View Full Version : Inverter Compressor

13-11-2006, 11:57 AM
Kindly explain what role inverter play in, let say In Diakins K series VRV unit or in Mitsubishi vrv units etc, I have only one chance so for looking into the vrv unit and simply couldn't understand the principle of inverter compressor system and what advantage it has and how it work, why its called inverter compressor.


13-11-2006, 07:29 PM
Hi Anisaamm

The other members will probably correct me or add to this post. The basics are a compressor that can alter its speed to compensate for different load conditions and start up using a reduced amperage very much suited to single phase electrical supplys.

No heavy amperage on start up that makes the lights dim in a domestic property,or as well reduced running cost's.

It reduces or increases its loadings as and when required and of course the customer gets Enhanced Capital Allowance as it is classed as and energy saver.

Kind regards

R. skiffington
14-11-2006, 11:10 AM
Hi Anisaam,

What Lrac has said is correct. Also there is less "Start up wear" like a car the most wear occurs on start up, with an inverter not only is the start up process smother but, unlike a conventional compressor, as the system creeps closer to set point the inveter just winds down and basically idles right on set point, giving much closer control in simple applications. With a conventional compressor, say the set point is 22C the compressor might cut in at 23-24C then cut out at 22C, the control inaccurate, yes it is possible to decrease the differential of the set point but then you risk creating too many starts for the compressor, shortening it's life, unless an anti cycle timer is fitted, although most systems today will have an inbuilt delay through the PCB.

Hope this helps.

R. skiffington
14-11-2006, 11:20 AM
Sorry Anisaam,

I forgot to mention, more specifically related to vrv's, the load varies on a vrv greatly, so the need for a compressor that can cope with this variance is imperative. Let's say you have a system with a cappacity of 80kw, The demand on that system could easily go as low 10kw, you wouldn't put a conventional compressor designed to cope with an 80kw load and install it in a 10kw system, imagine the pressures!! it would just never work, So the inverter reduces/increases it's capcity to cope with this variance, in a mitsi the unit varies the capacity of it's condensor coil, also to work with this varing load


21-11-2006, 03:07 PM
according heating load to change frequency of compressor input to change rpm ;to get varible refrigerant volume

23-03-2009, 07:16 PM
Hi can anyone help i got a fridge the hermetic is running but the fridge it self is not cooling i can hear what seems to gas or liquid being pushed around the system this is a fridge/freezer phillips/whirlpool

27-03-2009, 07:50 AM
Is the Inverter based direct expansion system is better than Chilled water system.

31-03-2009, 07:15 PM
Sridhar 1312,

meaty stuff to start a new thread probably;)
.. if not existing already somewhere in this ocean of information!!

13-04-2009, 03:37 AM
Inverters offer variable capacity which categorizes them as VRF systems. There is also the Digital Scroll compressor.
There are definitely application advantages of VRF over chilled water systems. You can compare temperature control, energy consumption, ease of installation and maintenance, flexibility and zoning capability. By far, VRF systems are gaining popularity especially in Asia because they tend to be better over chillers on the said criteria.

26-08-2009, 01:36 PM
Well better an electric pump than a manual one for 40bar at that volume.

How will the compressor drive the secondary pump and how will the secondary pump work?

04-09-2009, 01:43 PM
for me.. inverters are excellent for their ability to vary capacity much more than even a 2 stage or standard TxV system can.. for areas and buildings that are too small to employ a chilled water system (such as a home,conference rooms,pool halls, dance clubs, etc)..

I use modified minisplit units in my zoning system at home and the results are incredible as to how much the comfort level has increased and the energy bills have decreased...

in my business we put them in conference rooms... . these areas typically have much oversized equipment for cooling (which also means the furnace is usually oversized too. )

we find using ducted splits maintains a high comfort level in the space as well as still being able to remove the high humidity load that occurs when you pack a room full of people. when the people leave for a break or lunch.. the unit throttles down yet still runs pulling out humidity so the room is clean and fresh feeling when the guests return..

in my home, my 3 inverters (2 1 ton, and 1 1.5 ton) rated can basicilly allow me 5500 BTU of cooling(or heating) all the way up to a max of 52,000 BTU..

so on days where I want to leave the windows closed all day and let the climate control handle things the system runs at very low capacity and maintains the environment well..

on days where I want to leave the windows open for fresh air until the heat and humidity are ungodly awful inside.. then close up the windows.. I have the capacity to cool it down very quickly then let the inverters throttle down and take care of the humidity...

different brands do different things, however the reason they are called "inverters" is because of how the compressor motor is driven...

typically in AC (alternating current) motors.. speed control was best achieved on a 3 phase system... typically only large plants or businesses have access to 3 phase power....

enter the inverter..

the single phase electrical supply is first converted to DC.. and then from that DC, 3 AC signals are generated.. each 120 degrees difference in phase... alas giving us the 3 phase power needed to employ speed control to an AC motor..

sound inefficient? the process of rectifying to DC then inverting to AC is a little inefficient, however the efficiency is gained back in the operation of the HVAC unit over that of a conventional unit...

inverter HVAC units are only more efficient than conventional systems when they are running at less than their maximum capacity... which in most cases they never run at 100%.. or do only for a short time.. unless of course they are severely undersized....

when spec'ing inverters it is more important not to undersize them than it is to worry so much about oversizing.. although like with any HVAC design you dont want to grossly oversize....

the other biggest issue i find with inverters is when it comes time to recharge them. it seems the only clear and accurate way esp on a mini-split is to charge by weight...

gas-n-go's are a big no-no in this industry but even moreso when dealing with inverters.. R410A is picky about its charge and with most minisplits employing electric expansion valves(often inside the outdoor unit) it is very tough to measure superheat / subcooling. some of the brands have diagnostic modes that will place the system into a "charge" or fixed maximum capacity mode where the compressor runs full speed and the expansion device is at maximum....


24-05-2010, 03:54 PM
is compressor in inverter ever stop when reach desired temperature?
or compressor always run but with slower speed?

little turtle
25-05-2010, 04:02 PM
is compressor in inverter ever stop when reach desired temperature?
or compressor always run but with slower speed?

when the desired temperature reaches, the compressor will runs slowest but if the temperature is not increase... the compressor then will stop

Yuri B.
25-05-2010, 04:07 PM
is compressor in inverter ever stop when reach desired temperature?
or compressor always run but with slower speed?
All thermostats in a system satisfied : all exp valves get closed, so, where the way for compressor(s) to "pump" the refrigerant around ? - the compressors of course, stop.

James priyono
01-08-2010, 02:23 PM
how to return oil to compressor?

01-08-2010, 10:34 PM
how to return oil to compressor?

In the unloaded state oil return will be poor. In simple terms (which is about the limit of my knowledge!) the VRV's are programmed to run at full jib every so often to get the oil back to the compressor.
Digital scrolls don't need to do this however. When I've refreshed myself why I'll post the reason here. Somehow they pump out less oil under loaded conditions.