Variable Frequency Drive Reciprocating Compressor.

[Peter_1]

Some thoughts: first, USIceman is right, you will see the biggest benefits in a multiple evaporator setup like a pack/rack in a supermarket where the compressors can run in partial load.

The only advantage I see in a single setup is when lower ambient occurs you simultaneously reduce the speed of the compressor to maintain a LP as high as possible.

One of the benefits here in Belgium - and perhaps elsewhere - to use VFD's is the financial help of the Belgium government. They pay you a certain amount for a VFD for each kVA you've installed. (577 € for a 5 kVA, 1047 €for a 10 kVA, 1816 € for a 25 kVA, 2.678 € for a 50 kVA to give you an idea)

Core4Guy, I have no experience with Carlyle but we ran Bitzers for a longer time as low as 10 to 15 HZ as a test and monitored the oil pressure, all equipped with an oil pump. The oil pressure remained the same at 15 Hz like it was at 60 Hz.

We used several times Invertek inverters from the UK, cost far less then a Danfoss and performs just the same.
As with the Danfoss, you can connect direct your LP probe (4-20mA) to the inverter and let control the probe direct the inverter.

Then you have the not so cheap German Kimo inverters, specially made and programmed for refrigeration compressors. You can enter direct the used gas and the desired evaporating pressure in Pa or bars for example.

The "bypass speed" is also called the 'jump-speed'.