Hydro-air system not blowing cold air
Here's the message:
"One of the air conditioners downstairs and one upstairs are not working properly. They rarely blow cold air and make a lot of strange noises on and off."
What can I do to diagnose the problem?
Here are some pics from a while back just to give you guys an idea of what kind of system it is.
Comments
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Just FYI - I called it a hydro-air system. Some people call them PTAC systems. The cooling process works off a condenser.0
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It is sort of a cross between a ptac and a unit ventilator.
Did both stop working at the same time or did they just decide to call you now? If both were sudden then maybe look at power and control issues with the building.
You will have to look at what happens on a cooling call. Is the fan running and at the right speed (both indoor and outdoor, probably one motor but who knows). Is the compressor running, or does it try to start and fail? Is either of the coils completely clogged? My bet would be on one of the motor capacitors but could be the overload on the compressor or one of the controls too. Unless someone has opened the sealed system on something that old the sealed system actually having a problem would be low on my list.1 -
What are the refrigerant pressures? Super heat or sub cooling numbers?1
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Not much you can do at all except to call a competent professional.branimal said:
…What can I do to diagnose the problem?…
There was an error rendering this rich post.
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Got some more info from my tenant.mattmia2 said:It is sort of a cross between a ptac and a unit ventilator.
Did both stop working at the same time or did they just decide to call you now? If both were sudden then maybe look at power and control issues with the building.
You will have to look at what happens on a cooling call. Is the fan running and at the right speed (both indoor and outdoor, probably one motor but who knows). Is the compressor running, or does it try to start and fail? Is either of the coils completely clogged? My bet would be on one of the motor capacitors but could be the overload on the compressor or one of the controls too. Unless someone has opened the sealed system on something that old the sealed system actually having a problem would be low on my list.
Downstairs we noticed the issue about a week ago. Upstairs in the guest room we noticed it today. The inconsistent/warm air and noise are the main issues. Upstairs I would also say the buttons are easily stuck so there’s no real way to put the air on cold/low; high is the only button that really works.
Based on the email, I'm not sure when the units actually stopped working. I'm not sure if the fans or the compressor is running properly. I'm going to go to the rental this week to get a better look. I watched some videos on air conditioning systems and ptacs in particular and it sounds like the number one problem is the capacitor for the fan or the compressor has gone bad over time. I think this will prevent the compressor from running. Or the compressor tries to run, overheats and shuts down. This would explain the noise the tenant is complaining about. Does the capacitor typically sit under the control board? I have a multimeter that can read microFarads.
Here's some other things that might be causing problems:
1. Tenants run the a/c's continuously. One time I had to go to the apartment for a water leak emergency. The tenants were gone for a long weekend and the air conditioners were humming along. The temperature sensors on these units are blown and the unit doesn't shut off. So maybe over use is a contributing issue.
2. Tenants have a dog that sheds considerably.
3. Tenants had a mice issue b/c they didn't keep dog food in plastic bins. I went to the apartment to inspect for possible entry points. I found droppings on the floor once I pulled the PTAC cover off. Maybe the mice chewed some wires and shorted something???
4. The units are old. I'm going to guess the PTACS are from 1984-ish. Almost 40 years old. I bought the place in 2013 and really haven't touched anything on the air conditioning side beside cleaning / replacing the filters. Maybe the capacitor is shot. Finger crossed that's the problem.
***Just to clarify how the system works: The PTAC unit only provides cooling. The heat is provided by a gas boiler that runs copper pipe thru the PTAC unit. The PTAC unit's fans pushes the copper pipes heat into the apartment**
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Those pushbuttons aren't the most reliable switches, it is possible some of the contacts on them are not working.branimal said:
Got some more info from my tenant.
Downstairs we noticed the issue about a week ago. Upstairs in the guest room we noticed it today. The inconsistent/warm air and noise are the main issues. Upstairs I would also say the buttons are easily stuck so there’s no real way to put the air on cold/low; high is the only button that really works.
The compressor won't start and the starting current will trip out the overload on the compressor. If it is left doing this for a long time it could burn out the overload.branimal said:
Based on the email, I'm not sure when the units actually stopped working. I'm not sure if the fans or the compressor is running properly. I'm going to go to the rental this week to get a better look. I watched some videos on air conditioning systems and ptacs in particular and it sounds like the number one problem is the capacitor for the fan or the compressor has gone bad over time. I think this will prevent the compressor from running. Or the compressor tries to run, overheats and shuts down. This would explain the noise the tenant is complaining about. Does the capacitor typically sit under the control board? I have a multimeter that can read microFarads.
If the fan isn't running fast enough to move enough air the refrigeration cycle won't be operating at the designed point and could cause the compressor to be noisy. Or you might just hear the compressor if the fan isn't running.
The caps can be in lots of places, sometimes in with the controls, sometimes it/they are mounted inside the cabinet somewhere.
Most multimeters can't test caps that large. With the ohmmeter you could see a resistance that is lower and climbs rather quickly over time. If it is just open it is probably bad.
You can measure the current through the cap and voltage across it and calculate the capacitance and compare that to the rating if the motor will run.
capacitance = (current * 2,652)/ voltage
If it is cold out or it is very oversized and the evaporator ices and the thermostat isn't working to cycle it off to defrost the evaporator that could damage the compressor.branimal said:
Here's some other things that might be causing problems:
1. Tenants run the a/c's continuously. One time I had to go to the apartment for a water leak emergency. The tenants were gone for a long weekend and the air conditioners were humming along. The temperature sensors on these units are blown and the unit doesn't shut off. So maybe over use is a contributing issue.
It is possible but not my first thought.branimal said:
2. Tenants have a dog that sheds considerably.
3. Tenants had a mice issue b/c they didn't keep dog food in plastic bins. I went to the apartment to inspect for possible entry points. I found droppings on the floor once I pulled the PTAC cover off. Maybe the mice chewed some wires and shorted something???
I was guessing 60's or 70'sbranimal said:
4. The units are old. I'm going to guess the PTACS are from 1984-ish. Almost 40 years old. I bought the place in 2013 and really haven't touched anything on the air conditioning side beside cleaning / replacing the filters. Maybe the capacitor is shot. Finger crossed that's the problem.branimal said:
***Just to clarify how the system works: The PTAC unit only provides cooling. The heat is provided by a gas boiler that runs copper pipe thru the PTAC unit. The PTAC unit's fans pushes the copper pipes heat into the apartment**1 -
It is probably factory sealed, the process tubes used to charge it are brazed shut. Opening the system to test pressures will just make things worse unless something points to a low charge or a damaged component in the sealed system.branimal said:
I don't have a manifold gauge. Even if I did, I don't know if there's a port to plug into. I'll bring my Weber grilling thermometer and a laser heat gauge when I check the units out.HVACNUT said:What are the refrigerant pressures? Super heat or sub cooling numbers?
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It might be time to invest in your investment. Is the rent free until its it's fixed?2
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The tenants aren't asking for a concession. The bad units are in the guest room (probably not being used.) And there are 2 units in the living area. 1 unit can hold them over for a few days.HVACNUT said:It might be time to invest in your investment. Is the rent free until its it's fixed?
I've always worried about these units going bad on me. A guy in the building gut renovated his apartment and replaced all the PTAC systems. He recently told me that they don't work much better than the ones he previously had. FWIR they cost a pretty penny.
I'm hoping that the problem is the capacitor. Fingers crossed.0 -
I'm going to the apartment on Sunday morning to check things out. I asked the tenants not to use the malfunctioning PTAC systems.mattmia2 said:
The compressor won't start and the starting current will trip out the overload on the compressor. If it is left doing this for a long time it could burn out the overload.
If the fan isn't running fast enough to move enough air the refrigeration cycle won't be operating at the designed point and could cause the compressor to be noisy. Or you might just hear the compressor if the fan isn't running.
The caps can be in lots of places, sometimes in with the controls, sometimes it/they are mounted inside the cabinet somewhere.
Most multimeters can't test caps that large. With the ohmmeter you could see a resistance that is lower and climbs rather quickly over time. If it is just open it is probably bad.
You can measure the current through the cap and voltage across it and calculate the capacitance and compare that to the rating if the motor will run.
capacitance = (current * 2,652)/ voltage
I ordered a nicer multi-meter off Amazon. It claims to measure capacitance. Pic below.
I watched a video on how to test & replace a capacitor. Seems you need to short the capacitor before you test it for capacitance. This can be done by shorting the HERM to COMMON connector. And then the FAN TO COMMON connector.
https://youtube.com/watch?v=Onnocjra1H8
I am a bit worried about getting access to the capacitor if it's not behind or under the controls. FWIR it was very confusing on how to get past the fins last time I looked at it. That was 4 years ago. Hopefully I'm a little smarter now.
I also ordered some HVAC capacitors from Amazon.
- 40+5 MFD uf 370 or 440 Volt VAC Round Motor Dual Run Capacitor for AC Air Conditioner
- 45+5 uf MFD 370/440 Volt Dual Run Round Capacitor 45/5/440R for HVAC, Air conditioners
I might order some 30+5 and 35+5 MFD capacitors as well.
Free shipping / free returns. That way I only need to be one time. Hopefully it's the capacitor that is shot.
Is there anything special I should pack in my tool-bag for this job. Aside from nut drivers, impact driver, multimeter, assortment of wrenches, screwdrivers and kneepads.
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What is the capacitance range of that meter? They usually read 100 pf or so and motor caps are tens of mfd.1
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amana makes those and you can add the hydro coil to them ... I think even the heat pump. All over nyc0
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