Home A/C Questions...

[Gary Allan]

No. If it cannot be reached it should never shut off. I'm not familiar with your system ...but if there is no exchange going on ...that is, you're just recycling the same temp air ...then it's not working right in anyone's book. The duty cycle of the compressor may be different then the cycling of the fan ..but if you aren't reaching your setpoint ..the compressor, even if it is cycling due to reaching min evap temp, should never stop cycling.

That is, it doesn't "give up" and go home.

While it's "not working" ...go outside and observe compressor activity.

 

[mechtech]

Your system may be oversized for your size house, and is therefore cycling wrong.
This should be able to be adjusted, though.
Sometimes the older, simpler systems had advantages.

 

[Al]

Make sure all of your returns are open. Actually having returns very close to the floor is indicative of a poorly designed system. Returns for A/C should be as high as possible and returns for heating should be lower. Top of the line systems will have high and low returns (High for cooling and low for heating). Typically they compromise and put returns mid-level. If you have low and high returns on the same level..the lower ones should be closed and the uppers open. Having lowers open will short circuit the system and in combination with over capacioty could ice you up unless you have a low pressure shutdown.

What is your square footage and how many tons (or amps) are you running. If all else fails. Have the rotational speed of your indoor blower checked. That is a problem even the pros miss.

If changing the filter doesn't work. Either call the AC man or if you are ambitious check the temperature parameters like I suggested- they will give you the best bang for the buck. Get back to us..one of us will be able to interpret the info. I'm not an a/c technician and I'm sure others here can provide better suggestions. But these temps will allow us to figure out what's happening or at least narrow down the problem.

When you check the filter see if you can see the coils-are they iced or very dirty. If you have a clamp-on ammeter you could check the voltage at the outdoor unit.

 

[JavaMan]

If your not happy with it performance I would call the company back and tell them your not satisfied that it is working correctly. Have them check it out. If your not satisfied with their answer call someone highly recommended to give you their opinion or solution to the problem. I've done this before. It's just too much money to be laid out (at least for me) to have the unit running inefficiently or performing at a level that will increase repair and maintenance costs beyond labor/parts warranty. You said you bought "overkill"; I'm pretty sure I've been told by people in the business that this is not a good idea for efficiency reasons (if this is not correct I would like to know.).

 

[ScottB]

Al, we had to make some concessions because we want out 100-year old house to maintain it's original appearance, etc.
The return is a single unit, and indeed as low as it gets - in the floor in the rear of the house.
We have no vents whatsoever on the ceilings or walls - all are the original floor vents - plus a couple of new ones - in changed rooms. There was never AC before, only heat.

I don't have the gear to do the measurements, so I suppose I'll have to opt for bringing them back out to double-check things.
It's so **** hard to get someone to do everything right. I'm no AC guy, and we interviewed a number of places before getting these guys. I think they did well - maybe it's just some adjustments?

I truly appreciate the help from all of you guys. This has been a learning experience for me and a very useful thread...

to all of you and a virtual beer on me.

Scott

 

[Al]

The return is on the first floor? I am assuming that you have at least 2 levels? This is honestly a bad situation. I truly understand your wanting to do what you did. But if you have one low return on the first floor when you have an upper floor. That is an almost unworkable/inefficient situation. You must locate an upper return on the second floow..seriously.

The other thing is that with only a common return, you need to keep bedroom doors open and/or have the door cutoff at the bottom to provied say 1+ inch so the air can go somewhere.
Also you can close all of the supplies close to the return which short circuit this path. But then you could run into low air flow and that will give low pressures/temperatures/freezing coil.

I am beginning to think you may need someone who knows what he/she is doing.

But again I want to emphasize that my understanding of what you have may not be accurate. Sop don't panic. But at the very least move forward.

You first priority though is to make sure you don't have ice on the indoor coil. If you do running the fan full time will/can melt it.

Oh and make sure the line taking away the condensate from the indoor unit has a place to go.

 

[ScottB]

I got some new 3M Filtrete filters last night - they're the best that were available at the OSH store...
When I set the temp to be the same as the room temp, the fan will only run a minute or two then stop, so I think that's normal and what you guys are saying should happen.
I will see today if the better filters will help - maybe since my return is on the floor, it just picks up more dirt faster?

Thanks again for all your help - I'm shocked we have managed to NOT turn this into a political thread on the various coolant types

Scott

 

[Brett Miller]

Scott, those 3M filters can be too restrictive. Another issue that comes to mind could be the ductwork is too restrictive. Did your contractor run any calculations to verify the airflow of the ductwork?

 

[TooManyWheels]

It is normal for the blower to continue to run for 30-60 seconds after the compressor stops. This pulls the remainder of the cool out of the system into your house, and most importantly, converts the liquid refrigerant in the evaporator (the inside unit) into gas so that it doesn't "slug" the compressor when it arrives back.

If it runs longer than that then labman is correct, the blower relay is most likely stuck.

 

[ScottB]

The second level is mostly unused, sans one, small room.
When my daughter moves out, we're finishing that and will add ducts there - maybe I can have the return put there at that point.

My office-mate had what sounded like a similar issue with his 14-year old AC setup and the guys replaced the thermostat three times with no results. Then someone new came out this weekend and ended up disabling the "delay" on the outside unit and using the one on the thermostat - which they had disabled to prevent double-delays in the system kicking on. Now, he says it works - does that make sense? Is that something that could be my issue?
Could my controller/thermostat be bad?

The vented and put in proper drains, so it's draining properly.
The big problem is for me that in order to look at the actual heat/AC units, I have to go under the house, which is a PITA.

It seems to me that if I have my system set to 74° and whether or not it can drop my house that low due to poor insulation, etc., it should still be "trying" to cool and be flowing cold air - is that correct?

I thought this would be so simple and so enjoyable, and it's turning into a very expensive nightmare...

Thanks again for the help.

Scott

 

[Razl]

quote:

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Originally posted by ScottB:
It seems to me that if I have my system set to 74° and whether or not it can drop my house that low due to poor insulation, etc., it should still be "trying" to cool and be flowing cold air - is that correct?

Scott

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Like Gary said, "it doesn't 'give up' and go home."

 

[ScottB]

I called the guy and he was extremely nice/understanding. Being in the computer-support business, I didn't want to call him without details and giving it time for me to understand the setup, etc.
I wanted to digest everything here first, then call with ideas.

He's sending over his guy later today or early tomorrow. I'm not sure what it is, but I am pretty sure it's not behaving normally.

WIll post back - any other ideas/thoughts are still welcome

Scott

 

[Al]

What is the air temp coming out of the closest supply to the air handler. That should be the coldest. Should be in the low 50's or around 25 degrees colder than your average house temp.

 

[ScottB]

Just got a callback - the compressor is bad.
Since it really didn't fire properly since day-one (maybe day 8), I assume it was just a bad unit?
When they had finished, it was night and kinda cool out, so it did work when they tested...the next week was also relatively cool, so this last week was really the first one to see how it did.

Is this something that's "normal"?

Scott

 

[ScottB]

Wrong again.
I'm getting info through my wife which is like the game we played in school where someone says a word and passes it down through the whole class.
In other words, I'm not getting anything of use this way.

Will come back.

 

[Al]

Compressor crapping out is "unusual" but like anything else if it runs for the first 90 days it could be good to go for a while. The thing that knocks them out is generally power faults or bad electronics. The ultra high efficiency ones are (or at least ust be) very susceptable to this. That's why some installers don't recommend the ultra high efficiency.

 

[ScottB]

Al,

The compressor was fine. Someone put in filters (in the whole system) that were too restrictive. I added to that when I put in the Filtrete units. The others in the system were apparently the issue.
They put in those really cheezy old-school units which were what it needed.
Also, since we had the extra Hepa-system put in, the outgoing air is more restricted, and the whole setup didn't flow well enough.

My wife and son called stating that the house is now "freezing"
She also said he made an adjustment on the outside unit (with the fan) and now it's kicking on as soon as the temp hits the setpoint.

So, thanks to all - I think it's fixed (for now)
I've learned quite a bit, and I am now going to try and find out more to avoid feeling like such a nOOb down the road.

Scott

 

[XS650]

quote:

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Originally posted by Al:
What is the air temp coming out of the closest supply to the air handler. That should be the coldest. Should be in the low 50's or around 25 degrees colder than your average house temp.

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That varies according to how the system was designed. Mine is supposed to be 20F to 22F temp drop from inlet to closest outlet and if it gets to 25 it means somethings wrong, most likely restricted airflow.

The weapons shop I worked in in the AF in Turkey had an AC system that would drop the air 50 degrees on a pass through.

A bit oversized.

It wasn't done for us peones though, our systems could only be opened in a controlled climate and that part of Turkey in the summer was like living in an armpit.

 

[Al]

quote:

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Originally posted by XS650:
[QB] Mine is supposed to be 20F to 22F temp drop from inlet to closest outlet and if it gets to 25 it means somethings wrong, most likely restricted airflow. [QB]

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Yea 25 is ball ball park-its usually pretty close. Especially if you can add anogther parameter or two like the room temp, And that's why you would want to get a delta Temp across the outdoor unit. That way you know some idea of the load. And if you have a low supply temp and the room temps are high, that pretty much tells you you don't have enough flow.

Needless to say-a set of gauges rules. I was just trying to get some idea of what's going on. As mentioned..most times the filter is to blame.

 

[XS650]

quote:

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Originally posted by Al:
Yea 25 is ball ball park-its usually pretty close. Especially if you can add anogther parameter or two like the room temp, And that's why you would want to get a delta Temp across the outdoor unit.

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I wouldn't be suprised if a well designed system varies according to climate. When it's hot here, like the 108F we had today, the outdoor humidity typically is under 20% (12% today) so squeezing water out of the air isn't as high a priority as it is in a humid climate. I think my system is oversized because it runs less than 50% of the time on a 105F+ day, but it's comfortable.