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Old 06-07-2012, 08:14 PM   #1
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Too much Vacuum?


Hi All, new here... need some advice.

I just had a new electric furnace installed (20 kw) with a 3 ton air-conditioner/thermo pump installed. It was a retro-fit to an existing system that was insufficient for the home. The unit that was here was a 12 kw, had no air-conditioning and no ducts leading to the upstairs (they had base board heaters upstairs). Since we wanted air-conditioning we had to add ducts that run from the basement to the attic then back down into each of the bedrooms.

The installation was done on May 1st of this year. From the first day we used the air-conditioning, the airbox which is located below the furnace is leaking water. The installer has been back several times and can't find the problem. He has cut holes in the return ducts, drilled holes in the drain hose, with no luck. His next idea is to replace the 3 ton with a 2.5 ton... but I do not see any freezing what-so-ever on the cooling fins so am certain that is not the problem. Since he drilled a hole on top of the drain hose, I can see the water sit there while the unit is on. As soon as the unit's fan stops (it's regular cycle) you can hear the water immediately drain from the pan and into the pump (which then ejects to the outside). I am certain that the vacuum in the unit it preventing the water from draining properly... but how to I convince this moronic installer and/or how can I fix or prove that my theory is right? Would a second drain hose help? There is a second knockout a slight bit higher up from the one being used. The other question is why? Why would this happen, is it because of the retrofit? Are the returns simply not sufficient? Is the fan too powerful for the size of the airbox?

Any advice you can offer would be very much appreciated. Every time this installer comes back to "try" something I cringe at what I will see him do. The last time he re-ran a duct to have better flow but cut one of my joists... I almost had a fit.. now how to fix that. My wife was home alone, he told her there was no problem cutting it... needless to say if I can fix it without him that will be fantastic.

Thanks,
Adam

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Old 06-07-2012, 08:24 PM   #2
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Too much Vacuum?


You need a trap in the drain hose. If he used pipie then get some elbows and make a trap, if he used hose then just make a loop so the water will be trapped before it enters the pump, that will get rid of your vacumn issues.

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Old 06-07-2012, 08:43 PM   #3
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Too much Vacuum?


That would seem counter-intutive as if there would be more suction on the water in the drain however I dug up the installation instructions and sure enough they call for a J-trap on the drains... in this case they also recommend both drains be used. the installer put a staight hose to the drain with no loop. He then put in a hard PVC pipe, also directly to the drain with no loop.

Thank you for the advice, I will buy some hose tomorrow and give it a shot. At this point I have nothing to lose. Does it make any sense that he has come back 5-6 times now and hasn't tried this? The company claims they install 400 of these every year and this is the first that has this problem.
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Old 06-07-2012, 08:50 PM   #4
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Too much Vacuum?


The velocity of the air moving past the opening at the drain connection causes a venturi effect which draws air up your drain connector, the trap will create a seal which the suction caused by this venturi cannot overcome.

Believe me, I have installed more than 400 units personaly, and know this will work. Just cause the company has done a lot of work, doesn't mean this installer has ever read the instruction book, or done that much work himself, and to be fair to him, it doesn't happen every time, but yours is one of them .
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Old 06-07-2012, 09:04 PM   #5
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Too much Vacuum?


Yep, needs to be trapped.
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Old 06-07-2012, 09:13 PM   #6
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Too much Vacuum?


It definitely makes a lot of sense to me, thanks again for the quick response.
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Old 06-08-2012, 11:11 PM   #7
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Too much Vacuum?


So... I want to knockout the second drain plug as per the installation instructions, but I can't figure out how to do it. Is it possible to knockout when the drain pan is already installed?
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Old 06-09-2012, 03:01 AM   #8
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Too much Vacuum?


Yep, you can knock them out after they are installed.
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Old 06-09-2012, 11:32 AM   #9
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Too much Vacuum?


And is it just a matter of putting a screw driver in the center of the hole and hitting it with a hammer? Or should you drill out and then use some pliers to pull out the center?
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Old 06-09-2012, 01:07 PM   #10
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Too much Vacuum?


I tap them out with a screw driver toward the outside edge.

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