Toshiba R407c Reversing Valves

[Brian_UK]

I've been coming across Tosh RAV heat pumps running on R407c where the reversing valve has either stuck or is getting sticky.

The units have probably been working more on cooling than heating of late but ...

Has anyone else had similar problems ?

[Argus]

If you are talking about Tosh single splits, the reversing valve is a fairly robust device and it takes a fair amount to put it out of action.

Apart from a dud valve ? Tosh buy them in from Saginomiya, Ranco, and other valve OEMs as do most of the other Japanese manufacturers ? the reversing valves need at least 5 or 6 bar pressure differential to move the piston or internal chariot. Unless there?s a chunk of debris in there they tend to either work or not work. After all it has only one moving part.

But Tosh units have some peculiarities that may impact on the way the valve can work efficiently and not be immediately apparent. There is an unmarked filter in the system.

1. First, the compressor isn?t pumping. Obvious, I know, but it happens. I?m sure you?ve checked this because the pressures won?t be right. Some of the larger OD units have a schrader stub on the main suction return from the valve to the comp. It gives true suction pressure all the time, whereas the service valve port gives discharge pressure in heating.

2. The second gives the impression of a compressor not pumping and is unique to Tosh as far as I know. There is a small wire gauze filter in the suction pipe entry to the accumulator. It?s exceptionally difficult to see because it is in the pipe, covered in insulation and there are no marks to indicate its presence. The pipe at this point is ?? OD, so it?s small. It?s located about 70mm up the pipe on the entry side. If this blocks, the compressor gives the impression of not pumping or partial pumping. If pipes are shoved through walls uncapped, for example, this is the first place that masonry debris will collect. The pressures on the suction service valve and the suction stub will show a pressure loss across the filter if this is the case.

3. A third instance also involved the suction filter. Contaminated oil waxes up in the gauze makes a restriction and the resulting freeze solidifies more oil and blocks it. As soon as the temperature at this point rises, it dispersed and the unit worked until the next time. It happened intermittently in cooling. It?s very rare, but it does happen.

Frankly, that filter was a menace.

Hope this helps.

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[Brian_UK]

Noted, thanks Argus