compressor run time for energy calculation

[Lkg4Info]

Just looking for advice.

I am using an assumed compressor run time (use factor or cycle on time) of 50% for estimating energy use (kWh) and cost. Does that seem like a reasonable assumption?

[mad fridgie]

That is a hugh question? It really depend upon what the application is.
For instance in the olden days, when we sized for a cool/freezer room we calculated on a16hr/day run time, but as the industry has become more competative, the design run time has increase upto 20hrs (lower install capital cost), Then on larger systems, designers are increasing the diversity factors, so equipment is running almost 100% of the time.
Then you have to take into consideration the effecy of the weather, in winter you find that load can be close to "0".
To do the job so it has some sort of relevence you need to do an annual load profile, for the particular application in the particular area that it is in.

[cadwaladr]

i always use the belt and brasers approach,if the custumer wants cheap ring someone else,then dont ring me when he has rode off into the sunset.

[Lkg4Info]

Let me clarify. I don't do design work. I'm just looking for ballpark numbers for possible energy saving projects.

This particular application is a recip compressor chilled water system (for process water cooling).

[mad fridgie]

Let me clarify. I don't do design work. I'm just looking for ballpark numbers for possible energy saving projects.

This particular application is a recip compressor chilled water system (for process water cooling).

This going to sound rude, but it will explain things.

I am looking at string saving projects, I am looking for ballpark figures on how long are pieces of string.
(PS I do not know anything about string, other wise I would not be ask the question here) And the client is going to pay me a fortune for my "lack" of expertise.

There are 2 ways to look at savings
"A" you get skilled engineer who just makes the changes, because he knows (no regard for history or payback)
"B" An indepth analasice (real measurements) then bring, in the skilled engineer who then gets to make descisions based up the report.

or a third option
Guess the original data (as you are doing)
make changes.
Guess the out come data. (as you will do)
write a computer program, with assumptions, and adjustments to verify that saving have been made.

Many of us have done this "creative engineering"

Mad