compressor cut out ?????

[andyc425]

Hey fellas im working on an airdale v41d u64525
its comprised of 2 outdoor units, obviously with 2 compressors inside, now the problem is one of the compressors keeps tripping out,now iv checked the pressures suction is 66 psi, discharge is 225 psi as they should be
checked voltage thats fine
compressor is drawing between 10- 15 running amps
and windings are about 1.2 its really cold up here so if fan speed was too high could this be the problem any advive would be great its 2 o clock on a friday ... the pub is calling, cheers lads

[andyc425]

sorry guys running amp at compressor 10 amps

[sedgy]

hi andy ,
and what is the overload set at?
what gas are we on ? are we on heating or cooling ? whats the room temp? whats the set temp.? hum controle?

[andyc425]

r407c
LP = 6 psi out-40 psi in
HP = 385 psi out-man reset
in constant cooling
room temp 21 deg
humidity min 30 max 100 %
deadband humidity min 2 max 20 %
it has alarm for humidity on digin control no fault showing

[sedgy]

hi andy, just trying to establish the reason why one con,d unit is tripping ?
you say the room is 21c= ok whats the set temp? < is the room down to temp and so its dropped put stage 2 cooling ?
or < you say one comp, is tripping out <on what ? if its a standard airedale there is only the comp, overload to hold off the comp, only
on the outgoing side of the comp, contactor there will be an overload conected to the contactor by three prongs being held by three screws , on the side of the o-L there is adjustable plastic arrow to set the maximum amps the comp, will run at, so if the comp is taking 10 amp the overload must be set over that set point,
or is the suspect comp, feel very hot? hope you find the reason . sedgy

[charlie patt]

on that airdale one unit is cooling one controls humidity whats the indoor a scirroco? whats it tripping on signal?

[frank]

Have you megger'd the windings? Could be tripping under certain conditions if the readings are not in excess of 2M ohms.

And don't rule out that the MCB (breaker)for the compressor is faulty

[andyc425]

cheers for your replies lads,
i will check amp overload setting
i have already checked resistance on comp windings its 1.2 ohms
triple checked mcb
although im not that familiar with heater strip on outside of compressor it was boiling to touch possible cause, id say yes but as i said limited exp on crankcase heaters.also sedgy the compressor it knocking of prematurley and not because of 2 stage cooling it alarms on digin controll with no detailed description,do yoy think possible safety circuit is sticking open which is linked in line with comp?

[thebigcheese]

have 4 comp rooms with airdale units and at least 1 unit in each room tripped on this when we had a bad cold spell

on start up suction pressure was pulling down then comming back up to normal

a few times it hit low pressure settings

suspect this as snow ice build up around condensers

[install monkey]

test the insulation to earth with a megohm meter-less than 1mohm is earth leakage resistance of the windings will only show open circuit or an inbalance in the windings.test the contactor hasnt got pitted contacts as this can give a higher running current

[frank]

cheers for your replies lads,
i will check amp overload setting
i have already checked resistance on comp windings its 1.2 ohms
triple checked mcb
although im not that familiar with heater strip on outside of compressor it was boiling to touch possible cause, id say yes but as i said limited exp on crankcase heaters.also sedgy the compressor it knocking of prematurley and not because of 2 stage cooling it alarms on digin controll with no detailed description,do yoy think possible safety circuit is sticking open which is linked in line with comp?

Checking the resistance of the windings is not the same as checking the windings with a megger (insulation resistance to earth)
Out of interest, how did you test the MCB and determine that it was OK?

[andyc425]

i checked the voltage on each mcb the compressor was linked to which was 2 three point 240v mcbs. plus i checked the current to and from both mcbs up until the comp,also the earth onside of compressor was visually fine but no i didnt check earth resistance just checked windings 1 to 2 ,1-3 etc , Monkey i have never encountered inbalance before what should i look for an how do i rectify also my suspicion was safety circuit stuck open but without an electrical diagram i am stumped to what is linked it could be so many things
im back in tomorrow il have another crack at it then thanks all for your replies much appreciated.
cheers fellas

[andyc425]

i dont no how but it is now working everything seems fine for the moment cheers guys, like suggested probably safety circuit stuck open.