Duct Pressure and ECM Operation - Question


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Old 04-11-14, 02:50 PM
J
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Duct Pressure and ECM Operation - Question

I have a Rheem Model RGFD furnace that uses bypass duct work to reduce noise in my duct work ( I have 2 zone heating). I had a problem where the furnace tech said the ECM was not communicating. The problem I had was the furnace would ramp up and down and not stay on.

While the tech was evaluating the problem he noticed the damper arm on the bypass duct work did not have any weights on it. When this damper is working, it does not open very much which tells me there is not a lot of air going through it. I think that is why the weights were left off by a previous tech. Anyway, the tech said with the weights off, the damper could be vibrating and delivering an uneven pressure and causing communications problems with the ECM.

So, with a damper not opening that much, is it still possible that my damper could be vibrating and causing an uneven pressure? Before leaving, the tech put weights on the damper arm at a position up the damper arm to have minimum weight effect. Now, I am wondering if this damper is doing any good at all with the extra weights and could it vibrate without weights. The diameter of the damper is about 10 inches, so it is not small.

Thanks,
Jerry
4/11/14
 

Last edited by Jerry8A; 04-11-14 at 03:14 PM.
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Old 04-11-14, 05:26 PM
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I wonder what the static pressure is when only the smaller zone has a demand.
Is the blower operating correctly since the correction was made?
 
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Old 04-11-14, 05:57 PM
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The original problem was intermittent. So, when the tech came out it worked okay. However, he was able to access error codes from previous operation and the codes identified errors in ECM. With that information he has ordered a new ECM module. He did not mention anything about static pressure, so I don’t know if he measured it.

He seemed more concerned with my damper supposedly vibrating and causing resistance problems in the system. I have not had a chance to really check out the blower. The tech was here yesterday and it worked ok today. But, as mentioned above, the original problem was intermittent, so would need more time to confirm.

My concern is when the ECM is replaced, would a vibrating damper still cause a problem? Can a damper of this size vibrate and cause pressure problems? Seems strange to me.

Jerry
 
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Old 04-11-14, 06:37 PM
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I have seen high static pressure cause fault codes with ECM motors when a customer shut too many grill louvers.

Was your bypass damper able to shut when it should be open?
 
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Old 04-12-14, 08:54 AM
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I never really checked the damper operation. However, it moves freely when the furnace is not working. Currently, our weather is too warm for the furnace to operate.
 
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Old 04-12-14, 07:10 PM
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Jerry, I know you don't want to hear this but someone sold you a bill of goods. Zoned warm air systems just plain don't work or at least I've never seen one that did. With a true modulating burner & static pressure & temperature feed back to the burner & blower you might stand a chance, otherwise it's a complete waste of money.
 
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Old 04-13-14, 01:49 PM
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You are correct, that is not what I wanted to hear, but so be it. I was surprised your commnet about warm air zone systems not working. The people who sell zone heating surely won't always tell you that. I'm guessing some people who want that feature probably install two separate furnaces, but I can see that as being rather expensive and perhaps not having the space to do it. But, there still seems to be a lot of zone heating and cooling installed.

You mentioned “modulating burner.” This probably makes things worse, but I found out with zone heating, the modulating feature is not active for zone heating on my furnace even though my furnace supports it when using non-zone heating.

Do you know of any corrective action the heating contractor could take to correct my problem? However, I can say I have used this furnace for about 7 years and this is the first time this problem has occurred. So, I don’t know if that means anything.

Jerry
 

Last edited by Jerry8A; 04-13-14 at 02:57 PM.
 

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