Rheem starts with loud bang

[joecus62]

Hello all - I have a 5 year old Rheem central air unit. When it starts, there is a very loud bang. It does not happen every start-up but it does very often. I've noticed the problem happens when it's humid outside. I've had techs come here and the problem doesn't happen during their visit. They check the freon level is fine. Also, my house lights dim during the loud band indicating a huge load. The dimming only happens when it starts with the loud bang. Also, I've noticed the unit does not start immediately when the thermostat calls for air. The delay in starting is sometimes a few minutes. When is doesn't make the bang, it starts immediately when the thermostat calls. Please help if you have any idea. Thanks.

[paul52446m]

Hello all - I have a 5 year old Rheem central air unit. When it starts, there is a very loud bang. It does not happen every start-up but it does very often. I've noticed the problem happens when it's humid outside. I've had techs come here and the problem doesn't happen during their visit. They check the freon level is fine. Also, my house lights dim during the loud band indicating a huge load. The dimming only happens when it starts with the loud bang. Also, I've noticed the unit does not start immediately when the thermostat calls for air. The delay in starting is sometimes a few minutes. When is doesn't make the bang, it starts immediately when the thermostat calls. Please help if you have any idea. Thanks.

First, is this bang when its calling for cooling, or calling for heat? Is this a furnace with a split air con on it. Or do you have a air handler with air con. only?
is this bang on the indoor unit or on the outdoor unit? A lot of thermostats have a delay on make. If your stat is turning off the cooling and then back on real soon and the delay does not work, then the air con. compressor would be trying to start with a high head pressure and that would make a high amp draw and your lites would dim, and the compressor could make a noise.
Later Paul

[joecus62]

Sorry for leaving some information out. This is the outdoor condenser. It is an air conditioner only unit. The unit does start up immediately (a few seconds) when I first turn the thermostat on. After that, sometimes a long delay (when it’s very humid outside), the bang happens (after a long delay) I’ve noticed, when the thermostat reaches the desired temperature and shuts off then calls very quickly, long delay starting and big load (lights dimming) and the bang. Shouldn’t the unit (outdoor) always start the same (noise level)? When if comes on for the first time it’s not loud, actually very quiet. Someone told me there could be something that kick starts it (overload capacitor?) One more thing, I’ve bypassed the thermostat (connected the wires directly) and the same results, when the unit is cold, it starts right up quietly, if it’s been on (hot) the long delay and loud bang. Thanks a million for your help.

[HayZee518]

lights dimming could mean a large current draw getting the compressor started. a locked rotor would give that high a reading. if a hot start circuit is in there, that would account for the dimming until the motor is up to speed. there should be a delay circuit so the compressor won't start until the high and low pressures are equalized. nothing would destroy a compressor when trying to start against a high pressure head. 325 psig.

[joecus62]

I didn't mention, this has been going on since day when when the unit was brand new. Have you ever heard of a kick start capacitor? Why when it's hot would I get the loud bang? What would cause a delay starting (I've bypassed the thermostat) and then the kick start bang. This thing is so loud, I hear it in the house with the windows closed and the TV on. It's upsetting my neighbor. I think I have a lemon. Please help.

[paul52446m]

I didn't mention, this has been going on since day when when the unit was brand new. Have you ever heard of a kick start capacitor? Why when it's hot would I get the loud bang? What would cause a delay starting (I've bypassed the thermostat) and then the kick start bang. This thing is so loud, I hear it in the house with the windows closed and the TV on. It's upsetting my neighbor. I think I have a lemon. Please help.

With out having the gages and electric tester on it i could not tell you whats wrong. First of all it should not delay one time and not the next time. A lot of thermostats have delays for cooling In the compressor controls there can be delay on start or delays stop. Either one will stop the compressor from short
cycling. Some compressor need what we call a hard start kit on them, which
will be a bigger start capacitor. .
Things that can cause you problem, Valve sticking at times so the gases don't balance out and the compressor is trying to start under a hi head pressure. Start capacitor not giving the same start kick every time.
Have you checked you voltage at different peck times to see if it goes too low? Check amps on both sides of your contractor relay to see is you are getting a voltage drop that would cause a hi amp draw. Later Paul

[joecus62]

rheem

I know it has different delays not due to the thermostat since I bypassed them. When it's hot, the delay and bang. Therefore, I think there is something that is forcing the unit to kick start due to the a problem with a normal cold start-up. I don't really understand how to due the electrical testing, I will look into how to do this. Is a undercharge a possibility? What else would cause the need to use the kick start? This is still under warrantee and I need to do something quickly.

[HayZee518]

If it is still under warranty get a tech to check it out. Have him put gauges on both the high side and suction lines and see what shows up. Specifically have him check if there is oil in the system. the lubricating oil travels with the refrigerant in a mist and lubes the compressor. Stuck valves or broken valves would cause a bang. The piston may be hitting something inside. It is possible to under charge a system but you'd see a real drop in cooling capacity.

[joecus62]

Rheem Bang

I've had techs look and the freon is good. Is the oil level a different check?

[HayZee518]

there's no oil level to look at but for so many ounces or pounds of refrigerant, there's a certain amount of oil in the system. the oil is a moisture free mineral oil meant for different types of freon - R-134a, R-12, R-22 etc.

[joecus62]

Rheem

I have a tech coming Wednesday. He is going to check the system and send the information to Rheem to see if they can help. I have to pay $75 service fee. I've paid this numerous times, but now Rheem is going to help. Any suggestions on what I should look for when the guy comes?

[HayZee518]

Have him "sniff" all joints for leaks. That includes soldered joints and flanged fitting joints. Have him take an amprobe reading when the unit is running and at start. Check the compressor's anti shock spring or rubber feet. The motor torque is enough to cause a bang when it starts. With the gauge manifold attached and access valves open, record the suction and high side pressures when the unit starts. Any oscillations in the needle movement indicates an internal problem.

[joecus62]

Rheem

Thanks for such a detailed list. Maybe this will finally get fixed. I will let you know. Also, if anyone has something to add, please respond. Thanks a million.

[joecus62]

Rheem

I canceled the appointment due to the bad weather. I want him to be here when it's hot. I will let you know

[ulbhpy]

Hi Joecus62,

I also have a rheem outside condensor that starts with a bang almost every time. I had it installed in Dec 2010 and due to time of day and weather we did not insist that installer test condensor and now it has become annoyance very similar to your described case.

What was the final resolution?
Thanks.