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View Full Version : Danfoss TS2 TEV outlet connection reduced


mrfrost
25-07-2009, 08:36 PM
All cold rooms in the system i'm working on are fitted with Danfoss TEV with connections 3/8" x 1/2". However, the valve outlets are directly soldered to 3/8" copper tubing immediately after the TEV's. The evaporators, about 10' away, have 3/8" inlet tubing.

Will this affect the operation of the TEV's? Does this have to do with the frost over the TEV diaphragms?
carlfoster
27-07-2009, 10:10 PM
Hi mrfrost. It is good practice to fit the TEV as close to the inlet of the coil as possible as you will get a drop in duty the further away it is.

With regards to the frost, this normally happens if the suction pressure is too low. Have you checked the inlet filter for blockage? Have you checked subcooling?

The 1/2" to 3/8" shouldn't be a problem but the 10' distance definitely could be.
lowcool
28-07-2009, 01:37 PM
danfoss used to state no more than 7 times the diameter of the pipe,7 x 12 equals length
Peter_1
29-07-2009, 08:00 PM
... It is good practice to fit the TEV as close to the inlet of the coil as possible as you will get a drop in duty the further away it is.

Why's that? What about the expansion devices in AC's installed in the outdoor units?
carlfoster
29-07-2009, 10:52 PM
Why's that? What about the expansion devices in AC's installed in the outdoor units?

I'm sure you've noticed that the pipe after the expansion device is cold to touch. That means it's absorbing heat. Some of the liquid is boiling off before it reaches the evaporator.

Therefore, the evaporator doesn't receive the full amount of liquid and the TEV will have to open up more to keep the evaporator 'topped' up. This is fine as long as the condensing unit can provide sufficient liquid, but if the sizing is critical or maybe the weather is extreme then the system could suffer.

When the supply to the evaporator is short, the pressure drops and you could get the icing up situation.

Now, about the a/cs with the expansion device in the condensing unit; they have been specifically designed for this purpose. The pipe sizing is very rigid and maximum pipe lengths too prevent this situation from occurring. Also, you have to insulate both pipes now whereas you used to only have to insulate the suction.