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Question for the HVAC experts
Posted by: wurm
Date: August 09, 2022 10:10AM
In this heat wave, our central air conditioning has been working overtime. Lately we've noticed that when we lower the temp at bedtime, it's still not dropping the temperature inside the house to where we want it. I check the registers and they're blowing out cool-ish air. Definitely cooler than room temperature, but I've never really paid attention to whether it ever pushed out what I would call cold air. Is there a way to measure to know whether it's as it should be?

I just changed the filter (yes, it was dirty), and as I'm sitting here now at my desk, it's comfortable, and I can feel the air cycling occasionally, so the unit itself is clearly working.

I'm debating calling a local company to take advantage of their $99 AC Performance Tune-Up Special, which looks like it includes a pretty thorough going over. But part of me is always concerned that it's just an opportunity to upsell something and that they'll 'discover' a problem that might not exist.

Aside from changing the filter, anything else I can do to determine whether our unit is acting as it should? If it ain't broke, I don't want to fix it.

Thanks.
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Re: Question for the HVAC experts
Posted by: C(-)ris
Date: August 09, 2022 10:16AM
If your filter was super dirty you may need both the outdoor condenser and indoor evaporator coils cleaned. Not sure if the $99 deal includes both, but if it does go for it! If the evaporator coils aren't dirty you have the piece of mind knowing the filter is working, if they are dirty you will gain efficiency.



C(-)ris
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Edited 1 time(s). Last edit at 08/09/2022 10:17AM by C(-)ris.
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Re: Question for the HVAC experts
Posted by: wurm
Date: August 09, 2022 10:27AM
Thanks for the quick reply. Here's the coupon. Might be worth it if only for peace of mind. Maybe I'll see how we sleep tonight. The filter change may have been sufficient. smiling smiley

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Re: Question for the HVAC experts
Posted by: C(-)ris
Date: August 09, 2022 10:32AM
Quote
wurm
Thanks for the quick reply. Here's the coupon. Might be worth it if only for peace of mind. Maybe I'll see how we sleep tonight. The filter change may have been sufficient. smiling smiley


You will have to ask them if clean coils is outdoor only or both sets. It isn't specific in the coupon and the indoor coils might be an upsell.



C(-)ris
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Re: Question for the HVAC experts
Posted by: lost in space
Date: August 09, 2022 10:36AM
What we discovered in a similar situation was that the thermostat was situated in our hallway in the center of the house, and due to minimal insulation and old windows, the outer rooms were warmer than the center in summer. The problem was at its worst during extreme hot or cold weather. We ended up having to set it to a number lower than we wanted to make the bedrooms and study comfortable. In winter we had the opposite problem. Things improved greatly when we put in modern windows, especially summer heat. We still only have ceiling insulation, none in the walls.







Edited 1 time(s). Last edit at 08/09/2022 10:38AM by lost in space.
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Re: Question for the HVAC experts
Posted by: wurm
Date: August 09, 2022 10:50AM
Thanks. Right now my feet are freezing, so maybe the filter change was sufficient. wink smiley

Regarding the thermostat location, ours is also in the hallway in the middle of the house. We had new windows put in since we've been here and the Ecobee thermostat has been pretty good as far as regulating things.
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Re: Question for the HVAC experts
Posted by: gadje
Date: August 09, 2022 11:28AM
If you have Ecobee, then set it to use the remote sensor and place that sensor in your bedroom. It will ignore the temperature in the hallway and it will make sure that you are comfortable in the bedroom in the evening. Ecobee is so customizable that thermostat location is not important anymore.
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Re: Question for the HVAC experts
Posted by: wurm
Date: August 09, 2022 11:35AM
Ah, that's a good idea. Right now the remote sensor is in my studio/office, but I'll try moving it into the bedroom. Thanks.
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Re: Question for the HVAC experts
Posted by: Spiff
Date: August 09, 2022 11:50AM
Whatever way you go, get the system checked out. Would not surprise me if there is a crack in the coil and your coolant has leaked out.
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Re: Question for the HVAC experts
Posted by: macphanatic
Date: August 09, 2022 12:16PM
An air conditioner can only remove so much heat. If the difference between the outdoor and indoor temperatures are too much, setting the thermostat lower won't make a difference.

I would try spraying the condenser with a hose. Spray thru the top towards the radiator to push dirt and debris out. If you turn the breaker off or pull the disconnect, you can remove the guard over the fan to do a better job. Dirt and debris will have a negative impact on cooling efficiency.
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Re: Question for the HVAC experts
Posted by: chopper
Date: August 09, 2022 12:29PM
There's good advice here. A house baking in the sun for multiple days will struggle to stay cool. How is the insulation in your house?
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Re: Question for the HVAC experts
Posted by: Mr645
Date: August 09, 2022 12:40PM
Keep in mind the AC lowers the air temp by a certain amount. If it starts wit hotter air, you get hotter air out, cooler but still hotter than if cooler air going in
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Re: Question for the HVAC experts
Posted by: John B.
Date: August 09, 2022 01:43PM
Couple things in mind (since I'm dealing with some of this currently):

1. When I've had house inspections done, some of the inspectors have used a digital thermometer in the supply duct to determine the difference between temperatures of the air being "sent" by the HVAC unit and the temperature of the room. (So the room is 85 but the air coming from the HVAC unit is 75...something's wrong with the room/insulation if it's not cooling.)

2. The worst case, if the cooling unit isn't keeping up, and everything is clean, is that the refrigerant loop probably has a leak and it's not performing efficiently. We found this during an annual maintenance inspection on mine. Refrigerant pressures were low, system was still cooling. Put in a leak stop with UV dye and found that there are two leaks in the "A" coil (the coil inside of the furnace). Find a leak and then you might have options...looks like the leak stop held pressure for 10 days after it was applied, but my unit is still under warranty, so I'm going to have them warranty replace the coil. If not under warranty, you need to decide to monitor the leak with leak stop, replace the leaking coil, or replace the entire unit.
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Re: Question for the HVAC experts
Posted by: Grateful11
Date: August 09, 2022 02:02PM
Ours leaks and one of the best techs around here has checked it twice and can't find the leak with an electronic sniffer, it's very sensitive to freon leaks. He put 24oz. of freon in it at the beginning of the season. He put 3 lbs in it a couple years ago.



Grateful11
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Re: Question for the HVAC experts
Posted by: cbelt3
Date: August 09, 2022 02:10PM
Lots of good ideas. I'll also add that the condenser unit outside needs to be washed off a couple of times a year. More frequently if you have heavy tree activity. We have cottonwoods which fill the condenser solid with debris every year. I rinse that sucker off every week when it's tree fluff season.
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Re: Question for the HVAC experts
Posted by: wurm
Date: August 09, 2022 02:30PM
Yes indeed, lots of good ideas. Thanks. Maybe take a hose to that condenser and see what I can remove that way. I don't even see an inside condenser.

Meanwhile, I went ahead and made an appointment for next week for that "tune-up". Fingers crossed that the tech won't find something $$ to fix while he's here. Then again, we had the unit installed in April of '07 and have never had it serviced, so I guess I shouldn't be too surprised if they do find something.
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Re: Question for the HVAC experts
Posted by: cyclemax
Date: August 09, 2022 02:43PM
Measure the temperature differential between the supply air out of the registers and the return air at the return air grille(s). It should be a 14 to 20 degrees F differential. if it is not your system is not working properly. Could be low on refrigerant.
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Re: Question for the HVAC experts
Posted by: wurm
Date: August 09, 2022 03:52PM
Quote
cyclemax
Measure the temperature differential between the supply air out of the registers and the return air at the return air grille(s). It should be a 14 to 20 degrees F differential. if it is not your system is not working properly. Could be low on refrigerant.

Well, using my handy-dandy non-contact infrared thermometer, it's showing me 75 at the return and 68 at the supply, so there's that. Does refrigerant just go away or is it more like there's a leak somewhere?
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Re: Question for the HVAC experts
Posted by: JoeH
Date: August 09, 2022 04:02PM
Refrigerant does not just go away, that only happens if there is a leak somewhere.
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Re: Question for the HVAC experts
Posted by: wurm
Date: August 09, 2022 04:29PM
That's what I was afraid of. Guess we'll find out next Tuesday.
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Re: Question for the HVAC experts
Posted by: modelamac
Date: August 09, 2022 06:09PM
Quote
wurm
Quote
cyclemax
Measure the temperature differential between the supply air out of the registers and the return air at the return air grille(s). It should be a 14 to 20 degrees F differential. if it is not your system is not working properly. Could be low on refrigerant.

Well, using my handy-dandy non-contact infrared thermometer, it's showing me 75 at the return and 68 at the supply, so there's that. Does refrigerant just go away or is it more like there's a leak somewhere?

Wurm,
You could get those results if your condenser coils were dirty(air passages clogged). Make sure the Condenser(that big noisy mass outside that looks like a short cooling tower) gets cleaned during the AC house call. It needs to get rid of the heat that is removed from inside the house.

Get on Google or Youtube and learn how AC works.



Ed (modelamac)

I think I will just put an OUT OF ORDER
sticker on my head and call it a day.
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Re: Question for the HVAC experts
Posted by: wurm
Date: August 09, 2022 06:13PM
Yeah, I looked at the outside condenser earlier today. There was actually moss growing along the bottom on one side. I took a brush to it and removed some. Going to break out the hose before the guy comes next week. Yikes.
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Re: Question for the HVAC experts
Posted by: Rolando
Date: August 09, 2022 10:09PM
I've used a car wash attachment (low pressure) to soap up, wash off and rinse the outdoor coils. In the hottest part of the day, even giving them a good rinse will cool them off to exchange heat more efficiently.

Also, you can cool your house overnight when power is cheaper.
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Re: Question for the HVAC experts
Posted by: Bill in NC
Date: August 10, 2022 09:17AM
Quote
John B.
Couple things in mind (since I'm dealing with some of this currently):

1. When I've had house inspections done, some of the inspectors have used a digital thermometer in the supply duct to determine the difference between temperatures of the air being "sent" by the HVAC unit and the temperature of the room. (So the room is 85 but the air coming from the HVAC unit is 75...something's wrong with the room/insulation if it's not cooling.)

2. The worst case, if the cooling unit isn't keeping up, and everything is clean, is that the refrigerant loop probably has a leak and it's not performing efficiently. We found this during an annual maintenance inspection on mine. Refrigerant pressures were low, system was still cooling. Put in a leak stop with UV dye and found that there are two leaks in the "A" coil (the coil inside of the furnace). Find a leak and then you might have options...looks like the leak stop held pressure for 10 days after it was applied, but my unit is still under warranty, so I'm going to have them warranty replace the coil. If not under warranty, you need to decide to monitor the leak with leak stop, replace the leaking coil, or replace the entire unit.

Short of the compressor failing it's always going to be cheaper to repair than replace an entire split HVAC system.

Here it would now cost low 5 figures to replace my traditional split system heat pump w/ gas furnace backup.

Were my A-coil leaking I'd just pay for its replacement out-of-pocket.



Edited 1 time(s). Last edit at 08/10/2022 09:18AM by Bill in NC.
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Re: Question for the HVAC experts
Posted by: SteveO
Date: August 10, 2022 10:27AM
Our A/C is a 1994 unit, 2.5 tons. It is a builder grade unit but has proven to be pretty durable/reliable with near-yearly cleaning and checks. Consider as well your attic ventilation - is it good? If not, it will end up pushing heat into your home and making the system work harder/longer, stressing it esp in high temps.

We spent about $1k the past 4 months (a good portion of that was R22 old-school refrigerant) on a/c unit repairs...we are likely gonna get a new system here soon and probably go with the company that repaired it so we can recoup that money in add'l discounts off a new system (part of their deal). They are a good outfit, I've used them for about 10-15 years and I trust them.

Do make sure the fins on your outside unit are clean and not bent/damaged. Ours are somewhat damaged by storms and so not as efficient as they could be...another reason to upgrade.

Great advice and other points made above so I won't repeat them. Good luck, hope you get it worked out.
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Re: Question for the HVAC experts
Posted by: wurm
Date: August 10, 2022 03:35PM
Spent a little time out there this afternoon with a shop-vac and some of this stuff. Clearly something I should be doing every year, but I can recall doing it maybe twice in the 15 years we've had the thing. I took off the top fan unit just to get at the crap inside, but did not remove the side grates over the fins. Sprayed the stuff on from the inside, let it sit for fifteen minutes, then carefully hosed it through from the inside. If nothing else it looks cleaner. I'll be curious to see what the $99 tune-up person discovers and/or recommends on Tuesday.

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