Chilled Water Coil question

[BobbyBJr]

Hello,
I was sent to wire and start up a Trane air handler with a chilled water coil in it today and noticed that the water lines are connected backwards. The cold water is entering the water out connection and returning back out of the water in connection. This causes the water to flow the wrong direction through the throttling valve and the strainer and puts the water control valve in the water supply line instead of the return. I pointed this out to our supervisor and he said it will work fine, but I have my doubts. I am thinking the coil has water in and water out on it for a reason. What you all think?

Bobby

[absrbrtek]

Coldest water entering the coil should be on the air off the coil on multiple pass coils. If its piped wrong on you will reduce capacity.

[DeltaT]

And the supply needs to come into the coil at the bottom and out the top so the water will fill up the entire coil. Otherwise it's very possible that air pockets will form on the top of the water as it flows down hill.

[sirtab]

Originally posted by absrbrtek
Coldest water entering the coil should be on the air off the coil on multiple pass coils. If its piped wrong on you will reduce capacity.

Yep, Sounds like it is piped parrallel.
If you can imagine the air and water colliding (counterflow) thats what your looking for.
The more rows on the coil the greater the loss in capacity.
2 row coil 6%loss 4 row 12% etc.(approximate numbers)


[Edited by sirtab on 07-22-2004 at 11:10 PM]

[sirtab]

Originally posted by DeltaT
And the supply needs to come into the coil at the bottom and out the top so the water will fill up the entire coil. Otherwise it's very possible that air pockets will form on the top of the water as it flows down hill.

Yep

[BobbyBJr]

Thanks for the responses. I am fairly sure we are sending a crew to swap the lines in the morning. I don't deal with chilled water very often and just wanted some other ideas as to what I can expect to see if they leave it. Thanks again.

Bobby

[twcpipes]

Also, if the CHW valve is piped backwards there will be a very good change it will chatter, if not start banging, when it tries to shut.

[lew2]

If it is piped backward the air temperature leaving the coil will be higher than normal. This will likely result in the space humidity levels being higher than may be desired. This may provide more of an IAQ issue over time as well.

[BobbyBJr]

Thanks to everyone who took the time to respond. The responses were pretty much what I had expected. The guys did go back and change the pipes and as far as I know it is running. At least, I am on call this weekend and I haven't heard from it yet...lol. Thanks again.

Bobby