PDA

View Full Version : single phase copeland scroll running backwards



BlueShark
09-06-2011, 10:34 PM
I have just discovered that the Copeland single phase scroll type compressor installed in many AC brands have a tendancy to run backwards if power is interruped. I personally have caught a Trane, Carrier, Heil, and a Goodman unit compressor running backwards. I discovered it on a weekend service call. A Heil Heat pump package that we installed almost a year ago unit was not cooling after a slight power interruption. Upon arrival, discovered the compressor was off line due to winding temp. Checked all electrical connections and capacitor tolerances. After cooling down the compressor with a garden hose, was able to start the unit. Checked unit for proper opertion and refrigerant charge at that time and could not find any problems. Monday morning I called the Heil rep and asked the tech support fellow. He was perplexed until I informed him of the slight power loss. At that time, he informed me of the possibility of the compressor running backwards if the power is jocked off and on. Anyone experienced this issue?

jimj
09-06-2011, 10:45 PM
Yup, I believe that has been resolved on newer models. Manufactures many times used time delays to resolve the issue you have experienced.

Jamy
09-06-2011, 10:50 PM
Yes , I read about the DC compressor like the one used in Fojui ductless air conditioner and I had been told in my previous job that reversing phases in AC compressors could effected on the compressor's operation too .

Milk man
09-06-2011, 11:23 PM
My Lennox at home did it. Power jacked on and off.

lynn comstock
09-07-2011, 02:27 AM
Yup, I believe that has been resolved on newer models. Manufactures many times used time delays to resolve the issue you have experienced.Yes. Only a problem with older scrolls. Another complaint is that the customer will say the compressor made a loud HORRIBLE noise, they got scared and shut it off.

It takes a split-second power interuption to cause the reversal. The older scrolls would back up due to head pressure on shutdown. If the power was restored while the compressor was moving backwards, it would start and run backwards. "Momentaries" are split-second interruptions in service.

Redwood650
09-07-2011, 09:48 AM
Happened on a 2-3 yr old heat pump I was working on. Amana...

gregp
09-07-2011, 01:37 PM
delay on break time delay will solve that problem :cheers:

Stamas
09-07-2011, 03:19 PM
Digital T-Stat

mike robinson
09-07-2011, 05:36 PM
Digital T-Stat

Only if it is hard wired.

rojacman
09-07-2011, 05:45 PM
Yes. Only a problem with older scrolls. Another complaint is that the customer will say the compressor made a loud HORRIBLE noise, they got scared and shut it off.

It takes a split-second power interuption to cause the reversal. The older scrolls would back up due to head pressure on shutdown. If the power was restored while the compressor was moving backwards, it would start and run backwards. "Momentaries" are split-second interruptions in service. I wonder if that's why Carrier was sending out check valve kits to install in bunches of our rooftop scroll comp'rs??????? (in the discharge lines)....Jack:.02::grin2:

meoberry
09-07-2011, 06:29 PM
Common problem on older scrolls. Right along with the check valve sticking in the discharge of compressor. Acutually responded to call that the customer said the unit would scream when it shut off. The compressor would spin bacwards fast enough that the condesor fan would start turning. The solution for the running backwards after power surges is a time delay. Best solution for check valve sticking is a magna check valve. Make sure it can stand the discharge temps. since it has to go in the discharge line.:.02:

meoberry
09-07-2011, 06:34 PM
I don't know about the resolved part on newer scrolls. Had one do it last month on a wall hung Bard. Unit was three years old. Another company said it was cooling fine. I don't think they will call other company back again.:gah:

rojacman
09-07-2011, 08:56 PM
Yes. Only a problem with older scrolls. Another complaint is that the customer will say the compressor made a loud HORRIBLE noise, they got scared and shut it off.

It takes a split-second power interuption to cause the reversal. The older scrolls would back up due to head pressure on shutdown. If the power was restored while the compressor was moving backwards, it would start and run backwards. "Momentaries" are split-second interruptions in service. I wonder if that's why Carrier was sending out check valve kits to install in bunches of our rooftop scroll comp'rs??????? (in the discharge lines)....Jack:.02::grin2:

McLean Air
09-08-2011, 05:18 PM
Yeah, I have seen a few scrolls do that. Also the loud noise it makes when it shuts off will scare the hell out of you if you aren't ready for it. LOL

ACFIXR
09-08-2011, 10:15 PM
I don't know about the resolved part on newer scrolls. Had one do it last month on a wall hung Bard. Unit was three years old. Another company said it was cooling fine. I don't think they will call other company back again.:gah:

I've seen it on newer models also.It had a hard wired honeywell touchscreen. I don't think that the hardwired stats are a sure fire time delay on break like I think they are. Anybody else experience this also? Or is this just a rare occurance. Before programmable stats TD's were the norm.

Redwood650
09-09-2011, 12:18 AM
Happened to me today but I turned the system off before it tripped a limit. The furnace door switch closed, opened, closed as I was putting the panel back on.

timebuilder
09-09-2011, 07:23 AM
I've seen it on newer models also.It had a hard wired honeywell touchscreen. I don't think that the hardwired stats are a sure fire time delay on break like I think they are. Anybody else experience this also? Or is this just a rare occurance. Before programmable stats TD's were the norm.


If the stat cannot sense that the power was off, the batteries will keep the microrelay closed and there will be no interruption of the coil power.

Better idea is to go with the delay timer.

ACFIXR
09-09-2011, 08:37 AM
If the stat cannot sense that the power was off, the batteries will keep the microrelay closed and there will be no interruption of the coil power.

Better idea is to go with the delay timer.

I install a lot of TB822's and they come with batteries. I use the batteries to pre-program before start up then I remove them at start up.It is easier to track down a unit that is not working on a multi unit site when the screen is blank. :grin2: I'm going to start using delay timers again anyway.

meoberry
09-09-2011, 06:36 PM
I've seen it on newer models also.It had a hard wired honeywell touchscreen. I don't think that the hardwired stats are a sure fire time delay on break like I think they are. Anybody else experience this also? Or is this just a rare occurance. Before programmable stats TD's were the norm.

I have noticed that a few times myself. I think the t-stats take a little longer to go into a time delay. Than a regular time delay. Maybe takes a little longer to bleed of power stored up in circuits?:.02:

meoberry
09-09-2011, 06:42 PM
I install a lot of TB822's and they come with batteries. I use the batteries to pre-program before start up then I remove them at start up.It is easier to track down a unit that is not working on a multi unit site when the screen is blank. :grin2: I'm going to start using delay timers again anyway.

AW! Tell the truth you just keeping batteries for flashlight. Is a good idea though. I'll tell you another trick I use. Wire up float switch to kill 24 volt to t-stat. Has reduced after hours calls. Before customer would come home and turn t-stat down and wait till 6 or 7 at night to figure out it aint cooling. Now when he goes to turn down screens blank. They call right away.:.02:

ACFIXR
09-10-2011, 07:42 AM
AW! Tell the truth you just keeping batteries for flashlight. Is a good idea though. I'll tell you another trick I use. Wire up float switch to kill 24 volt to t-stat. Has reduced after hours calls. Before customer would come home and turn t-stat down and wait till 6 or 7 at night to figure out it aint cooling. Now when he goes to turn down screens blank. They call right away.:.02:

I like this one, it is far better to kill the stat than to have a float switch "chatter" the outside contactor that doesnt have a TD. :grin2:

Tommy1010
09-11-2011, 08:30 AM
I install a lot of TB822's and they come with batteries. I use the batteries to pre-program before start up then I remove them at start up.It is easier to track down a unit that is not working on a multi unit site when the screen is blank. :grin2: I'm going to start using delay timers again anyway.

curious;

since the batteries are gone, on a power interuption, does the stat go back to default settings?

if so, that could be an inconvieniance, and/or create nuisance calls.

ACFIXR
09-11-2011, 08:36 AM
curious;

since the batteries are gone, on a power interuption, does the stat go back to default settings?

if so, that could be an inconvieniance, and/or create nuisance calls.

A cap keeps the rom powered therefore it does not lose the settings.

CraziFuzzy
09-11-2011, 09:09 AM
Time delay on make, on the outside contractor. For the shutdown noise, some units have a solenoid bypass valve between suction and discharge.

Tommy1010
09-11-2011, 10:28 AM
A cap keeps the rom powered therefore it does not lose the settings.

does that cap get it's charge from the 24 volt ac signal from the transformer

remember, there is no common hooked up?

does it make much sense for a stat to have batteries and a cap

timebuilder
09-11-2011, 11:38 AM
I install a common wire.

CraziFuzzy
09-11-2011, 12:01 PM
In most cases, the batteries are there to keep the clock running. The cap is a filter, not really there to 'keep the memory'. The settings are usually stored in NVRAM, and as such, don't go away when the power is lost. The clock is the only real concern on power outages.

And yes, most digital stats should have a common wire...

meoberry
09-11-2011, 11:18 PM
In most cases, the batteries are there to keep the clock running. The cap is a filter, not really there to 'keep the memory'. The settings are usually stored in NVRAM, and as such, don't go away when the power is lost. The clock is the only real concern on power outages.

And yes, most digital stats should have a common wire...
Yep, just like the VCR that nobody can remember how to set. I just love going to a customers house and they have installed a t-stat they picked up at the local hardware store. They expect me to know how to program every t-stat ever made. Of course nobody remembers what happened to the book that came with it.:gah:

pony
05-04-2012, 05:54 AM
what is the symptom of compressor running backward pressure wise?thanks

garyed
05-04-2012, 08:24 AM
The compressor won't pump. The pressures are pretty much the same on both sides & it usually sounds funny too.

Dennis.Moore
05-04-2012, 10:32 AM
It's called "transient torque" caused when power company jumps sources and and the phase angles are not synchronized. It will unscrew the impellar of the old york chillers.

408-COUPE
05-04-2012, 03:56 PM
It's called "transient torque" caused when power company jumps sources and and the phase angles are not synchronized.

Cant wait to tell a customer that.

Jamy
05-18-2012, 03:50 AM
I would like to know the heating system used in Canada schools and in Alberta if any one can help

Dennis.Moore
03-31-2014, 01:05 PM
It's called transient torque.
When a power interruption causes a radical change in the phase angle the magnetics can spin the rotor the other way.
I've seen it happen on 3 phase motors in YORK centrifugal chillers the impeller actually unscrews and falls off.

And a Nest t-stat will power itself by tapping the cooling contactor if there's no ground wire (plays hell with an electronic damper control though).

BP1972
04-01-2014, 11:05 PM
I've been noticing this as well. The Ruud tech I called out on site for a brand new package unit showed me that a split momentary "glitch" in power can make them run backwards. From what I was told Copeland actually removed a safety in their compressors that prevented this thinking the overload would catch it. Well it doesn't. Most of the models I have found this on were the 2012 models. I'm not sure if they have fixed it yet but I have been installing delay on break relays on the contactors as the momentary bump in power won't trigger the board time delay or the tstat delay but will trigger the separate relay I install.

garyed
04-01-2014, 11:34 PM
If this is happening on Heat Pumps there's a possibility that it is the reversing valve sticking instead of the compressor running backwards. The symptoms are similar and there can be a grinding type sound though the noise is usually not as loud. Before they started using the quiet shift defrost boards it was a common problem. Even with the quiet shift boards they usually have a jumper that can disable the quiet shift.

MiGuy
02-01-2016, 11:42 AM
I have a large house with five Bosch geothermal units. One water to water, one split and three combo units. In January we had three power outages. Thanks DTE! No issues transferring to the generator (60Kw). Issue happens only when we transfer back to utility power. During the last power outage 4 out 5 of the units tripped out on thermal overload. Subsequent investigation and duplication of the issue revealed that the scroll compressors were in fact running backwards after transfer back to utility power!

The UPM (Unit Protection Module) is worthless and does not detect or protect the unit when this happens. The compressors run backwards until they trip out on a thermal overload. The units are blissfully unaware that this has happened and as a result the fan continues to run, etc. The water to water system takes forever to cool down and recover. The split and the combo units recover faster.

I am guessing that everyone that has this issue is being told the same thing. You are unique, we never see this and we don't know what is going on.

The truth is that it is rare, but not unique and can happen on any unit.

Seems they would rather replace compressors under warranty than address the root cause of a potential failure.

I have found a product (SureStart) that will detect this condition and shut the compressor down. I intend to get five of these and get them installed ASAP!

More to come...

toocoolforschool
02-01-2016, 01:21 PM
Overflow switch turning on and off real quick will cause it too
.

pecmsg
02-01-2016, 01:48 PM
I have a large house with five Bosch geothermal units. One water to water, one split and three combo units. In January we had three power outages. Thanks DTE! No issues transferring to the generator (60Kw). Issue happens only when we transfer back to utility power. During the last power outage 4 out 5 of the units tripped out on thermal overload. Subsequent investigation and duplication of the issue revealed that the scroll compressors were in fact running backwards after transfer back to utility power!

The UPM (Unit Protection Module) is worthless and does not detect or protect the unit when this happens. The compressors run backwards until they trip out on a thermal overload. The units are blissfully unaware that this has happened and as a result the fan continues to run, etc. The water to water system takes forever to cool down and recover. The split and the combo units recover faster.

I am guessing that everyone that has this issue is being told the same thing. You are unique, we never see this and we don't know what is going on.

The truth is that it is rare, but not unique and can happen on any unit.

Seems they would rather replace compressors under warranty than address the root cause of a potential failure.

I have found a product (SureStart) that will detect this condition and shut the compressor down. I intend to get five of these and get them installed ASAP!

More to come...

That's not a manufactures problem that's a utility supply problem.
There are a lot of power monitors on the market.

dlginfla
02-01-2016, 02:00 PM
The compressor won't pump. The pressures are pretty much the same on both sides & it usually sounds funny too.
What will the amp draw look like when this is happening?
How could you tell a broken crank shaft from a compressor "running backwards" ?

pecmsg
02-01-2016, 02:28 PM
What will the amp draw look like when this is happening?
How could you tell a broken crank shaft from a compressor "running backwards" ?

Sound, amperage, pressures!

MiGuy
02-01-2016, 02:46 PM
That's not a manufactures problem that's a utility supply problem.
There are a lot of power monitors on the market.

How exactly is it a "utility supply problem"?
I live in SE Michigan. Along with hundreds of thousands of other DTE customers I have to live with the power they deliver. Now I suppose it is easy to blame DTE, and believe me I do, but that doesn't change the nature of the world I, and my geo units have to live in.

If you saying it is "utility supply problem" because the power should never be anything but a perfect sine wave at a perfect voltage and never go out or have a phase disturbance then you aren't living in the real world.

It is easy to build a product that works in the lab with perfect lab grade power. Those are commonly known as "lab queens". A lab queen fails when confronted with real world conditions. Just like my geos. Good engineering organizations train their engineers to try and find ways to kill their products then try and find ways to prevent it. Bad engineering organizations allow engineers build devices that can't withstand the rigors of the real world then blame the real world for BEING THE REAL WORLD. One approach promotes the development of lab queens and the other discourages or prevents their creation.

Seems to me that a problem that:
#1 Exists in the real world and can happen for any number of reasons
#2 Is both detectable and preventable

Should be prevented.

The way it is now, some unknown number of compressors are failing each year because of this issue. Because of the random transient nature of this issue and the hand waving and ignorance by dealers and reps no one knows how many and it has zero chance of being fixed. I had one Bosch rep try to blame it on the "microprocessor". He might as well have said "evil spirits". Neither of the two reps that came out have so far suggested that this issue is caused by the compressor running backwards. They are still puzzled by the observations we made after I recreated the issue for them. I am waiting to see if they can come up with an answer.

pecmsg
02-01-2016, 02:54 PM
So what you want is a unit built outside of design conditions! The utility is required to supply clean power within 10% of ratings. When they don't how is this the manufactures problem. Yes there are a lot of compressors and electronics replaced because of dirty power and believe me "YOU" do pay for it one way or another

You've found the solution a power monitor, not sold with residential equipment. Unless you want to pay more of course.

MiGuy
02-01-2016, 02:54 PM
What will the amp draw look like when this is happening?
How could you tell a broken crank shaft from a compressor "running backwards" ?

The current draw was something like 7A when running normally and 2A - 3A when making the terrible noise and apparently running backwards.
Makes sense because the motor was obviously running but not having to work against the high pressure so it was essentially unloaded.

Other observations that hinted that it was running backwards:
Exit water temp was slightly higher than entering water temp
Exit air temp was slightly cooler than entering air temp.

Both of these were slight but persistent. Kind of makes sense that running backwards in heat mode was acting like it was in cooling mode.

Shaft not broken. Power cycle would restore proper operation.

MiGuy
02-01-2016, 03:15 PM
So what you want is a unit built outside of design conditions! The utility is required to supply clean power within 10% of ratings. When they don't how is this the manufactures problem. Yes there are a lot of compressors and electronics replaced because of dirty power and believe me "YOU" do pay for it one way or another

You've found the solution a power monitor, not sold with residential equipment. Unless you want to pay more of course.

Well, I am not sure that I have found a solution. I sure hope so but I can tell you for sure that not every power monitor will solve this issue.
I tried an ICM492. It didn't work and when I sent the scope trace of the power event to their tech support they confirmed that it WOULD NOT detect this issue.

I am 110% sure DTE would argue that they are within the 10%. Besides, ever try arguing with a public utility?

In the end I guess we differ on what exactly qualifies as "design conditions". I would say the design conditions should represent the real world.

Not sure exactly how to quantify "10% of ratings" for things like very brief power interruptions, and phase disturbances.
If DTE supplies perfect power for 24 hours and then has a 15 millisecond power interruption have they met their 10% requirement? 0.015/86400 is a pretty small number even when expressed as a percentage (0.000017361%) but enough to cause my issue.

Wait. didn't I just make the case that the equipment should tolerate this sort of power disturbance using your 10% numbers?

By golly, I think I did!

CraziFuzzy
02-02-2016, 04:53 AM
Any piece of equipment that can be damaged by a very short power dip or outage should have electronics in place to delay restart. The electronics to accomplish this are ridiculously cheap, so there's really no excuse.

GT1980
03-04-2016, 07:36 AM
Any piece of equipment that can be damaged by a very short power dip or outage should have electronics in place to delay restart. The electronics to accomplish this are ridiculously cheap, so there's really no excuse.

Hmm.
Absolutely!

and I found in 2006 the scroll reversal on a split 80+ feet away , 16 feet up, was simply while under pressures of operation, electrical glitch ALLOWED momentary back-pressure reversal of the scroll while it was re-engaged by power.

FIX: The check valve AND delay on make ICM.

Hydro-Temp of AR, dual compressor FIRSTS on SINGLE CIRCUITS of refrigeration for 3 speed: small + larger, then both compressors had SEVERAL reversing scrolls in 3-staging systems that had failed check valves, and no pick-up time delay in board parts.
Some were better-fixed by putting the time delay between the TX 24-AC out "red" feed and the board.
Stat was fine with battery back-up (always a 24vac thermoostat- 'common' connected with these Geo-T Ht Pumps (GHP's).

GT1980
03-04-2016, 07:45 AM
Even roof top dual condenser fan units had FAN MOTOR reversals, but NOT by any UT'y glitch:

A slower-starting fan , in gusty N-OH nw-winds coming in, would have both fans turning backwards at a starting time.
ONE was driven continuously in reverse...
A/C service calling us out...
had to see it twice before appeasing the 'hotter' heads that been.
Replaced with new fan motor, end of problems...
What is confusing a bit, is the slower-starting motor was the dragger that stopped sooner in proper rotation , run off at a stop, ( that one that would STAY in reverse rotation).

Either way, I had to show it to the building supv, catching it in reverse.

The'president' of a very large, and very field experienced mechanical, in part of the equipment maintenance with me, said "THAT CAN NOT HAPPEN."

40 years in the field: his 'first' again.

TechmanTerry
03-04-2016, 08:31 AM
As far as I know Copeland IS aware that this "problem" is out there. As far as I know Copeland says that their Scroll IS NOT damage by running backwards. As far as I know Copeland says the there IS NOT enough heat produced by a backward running Scroll to cause any damage. As far as I know Copeland says that the Thermal Overload opens when it is supposed to, protecting the comp. And, as far as I know Copeland says the when the comp overheats and the Thermal Disk shut off the comp, then when the T-Disk resets the comp will restart in the normal/proper rotation. Then if there is many/lots of "reverse problems" then IT IS "someone else's" fault!

Comps die this way?????????

GT1980
03-04-2016, 09:36 AM
Bristol: Now Danfos, have replaced 'em under war. Maybe not so many after reading the above...