installer will know all the important setup features of the IAQ and my duel fuel setup.

Thanks.

I had hoped the same thing, but my installer didn't know. I had to explain to the installer how the IAQ functioned, what it was capable of, where the tests were, etc.

Somethings to make sure they do:
1) wire your humidifier directly to HUM1 & HUM2
2) After the IAQ goes through the "AutoDiscovery" mode, the installer should go through every setup code and verify that each code is setup correctly. the IAQ will most likely default to settings that assume a <90% AFUE 1-stage furnace. Obviously that is NOT what you want.
3) Ensure the installer goes through each setup test at the end of the setup codes. That is:
a) The fan operates in fan-only mode,
b) the humidifier goes on,
c) Stage 1, 2, 3 each go on in your modulating furnace. There are there "tests" for this... he can hook up a voltmeter to W1, W2, etc to verify a signal is coming from the interface for each stage and monitor the furnace readout (probably a flashing LED) to confirm each stage.
d) other heat pump and A/C settings

Just my 2 cents that I learned the hardway when my installer screwed up the installation. Ironically, the installer has won "dealer awards" from both Lennox and York. Go figure!

[westlaker]

Thanks ChicagoJim,

Don't have a Humidifier, so will ensure CPH value is set correctly. Do you mean these settings for each of the stages 1-3.

1—1 cph used for steam and gravity
3—3 cph used for hot water system and high
efficiency (90% or better) furnaces
5—5 cph used for standard fossil fuel forced air
(less than 80% efficient) systems
9—9 cph used for electric furnaces
2, 4, 6, 7, 8, 10, 11, 12—other cycle rate settings

Which setting you referring to regarding fan only mode?

[ChicagoJim]

Yes, those codes are available for setting CPH for each of your heating stages (I think the G71MPP has three stages). The higher efficiency, multi-stage furnaces are designed to operate at low settings longer, so you'll want to use a lower CPH. Also, the IAQ will learn how long it takes to raise temp different amounts to setpoint temp at different outdoor temps. The IAQ will then use this "temperature recovery info" to compensate when it goes on, what stage heat is uses and how long it will run after it reaches the setpoint.

The only thing you need to watch the first winter then would be on the coldest days of winter, is the temp comfortable. If it's not, you might consider changing Stage 3 CPH to a higher value. What's happening is that if on the coldest day, the temp is not being maintained, the IAQ may be wanting to turn the furnace on more often than the 3CPH it is restricted to in the setup. So increasing the highest stage heat to say 5 CPH will allow it to turn the heat on more frequently on highest stage.

The benefit of changing only the highest stage to 5CPH means that on moderate winter days with lower heat demand, stage 1 heat (and stage 2 in 3 stage systems) will not be cycling on frequently because the CPH is still 3CPH.


Regarding System Setup Tests:

At the end of the Installer System Setup are 7 test options and an Error option.

When you or your installer selects a test, it puts the thermostat in that "mode" for you to verify with the H/W that the H/w is operating. So using the table below, selecting (activating) Test 2 and setting the value to 1 will turn the fan on. (Note for your convenience, when you move to other test, the test value reverts back to 0).


Here's the link to the entire IAQ installation manual: http://customer.honeywell.com/techli...0s/68-0287.pdf

The Installer SEtup screens start on page 13. The Installer setup test codes that I've attached are on page 20

I suggest you thoroughly read and understand what's available on pages 13-20 so you can double-check your installers setup.


Here's an illustration on how the tests are valuable for system setup validation and diagnosis:
In my case, one of the many problems was that unbeknownst at setup, the one stage A/C was looked up to Y2 on the T-stat and not Y1. When I educated the installer that there were system tests and demonstrated the tests, the Test 1 (A/C) would not work. The installer didn't know what the problem was said that it was too cold (which was wrong) and left in a hurry at 4pm. After he left, I discovered he wired the one stage A/C to Y2 and not Y1.

I'm by no means an expert... this is just what I've learned over the past 3 weeks (the last week being with the new IAQ and G61MPV).
Hopefully someone on this board will QA my comments.

[westlaker]

The installation of the Honeywell IAQ is in and appears to be working. Also the G71MPP is running in Variable mode after the installer flipped the dip switch. Confirmed by seeing the small h.

In Heat pump mode, fan appears to run the same.

He recommended leaving the Circ on though.

Thanks again Vettgetsmwet04,ChicagoJim and other for the responses.

[jason56]

I am hoping that someone can help me with my new furnace/ac install. I have a Honeyweel IAQ but have now to set it up. Can someone please post how tho set this up with a York YP9c, an LX 14 and an Aprilaire Humdifier. I am getting worried because my installer says he has no ideas how to hook it up! Please help!

[beenthere]

Jason.
Call your salesman, and talk to him about having a better installer/tech out to wire it, and set it up.

And don't hi jack other peoples threads.

[wyowanderer1967]

Elgoosh or others....my recently installed G71 flashes the code " H " when first starting up. I assumed it was a general code calling for heat. But after reading your post I understand that it should be flashing a small "h" which stands for variable? Did I read this correctly? Once my furnace ramps up it seems to flash the various codes associated with the demand and a small h appears before the other letters and numbers, for example
h40A540 or h80A740
Also, after running for about 1/2 hour it shuts off completely (when it is bringing the temp up 3-4 deg say in morning and running at 100 percent), then restarts again about ten minutes later. Is this normal?
Thanks.

[Briant73]

Elgoosh or others....my recently installed G71 flashes the code " H " when first starting up. I assumed it was a general code calling for heat. But after reading your post I understand that it should be flashing a small "h" which stands for variable? Did I read this correctly? Once my furnace ramps up it seems to flash the various codes associated with the demand and a small h appears before the other letters and numbers, for example
h40A540 or h80A740
Also, after running for about 1/2 hour it shuts off completely (when it is bringing the temp up 3-4 deg say in morning and running at 100 percent), then restarts again about ten minutes later. Is this normal?
Thanks.

I think the capital H when the call for heat happens is correct, the lowercase h appears once the furnace is heating in variable mode so I think that your g71 is operating correctly in that regard but I'm an end user and not a tech so maybe someone else can better explain.

As to the second question that sounds odd but people will need more information like house size, house age, furnace model size, heat you want inside, outside temperature.