toshiba 407c vrf problem

[philjd26]

hi,
have a tosh (mar) type given me grief...its coming up with a chek 21, which can be a number of things,,ie high pressure or high inv sump temp...
watched unit running for a while in cooling, everthing seemed ok,fans ramping up and down, suction temp @5c, discharge temp 70c..liquid temp 30c....however i did notice that a discharge by pass valve would open for 2-3 minutes raising the suction temp to 11c....as far as i know it opens if suction temp/pressure is abnormal also if discharge temp gets so high 110c i think...does any body else know why this would happen? as all sensors seem to be good! also would anybody have a list of the functions for all these sv on this particular tosh!

regrds phil

[The Viking]

Is this on a 2 pipe or 3 pipe system?


We have came across similar problems a lot lately on the 3 pipe ones. Turns out that a valve in the MC box is letting by, so when the indoor units are in mixed mode hot gas is going straight in to the suction....

If this is the case, you will see it if you run 1/2 of the units in cooling and the other 1/2 in heating, then the suction temp will rise. (if it doesn't on the first attempt then swap the units in heating/cooling)


Good luck

[philjd26]

hi viking ...yeah its a 3 pipe system will have a look at that, as was on too tosh and they want me to check if all units are getting heat through the mc to Hex....

cheers phil

[Jase]

Favourite would be one of the discharge solenoids within the mc box. Watch out for this as it switches neutrals and if you do find that the coil has burnt out then order a new pcb for the mc box aswell as 9 times out of 10 the coils will take out the relays in the pcb

Jase

[Loops]

Hi Phil,

21 code is either HP trip or compressor overheating (on a VRF that is).

From your description (pressure would be helpful) I think that the by-pass valve (SV2 I guess) is opening to try to raise the head pressure.

I suggest double checking the gas charge - lets face it it's an old system and each time a manifold is connected some gas is lost. Maybe that finally enough has gone and is now causing a problem.

I don't think that there is a valve by-passing in the multi-controller because your suction temp isn't getting high enough for that.

Cheers

Loops