Mitsubish city multi - not heating

[BROBERTSON]

Hi
I have an issue with a Mitsubishi city multi system not providing much heat.

system is circa 2001 - but still in reasonable condition. Outdoor is a PURY P250 YMF with 9 ducted PDYF P20 indoor units. I suspected it may have been short of gas - but recovered and gas charge - is as per commissioning sheet.

Hot gas seems to reaching the BC box(49c) - but air off temp at indoors is only around 22c

I got the following data from sw1

Comp freq 82
Discharge 20 bar
Suction 3 bar
BC box P1 47 P3 39
TH11 10.3
TH12 1.7
TH13 99?
TH14 99?
TH15 0
TH16 12.8
LEV 3 440

INDOOR LEV'S - ALL AT 2000

Any ideas?

[al]

What are your actual suction and discharge pressures? Do they correspond to what the system thinks the pressure transducers are reading?

[BROBERTSON]

Yes - gauges read the same as sw1 readings

[al]

Is it 407c? What discharge temp are you getting? Is compressor at full speed for above readings?

[BROBERTSON]

Yes it’s a 407c unit. I spent a bit of time looking at it today.one thing I found - was that th1 thermistor{ compressor discharge) was reading 123c even with the unit off, I changed the sensor but it made no difference, still showed 123c when running, when-pipe temp was only 76c.

Would this be enough, to stop the compressor ramping up to full load ? Im presuming it must be an issue with the main board causing the sensor reading error.

I have a board off a PUHY YMF C, it looks the same, but was going to check to see if it’s compatible with a PURY unit, as a replacement board is £350 .

[al]

Yes, i think this will prevent full load on compressor, big weird that just this thermistor is not reading right, worth checking board though.

[narkom]

If this is a PURY-P250 YMF-C unit than the discharge temp. probe is TH11 and not TH1.

[BROBERTSON]

Hi Narkom, thanks for your reply.

yes its a PURY - P250 YMFC CIRCA 2001

I was just going by the handbook I have image 2 pury ymf c .jpg sw1 .jpg

My manual doesn't list any SW1 switch settings for a th 11 - do you have them

thanks

[narkom]

This is the manual for a PURY-200YMF unit and not for PURY-P200YMF.
I have a manual for PURY-P400, 500YMF-C, hope this will help
https://www.mediafire.com/file/ijbxyd1se1zevb5/F1105_214.pdf/file