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Abe
29-10-2001, 11:07 PM
I read here somewhere that the "best" location for a sight glass is near the evaporator and not just after the condenser. This is so we can observe if there is 100% liquid head and prevent overcharging system. Apparently after the condenser there will still be bubbles !!

In the UK, I have seen 99.5% of installations , lets make that 100% , of systems, ( that I have come across) with the sight glass attached to the drier and located just after the receiver.

I have yet to see a sight glass near the evaporator. My next installation I shall place the sight glass bang right before the expansion valve, just to rock convention, and also because I want to test it out for myself.

Is there a right or wrong about this?

Prof Sporlan
30-10-2001, 04:04 AM
I read here somewhere that the "best" location for a sight glass is near the evaporator and not just after the condenser. Perhaps you read something the Prof published... :)

As the Prof has noted before, the only problem with locating the sight glass near the TEV inlet and downstream of the filter-drier is bubbles in the sight glass may indicate either a low refrigerant charge, a restricted filter-drier, perhaps a solenoid valve that doesn't fully open, or it may not mean anything significant if it is located near the condenser outlet.

When ascertaining why a refrigeration system is malfunctioning, the service mechanic will invariably have to determine if the TEV is regulating superheat correctly. Having the sight glass near the TEV inlet provides a quick means to diagnose an improperly working TEV. Excessive flashing will, of course, cause the TEV to starve, and determining the cause of flashing is generally not too difficult. If the sight glass is clear, the cause of a malfunctioning TEV lies elsewhere.

HoPpa
21-01-2002, 11:56 PM
In the UK, I have seen 99.5% of installations , lets make that 100% , of systems, ( that I have come across) with the sight glass attached to the drier and located just after the receiver.
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I agree with you that most are fitted like this here in the U.K but it does have a valid reason too imo .At the condensing unit is where you charge the system with refrigerant so it makes sense to have an indicator that you can see whilst doing this .Ya know you can always fit two sight glasses in a system one by the drier and one behind the T.E.V.
Hope this helps..
Hoppa:D

Gary
22-01-2002, 02:22 AM
I have long held that sight glasses are essentially useless, except as a moisture indicator, being far inferior informationwise to subcooling temperature at the receiver outlet. In fact, they can be counterproductive in that they lead people to overcharge systems.

However, installing a sightglass at the TXV inlet may have merit. If the subcooling is about 15F and the sightglass at the TXV is bubbling excessively, there is a problem in between.

Hmmmmmm...