SEER increase with TXV?

[star882]

If I replace capillary tubes with a TXV, roughly how much higher would the SEER be?

[Rtic]

You cannot replace the capillary with a TXV without installing a liquid receiver.

Have you done this - and may I ask why you would want to replace the Capillary with a TXV?

:cool:

[star882]

I'm working on an A/C that uses capillary tubes and I want to replace the capillary tubes with a TXV to improve efficiency.
http://toad.net/~jsmeenen/charge.html

From all my experience I can tell you that an air conditioning system is correctly charged when the liquid line leaving the condenser is full of liquid refrigerant. Adding more refrigerant will simply waste space in the condenser and reduce efficiency and raise the head pressure. The other issue is how well the refrigerant is being fed into the indoor coil. Most older residential systems use capillary tubes, newer equipment uses a drilled piece of metal called an accurator, piston or orifice, real systems use a thermostatic expansion valve (TEV) to regulate refrigerant flow. As far as I am concerned your system is not working correctly unless it has a thermostatic expansion valve. The difference is that mechanical restriction works only for certain conditions but a TEV. will deliver the right amount of refrigerant no matter what the head pressure is and allow a perfect charge (full liquid line without a drop more). Without this device you will have situations where you have to add excess refrigerant (full liquid line and a filling condenser) to raise the head pressure to push the refrigerant through the coil or the restriction (or a lack there of) lets too much refrigerant through and you have a liquid line that has hot gas mixed in with it and does what is called "flooding" or "slugging" the compressor (a bad situation). In either case the system is not working correctly and there is no "right" amount of charge that will make it work right. If you have restricted capillaries like we have seen on too many Rheem/Ruud units the coil will turn to a block of ice (cooling mode) and the compressor will run very hot no matter how much refrigerant you add to run up the head pressure. The solution to this is to replace the indoor coil with one that has a TEV. and a larger capacity and watch the system work better than when it was new.

[The MG Pony]

You DO NOT have to install a receiver, How ever you must really care fully charge it, basically it is a critical charge like a cap tube, how ever you must ensure it has sufficient starting torque. With a receiver it makes it much easier for charging as it is no longer critical.

A TXV will handle load much better then a cap tube, how ever for a R-22 unit you must select a VGA charge.

[momo]

Recently decommissioned (no gas left) a number of "prehistoric" (1980s) lower wall mounted systems (cooling only) found twin capillaries were attached to the evaporator coils, I was analizing the consequences of this etc in view of current styles of A/C:

1 longer liquid line: more refrigerant in circuit.
2 more critical charge (receiver (?) not visible - since removal at present of outdoor units was postponed)
3 noise of boiling refrigerant in indoor unit
4 thick wavy evaporator fins - out of fashion ? slits seem to be fashionable, nowadays with more rows
5 very heavy indoor unit (!) and built for a life time :)
6 simple electrics
... any other notes/comments of consequence?
Thanks in advance.

[The MG Pony]

With a Receiver the charge is not critical. With no receiver the Charge is critical.

All so the Condenser must be care fully sized, As once down to load you are basically using the condenser as the receiver for once the room is pulled down, under full load there must be enough to ensure the last bottom row is full and under partial load the last 4 rows are full for example.

[lana]

Hi star882,

What MG Pony said is absolutely right.

I don't agree with this part of your statement though.


TEV. will deliver the right amount of refrigerant no matter what the head pressure is and allow a perfect charge (full Liquid Line (http://www.refrigeration-engineer.com/forums/glossary.php?do=viewglossary&term=82) without a drop more).

Even TEV needs the design head pressure to deliver the capacity. This is why head pressure control becomes an issue during winter time.

BTW : I don't like cap tubes too:D .
Cheers