Central AC issues and questions

[JoeWras]

Gray Beard I had the same issue as the coils were an ice ball. I took of the cover and used fans to melt the ice. After 4 hours turned back on and temporary remove the filter in before the AC unit. (Before I get scolded by others, this was only temporary) this allowed the unit to keep going and not freeze up again on low Freon. I had to run like this for 7 days as that was as soon as any AC company would arrive. it keeps us comfortable if you need to buy some extra time.

On a side note read where they are going to discontinue 410 freon in the near future...Since the Tech recharged mine going well and hopefully wait a few years and buy a unit that will use the R32.

I think running in a melt-run-pause-melt-run scenario as emergency cooling is fine in the short term. Gives Graybeard time to carefully move forward. It just isn't tenable long term.

I should talk. I'm using a 30 year old dehumidifier that is low on coolant and freezes the coils. It is in a tool shed. I run it one hour per day on a timer. Has worked great to keep rust off my tools for about 10 years now.

 

[ncbill]

I wonder if the lines have been tested? I'm not familiar with the intricacies of this, but a lineset replacement will need to be done with a new system. Just a random thought.

I suppose a competent, honest technician could determine where the leak is. Maybe I'm wrong.

That's a scare tactic..usually from a tech who gets paid the most if you replace your entire HVAC ...."replace the system now or your compressor will blow & clog the lines" when in reality most 'failures' are from refrigerant leaks.

There was no problem pulling vacuum on my existing lines (running in the slab) & switching out from R-22 to R-410A for the replacement heat pump plus matching A-coil I had installed back in 2009.

Keep in mind starting next year R-32/R-454b will be the new refrigerants used by HVAC manufacturers here in the USA, so plan on R-410A going the way of R-22 soon enough...another reason I would not buy a new system this year if at all possible.

R-44b is the best "drop-in" replacement for R-22...had I an old R-22 system that was repairable (anything short of compressor failure) I'd go that route.

https://www.replacementforr22.com/rs-44b-faq/

Might have to hire a commercial-oriented HVAC company used to doing refrigerant replacements, though, since I bet a residential HVAC company wouldn't be willing to bother.

 

[38Chevy454]

That's a scare tactic..usually from a tech who gets paid the most if you replace your entire HVAC ...."replace the system now or your compressor will blow & clog the lines" when in reality most 'failures' are from refrigerant leaks.

There was no problem pulling vacuum on my existing lines (running in the slab) & switching out from R-22 to R-410A for the replacement heat pump plus matching A-coil I had installed back in 2009.

Keep in mind starting next year R-32/R-454b will be the new refrigerants used by HVAC manufacturers here in the USA, so plan on R-410A going the way of R-22 soon enough...another reason I would not buy a new system this year if at all possible.

R-44b is the best "drop-in" replacement for R-22...had I an old R-22 system that was repairable (anything short of compressor failure) I'd go that route.

https://www.replacementforr22.com/rs-44b-faq/

Might have to hire a commercial-oriented HVAC company used to doing refrigerant replacements, though, since I bet a residential HVAC company wouldn't be willing to bother.

Actually the P-T (Pressure-Temperature) curve for propane (R-290) is fairly close to R-22. It is also compatible with the mineral oil in R-22 systems. It can work as alternative for R-22. However, and this is a big however, propane is flammable and requires a leak-free system, and is illegal for home HVAC systems due to the flammability issue. Since R-22 is no longer manufactured, there are blended refrigerants that can mimic the R-22 P-T curve and are considered non-flammable.
^^^^^^Above provided for discussion purposes, not saying to use propane in place of R-22 in your home system.

 

[kgtest]

I read this quickly so maybe I missed it….low airflow is also a result of dirty/ plugged filters.

I turned my AC on this year and had terrible air flow. My A/C has screens like window screens and a filter...a really BIG filter. I blew out the screens and replaced the filter and had much better airflow.

My AC is 32 years old and needs replacing. Someone sealed a leak and refilled it 8 years ago. It is still cold, but it seems to run a lot (then again it has been hotter then he!! this summer.) I live in a 2 story where the temps in the walkout basement are MUCH cooler than the temps in the HOT second story that is exposed to some direct sunlight and also master in second story sits partially over our 3 car partially insulated garage.

I would say the temps from the basement to the second story vary from at least 15 degrees sometimes maybe more but I never actually checked.

I want to get a solid AC that can cool the upstairs too, but I feel like my 'too hot upstairs' problem would only be partially resolved with a more efficient, better functioning, stronger and larger a/c unit. Supplemental upstairs fans are in use as well, but I read putting a fan system in the attic could help, along with additional insulation and maybe an extra thermostat upstairs (which means the basement and middle levels would just run that much cooler). We spend most of our days in the main middle level, so it's fine until we go to bed at night (especially if we park our recently driven cars with warm engines in the garage stalls before bed).

I noticed a huge difference parking the hot engines outside on hot nights and leaving the garage doors closed as long as possible with those engines outside.

Having 2 a/c units, with separate HVAC for an upstairs zone seems like it would probably be a really good solution, supplemented by some efficiency improvements like attic fans, and better insulation.

My A/C makes a gnarly grinding noise sometimes when it shuts off as well. But it still pushes cold air when the filters are cleaned so maybe not a huge deal.

 

[Piper20]

Kgtest

Partially close some vents downstairs to push more cold upstairs. That may help.

 

[Graybeard]

Graybeard, at 23 years, it is also time to replace the air handler. Why? I'll give you a few reasons:

1) The control board has age and attic heat on it. Ditto the blower.
2) There's a good chance some condensate water has splashed and is causing some corrosion in the box. There might even be a little mold. But don't panic, I'm just saying it is a wet environment with a lot of years on it.
3) The coil has seen a lot of life. The coil could be where your leak is. This is a very abusive environment. The coil goes through temperature swings (expansion and contraction) and then is doused in condensation (water), cycle after cycle. Even the best metals and workmanship start to suffer after so many expansion cycles.

If it were 10 years, I'd have a different answer.

Thanks. I didn't know there was anything in it, I thought it just directed cold air to the ceiling vents. Guess it'll be all new, pay once cry once.

 

[Graybeard]

Gray Beard I had the same issue as the coils were an ice ball. I took of the cover and used fans to melt the ice. After 4 hours turned back on and temporary remove the filter before the AC unit. (Before I get scolded by others, this was only temporary) this allowed the unit to keep going and not freeze up again on low Freon. I had to run like this for 7 days was as soon as any AC company would arrive. A temporary fix that kept us comfortable if you need to buy some extra time.

On a side note read where they are going to discontinue 410 freon in the near future...Since the Tech recharged mine going well and hopefully wait a few years and buy a unit that will use the R32.

I'm not sure where the ice is. I have the unit outside and it is hot out there. The air handler is in the attic and it's probably 50% hotter than outside.

Going up in the attic is a PITA, pull down stairs, I only do it 2 times a year, after the cooling season is over and before the cooling season starts. I have to do this to disconnect the 2 air tubes that send air to the open floor plan of the living room/kitchen and stuffing insulation into the metal housing the tubes connect to. My woodstove is in that area and the ceiling is 12' high with 2 ceiling fans, I can't seal those 2 vents from the kitchen/living room so I do it in the attic. The temperature up on the ceiling is probably 110-120° in Winter as I heat the house with the woodstove. The 2 vents in that room allow hot air into the air tubes which cause condensation. One year the tubes were full of water! I seal off all the other vents in other rooms to stop heat from going up into them also but that can be done inside the house not in the attic. Closing the vents still allows warm air to get into them. I found water dripping out of the bedroom ceiling vent on to my cherry dresser! So I have to "winterize" the system by blocking off all avenues of hot/warm air getting into the tubes in the attic. I have no idea how other people deal with this, most don't heat with a woodstove exclusively.

 

[Graybeard]

Kgtest

Partially close some vents downstairs to push more cold upstairs. That may help.

I partially close the vents in all the rooms except for the kitchen/living room which is at the south end of the house and has a ton of glass on the walls. My theory is by limiting the volume of air flow in the other rooms where it is cooler due to being away from the south end, the air handler will push more cool/cold air into the kitchen/living room. The temperature difference at the north end vs the south is at least 5° due to all the glass. I have shades and blinds and if the AC is running they stay closed all day.

 

[latexman]

It's been recharged with R-22. When I Googled my unit, Trane High Efficiency XE 1000, it said 5-7 possibly 8.1 but I'm not sure. I just checked the paperwork, I may have said this is a 1 1/2 ton unit that is INCORRECT - it is a 2 1/2 ton unit..

Here’s what my research says, “Trane XE1000 is a discontinued 10 SEER split system heat pump with an HSPF of up to 8.10. Heating Seasonal Performance Factor (HSPF) is a heating efficiency rating for heat pumps”, it’s not a cooling efficiency.

Currently, Trane air conditioners range from 14.5 SEER up to 22 SEER. The higher the SEER, the lower your cooling cost, and the higher your investment. Btw, the gubmint sets the minimum SEER at 13 now. If you buy an 18 SEER unit, you’ll save 44% (1-10/18) on your cooling costs.

Try to get a replacement unit that uses R32 refrigerant. R-410A is scheduled for elimination from all new systems in 2023. I think you might have a chance to get ahead of this.

 

[Graybeard]

Here’s what my research says, “Trane XE1000 is a discontinued 10 SEER split system heat pump with an HSPF of up to 8.10. Heating Seasonal Performance Factor (HSPF) is a heating efficiency rating for heat pumps”, it’s not a cooling efficiency.

Currently, Trane air conditioners range from 14.5 SEER up to 22 SEER. The higher the SEER, the lower your cooling cost, and the higher your investment. Btw, the gubmint sets the minimum SEER at 13 now. If you buy an 18 SEER unit, you’ll save 44% (1-10/18) on your cooling costs.

Try to get a replacement unit that uses R32 refrigerant. R-410A is scheduled for elimination from all new systems in 2023. I think you might have a chance to get ahead of this.

Thanks, hopefully they won't be trying to unload the R-410A units and say no R32 are available yet! Things are working nicely, if I could use this until next Spring I'd be happy.

 

[Marita40]

This topic is topical for me. Just got a quote for $12,900 to replace my 20 year old Trane ac system with a new one— Trane 16 SEER. It is not running well and needs replacement. Amazing how expensive things are these days. But nothing runs like a Trane (I guess…)

 

[kgtest]

Kgtest

Partially close some vents downstairs to push more cold upstairs. That may help.

Good tip!

 

[kgtest]

This topic is topical for me. Just got a quote for $12,900 to replace my 20 year old Trane ac system with a new one— Trane 16 SEER. It is not running well and needs replacement. Amazing how expensive things are these days. But nothing runs like a Trane (I guess…)

My neighbor just got quoted $6,300 for a new a/c and furnace. I think she gets some rebate cash from the electric company as well. I doubt the models are trane though.

Is Goodman any good in terms of a brand?

 

[latexman]

Folks, a quote is almost useless without a description (A/C, heat pump, A/C+heat combo), SEER, tonnage, and HSPF, if applicable.

 

[kgtest]

Folks, a quote is almost useless without a description (A/C, heat pump, A/C+heat combo), SEER, tonnage, and HSPF, if applicable.

Good point. I'll have to ask my neighbors for the specs...something tells me they won't understand all of that, but maybe.

 

[latexman]

Good point. I'll have to ask my neighbors for the specs...something tells me they won't understand all of that, but maybe.

Dad was a HVAC guy and I was raised in the industry, so that’s why I’m so . . . techie, anal, etc.

 

[ERD50]

.... How does low freon cause frosting on the evaporator? It is counter-intuitive, because low freon should not cause increased cooling. No, the cooling is not increased overall, but rather it causes overcooling of one spot of the evaporator, while the rest of the evaporator is not cooled.

When freon pressure is low, but not too low that the system provides no cooling at all, the liquid freon evaporates immediately at the point where it enters the evaporator. This spot gets awfully cold and causes local frosting, but the rest of the evaporator is not cold. Overall cooling capacity is reduced.

If the freon pressure is higher, the liquid freon takes longer to evaporate, and gets to flow further down the evaporator while still in liquid form. This provides a more even cooling of the entire evaporator.

In short, this AC needs more freon again due to the ongoing leak.

I should have elaborated further on the frosting process of the evaporator.

The frosting first forms on the corner of the evaporator, where the liquid freon enters it. Once that corner is iced over, the airflow is blocked there. Liquid freon needs the warmth to evaporate, so it now stays in liquid form and flows further down the evaporator and flash-boils there. The frosting slowly spreads across the entire evaporator, and the airflow is eventually entirely choked off.
....

Thanks for that explanation! It always did seem counterintuitive to me that low refrigerant resulted in icing - isn't the very cold what you want? Why not run 'low' all the time, and use more air flow or a larger coil to get all the cold out?

Of course, I figured there was a good explanation, not an HVAC industry conspiracy, but could never find it when I tried searching. What you posted makes it clear to me - a localized cold spot rather than even across the entire coil, with the ice building as it goes.

-ERD50

 

[38Chevy454]

I'm not sure where the ice is. I have the unit outside and it is hot out there. The air handler is in the attic and it's probably 50% hotter than outside.

The ice is on the evaporator, which is in your attic. Evaporator is located inside the air handler as you call it. Outside is the compressor and condenser, it has hot compressed liquid/vapor from the compressor going into the condenser, which removes heat, and helps convert to liquid. All at high pressure like 200-300 psi range. In the evaporator the liquid expands back to gas at lower pressure like 30 psi range. This makes evaporator cold which the house fan blows over to cool the air. That's the basic A/C function.

 

[NW-Bound]

For R410a systems, the high-pressure side is higher than 400 psi. The low-pressure side is 140 psi.

I am afraid to measure the high side (what if the hose or the gauge bursts) and have only hooked a gauge to the low side. There's not a need to measure the high side anyway.

 

[travelover]

I read this quickly so maybe I missed it….low airflow is also a result of dirty/ plugged filters.

This is a really important point. The evaporator is trying to freeze and the air blowing over it is trying to warm it. So, if you have a dirty filter or a dirty A coil there is not enough air flow to keep the coil from freezing. You may well also have a low refrigerant problem, but before I spent big bucks I'd make sure the filter is not obstructed and peek at the A coil in the attic and see if it is all clogged up with pet hair or dust.

 

[JoeWras]

Meta-observation: people are really passionate about HVAC issues on this forum and bogleheads.

OK, back to our regularly scheduled thread...

 

[Graybeard]

The ice is on the evaporator, which is in your attic. Evaporator is located inside the air handler as you call it. Outside is the compressor and condenser, it has hot compressed liquid/vapor from the compressor going into the condenser, which removes heat, and helps convert to liquid. All at high pressure like 200-300 psi range. In the evaporator the liquid expands back to gas at lower pressure like 30 psi range. This makes evaporator cold which the house fan blows over to cool the air. That's the basic A/C function.

Thanks, great explanation.

 

[38Chevy454]

For R410a systems, the high-pressure side is higher than 400 psi. The low-pressure side is 140 psi.

I am afraid to measure the high side (what if the hose or the gauge bursts) and have only hooked a gauge to the low side. There's not a need to measure the high side anyway.

Yes, but OP's system is R22 that operates lower pressures than R410a.

 

[ShokWaveRider]

Must be AC Shutdown season. Yesterday our 10 year old Heat pump outside unit decided it was not going to cool, of course the 10 year warranty for parts ran out last month LOL., and of course the inside of the house got hot. The Air handler thought everything was cool, (Pun Intended) and was registering no Alerts or Error codes. The condenser cooling fan was on.

Here is what I did:

1) Removed cover from the condensing unit.
2) Checked the 220v going into the Contactor - Good
3) Checked the output of the Contactor - (Not Good, No 220v to the compressor)
4) The Compressor was not hot.
5) Removed power by switching off the exterior circuit breaker.
6) Let the voltages deplete for a couple of minutes.
7) Checked voltages to make sure there was none.
8) Removed wires from the Compressor Run Capacitor and shorted it out
9) Checked Capacitance (It was Good, 29 Microfarads, it is rated at 30.)
10) Tapped the contactor with the handle of my screw driver
11) Wiggled the wires on the High and low pressure switches and tapped them also)

12) Turned it all back on and still no go.
13) Called the AC company for a service call, we have a service contract with them
14) They could not come over yesterday evening and said they would come today
15) They advised me to turn off the breaker to the condenser and keep using the Air Handler fan to circulate air.

Decided to try it again this morning and all worked fine...... Go Figure.

I am still getting the Tech over to check it out as diagnostic visits are free under my contract.

No idea why it failed. I will find out hopefully later today.

 

[Graybeard]

Must be AC Shutdown season.

I know, isn't it funny how these AC units never fail in January when it's 15° for the high of the day and you really don't need to use the AC?