Central AC issues and questions

[jimbee]

If you're looking for a handy DMM, I've been happy with the UNI-T UT210E. I've owned it for a few years, and used it to check out my mom's A/C compressor and fan current draw in 2020, when her HVAC tech tried to scare her into buying a new system. (There was nothing wrong with the system, and I changed out the capacitor just in case).

The meter measures AC and DC current at the clamp. You can get it for about $50 on Amazon. https://www.amazon.com/UNI-T-Digital-Handheld-Resistance-Capacitance/dp/B0188WD1NE

 

[Time2]

No, it does not autorange, and you have to manually select either 60A or 600A.

My 10-year old Craftsman AC/DC clamp meter does not have autorange for the current measurement, and offers a 40A / 400A range select.

Not doing precision work, I find the 40A range plenty good because it reads out to 0.01A resolution. That's 10mA resolution.

PS. When working with electronics, I use old DVMs and wire them in circuit for current measurements. And that's why I have several DVMs.

I guess if the 60A range will read will read 01.10A, all is good,

I often insert a 0.1Ω or a 1Ω resistor in series and measure voltage across it. I don't have two meters, with the resistor, I can make two measurements, current and voltage without disrupting the circuit.
I have the Bryman 235 often touted by Dave Jones on EEV. I've had it 3 years and like it. it is 6000 count.

https://www.amazon.com/EEVblog-BM23...658610262&sprefix=brymen+bm235,aps,172&sr=8-1

 

[NW-Bound]

I guess if the 60A range will read will read 01.10A, all is good,

I often insert a 0.1Ω or a 1Ω resistor in series and measure voltage across it. I don't have two meters, with the resistor, I can make two measurements, current and voltage without disrupting the circuit.
I have the Bryman 235 often touted by Dave Jones on EEV. I've had it 3 years and like it. it is 6000 count.

https://www.amazon.com/EEVblog-BM23...658610262&sprefix=brymen+bm235,aps,172&sr=8-1

With a DC clamp meter, no more, no more of the series shunt resistor.

AC clamp ammeters have been around for decades. They use an inductive coil which picks up the alternating magnetic field but is useless with a constant DC field. It is the advent of the inexpensive Hall-effect sensor that gives us the DC clamp meter.

At low current levels, the Hall effect is down to the intrinsic noise level of the sensor, so the reading jumps around quite a bit at the least-significant digit. I still think it's a godsent.

 

[sengsational]

I never bother with the meter to detect a bad cap on the fan circuit...if it's humming and warm, but not spinning, replace the cap!

 

[travelover]

I never bother with the meter to detect a bad cap on the fan circuit...if it's humming and warm, but not spinning, replace the cap!

Yes, the capacitors often bulge or give other physical signs of death. Plus, if you can spin the fan by hand and it keeps running it s a sure sign of a bad capacitor.

 

[NW-Bound]

I never bother with the meter to detect a bad cap on the fan circuit...if it's humming and warm, but not spinning, replace the cap!

Yes, the capacitors often bulge or give other physical signs of death. Plus, if you can spin the fan by hand and it keeps running it s a sure sign of a bad capacitor.

Yes. If it hums but does not run, spin the blade to help it start, and it will come up to speed.

That tells you everything is fine, except for the cap. The cap helps the motor start going.

If you spin it in the wrong direction, it will happily keep going in that direction too.

 

[Al in Ohio]

If the system is under charged it can run colder (in the evaporator) and cause freezing up. Do you notice airflow reduction when the temps were not as cold? By shutting it off, you allow the evaporator to thaw. You basically are doing a manual defrost if you think about the process. Normal operating conditions the condensation drips off the evaporator, and ultimately drains to somewhere away. But if too cold, the condensation freezes on the evaporator instead of dripping off.

Since you needed topping off refrigerant last couple years, that indicates your system has a leak. Which also supports theory of being under charged as current problem.

I think you need to get an HVAC person out and check the refrigerant charge level, and potentially topping it off. Ultimately your system has a leak that will only get worse. So either find and repair, or look at new system upgrade.

This ^. IMO if it’s a 25 yo system don’t screw around with a leaky evap coil no one has yet to properly fix. Time to buy a new system anyway.

 

[sengsational]

This ^. IMO if it’s a 25 yo system don’t screw around with a leaky evap coil no one has yet to properly fix. Time to buy a new system anyway.

Or a new evaporator coil, if you have a cash flow problem. But if you get a full season of cooling after a top-up, that's also a low dollar way to proceed. There's a lot to be said about just having all new, but that ain't cheap. My house has two separate units, and I have a small window unit, so if one system goes down, it's not too uncomfortable. But if one day without A/C would be "really bad", then just dropping the cash would probably be best.

 

[ncbill]

Or a new evaporator coil, if you have a cash flow problem. But if you get a full season of cooling after a top-up, that's also a low dollar way to proceed. There's a lot to be said about just having all new, but that ain't cheap. My house has two separate units, and I have a small window unit, so if one system goes down, it's not too uncomfortable. But if one day without A/C would be "really bad", then just dropping the cash would probably be best.

Yep, top it off & replace the coil or whatever else is leaking.

A new split HVAC will be in the high 4/low 5 figures...doing the above instead will almost certainly be much cheaper.

 

[Graybeard]

Yep, top it off & replace the coil or whatever else is leaking.

A new split HVAC will be in the high 4/low 5 figures...doing the above instead will almost certainly be much cheaper.

Cheaper yes but this is a 23 year old system. I would like to add R-22 and address this next Spring but the cost will be in the $300 at a minimum to $500 range. One place said $160 just to come out and then the cost of the refrigerant which is really expensive. It may depend upon whether they can get and install something fast otherwise I may just gamble with adding more refrigerant and hope it fixes it for the next 2 1/2 months, no idea how fast it is leaking.

It's been brutally hot today and at 7 am it's supposed to only have cooled down to 78° and the dew point will be 73° and rising! It's 83° at the south end of the house and 78° at the north end. I think this is like living in the desert, hot but no humidity inside the house.

 

[freedomatlast]

Cheaper yes but this is a 23 year old system. I would like to add R-22 and address this next Spring but the cost will be in the $300 at a minimum to $500 range. One place said $160 just to come out and then the cost of the refrigerant which is really expensive. It may depend upon whether they can get and install something fast otherwise I may just gamble with adding more refrigerant and hope it fixes it for the next 2 1/2 months, no idea how fast it is leaking.

If you can't do it yourself, see if you can get someone to top it off with R22 and while they are doing that, add Cliplight Super Seal. I normally don't recommend 'fix in a can' type products but this stuff does work. I once got 12 more years out of an R22 system at one of the rentals using this. If you do this, follow the instructions to a "T".

The guys that come out will never suggest this or will tell you it doesn't work because they want you to buy a new system, but I have first hand experience that it does work if you follow the instructions.

 

[ERD50]

Cheaper yes but this is a 23 year old system. I would like to add R-22 and address this next Spring but the cost will be in the $300 at a minimum to $500 range. One place said $160 just to come out and then the cost of the refrigerant which is really expensive. It may depend upon whether they can get and install something fast otherwise I may just gamble with adding more refrigerant and hope it fixes it for the next 2 1/2 months, no idea how fast it is leaking.

It's been brutally hot today and at 7 am it's supposed to only have cooled down to 78° and the dew point will be 73° and rising! It's 83° at the south end of the house and 78° at the north end. I think this is like living in the desert, hot but no humidity inside the house.

I'm not sure this applies to your situation, but we needed a new evaporator coil (the inside one) on a 13 YO system, and the guy said that if/when the compressor side goes out, this coil can be used with the new system.

If that's the case for you, you aren't really throwing money away on the old system, it's a 'down payment' on the new one.

-ERD50

 

[NW-Bound]

.. if/when the compressor side goes out, this coil can be used with the new system.

If that's the case for you, you aren't really throwing money away on the old system, it's a 'down payment' on the new one.

-ERD50

Good point!

I am curious, if the leak is very small and takes years to cause the freon to run low, can you pinpoint where it is, in order to replace the correct part?

 

[freedomatlast]

I am curious, if the leak is very small and takes years to cause the Freon to run low, can you pinpoint where it is, in order to replace the correct part?

Most likely not, That's why it's a perfect application for an inexpensive product like the Cliplight Super Seal and might be worth a try.

 

[freedomatlast]

I'm not sure this applies to your situation, but we needed a new evaporator coil (the inside one) on a 13 YO system, and the guy said that if/when the compressor side goes out, this coil can be used with the new system.

If that's the case for you, you aren't really throwing money away on the old system, it's a 'down payment' on the new one.

-ERD50

With different refrigerants, the evaporators are sometimes sized differently. Also, many times not replacing all of the components including the line set will void the warranty on the system. At least that's what it said with the warranty papers with the last system I had installed several years ago.

 

[Graybeard]

Good point!

I am curious, if the leak is very small and takes years to cause the freon to run low, can you pinpoint where it is, in order to replace the correct part?

The 1st leak was 2005. In 2020 the capacitor was replaced but I can't remember if R22 was needed. In 2021 R22 was needed. It may be a once a year thing at this point... more on that later.

 

[Graybeard]

The guy that installed my central air 23 years ago is coming here tomorrow to discuss a new unit. The problem is 7:30 AM is when he can come! I'm barely moving at 8 or 9 despite getting up at 6, I am going to have to get up about 5 am to pull this off. I can't ask for a better time cuz I didn't think he'd be here until at least the end of the week so I have to be flexible.

The bad news is when talking on the phone today, his wife told me there's no way they could install it until at least the week of 8/8 and depending upon availability and it might be 4 weeks to get a unit. At that point it'd be the last week in August, the probability of 90+ degree days after Labor Day drops dramatically so maybe it is just better to pay for the service call and R-22 and then address this in April next year. AC functioned good today but cloudy and not that hot. This has become a soap opera!

 

[travelover]

..........The bad news is when talking on the phone today, his wife told me there's no way they could install it until at least the week of 8/8 and depending upon availability and it might be 4 weeks to get a unit. At that point it'd be the last week in August, the probability of 90+ degree days after Labor Day drops dramatically so maybe it is just better to pay for the service call and R-22 and then address this in April next year. AC functioned good today but cloudy and not that hot. This has become a soap opera!

Maybe you can pick up a used window AC off Marketplace or Craigslist to get you by, then resell it when you are done. I see them all the time at my local Habitat ReStore, as well. In the meantime leave the fan running constantly on the furnace, maybe with no filter, since you'll get a new coil anyway.

 

[NW-Bound]

Most likely not, That's why it's a perfect application for an inexpensive product like the Cliplight Super Seal and might be worth a try.

Never heard of the above sealant. Looked on the Web and found out that it was pricey. But if it works, it's cheap.

There is a version for auto AC, called Cliplight Super Seal 941kit.

I may want to try it on my motorhome AC, which has a small leak.

 

[freedomatlast]

This is the stuff I used in the past. It looks like they may not make it anymore but there are still some kits available. This may be a kit for systems 5 tons and larger. It's hard to tell from the picture. I used the kits for systems under 5 tons. It was less than $25 when I bought it several years ago.

https://www.ebay.com/itm/Cliplight-A-C-Super-Seal-HVACR-/352991084388

 

[Graybeard]

I may have gotten lucky.

Barry Cone just looked at this system, his company installed my AC in 1999. He was very impressed with the air handler and said it was top quality and it would be a shame to remove the unit. His suggestion was to not replace this system cuz both the condensing unit and air handler are excellent units. They have used a product called "Easy Seal" for 3 years with good results to seal leaks. The new refrigerant is RS-44b and costs ~ $70 a pound vs my R22 which costs $95 a pound. My system has 8-10 pounds so it'd be cheaper to just add more R22 vs draining the R22 and refilling it with RS-44b. The cost to do this is about $900 maybe $1000 (maybe less if not replacing the R22 refrigerant, that I didn't clarify) at the most vs a new system that would be $6,000. I'm going to call the office today, he thought they could do it on Thursday of this week.

 

[freedomatlast]

Wow, Barry sounds like a really honest guy. Nice to have someone like that available. This sealant is what many of the guys are using now since the Cliplight stuff is scarce:

https://www.zoro.com/nu-calgon-refr...o-5-tons-4050-02/i/G3936475/?recommended=true

 

[ShokWaveRider]

Well, our XP21 Condenser is still working after it's 1 day sabbatical. I had a tech come over as mentioned before and he gave it a clean bill of health and has no idea why it would fail completely then miraculously resurrect itself after 1 day of not working. That was almost a week ago now. I purchased a new contactor just in case, I will replace it if I get another unexplainable failure. I am just thankful to the AC Gods (That I know really do not exist other than in my mind) for working their miracle.

 

[ERD50]

Well, our XP21 Condenser is still working after it's 1 day sabbatical. I had a tech come over as mentioned before and he gave it a clean bill of health and has no idea why it would fail completely then miraculously resurrect itself after 1 day of not working. That was almost a week ago now. I purchased a new contactor just in case, I will replace it if I get another unexplainable failure. I am just thankful to the AC Gods (That I know really do not exist other than in my mind) for working their miracle.

Contactors/relays can definitely go intermittent. I also bought a spare at the start of the season, just in case. Cheap insurance, and a quick/easy job in most cases.

-ERD50

 

[ShokWaveRider]

Contactors/relays can definitely go intermittent. I also bought a spare at the start of the season, just in case. Cheap insurance, and a quick/easy job in most cases.

-ERD50

Agreed.