Is position of evaporator fan vs. coil critical?

[kengineering]

Provided the fan unit is sealed to only allow air to escape through the coil. Must an evaporator fan directly face the coil? Ken

[US Iceman]

Ken,

The coil performance is best when the fan operates in a draw-thru configuration, i.e., the fan pulls air through the coil. This provides a more uniform air velocity through the coil, so the heat transfer is more uniform.

Most of these small display cases use propeller type fans since they are cheap. These types of fans cannot provide, or overcome very much static pressure so it is important to have an idea of the implications.

It sounds like you are living up to your name. Are you trying to do all of the engineering for these cases?

What are your bosses doing?

[US Iceman]

The guy asked for some simple information about fans. Bringing surge problems into the discussion is like starting to discuss string theory when asked for directions.

This only complicates the discussion for new guys trying to learn. I don't have a problem with what you said, only that it might be premature to dive into a complex subject when it might not be warranted.

[Lc_shi]

Fans selection is very important for system. In most case ,the fan is in drawing（pull the air) mode.But in some special case--for example,in evaporator condenser,use fan in blowing mode which can prevent fan motor from moisture and no heat add to the air.
Centrifugal fan demand max motor power at max air flow and zero static pressure; Axial fan demand max motor power at max staic pressure and zero air flow.
Now the backward -curved centrifugal impellers begin to use in ac ,which can be used without scroll house,so its installation is flexible.
I understand Iceman's idea and hope this thread can lead the fan discussion from ABC to XYZ-

rgds
LC

[Lc_shi]

Hi Marc，
it's really a good stuff!
Tell something about your commisioned project. VAV system, what do you mean by"finding the correct position in the correct duct to place the index pressure transducer ". It's a very interesting topic,hope you share more with us.

regards
LC

[afeef]

hi everyone
an advantage of fan tha draw air from evaporator , is that the other side of evaporator can easly be cleaned after period of time
the dust and air contanination be adhere to the first coile and fins of evaporator , this side must always be easy to reach to the purpos of cleaning

[chillin out]

Fans selection is very important for system.

Oh yeh? ,,, just wait untill service lads get to site and the only motor they have is a 10w multifit. LOL

All this critical designing that people do , in case nobody knows, is a waste of time, because when the thing breaks down at stupid O'clock in the morning, It gets fitted with whatever is on the van.


Chillin

[kengineering]

It sounds like you are living up to your name. Are you trying to do all of the engineering for these cases?

US Ice, At 53 I have developed an appetite for knowlege. I wish someone in my shop could actually mentor me but it seems the office "engineers" are too busy having a pissing contest about who knows more. Fact is they're all just talk as they seldom help solve problems.

The nickname was given by the shop guys because I'm the guy who gets thier hairbrained designs to work.

Example;Today I adjusted the SH to get my coil properly flooded and the case running good. It worked perfectly. My boss, the "refrigeration expert" as I was told when he was hired, said he would have just turned the cut out down a bit. Lets see that would be a cut out of 31psi gauge for r22 to acheive my 20*f evap and 35*f cabinet? very curious .

I cant tell you all how very happy I am to have found this site.You all have helped with this new found quest for knowlege even though I sometimes have to read your responses a few times to get the picture. I would go back to school but there just isn't a learning annex in my area. Sorry didn't mean to drone on. Ken

[US Iceman]

Ken,

Always happy to help...

Don't worry about the going on part. The helping part, for me, is fun. We all learn from each other, so the more we share, the better.

Everyone of us has had a mentor at some time, so it is part of the job so to speak.

How about this... The more we learn, the more we earn!

[Jasno999]

Fans selection is very important for system. In most case ,the fan is in drawing（pull the air) mode.But in some special case--for example,in evaporator condenser,use fan in blowing mode which can prevent fan motor from moisture and no heat add to the air.
Centrifugal fan demand max motor power at max air flow and zero static pressure; Axial fan demand max motor power at max staic pressure and zero air flow.
Now the backward -curved centrifugal impellers begin to use in ac ,which can be used without scroll house,so its installation is flexible.
I understand Iceman's idea and hope this thread can lead the fan discussion from ABC to XYZ-

rgds
LC

Can you break this down into more detail for me. I guess since I have not done a lot of this in the past I don't know much about it. I was hopoing you could break down your discussion and explain it to me in more detail at a lower level for a person that does nto have much experience with the subject matter?