Need HVAC help

Turned on the central air yesterday and it seemed to run awfully long just to cool the house from 81 to 76. Like around 6 hours!
So first thing this morning I pulled the top and vacumned, blew, and hosed out the cooling fins on the compressor.
Turned it back on. I have the thermostat set at 76 with a 2 degree differential so it kicks on at 78. Is that too much of a difference? It came on at 78 around 10:30 this morning and it’s now 1:10 and hasn’t shut off yet. Still at 77. There are two lines coming into the house. One is about 1/2 to 5/8 diameter, wrapped in pipe insulation, and the other is about 3/8 diameter and feels luke warm to the touch. I know it could be low on refridgerant, but this unit is only about 5 or 6 years old.
Going to call the repairman tuesday, but just wondering if any of you might have some idea of what might be wrong.
Have never had a problem with it in the 3 summers we’ve lived here.

I assume you changed the filter too? Ever had your vents cleaned recently? I don’t know much about settings, though I really doubt mine is set to 2 degrees. Make sure the a/c unit itself has good flow though the fins. Make sure you vents are adjusted, my thermo stat is downstairs, so basically I only have vents to the up staris open, like wise if you have a basement make sure the vent are closed and the air returns aren’t blocked.

And yeah you could just be low on freon.

make sure the coil on the condensor unit is clean, (your outside coil) also make sure the fan starts when the compressor starts outside that takes the heat off the refrigerant, the two lines you are talking about going into your house one is the discharge line and one is the suction, the smaller one is your discharge and that should be warm or hot when the compressor is on and the bigger line is your suction line and that should be cool or cold when the unit is running, the only way it could be low on refrigerent would be that you have a leak in the system somewhere, the service guy will be able to tell you that with a leak detector. your A-coil could maybe be really dirty also, that is inside your house on the furnace itself, thats the part that gets cold and air goes through that to cool your house, hope that helps you out

You need a charge, I have to do mine every year because of a small leak I am to lazy to fix. A good repair man should know how to put in the right amount.

feel the suction line, if that is cold or sweating, chances are you dont need anymore refrigerant, should at least be cool to the touch

Ok, I’ll try to cover everything you guys mentioned.
The fan turns when the compressor kicks on. Got it.
I cleaned thoroughly the cooling fins on the compressor, Light shines through very well. Got it.
The suction line is cold and sweating and the discharge line is warm, but not hot. Got it.
Vents and return air are not blocked and ducts get cleaned every year. Easy to get to. Got it.
Now to the A coil. Have never seen one so I’ll have to do some investigation.
Thanks very much fellas,
herb

you have to take the plenum apart on top of the furnace to get to the a-coil, that could be dirty and restricting the air =flow, let me know what the service guy says

I sure will and thanks again.

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Turned on the central air yesterday and it seemed to run awfully long just to cool the house from 81 to 76. Like around 6 hours!

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It takes longer to cool a home than it does to heat it. So many customers will call and say that it takes so long. When you turn it on for the first time the humidity level is high and before the temperature drops the evaporator has more moisture on it and the temperature will take longer to fall. If the filter is clean, no cottonwood on the condenser, and the suction line is sweating, you are probably fine. If the coil inside was plugged, the suction line would freeze instead of sweat. If the refrigirant level was really low the suction line would also freeze.

Keep in mind to close the shades, this will really help your greenhouse effect. If it gets cool at night, don’t open the windows, you are just letting in humid air and the unit will have to work longer to remove the humidity. Setback only a few degrees when not home, or don’t setback at all.

You will probably have a tough time getting to the a-coil, most of those units don’t have access to them. If you can, check the temperature of the air before the a-coil and after it. That difference should be 15-20 degrees. You may be able to check it in the cold air return, and sometimes there is a vent after the plenum. If there is not a big temperature differential, then you may need refrigerant.

Sounds like it is working fine Herb. Residental A/C’s need to remove the humidity in the home first before it starts to cool. Took my house 8 hours to remove the humidity and cool yesterday after getting home from the lake. This is a good reason to keep your a/c running when your at work during the day..

I wouldn’t recommend taking your plenum apart to clean your a-coil. Let a duct cleaner do that. If you put a hole in your coil, its time for a new one..

Derek,
humidity was under control the first day of use. But the unit still runs continuously today. And now I only have a 1 degree differential in the thermostat setting. In other words it takes forever to cool the house that one degree. No reply yet from the repairman.
What I;m afraid of now is when he does get here the outside temps will have cooled down enough later this week that the unit won’t show the same problem as it does when it’s hotter outside.
Frustrating indeed.

How do know the humidity was under control? Did you measure it with a Sling Psychrometer? It will still continue to run on very hot days. Like mentioned above, if your suction line is cool and sweating, your ok. I could cancel your service call and save yourself the $$$. Your getting all you can out of that unit. If you insist on having the guy still come out, tell him to check the pressures and charge the system using superheat.

The only other issue you may have is with the anticipator in the t-stat if its a T-87 style stat..

Never heard of that ‘sling’ thing. The only guage I have is currently reading in the 56 to 57% range. I’ll have to try to come up with the paper work for the t stat. New last fall.

Then its probably not a T-87 if it was new last year.

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If you insist on having the guy still come out, tell him to check the pressures and charge the system using superheat.

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Or check subcooling if it has a TXV.

If you haven’t heard back from the company you called, call someone else. We are busy with this hot weather, but you always call the customer back to set up a time to meet. Even if the temps drop this week, you will still be able to tell if there is a problem.

Herb,

Have you measured the temp of the air coming out of the diffusors?

I would go around to the registers and check air flow, also you might want to close the diffusors that dont require cooling, basement, closets redirect air to where it needed.

The lines going to the condensing unit, the large line should be sweating and cool 45 to 60d approx. when the house is down to temp, the small line the liquid line should be warm to the touch. With the unit running

How old is the system? The “A” coil could be pluged or dirty.

Also is there water coming out of the condensate drain?

The unit is about 5 years old. We’ve lived here for 3 years. Everything is the same as in the past 3 years as far as vents closed and what not.
I notice there seems to NOT be the normal amount of air coming from the vents as in the past. That might indicate a plugged A coil right?
Yes, water is coming down the condensate drain.
Repairman is stopping by today.
Will let you know what he says.

Needed a shot of refridgerant. Made quite a difference.
I’ll also be adding to the cold air return to get more flow in the next day or two.
I’ll find out if all this fixes it when it warms up again.
Thanks again for all the suggetions you provided.

Did they fix the leak?

Since we have some expertise to tap, I’ve got another question:

Mine runs extensively during the hot days of summer, in fact in late July and throughout August, it seems like it runs nonstop. I’ve wondered whether the unit itself is a little undersized for my house, and have often been told that when it comes to A/C units, the bigger the better, since the larger units run more efficiently.

Is this all just a load of bunk, or is there a reality in there somewhere? Any idea what the savings would be? The other thing that could prevent me from changing it would be the finished basement between the outside unit and the furnace, would they have to change any of the interconnect?

Oh, and by the way, is it more efficient if you run the fan full-time?

Bigger isn’t really better, there is kind of a fine line between the 2, you want the unit itself to run long enough to take the humidity out of the air, if your unit is too big, it will run for a much shorter time and not take the humidity out ( and not feel as cool because of it), I’m pretty sure they have some good formulas out there for figuring out exactly what you need. Efficiency wise I kind of doubt it much more efficient to run the fan nonstop, but in my case it’s certainly more comfortable in my house. I’ve been told those fans do suck a decent amount of juice. Now there maybe more of an efficency benefit if there was an additional heating or cooling source, like a really cool basement for summer and cooling, or in winter if you have a lot of windows, to take in a lot of sunlight and warmth, I know I get a lot of free heat from my windows in winter.

Yeah I do not work as a HVAC person by any means, I do work for a utlilty and I’m cheap, and these are some observations I’ve made over the last couple years, with a bit of help talking to a HVAC trained co-worker of mine. I also had my a/c installed when I moved into my house, so I did a bunch of research back then.

G- Nick is correct. However if you have made any additions to the house after the a/c was installed, that can sometimes make a difference. I believe if I remember correctly the formula is 1 Ton of cooling per 900 sqft?

Having a coil to large will cause the t-stat to satisfy too quickly leaving the house damp and cool.

Too small, the case is the unit will run continuous. But there are probably 30 reasons why it will continuously run. Most of the time on very hot days, its normal for them to run non-stop until the sun goes down..

Thanks guys, I’m hoping that finishing the basement last year will have a positive effect on the A/C this summer. Last year it was open concrete, no walls, no insulation, and lots of windows & a walkout slider door. I got it insulated just in time last year for the summer to be completely over (September), but it did help greatly with winter heating bills.

Given the amount of insulation I did, you’d think I’d merit some sort of award or something… but I’ll settle for lower utility bills (happily).

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Bigger isn’t really better, there is kind of a fine line between the 2, you want the unit itself to run long enough to take the humidity out of the air, if your unit is too big, it will run for a much shorter time and not take the humidity out ( and not feel as cool because of it), I’m pretty sure they have some good formulas out there for figuring out exactly what you need. Efficiency wise I kind of doubt it much more efficient to run the fan nonstop, but in my case it’s certainly more comfortable in my house. I’ve been told those fans do suck a decent amount of juice. Now there maybe more of an efficency benefit if there was an additional heating or cooling source, like a really cool basement for summer and cooling, or in winter if you have a lot of windows, to take in a lot of sunlight and warmth, I know I get a lot of free heat from my windows in winter.

Yeah I do not work as a HVAC person by any means, I do work for a utlilty and I’m cheap, and these are some observations I’ve made over the last couple years, with a bit of help talking to a HVAC trained co-worker of mine. I also had my a/c installed when I moved into my house, so I did a bunch of research back then.

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I hope you did not get any advice from Bruce S.

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I hope you did not get any advice from Bruce S.

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Both you and I know he subscribes to the bigger is better theory in everything in life.

Oh, A guy that fixes everything with a BFH?

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Oh, A guy that fixes everything with a BFH?

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No not a bigger hammer, more money