Just Another One of Those Days!

[Birdhunter1]

Bird I used to work on Ruud units, same as rheem, about 10 years ago. One thing that can happen is when you take the blower door off everything looks fine, but with the door closed and the fan running it can pull the insulation off the inside of the unit and restrict air getting into the blower itself. Is the blower clean? The blower is not hard to pull out, should be a plug with all the wiring connections in it, just unsnap it, should be 2 sheetmetal screws to remove and the blower unit slides out. Other than that pull the filter and look in the return duct and see if the insulation is coming loose and blocking the filter.

These things above are probably not happening if the pressures looked ok, and if they were happening you would probably have a coil freezing up. Also with the blower unit out you should be able to look up through the air handler and see the bottom of the coil (upflow I assume) and see if it is dirty.

Does your outside unit sit in a position with the sun directly on it? Does your outside unit have stuff growing near it possibly blocking air to it?

Aside from those things drill a small hole in the supply duct just ahead of the coil and see what your discharge air temp is.

 

[2manyrocks]

Checking your air temperature in the duct is a good idea to determine if the unit is really cooling, but maybe a control is messed up and turning it off before it totally cools your house.

Did it just start this when your power went off or have you had any cooling problems before this?

Do you have a simple T stat or some kind of electronic, programmable T Stat?

Was there a power surge that damaged the controls?

 

[Bird]

Does your outside unit sit in a position with the sun directly on it? Does your outside unit have stuff growing near it possibly blocking air to it?

Yep, the sun is on it most of the day, but nothing is growing around it that could block the air to it.

have you had any cooling problems before this?

No.

Do you have a simple T stat or some kind of electronic, programmable T Stat?

It's a digital display, programmable, but I've never used the programmable feature. I keep in on "manual" and never change anything except to raise or lower the temperature setting and very rarely do even that. We leave it on the same termperature setting 24/7.

 

[Birdhunter1]

Bird this is a simple question, but when was the last time you changed the batteries in your T-stat? I have seen that right there cause some strange problems, but usually the stat doesn't work at all if the batteries are bad. (reminds me I need to change mine)

Only other thing I can figure is if your unit is in the sun it will work harder, but you said it has worked fine for years up until recently.

 

[Bird]

when was the last time you changed the batteries in your T-stat?

I can't find where I made myself a note like I usually do. I know I changed the battery once, and we've been here 3.5 years, so I'll try to remember to check that tomorrow.

One thing I've always known about this thermostat is that it always shows a higher temperature than the actual temperature. All summer, I keep it set for 77 degrees, but that's actually 71 or 72. Now early this morning, it was set for 77, showed to be 77, but I didn't check the actual temperature. However, it has run continuously all afternoon. Although the setting has stayed on 77, it showed the temperature got up to 81.

Now the oddest part. Even though the unit is still running and showing 80 degrees, I just checked with a better thermometer and right at the thermostat, it's 74 degrees. Then I went to one of the registers in the ceiling closest to the unit in the attic and the air in that duct is 59 degrees.

I'll be getting up in the attic Wednesday and do some more checking up there then.

And I appreciate everyone's help and suggestions.

 

[Birdhunter1]

One thing I've always known about this thermostat is that it always shows a higher temperature than the actual temperature. All summer, I keep it set for 77 degrees, but that's actually 71 or 72. Now early this morning, it was set for 77, showed to be 77, but I didn't check the actual temperature. However, it has run continuously all afternoon. Although the setting has stayed on 77, it showed the temperature got up to 81.

Now the oddest part. Even though the unit is still running and showing 80 degrees, I just checked with a better thermometer and right at the thermostat, it's 74 degrees. Then I went to one of the registers in the ceiling closest to the unit in the attic and the air in that duct is 59 degrees.

So does your house feel cool enough?
Change the batteries and see what happens. All of them I have ever dealt with take 2 double A batteries. it sounds like your t stat isn't functioning right.

 

[jinman]

Now the oddest part. Even though the unit is still running and showing 80 degrees, I just checked with a better thermometer and right at the thermostat, it's 74 degrees. Then I went to one of the registers in the ceiling closest to the unit in the attic and the air in that duct is 59 degrees.

I'll be getting up in the attic Wednesday and do some more checking up there then.

Sure sounds like you are losing cold air from the duct or the duct is not insulated well and is taking on heat from your attic. You know it must be hotter than hades up there during this weather. 59 degrees at the register seems to indicate your evaporator is working just fine. Of course, I don't have an attic. I have 4 in of foam with reflective foil and over 2" of wood between my loft ceiling and the top of my house. That and my metal roof seem to really be efficient. All my ducting is between the floors or inside a fir-down in my garage. Good luck Bird, and be careful in the attic in this heat.

 

[Bird]

My wife thought the 2 AA batteries in her TV remote were weak, too, so I went and bought new batteries this morning and put new batteries in her TV remote and in the HVAC thermostat. But then I went and got my multimeter and found the old batteries from the TV remote showed 1.3 volts, but the ones from the thermostat showed 1.5 volts. They are Duracells with a date on them of Mar 2013, so I don't think those batteries were the problem, but I left the new ones in anyway. And the A/C is cycling normally this morning.

Jim, I guess it's possible that there's a leak in the ductwork, but I don't see how that could have happened since no one has been up there except me or that service man and I was there watching what he did. This house has the round flexible type ducts in the attic, and very deep (a foot or more) insulation up there. I go up once a month and put just a little bleach in the condensation drain, and yes, it's hotter'n hades up there.

 

[Egon]

Without any knowledge at all could one of the electronic component control units be heating up over time and stop working correctly??

I'm saying this as it has worked well in the morning but as the run time increases it starts to fail.

 

[RobertN]

A no load voltage test will only tell if you have voltage. A worn battery might show good voltage, but not flow any current under load.

Kinda like having poor flow from a hose attached to a water tank. The water tank may be full(like measuring 1.5 volts on a 1.5 volt AA battery). But, the hose may be restricted or clogged(ie no current flow from the battery).

My wife thought the 2 AA batteries in her TV remote were weak, too, so I went and bought new batteries this morning and put new batteries in her TV remote and in the HVAC thermostat. But then I went and got my multimeter and found the old batteries from the TV remote showed 1.3 volts, but the ones from the thermostat showed 1.5 volts. They are Duracells with a date on them of Mar 2013, so I don't think those batteries were the problem, but I left the new ones in anyway.