Non Aviation, HVAC question.

[Mcstealth]

Does anyone know of a resource similar to our home here, that deals with commercial AC units? I am hearing what I consider rather dubious mutterings of what is wrong with two of my three Carrier units on my roof, and want to chat with knowledgeable folks. 

Any direction?

David

 

[Hank]

Have you tried airconditionerspace? Seriously, your best bet will be someone local. I'd start with whoever does your annual maintenance and spring tuneups. If that's "nobody," then may I suggest that you've found the source of your problems. Who takes care of the restaurant's HVAC?

[Mcstealth]

13 hours ago, Hank said:

Have you tried airconditionerspace? Seriously, your best bet will be someone local. I'd start with whoever does your annual maintenance and spring tuneups. If that's "nobody," then may I suggest that you've found the source of your problems. Who takes care of the restaurant's HVAC?

 No that's not it. I have had my HVAC maintenance  Company look at my units. What they are saying makes me scratch my head. 

 Just looking  For some knowledge. I have one company wanting me to dumpster 2 of my units that are only 8 years old

 

[A64Pilot]

HVAC is simple, I don’t know of any forums but I’m sure there are some, there is a forum for everything.

‘But I’d buy a HVAC for dummies book or similar, the principles are the same but things are getting more complex, used to be you had one expansion valve in a heat pump and it was driven off of a temp bulb, now for the more efficient units, there are two and they are electronic and driven by stepper motors and have of course control boards and a temp sensor, more precise and more efficient.

Getting licensed isn’t hard, even I got one.

[larryb]

Tell us. I’m an EE but have a passing knowledge. And I have a brother in law who had his own HVAC business for 20 years. I’ve seen one HVAC forum but every piece of advice I’ve seen there is to call a pro. Not very DIY friendly.

[Tim Jodice]

https://www.hvac-talk.com/vbb/

[Mcstealth]

On 3/26/2021 at 9:27 PM, larryb said:

Tell us. I’m an EE but have a passing knowledge. And I have a brother in law who had his own HVAC business for 20 years. I’ve seen one HVAC forum but every piece of advice I’ve seen there is to call a pro. Not very DIY friendly.

Ok. Let me get on the roof and get the model numbers. Just for accuracies sake. 

[N201MKTurbo]

It would help if you would tell us what the problem is. I've determined that all AC maintainers are crooked. I maintain all my AC equipment and it runs great. There is a commercial on the radio around here where they emphatically state that air conditioners only last 11 years. That's total bull! In the last few years I have replaced both of my condenser units. the first one lasted 24 years and the second lasted 30. Not much to maintaining them. Check the charge, oil the motors and replace the starters and capacitors when they fry. It doesn't hurt to hose off the condenser coils once in a while.

[Jerry 5TJ]

On 3/26/2021 at 9:08 PM, A64Pilot said:

Getting licensed isn’t hard, even I got one.

Getting the EPA608 card is easy, true. I did that so I could buy the refrigerants and work on my own HVAC systems.  
 

Question:  How do you spin the compressor on your airplane AC without running the engine?   

[Mcstealth]

2 hours ago, N201MKTurbo said:

It would help if you would tell us what the problem is. I've determined that all AC maintainers are crooked. I maintain all my AC equipment and it runs great. There is a commercial on the radio around here where they emphatically state that air conditioners only last 11 years. That's total bull! In the last few years I have replaced both of my condenser units. the first one lasted 24 years and the second lasted 30. Not much to maintaining them. Check the charge, oil the motors and replace the starters and capacitors when they fry. It doesn't hurt to hose off the condenser coils once in a while.

There is a restriction is what I am being told. The one tech has said, and I quote, "inside the evaporated coil manifold, there is an internal valve that you can not service. If it get gums up, you can't service it". "It is internal, not external" "if you run solvent, you can damage the compressors "

These were his quotes. 

 

[N201MKTurbo]

1 hour ago, Mcstealth said:

There is a restriction is what I am being told. The one tech has said, and I quote, "inside the evaporated coil manifold, there is an internal valve that you can not service. If it get gums up, you can't service it". "It is internal, not external" "if you run solvent, you can damage the compressors "

These were his quotes. 

 

It sounds like he is talking about the expansion valve. I haven’t worked on many all in one units, but I’ve never seen one that wasn’t replaceable. On a split system you can close both isolation valves, recover the refrigerant from the evaporator and then flush the evaporator, which would flush the expansion valve. 
 

what symptoms are you seeing that suggest a clogged expansion valve? They usually get clogged  When the compressor starts making metal. You have to consider my first statement in my first post.

[Mcstealth]

Hi head pressure triggers the safety that turns off the compressors. Gasses are not flowing. 

[Mcstealth]

One tech has said, We can only check for leaks with the actual refrigerant, and not nitrogen. 

I  called BS on that one as I know for years techs have used nitrogen for listen for leaks. 

[N201MKTurbo]

If there is high pressure on the compressor side and low pressure on the suction side, that would be caused by clogged expansion valve. 
 

He is correct about the leak checker. They are looking for the refrigerant. They are a lot more sensitive than listening for leaks.
 

I wonder if they were commissioned properly? Let’s say they were designed for R22 with a mineral oil charge but were charged with R-410 which requires PAG oil. This would lead to early failure due to lack of lubrication. 

[Mcstealth]

More info tomorrow 

[A64Pilot]

On 3/28/2021 at 10:29 AM, Jerry 5TJ said:

Getting the EPA608 card is easy, true. I did that so I could buy the refrigerants and work on my own HVAC systems.  
 

Question:  How do you spin the compressor on your airplane AC without running the engine?   

What kind of compressor are you referring to?

I won’t have AC on a small airplane, but if I did I’d want it to be electric, the reason is that if done properly you could pre-cool the airplane before pulling it out of the hanger.

‘I assume but do not know that you can do this with electric cars, if not then they aren’t very smart, it’s the initial cool down that uses the most energy, once cool it’s not so hard to keep it that way.

‘The AC unit we installed in Crop Dusters was essentially a golf cart motor hooked to an automotive compressor, what would better is a brushless DC motor, I believe the Prius is that way, that would give you a variable speed compressor.

I got my HVAC card to work on the Longbow AC’s if needed, a Longbow has dual 7.25 ton AC’s to keep the avionics cool. heat from bleed air.

I never needed the card, the AC’s were extremely reliable

Edited March 29, 2021 by A64Pilot

[Jerry 5TJ]

8 hours ago, A64Pilot said:

What kind of compressor are you referring to?

The belt driven kind found on Mooney and Piper airplanes.