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remwel
05-02-2015, 12:50 AM
Hi All,

Please help me get this thing cleared.:(

We installed a TXV (Sporlan) for our 38AP/39HQ Carrier system.

There was a decision to cut the 1/4" equalizing line of the TXV and re-install with a flare connection. The decision was based from concerns on the test by which the liquid line and suction line will be simultaneously tested (300 and 550 psig respectively - isolated by valves). The line will be separated (from the flared coupling) and plugged to make sure (unfounded) that the valve will not be compensated from differing pressure of the low side and high side under simultaneous test.

I need professional info on whether this is sensible thing to do. Will there be problem (aside from the flared connection coming loose from vibration in the long term) because this is the first time that i installed a TXV with such connection. Normally as it is fixed I've tested systems not needing to isolate this equalizing line.

Your valued wisdom will be much help to me in explaining this to our client.

TIA

11956

monkey spanners
05-02-2015, 04:49 PM
Why not either braze the connection in once you have pressure tested or even fit a small ball valve in the line if you want to avoid flares.

Rob White
05-02-2015, 05:13 PM
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I don't understand what the problem is.

The External equalising connection is down stream of the TEV valve seat
and therefore the pressure on both sides of the line will be at 20 bar (300 psi).

If you close the ball (as per drawing) downstream of the TEV and pressurise
the liquid side to 32 bar (500 psi) you will equalise across the solenoid valve and
across the TEV? This is not normally how it is done.

For you to be able to completely isolate the high side from the low side you need the
ball valve (isolation valve) just before the TEV and then the high side will be upto that
valve and the low side will be after that valve and that will include the TEV.

Fit in a permanently brazed, equalising line or use a schrader connection but you do not
want any connections in the equalising line because that is just extra work and another potential leak.

In the drawing above you need to fully isolate the highside before the TEV not after it.

I notice you have Schrader fittings in the lines upstream of the liquid shut off valves
and downstream of the suction valves. How are you expected to measure the pressure
inside the evap with them there. You need at least one schrader fitting on the evaporator
(upstream) side of the suction valve.

Regards

Rob

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