As I mentioned in a previous post, we just replaced our furnance and evap coil in the garage and left our old condeser outside.

Well, today was a hot one and the a/c has been running a lot.

I noticed about an hour ago that we were not getting cold air.

The fan is just recirculating the air in the house. I checked the outside unit and I can see that the fan motor is running but the air doesn't feel hot coming out.

Does it sound like we have a freon leak?

Anything else I can check before calling a pro?

Thanks,

Drew

If you put your hand on the larger outside tube that is attached to the condenser, it would be cold if the outdoor unit compressor was running and the charge was correct. There is litle to do other than to call the tech.

I turned the whole system off for a couple of hours and turned it back on about an hour ago because we were starting to melt and it started working again. We are now back down to 75 degrees.

I wonder if the evap coils could have gotten froze up?

I'm not sure if I mentioned this before but we have a two story house (1400 sq ft) and only this one a/c system to do the job. Needless to say, the upstairs is always warmer than the downstairs.

In an effort to equalize the air flow, I closed off two vents downstairs and it did seem to make a difference. However, I wonder if this is bad for the system? Could this cause the coils to freeze up?

Any other idea why it would just start working again?

Thanks,

Drew

Drew,

Lack of air flow can cause the coil to freeze up. So I take it the furnace/air handler w/ the A/C is just cooling the upstairs area along with a couple of vents for down stairs?

For the A/C unit how many vents does it have? If it have say 5 vents, and you close off 2, for sure you will have some problem.. Also how many BTU/Ton is it?

I think it's a 3 ton unit for a 1400 sq foot house. This one unit serves the whole house.

There are 4 vents upstairs and 4 vents downstairs.

The vents downstairs have the most airflow, however.

It would be nice if there was a way to divert more air upstairs without closing off the downstairs vents.

Also, we have this return air duct in the upstairs hallway which doesn't do a thing as far as I can tell. If you put a piece of tissue up to it while the a/c is running it won't even stay in place.

Drew

It would be great and solve all problems if the blower and exchangers on an air flow system had no relationship to the air that flows through it. However; it seems an unfathomable secret to the majority of posts on DIY sites that an air cooling or heating system is directly related to air flow.

Choke off the windpipe of the same posters and it is understandable that air is a definite amount that carries either heat or oxygen. The point that there is an absolute minimum amount of air to operate devices that depend on air would be very apparent.

What is not hard to understand also, is the idea that a duct installer is most likely not to install ducts that are too large. In fact, the majority of examinations show that ducts are too small because that is difficult planning and math for many - and charity is not profitable business. So choking off and moving dampers is more often a precursor to short life of the equipment.

For cruel people, it is simple, just choke off the windpipe until the results become obvious. With air systems, the results are not as apparent. A feeling of air flow over the hand, or paper moving by a return grill may not prove much. That is why AC techs have thermometers and air pressure and flow reading devices and take a year to learn how to set up air conditioners. There has to be a time to call a trained professional who is able to write down the test data and express the situation eventually.

(However; it seems an unfathomable secret to the majority of posts on DIY sites that an air cooling or heating system is directly related to air flow.)
Lmao now for the good part
(That is why AC techs have thermometers and air pressure and flow reading devices)
HOLLLLD It Harold First you say it has nothing to do with air flow , Which even i knew ya was full of crap with that.. Then techs have Flow rate Testers, what for u say it dont have anything to do with air flow . I belive its time for you to be dismissed permently , U contradict your self more times in one day than any man i have ever known

Drew,

If it just 8 vents, sure don't have enough (depends on size) vents. As for the return, if it not holding a tissue paper, is there any type of air flow going in it? If you feel nothing, I'd go up take a look! Duct may of came undone, and you are pulling hot air out of the attic.

Well, maybe so Briggs, if the moderator can figure out what a truck mechanic is doing in an air conditioning post ranting about oil nozzles.

So what is my best course of action with respect to the vents?

Keep them all fully open or can I close some of them partially?

Are there any vents that are crucial to keep fully open, such as the one closest to the blower?

Drew

You just replaced the indoor unit. Have a tech document the air flow and temperature conditions of the ductwork, equipment and outside air so you have a known starting point. The data will indicate whether you have just how much air flow to be able to carry heat in the air. When you have some definite data to show you have adequate air for the equipment to operate correctly, you can predict what will happen.

Otherwise, as of now, with no data, it is still another "How much space does a pound of feathers take up?" question. You can try this and try that with varying results. Eight runs are usual for 2 to 2-1/2 tons. Once you prove you have enough air flow for 3 tons, you can work from there.

I have yet to have a company suggest this. Nothing against the guys that installed my unit, but I doubt they are competent at doing these types of calculations.

The other "service man" that we had out was more intersted in selling us a new $5,000 a/c system than doing anything that required actual work.

Drew

Yes, that is the most prevalent attitude. There is actually no excuse for inadequate air flow. For $4 a month a company can use my estimation progarm (www.heatpro.info) which tells them the right size air conditioner and how many ducts go to each room of what size.

However, this does not sell larger units and it prevents early failure of equipment. Sales is the purpose of a business; fewer will settle for doing the right thing. Marketing managers are more likely to cover up education than really support it. The people that stick to honest repair technology are the suckers to the sales force.

Our a/c system stopped putting out cold air again today.

I was able to get the guys that installed our coil back out and they determined that evap coils were NOT freezing, but the compressor was not coming on all the time. Apparently, when the old compressor gets overheated it just shuts down.

So, to get us through for another day or two they installed a "hard start" or "kick start" on the outside unit. Looks like this big capacitor.

Anyone familiar with this technique?

They said it might not last long...

Drew

It is an old technique. Hard start kits are usually on the more expensive systems that use a more precise refrigerant metering system (TXV) that makes a higher pressure for the compressor to start against. Hard start kits last as long as original equipment that uses them.

The 'may not last long' has little meaning other than hoping to sell another unit soon rather than not let you worry. There is no reason using a hard start kit would make the unit last a shorter time, most likely longer, as the compressor would start easier and overheat less (as long as there is a proper charge of refrigerant to cool the compressor as it runs.)

Cool...maybe we will make it through the summer after all.

Is this a typical situation with an old compressor requiring the hard start kit?
What exactly is wrong with the compressor that it won't come on without the extra "kick"?

BTW, do you think I'm ready to start my own a/c repair service now?

Drew

No, a compressor tends to start becoming easier to start because the clearances become wider due to wear. The hard start kit was probably a misdiagnosis, with the superheat adjustment needing fine tuning and non-condensibles needing removal.

No, you should be getting the clue that you haven't the foggiest and it is time to start taking refrigeration and HVAC courses before you start doing anything to AC.

Damn, and I thought the hard start kit was the cure all of the a/c biz.

I doubt I'll take any courses, but this a/c stuff is pretty fascination what with the physics and all.

I think I'll stick to writing software, although I would probably make more with the Texas a/c service.

Drew

A day in the Texas sun fixing non-working AC would cure the itch. As a fellow progammer, stick with the air conditioned coomputer office.

Forgot to mention this, but I had the service tech take a look at my upstairs return vent that wasn't doing anything and turns out it had been drywalled in!

He cut a hole in the drywall downstairs where it was supposed to meet with the downstairs return and viola it's sucking some air. It's not pulling in as much as the downstairs return, but at least it's doing something now.

I suspect it's been this way since the house was built 20 years ago!

Drew

Superheat adjustment is done by a certified tech using the service gauges and thermometers at the outdoor unit suction service port and more infrequently at the indoor coil. The step-by-step procedure is a key part of refrigeration/AC vocational courses in concert with diagrams and theory. You will often see posters taking the name 'superheat' once they catch on to the techie meaning and 'cool' fundamental concept that is involved in the fine tuning of a system. Relatively fewer installers get to that point; thus there is some well-earned pride in getting that far.