HVAC experts???

pmanton

pmanton

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Indian Hills Airpark Salome, AZ
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I've been having my AC ice up at night. We normally set it at 75 during the day. It functions just fine even when the outside temp is 114+.
At night we normally set it at 65-68 since we like it cool to sleep. It's been icing up at night. The humidity is single digit and the outside temp drops to the 90s. The temp differential at night is much less than the daytime differential yet it ices at night.

We're in AZ so humidity is very low.

Does anyone have any suggestions how to prevent icing?

Thanks.
Paul
Salome, AZ
 
I suspect you are low on coolant.
Ice probably isn't going to form in the 114+ heat of the day but when the temp drops at night, the ice can form.
That is just a guess from someone with a "little" knowledge. (You know, the worst kind of knowledge).

But regardless, you need a competent A/C technician to check your system out. At those temps, you want it to be as efficient as possible.

By the way, I assume you have checked your filters recently?
 
Filters clean? Are you using pleated filters? Evaporator coil inlet side clean? Blower housing inlets clear? Does blower motor sound like it is running as fast as it did when it was new? Blower motor run capacitor good? Temperature difference between return and supply air? Suction line(larger insulated one) temperature at outdoor unit during the hottest part of the day? Are all of your supply registers open? Does evaporator coil have a TXV(thermostatic expansion valve)?

It is best to call a good HVAC tech like already mentioned. If you find it is 2 Lbs or more low on refrigerant, have them find the leak and repair. Otherwise you risk ruining your compressor.
 
Most common cause is dirty filters. Restricted airflow, meaning less heat (from the house) getting to the evaporator coil.
Too much cold coming in, not getting transferred to the air (from restriction), and forms ice.

Alternate cause: the fan is blowing too weakly, leading to the same effect.

Alternate cause: Make sure all the vents in the house are open, and not blocked by anything. Blocked vents can increase backpressure, reducing airflow over the evaporator, then ice.

Other alternate causes require an AC tech to check out your systems.
 
after checking airflow - all filters clean, get a thermometer and gauge set and check your temperatures and pressures - you're looking for superheat (google the term). If it is not an airflow problem then it is a coolant problem, either it's contaminated and freezing or it is insufficient charge. Be careful but it's not rocket surgery...

Also, you probably can't legally work on the AC system so maybe just call the tech.
 
Clark1961 said:
Also, you probably can't legally work on the AC system so maybe just call the tech.
Click to expand...
I'm not aware of any legal prohibition against anyone working on their own AC system, can you elaborate on that? Might be tough to purchase refrigerant but other than that...

I understand that one has to be licensed to offer this kind of service to others but the same exists for electrical work and a homeowner can legally replace a light bulb, circuit breaker, or receptacle in their own home AFaIK.
 
DIY'ers usually spend as much or more money fixing it themselves and take several days to do it. That is if the correct part is replaced. How many homeowners have the proper tools and test equipment? It may not be rocket science to some of you, but I spent 2 years going to hvac tech school(while overhauling jet engines) and 6 weeks in PP flight training. You can get killed doing both without the proper training and equipment. It may be legal but is it safe? Some family may buy that house next month. Would you want the average DIY'er working on your plane?

For homeowners, I recommend checking breakers, filter, thermostat and drains. Call a tech for anything else.
 
gismo said:
I'm not aware of any legal prohibition against anyone working on their own AC system, can you elaborate on that? Might be tough to purchase refrigerant but other than that...

I understand that one has to be licensed to offer this kind of service to others but the same exists for electrical work and a homeowner can legally replace a light bulb, circuit breaker, or receptacle in their own home AFaIK.
Click to expand...

Mostly I was referring to handling refrigerant. As I understand it just about any venting is prohibited. Adding refrigerant to a system that leaks is also prohibited. Of course my knowledge of the law is limited to what I was told in the one week AC class from 20 years ago. YMWV.
 
RV10flyer said:
DIY'ers usually spend as much or more money fixing it themselves and take several days to do it. That is if the correct part is replaced. How many homeowners have the proper tools and test equipment? It may not be rocket science to some of you, but I spent 2 years going to hvac tech school(while overhauling jet engines) and 6 weeks in PP flight training. You can get killed doing both without the proper training and equipment. It may be legal but is it safe? Some family may buy that house next month. Would you want the average DIY'er working on your plane?

For homeowners, I recommend checking breakers, filter, thermostat and drains. Call a tech for anything else.
Click to expand...

The AC/heat pump on my FL home quit the last time I was there on the day before I was planning to leave for the summer. I was able to determine that the capacitor for the compressor was NG and I picked up a replacement for far less than the minimum service charge from the two shops I called. I would have had to changed my schedule or enlist a neighbor to let the tech in the house to perform the repair. But if I find I have a refrigerant issue I'll pay for a tech with the proper tools and supplies.
 
pmanton said:
I've been having my AC ice up at night. We normally set it at 75 during the day. It functions just fine even when the outside temp is 114+.
At night we normally set it at 65-68 since we like it cool to sleep. It's been icing up at night. The humidity is single digit and the outside temp drops to the 90s. The temp differential at night is much less than the daytime differential yet it ices at night.

We're in AZ so humidity is very low.

Does anyone have any suggestions how to prevent icing?

Thanks.
Paul
Salome, AZ
Click to expand...

Low on freon. The only reason it will ice up is low freon. It actually cools too much with low freon. Clean filters and out side units only decrease efficiency.

More than likely you have a small leak somewhere. A good tech can find it and fix it for you.
 
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gismo said:
I'm not aware of any legal prohibition against anyone working on their own AC system, can you elaborate on that? Might be tough to purchase refrigerant but other than that...

I understand that one has to be licensed to offer this kind of service to others but the same exists for electrical work and a homeowner can legally replace a light bulb, circuit breaker, or receptacle in their own home AFaIK.
Click to expand...

It is illegal to work on AC equipment (freon system) unless you are certified and have the correct equipment to work with freon. I use to do all my own AC work, but then the regs changed. You can change contacts, capacitors, fan motors, burnt wires, ect. But you cannot (legally) work with freon.
 
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Geico266 said:
Low on freon. The only reason it will ice up is low freon.
Click to expand...

This is not correct. Contaminated freon will cause the evaporator to ice up. If it is treated as low on freon then when the contamination block clears suddenly the freon system is overpressured and ruptures. This is why a lot of old AC folks have one eye. I've seen this myself (overpressure, not eye loss) on a couple occasions. It gets your attention fast.

Now days it's SOP to clean a system by pulling a vacuum three times and then charging it by the book. This procedure is good and results in an operating system.
 
Clark1961 said:
This is not correct. Contaminated freon will cause the evaporator to ice up. If it is treated as low on freon then when the contamination block clears suddenly the freon system is overpressured and ruptures. This is why a lot of old AC folks have one eye. I've seen this myself (overpressure, not eye loss) on a couple occasions. It gets your attention fast.

Now days it's SOP to clean a system by pulling a vacuum three times and then charging it by the book. This procedure is good and results in an operating system.
Click to expand...

Wrong.

You are arguing the same point. Low freon whether contaminated or not is the reason it ices up. The contamination is causing the low freon condition.

Is it really worth arguing about? The point is in my post to call for a tech, but you convienently left that out as a point of self grandization.

:mad2:
 
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Geico266 said:
Wrong.

You are arguing the same point. Low freon whether contaminated or not is the reason it ices up. The contamination is causing the low freon condition.

Is it really worth arguing about? The point is in my post to call for a tech, but you convienently left that out as a point of self grandization.

:mad2:
Click to expand...

Nope. You are very wrong. For low freon, the proper course is to fix the leak and then recharge. For a contaminated system the proper course is to fix the cause of contamination then purge the system prior to recharge.

I'm not going to argue it. I've seen it. You can believe whatever you want.

I'm sorry that you think that everyone must submit to your beliefs or they are wrong.
 
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Low freon. When it's low, the pressure in the evaporator drops, which causes a corresponding drop in temperature (low fluid == low pressure, kinda makes sense). A tech can top it off easily enough, but the real problem is finding and fixing the leak. If your system is more than 10 years old, brace yourself for a new air conditioner purchase.

I design these type of systems for a living, FWIW.
 
Here is a pressure temperature chart like I use.

http://www.advantageengineering.com/fyi/289/advantageFYI289.php

One can see for R-22(most common for home a/c applications) we do not want less than 57.5 PSIG or it may freeze up. Low charge is one of several reasons the coil may freeze up. We normally want a 40F evaporator temp, so 68.6 PSIG. Like flying, there is always more for us to learn.
 
Geico266 said:
It is illegal to work on AC equipment (freon system) unless you are certified and have the correct equipment to work with freon. I use to do all my own AC work, but then the regs changed. You can change contacts, capacitors, fan motors, burnt wires, ect. But you cannot (legally) work with freon.
Click to expand...
When I was in high school several decades ago a new addition was added containing an electronics lab and a "computer room" (the only "computer" we had besides the dirt simple calculator I built was a teletype) which shared an air conditioning system located in the storeroom between the lab and computer room (no other areas in the school had AC). As I was several years ahead of my classmates WRT electronics and was enrolled in a "self directed" program I set up my own "lab" in the storeroom where I engaged in several projects.

When the outdoors heated up in the last couple weeks of the school year I decided to fire up the AC to cool things down. I got it running right away but it kept shutting down shortly after cool air began wafting out of the vents. A little sleuthing led to the discovery that the squirrel cage blower was turning backwards which was quickly cured by swapping two wires of the 3 phase power input. This epiphany occurred about halfway through the class period and when I fired the system up with the blower turning the correct direction I expected a slightly different reaction from the students and teacher in the classroom than I got.

I heard some shouting and thinking this was related to the joy of cool air blowing into a room with 80+ temps and high humidity I stuck my head out the door into the classroom to absorb the student's appreciation. But that wasn't what I got. It turned out that the ductwork was chocked full of construction debris consisting of sheet rock dust, dirt, and a few assorted nails and other metallic objects, all of which got dumped on several of the students from the overhead vents. They were so mad they didn't even notice that the room was cooling off nicely and I wasn't able to enjoy the cool air either as I concluded I'd best hightail it out of there before things got seriously unpleasant for me.

So I guess this proves your point that DIY repairs to A/C systems is dangerous.
 
You can do whatever you want to the thing as long as you don't handle the refrigerant. That takes a license (for practical matters, it is only required to buy or recycle the refrigerant, but technically, you're supposed to have one to do anything involving the refrigerant).
 
Had the same problem 141$ to have them add refrigerant I don't think a whole lot of systems are left that use freon. Hopefully its a very slow leak because my system is ancient.
 
While some of the refrigerants are worse than others for the environment all the fluorocarbons refrigerants are regulated. Frankly, a tech should not be putting refrigerant in a leaking system without fixing it first.
 
My A/C was not producing as much cold air as I remember it should so I changed the furnace filter which made a huge difference. The air is colder and dryer now.
 
flyingron said:
While some of the refrigerants are worse than others for the environment all the fluorocarbons refrigerants are regulated. Frankly, a tech should not be putting refrigerant in a leaking system without fixing it first.
Click to expand...

The leak repair rules are for all appliances that have a refrigerant charge of more than 50 pounds. Most residential HVAC system contains 3-20 Lbs. At a typical 2 lbs/yr. leak rate here is our options...

1. Recharge annually= $135-200.
2. Find leak without recharging= $135-200.
3. Find leak and recharge= $195-260.
4. Replace most commonly leaking evaporator coil, recover refrigerant, purge with nitrogen, replace coil, replace or add filter drier, nitrogen pressure test, vacuum, new R-22 refrigerant= $1500-2500.

Let's see, which would I choose if I was the typical American living paycheck to paycheck? It all depends on the system age, repair history, difficulty changing out system, etc.

They are already talking about phasing out the latest R-410A refrigerant now. Then we can carry three different refrigerants and gage sets on our truck.
 
I do not have a HVAC license, certificate, or anything. I installed two full systems in my home, the upstairs was a 2 ton, and the downstairs was a 5 ton. I used a dual speed fan unit downstairs for better efficiency. Once I did all the install, brazing, and connections I rented a cryo-vac like we used on cars and vacuumed the system for 4 hours, then let it sit for a while, then I tapped in with my nitrogen tank and checked the pressure for 6 hours with no loss of pressure. After that, I vacuumed it down again, and called around for an AC guy that would come out and fill it. The best price I found was $130 for the service charge and a couple bucks for the refrigerant. He looked at my work and was fine with filling it and checking the pressures.

If you don't feel comfy brazing and running wiring hire someone. It's not rocket surgery, but it's not super simple either. Ice formation can be low freon but it can also be the expansion valve sticking, or the capilary tube failing.
 
Remember if you buy online any manufacturer's warranty is void.
 
docmirror said:
I do not have a HVAC license, certificate, or anything. I installed two full systems in my home, the upstairs was a 2 ton, and the downstairs was a 5 ton. I used a dual speed fan unit downstairs for better efficiency. Once I did all the install, brazing, and connections I rented a cryo-vac like we used on cars and vacuumed the system for 4 hours, then let it sit for a while, then I tapped in with my nitrogen tank and checked the pressure for 6 hours with no loss of pressure.
Click to expand...

I hope you purged with nitrogen before brazing.
 
Gee, is that you over there -- walking on water? Hey, can you turn the glass of water into wine for me? Do those nails hurt your palms? :lol:
 
Where problems arise are after one does an "excellent job" installing that cheap online equipment with no warranty, had the licensed guy do the start-up and then have problems with it a year later. I get a call, find a compressor bad, quote $1,500 to replace a locked up compressor, drier, refrigerant. Now I am ripping him off because he only paid $1,500 for the entire system. His neighbors and friends saw me do the start-up and now I am back. Guess who gets blamed. So, no I do not do start-ups behind DIY'ers. When they break down the road, I may work on them if I am slow. I do not give them or my competitors customers any breaks like I would a system I sold and installed.
 
You are only prohibited from working R22 . . . I'm pretty sure you can work R-410 yourself . .
 
comanchepilot said:
You are only prohibited from working R22 . . . I'm pretty sure you can work R-410 yourself . .
Click to expand...

There is no additional EPA certification for handling R-410A. I doubt my distributors would sell a jug of R-410A to a DIY. R-410A still must be recovered like R-22, no releasing to the atmosphere. Unless you have R-410A gages, recovery machine and recovery tank, I doubt one could work on the refrigerant circuit.
 
Before I left the states, I had to replace a hot water tank in my home. Went down to Lowe's and picked out a unit, but before they would sell it to me they needed the name of the installer. Seems local ordinance specified that only "licensed" plumbers may install hot water tanks. :rolleyes2:

Told them I was from the next county over, loaded the tank and went home to install. :rolleyes:
 
RotorAndWing said:
Before I left the states, I had to replace a hot water tank in my home. Went down to Lowe's and picked out a unit, but before they would sell it to me they needed the name of the installer. Seems local ordinance specified that only "licensed" plumbers may install hot water tanks. :rolleyes2:

Told them I was from the next county over, loaded the tank and went home to install. :rolleyes:
Click to expand...

Most DIY electric water heaters don't have the T&P relief valve plumbed outside, expansion tank, a drain pan beneath wh, a disconnect at wh, shut off valves on hot & cold. Gas wh usually do not have proper venting, gas supply or stand. There is a reason for licenses and certificates(pilots). Not saying you did not do a perfect job, but I do go into a lot of homes everyday. Here is a video of a wh exploding...

http://m.youtube.com/#/watch?v=9bU-I2ZiML0&desktop_uri=/watch?v=9bU-I2ZiML0
 
RV10flyer said:
Most DIY electric water heaters don't have the T&P relief valve plumbed outside, expansion tank, a drain pan beneath wh, a disconnect at wh, shut off valves on hot & cold. Gas wh usually do not have proper venting, gas supply or stand. There is a reason for licenses and certificates(pilots). Not saying you did not do a perfect job, but I do go into a lot of homes everyday. Here is a video of a wh exploding...

http://m.youtube.com/#/watch?v=9bU-I2ZiML0&desktop_uri=/watch?v=9bU-I2ZiML0
Click to expand...
I have an electric water heater, and I think it was installed by the builder. It has shut off valves, relief valve is not plumbed outside and there is no drip pan. I would be hard pressed to do a worse job if I replaced it.

I did have some icing recently, apparently somehow pet fur got past the filter and clogged the coils. It was ugly and messy, but not very serious work.

A few years back I checked into what it would take to be legal to charge air conditioning systems, as learning how to repair them was part of getting my A&P. At the time there was a test on the EPA website to get certified. I would need the recovery equipment, and someone to take the recovered material. I think it would be less expensive to hire someone. Even if it were not, I still wouldn't trust my own brazing on an initial installation. I have no problem with replacing blower motors, etc.. The electric part is not very complicated.
 
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