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marc5180
12-12-2007, 02:29 PM
Hi guys, just been called back to a unit that i went to the other day. I got called to it and on the HVAC panel It was showing up as a Fault on the Lennox unit...it doesnt show what the fault is/was. So i opened up the condensor (there are 2 circuits feeding a large ducted evaporator) and found the condensor coil iced up and so no airflow was getting through which led me to beleive it was causing the fault. I cleaned both coils throughly, checked both fans on the condensor and the evaporator of the circuit that was faulting (circuit 1) circuit 2 is fine as is working as it should.
I changed the setpoint down to 18 which made the unit run on cooling and it ran fine all day. then i changed it over to heating and for an hour it was ok, then the coil started to ice up again up to the distributor, which seems to cause the condensor to Ice up then trip out on what i imagine to be low/no airflow.
Btw i also took the gas out and the correct charge was in it so that can be ruled out. Any ideas?

philjd26
12-12-2007, 04:20 PM
hi marc
i had a simular on a york package unit....take a look inside controller panel and see if there is a defrost board...if so might wanna see if there is a way of testing this operation,on the unit a i was looking at it had two pins displayed as test, short these pins with a screw driver for 5 sec and that should send voltage to a relay which inturn shuts off condenser fans and energises 4 way valve if faulty board...

also on the defrost relay there should be a n/o defrost termostat on the neutral side this, should be closed when ice is on the condenser if not faulty stat..

rgrds phil

marc5180
12-12-2007, 05:55 PM
Hi Phil, When i arrived on site this afternoon i found the 3phase breaker had tripped....:eek: So reset it and turned everything on. The bottom of the unit was full of water about an inch high because the unit isnt quite level it isnt draining properly. The unit is sat on a ledge so it isnt just a cse of lowering down one side, insead i made a new drain from the bottom of the unit and the wter inside drained away fine.
BTW The model number is KVHK 48.D VFC. I found the defrost thermostat board and found the defrost thermister strapped to the liquid line before the condensor. Tested the resistance values and they were fine.
I spoke to a guy from Lennox who seems to think that it is a problem with the water lying in the bottom of the unit and somehow tripping the unit.
As there is no fault code on the controller i cant tell what it has tripped on:(

philjd26
12-12-2007, 06:28 PM
hi marc.. you mean liquid line after condensor? might wanna take a look where its located, be sure your getting a good reading of outdoor coil temp..somewhere mid way between tev in and outlet....

is it a pre set temp/time for defrost,have look at that aswell....

mcb tripping is probably like you said water getting in amoung electricity...suppose checvk the usual operation of indoor blower, compressors,fans etc...gud luck

rgrds phil

Brian_UK
12-12-2007, 10:50 PM
Hi Marc,

Some tech details for this unit if you want.. pdf file, some basic wiring diagrams that's all but....

http://www.lennoxeurope.com/transfert/E-IOM-Compactair-KVCK_KVHK-0404.pdf
or
http://www.lennoxeurope.com/transfert/E-IOM-Compactair-LVCK_LVHK-0304.pdf

marc5180
12-12-2007, 11:01 PM
Cheers Brian, Iv left site now and since iv been with it over 5 hours from 2pm this afternoon it has worked fine and hasn't tripped out at all.
To test the defrost was working i decided to cover the condensor when it was on heating which in turn caused the condensor to ice up heavily and then after a few mins the 4way valve switched over and sent hot gas through the coil. I did this several times throughout the day ad not once did it trip out. I'm leaning towards a possible faulty MCB or a freak accident that water got carried over to the electrics (doubtful i know but..)

Brian_UK
12-12-2007, 11:06 PM
I haven't worked on one of those models but have had similar problems which turned out to be the defrost board on one unit a faulty solenoid coil on the other.

I wish you well with it anyway. :)

marc5180
12-12-2007, 11:47 PM
I haven't worked on one of those models but have had similar problems which turned out to be the defrost board on one unit a faulty solenoid coil on the other.

I wish you well with it anyway. :)
Thanks i think i'll need it.:o

marc5180
13-12-2007, 09:05 PM
Went back to the unit again today and found circuit 2 coil totally frozen over although the unit hadn't yet faulted on the HVAC panel. Decided to conect the guages and watch the system, to see if the defrost and LP switch worked.
The SP was 1.0 bar and the DP 9bar.
The LP switch should cut in at 0.5 Bar although it didn't cut in whilst i was with it.
I watched the defrost take place several times ( fan stops, compressor keeps running, 4 way valve supposed to switch to cooling thus sending hot gas to the frozen coil)
The fan stopped but it seemed that no hot gas was sent down into the coil, i was watching the distributor waiting for it to melt all of a sudden... but it didn't happen.
I then got my solonoid magnet and tested the working 4way valve and as soon as i put on a magnet it switched over to cooling and defrosted and the ice build up on that circuit but on circuit 2 noting happened. Iv checked power to the coil of the 4 way valve which it has.
I then decided to remove the refrigerant and took out 4kg of R407c there should be 6.3kg so also the circuit is 2.3kg short.
I turned circuit two off but left circuit one running so they at least had some heating/cooling and i then ordered the 4 way valve which should be here by monday.
Just thought i would update you guys, i've never had a 4 way valve stick on me so this is a new one.
Cheers

Brian_UK
13-12-2007, 10:20 PM
They can fail due to shortage of gas because the discharge temperature starts to climb and cooks oil or internal parts of the valve.

Not always, but can happen.