possible faulty fan board??? PUHY-P200

[DL A/C]

well folks, came across a unit today, the above outdoor unit, with four indoor 4-way casettes. they are piped through a 4branch kit with 1 controller.

anyway, on cooling mode the temperature off the indoor coils was 25*C, checked operation of outdoor unit and found cond fan motor turning very slowly, liquid line leaving the unit was very hot, checked power going to fan control board, 230v on each phase going in, 45v leaving the board.

changed the board with a unit next to it and got a reading of 84v leaving the board but performance was much better on the indoors, getting 10*c off the coil and liquid line much cooler.

would that little difference in voltage affect condenser performace that much?? looking for another opinon befor we go changing the board.

thanks alot

Alan

[Thermatech]

Did you take some data readings at the outdoor unit ?
suction & discharge pressure
suction & discharge temperature
Did you compare gauge & temperature instrument readings with outdoor data taken from display & dip switch settings ?

Which outdoor model ?
YM
YMF
YMF-B
YMF-C
YHM-A

What refrigerant ?
Was the subcooler LEV valve working to subcool the liquid line ?

Outdoor fan control stratagy depends on model type also correct temperature & pressure data.

For instance
On most R22 PUHY models the cooling target is evaporating temp = 0 at TH2 when outside air is >27deg C at TH6 which today I suspect it was.
So correct data from TH2 critical for correct operation of fan speed.

[DL A/C]

sorry my bad, just checked the specsheet and its a PUHY-P250YEM-A.

its running on R407C.

Had a suction pressure of 5 Bar and discharge pressure of 21 Bar when the the original fancon board was in it, when i swapped it, it had 3.5 Bar suction and 15 Bar discharge pressure with 10*C off the coils and suction pipe nicely sweating, also the liquid line no longer hot to touch. As soon as i swapped the orignal board back, it went back to acting up again!!

I did not check the data readings as im not familiar with the procedure.

[Thermatech]

For YEM-A model
outdoor unit target evap at TH2 = 0 when outdoor air temp at TH6 is > 10 deg C.
but
I think the outdoor unit will have lower target for first 10 mins of comp operation & then after first 10 mins change to tartget of 0.

So 3.5 bar suction for 1st 10 mins would seem about ok & 5 bar suction after 10 mins would seem ok.

So I am not sure the fan control board has a problem in this instance.
On this unit there is a refrigerant composition circuit & TH2 temp sensor is on that.
The composition circuit estimates the composition mix of the R407c.
If the R407c composition is not correct then the outdoor unit can change compressor speed & fan speed to compensate for incorrect refrigerant mixture. It uses data from Th2 , Th6 & HP sensor , Lp sensor. So for this composition sensor circuit to calculate correct refrigerant composition it needs correct data from these sensors.
It would be a good idea to check the CS sensing circuit refrigerant strainer & capillary for blockage & TH2 , TH6 for correct temperature data & LP , HP sensors for correct operating pressure data.
You can monitor the composition sensing circuit target & achived @OC composition data by monitoring with the SW1 dip setting & the outdoor control board display.
This outdoor unit also has two outdoor coil circuits with solenoid valve control. The outdoor unit will only use both outdoor coils at high load conditions so you need to confirm that the solenoid valve is operational & refrigerant can flow through both outdoor coils.
You also need to confirm that the subcooler circuit is working ok so that the liquid is being subcooled. For this you need to monitor Th5, Th7 & TH8.

You will need the service manual to uderstand the operation of the outdoor unit & how to minitor the data at the outdoor control board display.

If you are sure of the following
1/ The refigerant charge is correct
2/ The composition CS circuit has correct data
3/ The subcooler circuit has correct operation
4/ The refrigerant flow through both outdoor coils is correct at high load conditions

then go for change the fan speed control board & see if it resoves the problem.
But I suspect its more likely to be incorrect data from one of the sensors or blockarge at strainer/ capillary which is tricking the unit to carry out poor cooling operation.

[DL A/C]

thanks for all the info man, your a great help!! do you have service manuals that i could download maybe?? turs out i could be waiting 2 weeks for a board so i might try those things when i go back on site. id take it id have to recover the refrigerant to check the strainer yes??

[DL A/C]

ya, we got a fan board but still no luck, we were able to send it back so not so bad.

its very strange, we changed the main board with another unit and still the same. its works fine on heating mode, and when we disconnect the 4-way valve it shoots down to 7*C off the coils. we are due back on site soon for maintenance, will need to check other routes then

[Oleg]

Well,

I would ask... is this indoor is last in the line or on longest pipe.
If yes - looking for gas charge
If no - you did right thing - 4 way valve. Play with it... do 2-3 cycles on test run valve on/ valve off.
If helps or solenoid or valve. This is popular fault if installation was poor.
I had Daikin VRF where on branch box pipes were cross swapped.
On PUHY systems, newer ones Invertor goes from 60% up with 3 - 4 cycles in in 1 hour takes all load.
How to check sensors... no magic.
Take sensor out of housing and hold a) in fingers b) in your warm cup'a /don't say, you don't like tea time/. Then watch what happens with indoor
Solenoids.... put screwdriver inside and feel magnet :)
Remember, take your time. Better spent more but never come back.
Anyway. Have your company found the fault?
Maybe try Mitsu tech support in UK. Sometimes they're helpful.

[marc5180]

Or follow what Thermatech told you.