Mgraw
Senior Member
- Location
- Opelousas, Louisiana
- Occupation
- Electrician
When the blower goes out and the compressor keeps running why would you think the unit would have a high head pressure? The head pressure would drop significantly.
Heat Pump Failure (who's fault?)
- Thread starter derekk
- Start date
- Status
ptonsparky
Tom
- Occupation
- EC - retired
Head pressure for the compressor will go up, not down.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Nope, loosing the evaporator fans will cause a low pressure condition in the return line to the compressor, this should open the low pressure switch.
Loosing the condenser fan will cause the head pressure to go up, this should open the high pressure limit switch.
Electric-Light
Senior Member
There is a difference between radiator hose bursting in normal use vs a service personnel forgetting to fill the coolant before taking it out for a test drive and frying the engine. You're essentially simulating loss of coolant, but the court is not going to be impressed with your argument.
If I was the building and you won't pay, I'll probably contact my insurance and file a claim that it was damaged during service and service contractor won't pay and let them quash it out with you and/or your insurance. Commercial property insurance often covers these things, but if they feel that the damage was caused by a vendor rather than their in-house staff, I'm sure they'll seek recovery from you.
You/your tech screwed up and you know it. Pay up. Stop whining that your mechanic shouldn't be at fault for test driving with no coolant, because the car didn't have protection or protection wasn't working right.
If it ends up in court, you can be assured you'll definitely lose goodwill.
You are to blame, because it was a user error, although for design revision, the compressor could use a lockout similar to what's used on furnace draft inducer. Every once in a while, draft inducer motor seize up and if the furnace fired up without flue exhaust, it can create dangerous conditions.
Some units use a centrifugal switch to prove fan operation before furnace will fire. Some use pneumatic static pressure switch.
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Electric Light, Sorry, but I have to take issue with your comment about this being user error. There isn't a single warning or comment that even remotely concerns this issue in any of the technical literature provided by the HVAC manufacturer. Someone reading the entire Installation Instructions and Operating Manual will find nothing to tell them there is any danger of damage to one unit if they are not both turned off together and if there is, then some sort of interlock should be mandatory.
Our technician is an electrician, not a mechanical system expert and he wasn't working on the mechanical system. When a building maintenance person changes the filters (and that is frequently done by someone in that capacity), the act of opening the cover usually opens a switch and also shuts off the fan. Do you expect that person to also go all over the building to figure out where the matching exterior unit is and disconnect it before he changes a filter? What if the heat pump serves several FCU's, do they all have to be shut off as a group? Or only if more than some percentage of the air flow is reduced?
I think the average journeyman level electrician is not going to think to find a remote piece of equipment to disconnect to work on a panel (especially when there is no labeling or warning telling them to). Is that really your expectation - that every electrician will trace through every single circuit on any panel they work in to make sure that there is not some interlinked equipment located somewhere else in the building that might fail?
No, equipment which is meant to work as an integrated system, be it a large manufacturing process line or a single commercial oven with an exhaust fan, etc. needs to be controlled as a unit either through the power wiring or control wiring. I think this is poor system design by the manufacturer and/or Mech.
Yes, our work initiated the event that caused damage to this equipment, but my point is that it should not have caused any damage at all and if it could have, then the manufacturer needed to include this information somewhere on the unit or in the literature.
Our technician is an electrician, not a mechanical system expert and he wasn't working on the mechanical system. When a building maintenance person changes the filters (and that is frequently done by someone in that capacity), the act of opening the cover usually opens a switch and also shuts off the fan. Do you expect that person to also go all over the building to figure out where the matching exterior unit is and disconnect it before he changes a filter? What if the heat pump serves several FCU's, do they all have to be shut off as a group? Or only if more than some percentage of the air flow is reduced?
I think the average journeyman level electrician is not going to think to find a remote piece of equipment to disconnect to work on a panel (especially when there is no labeling or warning telling them to). Is that really your expectation - that every electrician will trace through every single circuit on any panel they work in to make sure that there is not some interlinked equipment located somewhere else in the building that might fail?
No, equipment which is meant to work as an integrated system, be it a large manufacturing process line or a single commercial oven with an exhaust fan, etc. needs to be controlled as a unit either through the power wiring or control wiring. I think this is poor system design by the manufacturer and/or Mech.
Yes, our work initiated the event that caused damage to this equipment, but my point is that it should not have caused any damage at all and if it could have, then the manufacturer needed to include this information somewhere on the unit or in the literature.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Well in spite of some of the others opinions, heres mine for what its worth:
For a system to be designed properly it must be design with enough fail safes that in the likely event one part or another stopped running there would have to have been a fail safe to prevent failure of any other parts still running, for a system to not be design with this, it would be called a self destructive system, this would be guaranteeing the manufacture of the equipment a guaranteed income, and I would believe this would be illegal, I have been around many walking coolers, freezers, and many other type of cooling equipment, and I have never heard of loosing a compressor because of no air flow over the evaporators, almost all cases they would have a low pressure switch on the suction line that would turn off the compressors, in fact many coolers operate in this fashion to control the temp of the cooler.
I would tare this up in court. I would personally get hold of this manufacture and ask about what fail safe they should have installed, at least have a competent HVAC person who would be non-biased, to look at this installation to see if it was installed to factory specs, if it was and it was design to fail like this, I would go after the factory with guns blaring, but if it wasn't then I would be telling some one to go after the company who installed it.
No way would I accept what they told you, this whole thing sounds like a scam, because the compressor would have not been replaced by the manufacture if there wasn't a problem with the system. kind of like being hit by a driver and it was their fault, but saying you have to pay for the labor, but they will pay for the parts:roll: does this even sound right??? and 10k for labor and gas to replace a compressor??? kind of high if you think about it.
For a system to be designed properly it must be design with enough fail safes that in the likely event one part or another stopped running there would have to have been a fail safe to prevent failure of any other parts still running, for a system to not be design with this, it would be called a self destructive system, this would be guaranteeing the manufacture of the equipment a guaranteed income, and I would believe this would be illegal, I have been around many walking coolers, freezers, and many other type of cooling equipment, and I have never heard of loosing a compressor because of no air flow over the evaporators, almost all cases they would have a low pressure switch on the suction line that would turn off the compressors, in fact many coolers operate in this fashion to control the temp of the cooler.
I would tare this up in court. I would personally get hold of this manufacture and ask about what fail safe they should have installed, at least have a competent HVAC person who would be non-biased, to look at this installation to see if it was installed to factory specs, if it was and it was design to fail like this, I would go after the factory with guns blaring, but if it wasn't then I would be telling some one to go after the company who installed it.
No way would I accept what they told you, this whole thing sounds like a scam, because the compressor would have not been replaced by the manufacture if there wasn't a problem with the system. kind of like being hit by a driver and it was their fault, but saying you have to pay for the labor, but they will pay for the parts:roll: does this even sound right??? and 10k for labor and gas to replace a compressor??? kind of high if you think about it.
Electric-Light
Senior Member
I'm neither an insurance adjuster nor an attorney. So, if I was with the building, I'll just stop arguing with you, and call up my insurance and file a claim. If it pays the claim, I'm gonna go wash my hands. It's a battle between my insurance company and your company if it wants to hold you accountable for the claim it paid out. The insurance company may solicits expert opinion on its own, and if you disagree with theirs, you are free to hire another company at your expense to challenge the insurance company hired expert. The attorney gets involved if insurance won't cover it.
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Electric-Light
Senior Member
Mgraw
Senior Member
- Location
- Opelousas, Louisiana
- Occupation
- Electrician
Manufacturers will usually replace the first compressor failure without looking into the cause. If there is more than one failure then they will start asking questions. If the motor winding burned the entire system was probably contaminated with acid. To flush out a system to remove the acid is expensive. Filters to remove any remaining acid would need to be installed.
As for an interlock connecting the two systems there is one. It is called a thermostat. Switching the thermostat from cool to off would have shut off the compressor.
Did the OP cause the unit to fail? In my opinion yes.Weather or not the OP is responsible is for others to decide.
Electric-Light
Senior Member
Assumption of lack of common sense must be a common defense.
It isn't just consumer products where you see "knife is sharp" kind of warning.
You see stuff like these in service manuals...
"disconnect power before servicing"
"do not use a match to look for gas leak"
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
On car sun-shade: "Do not drive with shade in windshield."
On box of candles: "Caution: Contents flammable!" (I hope so)
On lemon-scented dish soap: "Not a beverage; do not drink!"
On box of candles: "Caution: Contents flammable!" (I hope so)
On lemon-scented dish soap: "Not a beverage; do not drink!"
ptonsparky
Tom
- Occupation
- EC - retired
Nope, loosing the evaporator fans will cause a low pressure condition in the return line to the compressor, this should open the low pressure switch.
Loosing the condenser fan will cause the head pressure to go up, this should open the high pressure limit switch.
Yup, I got it backwards. HUA syndrome.
One-eyed Jack
Senior Member
- Location
- Scotland Neck, NC
Not necessarily he did say it was a heat pump. Lose indoor fan in heat mode and you get high head. IMO this failure was a co-incidence. As others have said cutting power on air handler normally shuts entire unit down. If it was only 3 years old it had the appropriate controls to shut it down on low and or high pressure. If it continued to run it is more likely original install error.
"As the
con rods and pistons are broken, large pieces of debris
are thrown around the compressor shell and motor
area, these can cause motor winding insulation
damage and motor burn out. Very often the initial
diagnosis is the motor burn out, but the actual failure
was refrigerant flood back."
http://www.danfoss.com/NR/rdonlyres/D0C839C3-3076-49F5-9F35-6911FD22784F/0/FSN006web.pdf
I believe the arrangement was partly at fault. If the compressor were located much higher than the DX coil, it would have been impossible to fill the gas suction riser with liquid refrigerant and flood the compressor gas suction side. With the compressor located much lower than the DX coil, liquid passing through the DX coil falls down the riser and accumulates in front of the compressor gas suction side. Gas is separated from the liquid in the riser.
Key words "accident waiting to happen". If it was not reasonably forseeable, negligence is out. The owner has a duty to mitigate damages and may be responsible for the building's other systems during the shutdown, depends on some variables, onsite staffing. The plumbing arrangement was a weakness, though I do not know if it was a deficiency. Definitely a mechanical problem, though when the SHTF, it tends to splatter everyone.
If instead of shredding the compressor, if it blew apart and hurt someone, would the cause have been cutting power to the DX coil fan? Depends ... , primarily on if it was installed according to the manufacturer's spec's, and if so, the manufacturer is also liable.
Should count themselves lucky the claim is not large enough to justify litigation, though they may not have the brains to see it that way.
con rods and pistons are broken, large pieces of debris
are thrown around the compressor shell and motor
area, these can cause motor winding insulation
damage and motor burn out. Very often the initial
diagnosis is the motor burn out, but the actual failure
was refrigerant flood back."
http://www.danfoss.com/NR/rdonlyres/D0C839C3-3076-49F5-9F35-6911FD22784F/0/FSN006web.pdf
I believe the arrangement was partly at fault. If the compressor were located much higher than the DX coil, it would have been impossible to fill the gas suction riser with liquid refrigerant and flood the compressor gas suction side. With the compressor located much lower than the DX coil, liquid passing through the DX coil falls down the riser and accumulates in front of the compressor gas suction side. Gas is separated from the liquid in the riser.
Key words "accident waiting to happen". If it was not reasonably forseeable, negligence is out. The owner has a duty to mitigate damages and may be responsible for the building's other systems during the shutdown, depends on some variables, onsite staffing. The plumbing arrangement was a weakness, though I do not know if it was a deficiency. Definitely a mechanical problem, though when the SHTF, it tends to splatter everyone.
If instead of shredding the compressor, if it blew apart and hurt someone, would the cause have been cutting power to the DX coil fan? Depends ... , primarily on if it was installed according to the manufacturer's spec's, and if so, the manufacturer is also liable.
Should count themselves lucky the claim is not large enough to justify litigation, though they may not have the brains to see it that way.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
The facts and theories be what they may, but, my stance would still be that I'm not responsible unless and until it's proven that I am, and not the other way around.
Mgraw
Senior Member
- Location
- Opelousas, Louisiana
- Occupation
- Electrician
This is just not right. In residential it is normal for the air handler to shut off the condensing unit when power is shut off. In light commercial 7.5-20 tons it is normal for the condensing unit to shut off the air handler when power is shut off.
The low pressure control is set around 30-35 psi. The evaporator coil temperature would have to be in the low teens before the pressure control would shut it off. This could take a long time.
The install had nothing to do with the compressor failure. If you don't know how equipment operates you should find someone who does before you start shutting things down.
I appreciate the comments you have made. As far as this particular customer is concerned, whether or not the system is designed correctly or not isn't really their issue. Even though I feel this wasn't our fault and shouldn't have happened, I can't make my customer pay for it either. I ran a report today and we have accumulated ~$58,000,000 in revenue during the past 8 years without a single liabilty claim against our insurance. Given the thousands and thousands of dollars we shell out to our insurance company every year, I think this is probably one of those cases where it makes sense to let the insurance company and their lawyers handle it. They will probably get alot more attention from the HVAC manufacturer than we woudl anyway.
Those of you who are contractors, please take this as a cautionary tale and tell your journeymen about what happened as we sure as heck are going to.
One final comment, to the person who mentioned the T-Stat as the interlock device (which is a good point, by the way), my employee was smart enough to find two thermostats and turn them off, but it turned out that there were three thermostats controlling this particular unit. On any designs that I personally handle in the future, I will be making sure that some type of electrical interlock is in place.
Those of you who are contractors, please take this as a cautionary tale and tell your journeymen about what happened as we sure as heck are going to.
One final comment, to the person who mentioned the T-Stat as the interlock device (which is a good point, by the way), my employee was smart enough to find two thermostats and turn them off, but it turned out that there were three thermostats controlling this particular unit. On any designs that I personally handle in the future, I will be making sure that some type of electrical interlock is in place.
How on earth did that compressor fail?
I've always been told that before you take any A/C equipment off-line, you pump the refrigerant back into the compressor and then release it when the supply is restored.
Things may have changed or I could be wrong.
Just my 2 cents worth.
I've always been told that before you take any A/C equipment off-line, you pump the refrigerant back into the compressor and then release it when the supply is restored.
Things may have changed or I could be wrong.
Just my 2 cents worth.
Horror stories would make a pretty good thread. I'm sure the guys have stories, some of which they may be too embarassed to tell or stories that took them out of the field.
Early in my business I wired a large turbine air compressor for a producton cabinet shop, 25 Hp or so. One look at the unit told me they were nuts. I took note that it was a no name unit with 18,000 hours on the meter, bumped it for rotation and running load and turned it off. Really put my neck in the guillotine for them, spending an hour cleaning one of their old bus plug switches, climbed an extension ladder to plug it in.
I was done, I told them I doubted a unit with 18,000 hours on it and told them to have whoever sold it to them come in and do the mechanical startup.
Got a call the next day, the thing had gone off like a bomb in the back of the shop. First thing they said was it was my problem. First thing I said was I was sure it did not blow up because of the wiring, the wiring was tested and it was good. I got the facts that they knew, a radiator had let go and blown oil all over the back of the shop. No one had been hurt and they were surprised how little damage there was for the sound it had made.
They had gotten lucky by placing the unit 10 ft up on racks in an unoccupied space in back. I repeated that I had told them the unit had 18000 hours on it and I had told them to have the seller come in and do mechanical startup. That was the last I heard about it. Pretty sure I never saw a check for the work.
Early in my business I wired a large turbine air compressor for a producton cabinet shop, 25 Hp or so. One look at the unit told me they were nuts. I took note that it was a no name unit with 18,000 hours on the meter, bumped it for rotation and running load and turned it off. Really put my neck in the guillotine for them, spending an hour cleaning one of their old bus plug switches, climbed an extension ladder to plug it in.
I was done, I told them I doubted a unit with 18,000 hours on it and told them to have whoever sold it to them come in and do the mechanical startup.
Got a call the next day, the thing had gone off like a bomb in the back of the shop. First thing they said was it was my problem. First thing I said was I was sure it did not blow up because of the wiring, the wiring was tested and it was good. I got the facts that they knew, a radiator had let go and blown oil all over the back of the shop. No one had been hurt and they were surprised how little damage there was for the sound it had made.
They had gotten lucky by placing the unit 10 ft up on racks in an unoccupied space in back. I repeated that I had told them the unit had 18000 hours on it and I had told them to have the seller come in and do mechanical startup. That was the last I heard about it. Pretty sure I never saw a check for the work.
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