Mitsubishi City MULTI 1501 FAULT

I have a problem with a city multi system on our site.

Its a PURY P250 YMF with 10 indoors, been on site for around 10 years. But for about the last year It keeps cutting out on a 1501 fault generated mostly from the outdoor but occasionally from the BC box. The System has, 2 units which run continuously 24 /7 and the rest on a 6am - 6pm schedule. The fault generally occurs after 6pm.

The system has been vac'd, leak tested and recharged with new 407c. But because the fault is intermittent when the service checker has been installed all expansion valves etc seem to be operating ok.

I tried running 5 units 24/7 as I know only running a couple can cause issues - but even with 5 running 24/7 it still cuts out once or twice a week. Maintenance Contractor have been out about 5 times - but can't seem to find what is causing it and is unwilling to leave their service tool connected. The only solution they have offered is replacing the entire system!

Unfortunately it is on the floor that we rent out and serves individual offices and because the units won't run until the error is manually reset the tenant is frequently coming in to cold rooms.... not happy bunnies

Any ideas anybody

1501-. When the unit condition is as
follows, the compressor is
stopped (1st detection) and after
3 minutes, the compressor
is restarted automatically.
PUHY-P200·250YMF-C
1 F<60Hz and TH10>85°C
continuously for 60 minutes.
2 F<60Hz and TH10>95°C
continuously for 15 minutes.
3 F 60Hz and TH10>100°C
continuously for 60 minutes.
4 F 60Hz and TH10>110°C
continuously for 15 minutes.
PURY-P200·250YMF-C
1 F<60Hz and TH10>85°C
continuously for 60 minutes.
2 F<60Hz and TH10>95°C
continuously for 15 minutes.
3 F 60Hz and TH10>100°C
continuously for 60 minutes.
4 F 60Hz and TH10>110°C
continuously for 15 minutes.
2. If the temperature rises again as
above within 2 hours after the outdoor
unit is stopped (2nd detection),
an error stop is performed, and the
check code 1501 is displayed.
3. If the temperature rises again as
above within 2 hours after the outdoor
unit is stopped, it becomes the
first detection again, and operation
is the same as in 1 above.
4. The 2 hour period after the outdoor
unit stops is the abnormal delay period,
and LED display is carried out
during the abnormal stop delay.

How this mistake in a manual is described? I looked 2 manual in the Russian and American option, both speak about the underestimated overheat on discharge, in other words the invertor compressor fills in. How it is possible with a huge barrel of a separator of liquid not clearly) something can happens to a discharge thermistor?

Quote:

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Originally Posted by beebarron

I have a problem with a city multi system on our site.

Its a PURY P250 YMF with 10 indoors, been on site for around 10 years. But for about the last year It keeps cutting out on a 1501 fault generated mostly from the outdoor but occasionally from the BC box. The System has, 2 units which run continuously 24 /7 and the rest on a 6am - 6pm schedule. The fault generally occurs after 6pm.

The system has been vac'd, leak tested and recharged with new 407c. But because the fault is intermittent when the service checker has been installed all expansion valves etc seem to be operating ok.

I tried running 5 units 24/7 as I know only running a couple can cause issues - but even with 5 running 24/7 it still cuts out once or twice a week. Maintenance Contractor have been out about 5 times - but can't seem to find what is causing it and is unwilling to leave their service tool connected. The only solution they have offered is replacing the entire system!

Unfortunately it is on the floor that we rent out and serves individual offices and because the units won't run until the error is manually reset the tenant is frequently coming in to cold rooms.... not happy bunnies

Any ideas anybody

---

Just a thought the 1501 is lack of refrigerant fault and below is the symptoms that will create the fault code 1501

1
F<60Hz and TH10>85°C
continuously for 60 minutes.
2
F<60Hz and TH10>95°C
continuously for 15 minutes.
3
F 60Hz and TH10>100°C
continuously for 60 minutes.
4
F 60Hz and TH10>110°C
continuously for 15 minutes.

I presuming the 24/7 units are supplying a server room with low humidity. This can lead to low suction pressure and higher discharge temperatures so i would say it may be one of three issues

1. Slight lack of refrigerant
2. Discharge pipe thermistor out of calibration
3. Low indoor humidity (server room) 24/7 leading to low suction pressure and higher discharge temperatures

My question is:

1. How long has this fault been occuring and is there any relation to the units operating 24/7 and the fault 1501?

http://yadi.sk/d/1MHpNb3i1xi-y

look at flow

The system is low loading, with only the two units left operating , the same would occur even with the five units left running, as the units reach set point and drop off .The indoor unit that is placing the demand on the outdoor to run is to far below the diversity threshold.
This combined with refrigerant effectively becoming trapped out in the other indoor units and the BC when all the LEV's and solenoids close cause the back pressure to drop off rapidly which in turn drives the discharge temperature up.
Solution is to maintain diversity above 35% or replace the two units with the 24hr operation with splits.
Cheers
Stu