Need Help!

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Posts: 1
Joined: Sun Jun 28, 2009 12:02 am

Need Help!

Post by rmendez »

Hello. I am not in anyway an HVAC guy. I usually fix electronic and mechnical issues and have ALWAYS called an HVAC person when I got to that point. I have a basic understanding of how the system works and I am willing, with some help, to try a fix. So, here is what I have spent the last 4 hours figuring out.
I have a 2,300 sq. ft. 2 story house. We moved in last September. We live in Texas, so it was HOT as usual. I have a single Puron unit outside. In the attic is a Carrier system. The thermostats are Carrier also. Also in the attic is a EWC BMPlus3000 control board. On the board, Zone1 and Zone2 have wires that come off of the terminals and to the motors. I would think the dampers are square because the duct is square. The motor sticking out looks like the one on an ND-RSD damper. This is just what I have observed. Upstairs and downstairs both have returns. We have always kept our house at 70-72 degrees. Yes, we like it cool in here. So, here is the issue:
If the AC is only supplying downstairs, the vents blow strong and the AC only runs for a couple of minutes. Same thing if only the upstairs is on. If they both come on, the AC will run all day. Plus, whichever level was already being supplied air, that level will suffer the biggest loss of air out of the vents. So, if downstairs was on and blowing strong and then the upstairs opens, the downstairs will barely blow. If I use the thermostat to turn off the downstairs supply, and then turn it back on. The downstairs will start to blow strong again and make the upstairs weak. This situation is making the AC run all day and the temperature will increase on both levels at least 3 degrees and never reach the setpoint. The only time they both reached the setpoint and turned the unit off was around 1 a.m. this morning. Going back to last September, it never had this issue. In fact, the unit would hardly ever kick on. Keeping our house around 71 and with 4 people (2 kids leaving every light on) our bill has never been higher than $155 for a month. I can only imagine what it will be now. So, with all that. Does this sound like a control issue (BMPlus3000) or a unit issue. Having a basic understanding of how the system works, I would think that if you are supplying one level, and then open a damper to supply another, the speed of the fan would have to increase to push a greater volume of air. Am I wrong? And why does the level you turn on last always get the greater volume of air. What I mean is, I understand one level blowing strong and then opening a damper will cause a drop in volume, but they should both drop and be about the same if it is truly a 50%split. But the last level you turn on gets the most volume leading me to believe it is a control issue. ???
Sorry for the long post, but I wanted to give all info for a good diagnosis.

Note: The status LED has a heartbeat and the proper zoning LED's light when activated.

John B.
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Joined: Fri Mar 13, 2009 8:57 am

Re: Need Help!

Post by John B. »


The problem you have described sounds like there may be a sticking zone damper (half open or half closed) or maybe a bypass damper sticking. It also sounds like the duct-work needs to be balanced....

The balancing cannot be performed until all dampers are confirmed to function correctly. If you have an ND-RSD it could possibly be sticking and it may be due to pressure and/or location....It may be necessary to change to the regular ND for additional torque. Your damper has a 5 year warranty. If it turns out the damper is sticking, we will replace it, but you may have to pull an additional wire.

Once the zone dampers and the bypass damper are confirmed to operate correctly, balance the airflow by adjusting either the zone dampers or individual butterfly volume dampers (if they exist on your system) and the system should behave.

Thank You,

John Brown
John Brown :geek:
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