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Old 12-29-2012, 11:32 PM   #1
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Lennox G61MPV - is a very slow fan speed possible


I have a Lennox G61MPV-36B-071-12 gas furnace. As best I can understand from the manual the low speed fan air flow is around 700 cfm. That causes quite a draft of cold air when the fan runs (without heat) by itself, pulling air in from outside. As a result, we don't use it as a means of fresh air circulation. If the fan could be slowed to say 150 cfm then the draft feeling would be less noticeable. Is it possible to do that? And if so, how? It has an ECM (I think that is what it is called -- low energy consumption, variable speed) motor.

I am considering adding an HRV to warm the incoming air to reduce the cold draft feeling further. It would tap into the cold air return for both outgoing and incoming air. I understand that the air handler on the furnace needs to run when the HRV is configured this way. Thus the reason for lowering the furnace fan speed to that of the HRV, which is 150 cfm.

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Old 12-29-2012, 11:57 PM   #2
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Lennox G61MPV - is a very slow fan speed possible


no it is not possible...... 700 cfm does sounds hi..... I believe the lowest continous fan is 30% of 2nd stage cooling speed.... others will chime in..getting old memory failing......

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Old 12-30-2012, 12:53 AM   #3
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Lennox G61MPV - is a very slow fan speed possible


I was hoping it would be possible since it is a variable speed electronic motor.

I guess the next angle to pursue would be if I could have just the 150 cfm HRV distribute fresh air through the duct work without the furnace fan needing to be used. (The furnace doesn't run much as we are on the west coast and the gas fireplace does a lot of the heating - less efficient than the furnace I know but a big pleasure.)
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Old 12-30-2012, 01:21 AM   #4
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Lennox G61MPV - is a very slow fan speed possible


hrv wont push air far enough..... furnace fan distributes air....
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Old 12-30-2012, 02:50 AM   #5
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Lennox G61MPV - is a very slow fan speed possible


If you have only one return for your furnace, have the HRV's stale air inlet installed in a hallway, and its fresh air discharge installed into the furnace supply plenum/duct.

If your gas fireplace gets its combustion air from the home. then using it is what is causing so much cold air to be brought into the home.
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Old 12-31-2012, 10:04 AM   #6
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Lennox G61MPV - is a very slow fan speed possible


Actually it is possible. They are set from the factory for around 450 cfm for low speed. On those furnace if you look very carefully inside the viewing port on the lower door there should be a small series of red LEDs. There is a way to read the fan speed but you need to read a service manual. If I remember you count the flashes and each flash is 100 cfm and then there is a pause and it starts over again. If it is higher than 4-500 then the installer changed it and it can be put back down by flipping some dip switches.
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Old 12-31-2012, 04:51 PM   #7
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Lennox G61MPV - is a very slow fan speed possible


Ain't gonna get it down to 150 CFM like he wants.
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Old 12-31-2012, 04:54 PM   #8
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Lennox G61MPV - is a very slow fan speed possible


Quote:
Originally Posted by yuri View Post
Actually it is possible. They are set from the factory for around 450 cfm for low speed. On those furnace if you look very carefully inside the viewing port on the lower door there should be a small series of red LEDs. There is a way to read the fan speed but you need to read a service manual. If I remember you count the flashes and each flash is 100 cfm and then there is a pause and it starts over again. If it is higher than 4-500 then the installer changed it and it can be put back down by flipping some dip switches.
I trust ya man....... but never seen one supply 150 cfm....... you know something I don't

Last edited by carmon; 12-31-2012 at 04:59 PM.
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Old 12-31-2012, 05:02 PM   #9
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Lennox G61MPV - is a very slow fan speed possible


I said it could go down to 450 not 150 which is impossible. I doubt he will feel drafty at 450 as we sold 1000s of them and a lot to elderly people and not one complaint. Actually I can tweak that down another 10-15% with the dip switches too.
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Last edited by yuri; 12-31-2012 at 05:04 PM.
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Old 12-31-2012, 05:06 PM   #10
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his question was is 150 possible.... I ....said its not..... you said it is..... never mind Just kidding.... have a happy new year Yuri
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Old 12-31-2012, 05:14 PM   #11
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Lennox G61MPV - is a very slow fan speed possible


No problema. 450-10% should make him Happy. Hopefully the Next Yr is a good one. Health wise the last one has been horrible. Freedom 55 cannot get here soon enough.
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Old 12-31-2012, 05:17 PM   #12
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Lennox G61MPV - is a very slow fan speed possible


I hear ya man.... we had a great year moving into new housing..... very lucky to have a few great builders that pay there bills..... and the Lennox Line has been flawless..... zero failures in 3 years.... yes 100% zero failures....
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Old 12-31-2012, 05:26 PM   #13
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Lennox G61MPV - is a very slow fan speed possible


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Originally Posted by yuri View Post
No problema. 450-10% should make him Happy. Hopefully the Next Yr is a good one. Health wise the last one has been horrible. Freedom 55 cannot get here soon enough.
As Carmon said, he was asking for 150. Thats why i said ain't gonna happen.


Sorry to hear about your health.
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Old 12-31-2012, 05:28 PM   #14
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Lennox G61MPV - is a very slow fan speed possible


Ya me to ...... sure hope you are feeling better..... you are a smart tec..... love reading your posts..... stay healthy
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Old 12-31-2012, 06:12 PM   #15
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Lennox G61MPV - is a very slow fan speed possible


Thanks for the wishes. Gotta stop running around like Superman trying to solve everyones problems around me.

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Last edited by yuri; 01-02-2013 at 09:52 AM.
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