Indoor/outdoor mismatch

[Temprite]

Hello all.
Have a small problem just wondering which way to go with this.
Thought some of you chaps may may be able to help.

One of our mechanics diagnosed a burnt out compressor on a split(that we did not install). He correctly ordered the new compressor for the unit and installed it.

After weighing in the gas charge he tested the system.System was running very low suction pressure.Switched system to heating and head pressure extremely high.

At this point he gave me a call.After inspecting this I went and compared the model numbers.
This is what I found.

Daikin
Outdoor RY60EV1A
Indoor FVY453CBV1

Incorrectly matched units!:mad:

Now I have a problem because the units are not manufactured any more.

I think the units are probably about 8 years old so they were working for that period.

As far as I see I only have a few options.

1.Find a used outdoor unit of the right capacity(Which isn't practical because customer has paid for a new compressor.)

2.As we use splits here for mainly heating, adjust the gas charge so that the head pressure isn't so high on heating.

3.Find a current Daikin outdoor unit of the right capacity (If there is one available) and swap the electronics over.

Does anybody have any suggestions?
Thanks in advance.

[botrous]

Hey , i had a similar problem and i'm still searching for what to do ....
A customer called me , so i sent a friend that judjed the compressor is burned and he was right , but he ordered a 21000 btu shanghai hitachi compressor instead of a mitsubishi 24000 btu , the unit is haier 22000 btu . . . so now the compressor is heating a lot . . . no real cooling .... and the customer paid for the new compressor .... what's practical to do . . . .

[frank]

The outdoor unit is a 6kw E series and the indoor is a 4.5kw C series. I'm amazed that the electronics talk to eack other.

The ceapest suggestion I can offer is to reduce the effective area of the outdoor condenser by 25% by pinching off a few rows to effectivly make it a 4.5kw coil and then reduce the gas charge accordingly. If the electronics are working ok then the fan speed regulator should kick in OK. To ensure that the compressor duty is reduced accordingly you could fit an inverter and control the maximum frequency but I expect that the cheaper option for this would be to source a replacement indoor fan coil.

Incidently, we had a similar mismatch at a customers server room (not one we fitted :D ):D some years ago and ended up fitting a new system

[rbartlett]

surely the best way to de-rate it would be to put a brick on the incoming mains to stop some of those wiggly amps getting through..-

keep squeezing by adding a brick till you get 75% of the full running current and volia a 60 becomes a 45..it's a real piece of piss this a/c lark ;-)

cheers

richard

[frank]

surely the best way to de-rate it would be to put a brick on the incoming mains to stop some of those wiggly amps getting through..-

keep squeezing by adding a brick till you get 75% of the full running current and volia a 60 becomes a 45..it's a real piece of piss this a/c lark ;-)

cheers

richard

Geez Richard, was all that info on the B&Q CD:D

[rbartlett]

[QUOTE=Temprite]Hello all.
2.As we use splits here for mainly heating, adjust the gas charge so that the head pressure isn't so high on heating.

QUOTE]


hey be careful -your're letting the cat out the bag regarding australia always being hot !!

cheers

richard

[Temprite]

[QUOTE=Temprite]Hello all.
2.As we use splits here for mainly heating, adjust the gas charge so that the head pressure isn't so high on heating.

QUOTE]


hey be careful -your're letting the cat out the bag regarding australia always being hot !!

cheers

richard
True, but the wind that's blowing in from antarctica at the moment is anything but warm.:)

[Temprite]

Just an update.....

Trimmed gas charge today so that unit was operating ok.

There is an outdoor unit model RY45EV1A that is still available,apparently the electronics are the same as the RY45CV1.

Recieved a voice message late today telling me that this indoor/outdoor mismatch was used in previous years.Have to make a call tomorrow to find out.

Thanks for the replies.

[Temprite]

The outdoor unit is a 6kw E series and the indoor is a 4.5kw C series. I'm amazed that the electronics talk to eack other.


Daikin are aware of the mismatched units apparently you were allowed to hook them up this way but you had to change a PCB in the indoor unit.
The reason for doing this was to obtain more capacity from the indoor unit.

[Abe]

surely the best way to de-rate it would be to put a brick on the incoming mains to stop some of those wiggly amps getting through..-

keep squeezing by adding a brick till you get 75% of the full running current and volia a 60 becomes a 45..it's a real piece of piss this a/c lark ;-)

cheers

richard


Richard.....plz tell this uninitiated what a brick is.......
:confused:

[moperer]

I've seen this work before too, did you decant all the oil before replacing the compressor?

[Temprite]

I've seen this work before too, did you decant all the oil before replacing the compressor?

I didnt change the compressor myself.
Why?
Remaining oil in the system?

[Gary]

Possibly the indoor fan speed can be increased?

[Temprite]

True but it is factory set and I couldnt rely on the customer to keep it on high speed.

[Temprite]

Still having trouble with this unit.

Gas charge was weighed in 2.4kg according to daikin for this model(model number is visible but charge is not due to label fading.)

Customer rang and said operation light was blinking.Arrived on site fault E5 compressor o/load.

Ran unit on cooling.
Suction pressure about 24 psi
indoor air on 16 degrees c
indoor air off about -4 degrees c
indoor coil sensor was reading -9 degrees c.Had daikin transmission monitor hooked up to unit which gives you all the sensor readings.Also checked indoor coil sensor against my k type thermocouple to prove it was reading o.k.

Ran unit on heating.
Discharge pressure went up slowly and got to the end of my gauge after approx 10 mins (450 psi).
Indoor air on about 21 degrees c
Indoor air off was over 50 degrees.
Discharge pipe temp at gas service valve about 103 degrees c.
Indoor coil sensor 49 degrees c.
Outdoor fan was running on low fan speed(apparently outdoor fan stops on heating when indoor coil temp sensor gets above 60 degrees c)
(r22 refrigerant)
The elbow that the indoor coil sensor is attached to was distinctly lower in temp than the rest of the coil and this is on the very bottom pass of the indoor coil.The inlet and outlet are about 5 passes higher.
As a previous post by moperer said.I am thinking that some of the oil from the old compressor is trapped in the indoor coil and the indoor sensor is telling the out door fan to continue running when it should be stopping.

Outdoor pipe connections are 5/8" and 3/8" this pipe runs all the way to the indoor unit and is reduced 3" before the indoor unit to 1/2" and 1/4".
Speaking to the tech support they suggested that there may be a kinked gas pipe or a restriction in the indoor coil. I dont thing there will be a kinked pipe because the pipe has not been touched since the unit was new.Which I am estimating that it is about 8-10 years old.

Any advice is always appreciated.

[frank]

Ran unit on cooling.
Suction pressure about 24 psi
indoor air on 16 degrees c
indoor air off about -4 degrees c
indoor coil sensor was reading -9 degrees c.Had daikin transmission monitor hooked up to unit which gives you all the sensor readings.Also checked indoor coil sensor against my k type thermocouple to prove it was reading o.k.

This appears to be a restriction in the system. Suction pressure that low with an air off of -4 is a serious fault.

[Gary]

These numbers confirm what I posted earlier. The indoor coil needs a lot more airflow. In fact it is worse than I first suspected. You may in fact have air blockage.

[Temprite]

[QUOTE=Temprite]Hello all.
2.As we use splits here for mainly heating, adjust the gas charge so that the head pressure isn't so high on heating.

QUOTE]


hey be careful -your're letting the cat out the bag regarding australia always being hot !!

cheers

richard

I think you must have cursed me:D .Today it snowed here, which is strange because we are at sea level right next to the ocean. Or backyard had about an inch of snow.
Apparently it has never snowed here before. About half the calls that came in today were confused people wondering why there split systems kept stopping.

[Temprite]

OK
Have finally sorted this problem.Ran unit with outdoor unit covers off so I could see all pipe work.
I could see frost forming after capillarys on outdoor unit. Similar to low gas charge, except gas charge was Ok in this case.
Ordered new capillary assembly,which arrived late Friday, replaced in the dark (customer had waited long enough).Leak tested,evacuated and recharged unit.
Operates good now
Discharge pressure 270psi.
Return air at indoor about 20 degrees.


This unit will always run a slightly higher discharge and lower suction due to mismatched units.

I have replaced blocked capilarys in split a/c units before but the head pressure didnt rise so quickly and so high.
I didnt think a restriction in the capillarys would cause such a high discharge pressure(over 450 psi).Again I think smaller indoor unit made this problem worse.
Gary couldnt the high TD be also be caused by too small indoor coil?

This unit had a copper spun bi flo dryer which i replaced with an 053 type. Anyone know where to obtain these because the 053 was a tight squeeze.
Thanks all for suggestions.

[Gary]

OK
Have finally sorted this problem.Ran unit with outdoor unit covers off so I could see all pipe work.
I could see frost forming after capillarys on outdoor unit. Similar to low gas charge, except gas charge was Ok in this case.
Ordered new capillary assembly,which arrived late Friday, replaced in the dark (customer had waited long enough).Leak tested,evacuated and recharged unit.
Operates good now
Discharge pressure 270psi.
Return air at indoor about 20 degrees.


This unit will always run a slightly higher discharge and lower suction due to mismatched units.

I have replaced blocked capilarys in split a/c units before but the head pressure didnt rise so quickly and so high.
I didnt think a restriction in the capillarys would cause such a high discharge pressure(over 450 psi).Again I think smaller indoor unit made this problem worse.
Gary couldnt the high TD be also be caused by too small indoor coil?


It is the dT, not the TD that tells us about airflow. The high TD is indeed caused by the mismatch. This can be compensated for by increasing the indoor airflow.

Are the new capillaries the same size as the old capillaries? Are they sized for the indoor unit or the outdoor unit?

[Temprite]

Sorry I always get TD and dT mixed up.

The capillarys are a direct replacement part from Daikin they are in the outdoor unit. They are sized to suit the larger outdoor unit.

Unit is working ok now but I advised the customer that they keep the fan on high where possible. The only possible way to up the fan speed would be to replace the indoor fan motor with one from a larger model.

Unless......
If I look a bit further into it there may be a jumper on the indoor board that you can cut that will increase indoor fan speed, but I doubt it.

[Gary]

A change in temperature of a single thing is a delta-T.

A comparison of temperatures of two different things is a TD.

If you subtract air on from air off you are measuring the change in temperature of a single stream of air, therefore it is a dT.

If you subtract air temperature from refrigerant temperature you are comparing the temperatures of two different things, therefore it is a TD.

I would start by making sure that the indoor airflow is not obstructed, coil clean, fan blades clean, fan running in the right direction, etc. Then I would ensure that the fan always runs at its highest speed.

Measure the air on and air off temps to see if it is enough airflow.