Perhaps aux heat that is on?

Posted By jonr on 09 Jul 2010 10:59 PM
Perhaps aux heat that is on?

Good idea.  This has happened before. 

Had one last month - only 5-7 degree split across unit, evap line felt like the classic "beer can cold" (That's no substitute for a proper measurement of superheat but I lacked tools at the time)

1600 SF house with 3 ton unit. Previous tech replaced a cap to get the unit going and diagnosed problem as need for a 4 ton unit.

I brought out my el-cheapo clampmeter and found strips were drawing 37 amps. Homeowner had replaced thermostat and miswired one little connection...

I asked Mrs. Homeowner for the last light bill and compared it with the current meter reading, approx 25 days into current cycle.

Good news - I fixed the problem with no need for a 4 ton retrofit. Bad news - $700 utility bill that month.

Hi Bill:

Preventative maintenance is far more than simply changing air filters. It includes checking Freon levels, that the heat exchanger is clean, pumps are working smoothly, and more and more.

Let me explain a bit:
- Change air filter monthly. This is an old rule of thumb (change the air filter when you mail your mortgage payment). It is a simple rule for people to remember and sounds good. A better rule would be to change the air filter when air flow decreases by XX amount. But joe homeowner has no way to identify when the air flow decreases. If your home is clean and the filter is not getting clogged then changing it has absolutely no value. If you have a very dusty home you might need to change it more often to keep up the air flow and to prevent the exchangers from getting dusty.

- incorrect Freon. Incorrect Freon levels can have a significant impact upon unit performance. A slight under/over charge will have a very minor impact but it will impact performance. About 40% of home owner HVAC units are over/under charged. Sometimes after they are "charged" they are incorrectly charged. Incorrect charges also cause more wear and tear on the unit. Thus the unit may wear out sooner or break down sooner or cease performing at the highest level sooner.

That is just two items. If the air flow does not slow down you will never see any benefit from changing your air filter.

Thus it comes as no surprise that noise over comes your data.

Does that help explain for you?

Alex

Posted By Alex_in_FL on 10 Jul 2010 12:10 PM
Hi Bill:

Preventative maintenance is far more than simply changing air filters. It includes checking Freon levels, that the heat exchanger is clean, pumps are working smoothly, and more and more.

Alex

With the exception of Earthlinked (that permits you to check refrigerant through sight glasses), every manufacturer I'm familiar with refers to "checking freon levels" as a last resort. Each time you hook your gauges to a system, you impact the charge and risk contamination.
A factory built package unit is charged by weight, so if water pressures, amp draws, air and water delta T's, heat of extraction or rejection and air flow are in spec., charge will be too.
Do not feel badly if your servicer does not "check the charge", be greatful, it's manufacturer recommendations.
Joe

Posted By Alex_in_FL on 10 Jul 2010 12:10 PM
Does that help explain for you?

Many thanks!

Best regards,

Bill

Posted By Alex_in_FL on 10 Jul 2010 12:10 PM

- incorrect Freon. Incorrect Freon levels can have a significant impact upon unit performance. A slight under/over charge will have a very minor impact but it will impact performance. About 40% of home owner HVAC units are over/under charged. Sometimes after they are "charged" they are incorrectly charged. Incorrect charges also cause more wear and tear on the unit. Thus the unit may wear out sooner or break down sooner or cease performing at the highest level sooner.

Alex

Putting a gauge set on a GSHP is NOT recommended unless there is a problem indicated by the Heat of Extraction/Rejection. It only takes a few times to affect the refrigerant charge enough to impact performance.

Bergy

I wouldn't mess with the charge in a package unit unless I was prepared to recover and weigh in the correct charge, and then only after being sure of all heat transfer calculations and compressor power measurement.

I looked at my father-in-laws filters, and they were surprisingly clean, he says he washes them out time to time. I can't say I like them too much, they are some kind of nylon mesh filter that is basically a 1 inch multi-layer screen. It's no where near as tight a weave as the 3 inch filters I have. I can't help wonder how much dust is passing right thru the filter and onto the heat exchange. I didn't any more involve with checking out the unit, my expertise isn't enough to know what I'm looking for. I feel a lot more comfortable messing with my own units, then someone else's. I don't want to get involve with it broken and you where the last to touch it situations.

He's a major pain in the ass. I was trying to help him wire up his shed he moved from his old house, there was only two 12-2 wires at the shed's junction box, I told him there should be another one, cause he has a 3 way in the house to turn off the shed flood light from inside the house. He sweared up and down there was only 2 wires, so I ran power from the house and a 3wire for a 3 way light switch, to switch the shed outside flood lights off and on from the house or the shed. Anyway, something wasn't working right, the lights on the shed where too dim when they were switches on. I wanted to open up every fixture on the shed to figure out what was going on, but he came to the conclusion I didn't know what i was doing. (I spent over 2 years as an electrician helper, trust me I can wire a frigging shed). Anyway It was beyond his understanding why I ran a 3 wire to the shed and not to the panel box, so he ran a 3 wire from the switch to the panel box, after i told him not to. He ripped the hell out of the wall, instead of making a small hole at top and bottom of the wall to fish the wire down he ripping out the wall all the way down the wall to get it into the panel. Anyway he ended up calling an electrician who charged him $1,000 to trouble shoot the problem. Turns out there was a third wire under the shed, just like I suspected, but was told I don't know what I'm talking about. I try not to get involved with fixing anything for him anymore if i can help it.

Thanks for the update. I can relate. I stopped fixing my mother-in-law's computer years ago. I made it run like new (about two dozen times) and she promptly messed it up each time within 4 weeks. I explained "do's and dont's" to her many times to no avail. She understood, but still refused to take my advise. She has purchased 2-3 new computers since then and has brought each of them to a grinding halt. She started paying someone to fix them, but she lacks sufficient disposable income to pay for this ongoing service.  She has been without an operational computer for 3 years now.  It can be hard, but sometimes you just have to say enough is enough.  :-)

Don't get me started on in-laws. lol.
I can't begin to quantify the hours of business and technical hvac advice I've recieved from mine.....
j