VRV-S heating operation

[mchild]

I have a VRVII-S that during heating operation will periodically stop one fan and drop the speed rather low on the second fan of the outdoor unit. This lasts for only a short bit – maybe 30-60 seconds and then both fans ramp back up to full speed. Indoor units continue to operate with blowers running during these periods. This can happen as frequently as 5 - 7 minutes. No fault codes are showing.


In reviewing the service manual, it states that if the high side pressure is greater that 454psi the fans will drop from Step 8 (both fans at full RPM) to step 1 where one fan stops and the second fan drops to 250 RPM. Is it reasonable to assume that is the operation I am observing and is it an issue that it happens as frequently as 5 minutes apart? Is this a normal part of the heating operation?


Thank you.

[Brian_UK]

Yes, it is a means of capacity control.

It reduces the amount of energy that the system can extract from the ambient air.

You will find similar control methods used on split system heat pumps also.

[wozza]

Does the compressor speed alter? If it does then it soiunds like it is going into a safety control to lower pressure tenperture so it does not tripo out.

[mchild]

Does the compressor speed alter? If it does then it soiunds like it is going into a safety control to lower pressure tenperture so it does not tripo out.

With the air noise from the fans running it is a hard to hear the compressor until the one fan has fully stopped and the second fan is down on step 1 - 250 rpm. And then, almost as soon as the fans are at that point they start back up to run at full speed. So, there is a very short period that I can hear the compressor. It may have been slowing - but hard to say with out any test instruments.

Is this an operating condition that I should be concerned about or is it normal with the system managing it as it is supposed to?

Thank you.