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Air Conditioning Mystery

Mon Jul 17, 2017 9:05 am

Our home is a Brick "Row Home" in South Philadelphia, built in 1920. The front exterior facade was completely replaced from the ground - up with brand new red brick. The bricks are "tight" and pointed. The Master Bedroom has knotty pine floors that leave a 1/2" - 1" gap where it should meet the front wall. Above that is Cast Iron baseboard heating.

As we begin to spend our first summer in this house, we installed a 8K BTU window unit Air Conditioner (the room is 144 Sq Ft). Temperatures are climbing and we quickly noticed that our 8K BTU AC unit wasn't getting the job done... which it very well should! We decided to purchase a 10K BTU window unit - same issue. The Air wasn't reaching the frigid lows that it should in a small room like this. Not to mention, the aging Pella Windows had a tough time supporting this monster AC unit. We returned that, and opted for a 10K BTU Portable AC by Hi Sense. We were drawn to this for the lower stress on the window frame. Again... this unit is not producing the COLD temps that it should.

Troubleshooting: We made sure the air vent was properly sealed around the window, I addressed the gap in the floor (under the baseboard) by stuffing foam into those gaps, or as many as I was able to access without removing the baseboard, The door to the bedroom - ensured that the area around the door was as "air tight" as possible. Still - the same results despite my insulation attempts.

2nd Round of Trouble Shooting: Called in an electrician to assess the electric supply to the unit. The house has a lot of Knob & Tube wiring. We ensured that we were getting 110 out of the outlet, but the outlets in this room aren't grounded. The Manufacturer recommends a grounded outlet and no use of extension cords or 3/2 Plug Ground adapters. NO improvement. Our bathroom has a properly ground, brand new home run to our breaker box - I ran a 10 gauge extension cord to the AC - just to see if it performed any better. NOPE.

I'm pretty convinced that the unit is in good shape, as we've had similar performance for 3 air conditioners at this point.

My latest thought is that there is air escaping from around/behind the cast iron baseboard heating panels.
I am going to try an experiment tonight, by "sealing off" the area around the baseboard with a sheet of plastic and some tape. If I'm able to successfully prevent the hot air from continuing to enter the room... that will reveal my problem.

If this experiment is successful... Is it possible to "shoot or spray" insulation behind these cast iron panels? I'd hate to disrupt the installation or the heating. We had the bedroom's plaster walls skim coated, painted, hard wood floors refinished, etc... I'd prefer to be invasive or destructive in remedying this issue. Any thoughts or suggestions??
It's extremely frustrating. We know that a 10K BTU AC should render this bedroom into a Meat Locker!!!

Re: Air Conditioning Mystery

Thu Jul 20, 2017 10:24 am

We bought a portable unit and have had the same frustration. They just are not very efficient. However the window units should have done the trick. A lack of a ground shouldn't cause a performance issue, but low voltage could. Was voltage at plug checked?
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