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 Repairing and Servicing Lennox Products
 Repairing / Servicing Lennox Heat Pumps
 CB31MV-51 no high speed blower on heat
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BC1iron

5 Posts

Posted - 12/30/2010 :  10:23:47 PM  Show Profile  Reply with Quote
Gear;
CB31MV-51-2P Air handler with Aux Electriv Heat
HP27 Heat Pump (single spd)
Honeywell RTH 8500 T Stat
No Sig Stat or humidity control.

Tap jumpers set to factory;
Adjust pin #3
Heat Pin #1
Cool Pin #2
Delay Pin #3

Condition;
When call for heat from Heat Pump blower speed 1150 cfm. When heat call moves to Electric heat,blower speed reduces to 700 cfm.

When I move the "adjust" pin to #4 (+10%) thats exactly whay I get.
Moving the heat pin to #4 increases heat blower top speed, but only slightly to 900 CFM.

I actualy get higher blower speed with fan on manual than in any heat/cool with fan set on auto.

I have checked and rechecked wiring, replaced control board (BDC3), verifide both legs of power to the motor.

Could this be an ECM issue?

Thanks,

BC1iron

Cozy.Support

5757 Posts

Posted - 12/31/2010 :  4:04:14 PM  Show Profile  Reply with Quote
Is the jumper between R and DS still in place on the thermostat terminal strip?

Is the Y1 to Y2 jumper still in place on the thermostat low voltage terminal strip.?


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Once you know what part you need, you can contact the Cozy parts department by using the link below
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BC1iron

5 Posts

Posted - 01/04/2011 :  8:55:45 PM  Show Profile  Reply with Quote
R is NOT jumped to DS

Y1 IS jumped tp Y2

Asa side note, DS IS jumped to Y1

BC1iron
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Cozy.Support

5757 Posts

Posted - 01/04/2011 :  9:14:43 PM  Show Profile  Reply with Quote
If you do not have the jumper to the DS terminal, and no other dehumidification control connected to the DS terminal, the blower will slow down below the design flow CFM because the system is trying to dehumidify.





CozyParts.com, Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
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BC1iron

5 Posts

Posted - 01/04/2011 :  10:04:33 PM  Show Profile  Reply with Quote
Thanks for the quick responce,

Just to be clear;

R should be jumped to DS
Y1 should be jumped to Y2

Should DS be jumped to Y1?



BC1iron
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Cozy.Support

5757 Posts

Posted - 01/04/2011 :  10:20:18 PM  Show Profile  Reply with Quote
Yes... the ds jumper and see if your air flow comes up. DS really should not affect the heat speed, but not completely sure what is going on with your system.



CozyParts.com, Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
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BC1iron

5 Posts

Posted - 01/04/2011 :  10:55:22 PM  Show Profile  Reply with Quote
OK, i jumped DS to R,
Two results;

#1, have constant fan even when no call for Heat with fan set to auto
#2, fan speed- no change.

Checked instalation manual, Cannot see any referance to DS - R jumper in schematics for Heat pump with electric heat no humidity control.

Any thoughts....

BC1iron
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BC1iron

5 Posts

Posted - 01/04/2011 :  11:21:50 PM  Show Profile  Reply with Quote
I should add that I am opperating in EM Heat (electric) as it is to cold at this time to run the Heat pump. Would a Jumper from G to DS serve the same purpose but only run the fan when G is energized?

BC1iron
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Cozy.Support

5757 Posts

Posted - 01/05/2011 :  06:51:50 AM  Show Profile  Reply with Quote
Do you have any other wire connected to the DS terminal? Connecting DS to 24 vac should not have turned on the blower.

DS should only work in the cooling mode fan speeds, but we had you connect it because it is normally connected to 24 VAC unless you have dehumidification controls. There is a jumper from R to DS when the air handler leaves the factory. The jumper is removed when you had dehumidification controls to the unit.



CozyParts.com, Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.

Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx
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