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Markie
06-01-2017, 01:07 PM
Hi all,

I've recently started looking after a site that has a lot of old R22 indoor fan coils connected to either VRV 407c or VRVIII annd VRVIV 410a outdoor units. Quite a few of the old 407c systems are constantly throwing up F3 faults (high discharge temp). We've looked at them with a service checker and, although some of them appear to be obviously short of gas by the condensing and evaporating temp reading, a lot of them don't but still generate the fault every couple of days or so.
The sytems are 2 pipe only and have 8 indoors per system. When I run all 8 indoors on heating they tick along ok with a discharge temp of roughly 90-95C and liquid injection coming on periodically when temp rises and bringing it down again ok. I then tried switching off 4 indoors and found that the discharge temp rises to over 100C and injection coming on more frequently. Two units only on raises temp further and then with only one indoor on the discharge raises again to the point of cutting out compressor, going into discharge temp retry and ultimately into an F3 fault.
The indoor sensor readings would indicate that all the LEVs are working ok in heating and cooling. There is no issue with discharge temp at all in cooling. The 4 way valves and hot gas bypass valves also appear to be operating correctly.
This problem is currently occuring with 8 systems and they all react the same way i.e. the fewer indoors running the higher the discharge temp annd the F3 fault only occurs when there are only 1 or 2 indoors calling for duty. This doesn't seem to support the idea of a shortage of refrigerant as they will run all day ok with all the indoors on.
Any help anyone can give with this would be greatly appreciated!

Cheers,

Markie.

Neddy
06-01-2017, 05:08 PM
Hi Markie,

Firstly just to Confirm, the site has R22 indoors connected to R407C VRVs and R22 indoors connected to VRV III and VRV IV?

Tayters
06-01-2017, 09:36 PM
Overcharged or poor airflow across indoor coils?

qcfish
07-01-2017, 02:21 AM
The R22 thing is confusing to me. R22 older units retrofitted with 407C?


Ditto to indoor dirty coils but the compressor should be limited by many things including discharge pressure. Check target ranges.

Verify head pressure and the service checker show the same pressure. Discharge transducers can be off. What is your suction superheat? May want to pull and weigh the charge if there is any doubt. High suction superheat or high compression ratios can cause high DSH.

Markie
09-01-2017, 04:10 PM
Thanks all for replies. Yes, they are old R22 indoor units that have been retro fitted with 407C and some have since been replaced again with VRV IVs (RYYQQ 410a units).
The dirty coil idea could definitely be a factor. I'm told that the filters have always been cleaned on the maintenance schedule every 3 months since the year dot but that could be the problem, they've been in for over 20 years now. Access to the indoor units is restricted to say the least. Its a solid ceiling with only access through the filter, so if you need to get to pipe sensors you have to drop the whole fan deck out and you can only see that side of the coil as drip tray can't be dropped out.
In the next few days I will check what the actual gauge and pipe temp readings are against what the service checker is telling me to eliminate dodgey thermistors/transducers and then get one of these sytems reclaimed to see how much is in it. Looks like I'll be measuring pipe runs too (mostly above solid plasterboard ceilings!) as there is no markings on units or any commisioning paperwork to say how much additional charge is in systems. Brilliant!!
Ok, cheers for now.

Markie ;)

frank
09-01-2017, 10:12 PM
Sounds like the compressor is short of oil. With a normal discharge temp arounf 90 rising above 100 it doesnt take much for the unit to go into compressor protection mode.
Use a thermometer over the full height of the compressor when it is off to see the oil level.
If you add some oil to the pot does the discharge temp come down?

Blata
12-01-2017, 08:02 PM
Had the same problem with crossed wiring from another system, Poor airflow is also a possibility.

Expansion Valves not opening correctly etc from the sound of it you have a bitzer system, only one I know like that is in a large hotel in London.

frank
12-01-2017, 08:26 PM
Had the same problem with crossed wiring from another system, Poor airflow is also a possibility.

Expansion Valves not opening correctlyetc from the sound of it you have a bitzer system, only one I know like that is in a large hotel in London.

How can a Daikin VRV be a Bitzer ?

Blata
14-01-2017, 05:39 PM
How can a Daikin VRV be a Bitzer ?

I Know the site it has been upgraded over the years keeping the same fan coils and changing the PCBs, condensers, this has been done twice since the original install. The second floor was the First Daikin three pipe in the Uk, which has now been replaced

So as far as I am concerned its a Bitzer, bits from different models

Markie
16-01-2017, 12:50 PM
Yes Blata, I think you are indeed talking about this site. We have found a couple of systems cross wired but these were having pressure faults. Of the the systems with F3 faults I've found 3 that have no condenser fan running when calling for high speed as relay stuck on main pcb, a couple with dodgey discharge thermistors that were starting to give fluctuating readings and some others I will be checking the gas charge on.
There is good airflow and TD across the indoor coils but they do look a bit grimy so will be looking to give them a clean as I go along.
Many thanks for all your answers guys as it has given me good suggestions for what to look out for.
Cheers,

Markie. ;)

hyperion
16-01-2017, 11:16 PM
Markie,
I think I know the site that you are talking about, just off Cromwell Road? Changed many a compressor there in the past. The condensing units on the roof work fairly well, but not so the ones in the plantrooms on each floor.

Markie
17-01-2017, 02:36 PM
Markie,
I think I know the site that you are talking about, just off Cromwell Road? Changed many a compressor there in the past. The condensing units on the roof work fairly well, but not so the ones in the plantrooms on each floor.

Yes you are correct. I take it you worked there for a while. The units on the roof are mostly the old VRV 407c and some VRV IIIs. The 407c are the ones with mostly F3 faults. The units in the indoor plant rooms are pretty much all VRV IV (Q type R22 replacement) units and are quite new. The common fault with these is main pcb failure.

Blata
17-01-2017, 03:47 PM
If its any help I have a couple of sites with numerous failed Main PCBs on VRV 4, have already started a thread earlier asking I am the only one with failed main PCBs

So far three units showing LC14 faults fault, it is normally traced to inverter board or compressor Daikin assured me that it could not be the main PCB it was.

Three units showing expansion valve failure also main PCB

One unit showing low pressure in heating traced to main PCB no output to one of the 4 way valves

Daikin what the heck have you done

Markie
18-01-2017, 08:35 AM
If its any help I have a couple of sites with numerous failed Main PCBs on VRV 4, have already started a thread earlier asking I am the only one with failed main PCBs

So far three units showing LC14 faults fault, it is normally traced to inverter board or compressor Daikin assured me that it could not be the main PCB it was.

Three units showing expansion valve failure also main PCB

One unit showing low pressure in heating traced to main PCB no output to one of the 4 way valves

Daikin what the heck have you done

Ditto mate. Have had multiple faults here with E2, E3, LCs that have all been caused by faulty main pcb. Now if a fault code is not confirming something obviously amiss first thing I do is swap the main board with a system that's working ok. A lot of times I've found that the fault follows the board into the previously working system and the system that had the original fault starts working ok, hence faulty main pcb. Definitely seems to be a problem.