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  1. #1

    Confused Taming the Beast: Variable Speed Blower Control

    Is anyone here familiar with Armstrong (Lennox) equipment? I have recently purchased a 3-ton 13SEER Armstrong heat pump to replace our old 8SEER system. Overall, I am pretty happy with the new pump. The outdoor unit (2SHP13LE136) is quiet and generates enough heat to keep the house warm down to about 25oF outside. It came with a variable speed air handler (EVF16CCP-1A), a modular coil (EC1P36CG-1), and a 20kW electric furnace (10kW x 2 with separate breakers).

    The trouble starts when the thermostat calls for auxiliary heat (when it gets colder or during the defrost cycle). The 4-ton blower (¾ hp ECM motor) produces the max airflow of 1,600 CFM. The contractor said this much air is required to prevent the new heat strips from melting (the old air handler had an 18.5 kW heater and it did just fine at much lower CFM). We have uninsulated sheet metal ductwork in much of the house and the noise the new blower creates is very annoying. When the air rushes through the 6” round ducts at 8,000 FPM into our living room it sounds like a jet during takeoff. Closing the dampers and registers on those ducts doesn’t make much difference (I am thinking about replacing them with R8-insulated flexible ductwork).

    Since we use only one of the two 10kW strips (it works fine even when the outside temperature drops to 0oF), I tried to adjust the maximum blower speed down to 1,200 CFM. I set the jumpers in the motor control board to D position (see Figure 2, Page 6 of the attached manual), which corresponds to 1,200 CFM based on the information in Table 3 (page 7). I also disconnected the W wire from the motor control board, because the contractor said it switches on the relay that overrides the jumper settings on the board. All to no avail. There is a LED on the board that flashes once for each 100 CFM. When the furnace is on, the CFM LED is flashing 16 times and the motor is going full blast …

    I would appreciate any suggestions.
    Last edited by strombidium; 02-17-2008 at 03:15 PM.

  2. #2
    Join Date
    Jan 2008
    Posts
    1,970
    We do Armstrong everyday. But no one here is going to tell you what adjustments to make. No diy. Have your contractor fix it. If he can't, he doesn't know what he's doing.

  3. #3
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,520
    Call your contractor back and have him look at, if he won't, pay somebody else to come out. I doubt anybody here will help you. You're already getting in too deep for your own good and just might create a mess that nobody here wants a part of. I would insulate the ducts, it might help some. Good luck.

  4. #4

    Hmm

    Thanks for the advice, I'll do just that. Thought it was easy to fix....

  5. #5
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,520
    FYI. I would call somebody else out. Your contractor told you the heat strips would melt. That is a bunch of bahooey. Anything is possible, but they have overloads built in. Otherwise, everytime I have to replace a blower motor that went out on a fan coil during the wintertime. I would have to replace the heat strips as well. Which I have never done and I probably change 10 or so blower motors in the winter time on fan coils and have never replaced heat strips. I have never had to replace heat strips, maybe a component here and there. My professional advice is to call somebody else.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,765
    Before you call your contractor back.

    Turn off the breaker to the outdoor unit. Then set your thermostat to cool, and turn it down low so the air handler runs in cooling mode. Let it run for 8 to 10 minutes.
    If it makes the same air noise as in heat mode, you have more of a problem then just the blower set to too high of an air flow in heat mode.

    Your ductwork may be too small. And ou may not have enough supply and return for the unit.

    Let us know the result.

    What size was the old unit.
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  7. #7
    Quote Originally Posted by beenthere View Post
    Before you call your contractor back.

    Turn off the breaker to the outdoor unit. Then set your thermostat to cool, and turn it down low so the air handler runs in cooling mode. Let it run for 8 to 10 minutes.
    If it makes the same air noise as in heat mode, you have more of a problem then just the blower set to too high of an air flow in heat mode.

    Your ductwork may be too small. And ou may not have enough supply and return for the unit.

    Let us know the result.

    What size was the old unit.
    OK - I did exactly what you recommended. Everything is nice and quiet in cooling mode. The same in heating mode, except when the heat strips are on (or the defrost cycle). The old unit was a 3 ton 8 SEER Armstrong (don't remember the model).

  8. #8
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Quote Originally Posted by strombidium View Post
    Is anyone here familiar with Armstrong (Lennox) equipment? I have recently purchased a 3-ton 13SEER Armstrong heat pump to replace our old 8SEER system. Overall, I am pretty happy with the new pump. The outdoor unit (2SHP13LE136) is quiet and generates enough heat to keep the house warm down to about 25oF outside. It came with a variable speed air handler (EVF16CCP-1A), a modular coil (EC1P36CG-1), and a 20kW electric furnace (10kW x 2 with separate breakers).

    The trouble starts when the thermostat calls for auxiliary heat (when it gets colder or during the defrost cycle). The 4-ton blower (¾ hp ECM motor) produces the max airflow of 1,600 CFM. The contractor said this much air is required to prevent the new heat strips from melting (the old air handler had an 18.5 kW heater and it did just fine at much lower CFM). We have uninsulated sheet metal ductwork in much of the house and the noise the new blower creates is very annoying. When the air rushes through the 6” round ducts at 8,000 FPM into our living room it sounds like a jet during takeoff. Closing the dampers and registers on those ducts doesn’t make much difference (I am thinking about replacing them with R8-insulated flexible ductwork).

    Since we use only one of the two 10kW strips (it works fine even when the outside temperature drops to 0oF), I tried to adjust the maximum blower speed down to 1,200 CFM. I set the jumpers in the motor control board to D position (see Figure 2, Page 6 of the attached manual), which corresponds to 1,200 CFM based on the information in Table 3 (page 7). I also disconnected the W wire from the motor control board, because the contractor said it switches on the relay that overrides the jumper settings on the board. All to no avail. There is a LED on the board that flashes once for each 100 CFM. When the furnace is on, the CFM LED is flashing 16 times and the motor is going full blast …

    I would appreciate any suggestions.
    Well congratulations on completely voiding your warranty. Homeowners should never mess with their own HVAC equipment. Let alone any Lennox product.

    You need to call your contractor to come out and resolve the problems. If they can't do it, get yourself a new contractor. As far as any help on here, your probably not going to get it. This site is for advice on HVAC equipment, not a handy way for you to fix it yourself.

    There is a reason why we are all highly trained and are required to have certain licenses/certificates.

    As said before, call a contractor, Do not attempt to change CFM settings on your own. And if you have 8000 FPM coming out of 1 vent, you have major issues that a switch will not fix. Thats outrageous, get some professional help.

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,765
    Quote Originally Posted by strombidium View Post
    OK - I did exactly what you recommended. Everything is nice and quiet in cooling mode. The same in heating mode, except when the heat strips are on (or the defrost cycle). The old unit was a 3 ton 8 SEER Armstrong (don't remember the model).
    Ok, then your contractor just needs to make an adjustment or 2.
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