VFD for Chilled Water Pumps and Condenser Water Pumps

If they really want to save energy and money start by firing people in the upper office levels until they are down to just enough people that everyone is actually working as long and hard of hours as the people at the bottom are!

Instead of spending millions to save thousands you could end up saving millions and actually become a more efficient company too which would really be worth value in the end.

Before investing in VFDs, try other things.

Why not just try turning off the lights when you leave the room first.

Explain why it is not possible for piston type compressor to use VFD?

It is possible.Also you can use it for chiller sas wel

All things are possible - reciprocating loads can cause issues w/ VFD's that typically are not seen w/ across the line MSP's - because the VFD can / does react faster to changing load, etc. on / at the motor. Sometimes just oversizing the VFD is enough.

Centrifugal pumps are less of a problem, forget the word for the principle, simply put the pump curve changes as a function of speed (NPSHR, TDH, Q, HP). Generally in mostly inconvenient ways, but can and is done.

And think a little about changing speed on lubricated equipment, e.g. compressors.

Yes it is. I'm not sure what the ROI will be.

Get the bean counters upstairs to work that out.

You can do lots of things but it doesn't always yield a real saving.

Of course if you just want to reduce energy consumption because of either a supply/resource limitation or your company needs a green halo and not doing it to save money then knock yourself out.

What is the capacity of these pumps and its operating pattern. How big is the size of the chiller. If you consider VFD for pumps then why nit at AHUs?. By observing the operating parameters and carrying gout regular maintenance is another way to save energy in central a.c plants.

" it is not possible to use VFD on piston type refrigeration compressor "

Has your recip compressor unloading/partially loading facility?

jhunair,

In one word, yes. Centrifugal pumps follow what are often called the "fan laws", which relate changes in speed to changes in power and flow. Most of the time, pumps are originally designed and installed with somewhat excess power compared to the actual load. If you have a good design for control, a VFD will allow the pump speed (and volume) to match the load, particularly as the load changes because of changes in refrigeration loads. This will result in considerable savings when the loads are light. A phrase often used is "the devil is in the details". Probably you have a similar form of statement in your country.

--JMM

The reciprocating pumps are not as easy to control as say a vane pump but you can still use a VSD. Turndown will only be partial though compared to a vane pump.

Condenser water pumps connect to cooling towers that are fitted with nozzles which have a fairly narrow max/min flow requirement. Inadequate flow will cause scale build up. Also, cooling tower fan motors connected to centrifugal fans could overload with reduced water flow. VFD's on condenser water aren't such a good idea.

They are great for cooling tower fan motors. OK for chilled water as well as long as flow doesn't become laminar at the heat exchanger.

Hello Sirs,

Thank you for all the inputs I thought adding VFD can have effect on energy savings you have to consider many factors.

First of all u have to see how long pumps are going to run at Different load conditions and then what variations.If it is going to be a operation for short time initially and then run on full load it may be sensible to use a smaller pump and then switch over.Whole process needs to be analysed before a decision and investment is made.