TXV pressure

Any idea on how much pressure is usually (if there is a standard; or a sort of) used by manufacturers in a TXV bulb?

:)

Hi Before
I was told a by tutor that it was a secret but he suspected it was the refrigerant used in the system of an unknown charge. Like on an R22 system R22 was used...

Thanks Tesla.

As you can see in this picture, I have done the same modification for 2 TXVs here in order to use them with other refrigerants than those they were rated for.

The modification itself is quite simple: brazing a captube along with a schrader valve on the bulb. BTW I'm just wondering about the pressure to use... I guess this is not a matter of refrigerant (if the same refrigerant is used for both the system and the TXV) but of pressure. The TXV probably needs a particular range of pressure to work properly.

http://img691.imageshack.us/img691/1654/img9051o.jpg

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If the refrigerant in the bulb is the same as the refrigerant label on the valve (they mostly are)
then there is a saturated pressure temp relationship and the pressure will be obtainable by
measuring the temp and comparing it on a comparitor...

So on your system you would need to put a small charge of liquid into the phile bulb and work from there.

coolrunnings

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Unless the valves are MOP then things change a little.

Seems a very expensive way of replacing broken TXV's, or is this a test bed? Even so, all that work has already been done by the various manufacturers.

Hi Brian
I slightly disagree with you - Two weeks ago I was requested to change the element for an R22 TEV but the supplier said they no longer sell it as a separate item so I had to spend a whooping AUD$500 on a new valve for a chiller. It appears the distributors are ripping us off.
Before that is a great experiment - I like it, so please let us all know the results on control of superheat and the weight of charge you use. On reading through my old notes there are many different types of charges - liquid, gas (MOP), cross, and absorption (Activated Carbon).

What valve was that Tesla? Bought valve complete for 30yr carrier ( runs carrier 6D79 compressor, 3 ph), for around 380 bucks, still got the old one here.. Sporlan, PVE 8, ext equalised ;).. Mike.

Hi Mike
It was for an old 1971 HL 060A Chiller with a couple of 06E 275 compressors. I think the valve used to be an Alco but now rebadged as Emmerson. I paid around $500 for TRAE+30HC Ext Equalised from Actrols. Not sure what type of valve it was but thinking it is a critical charge with no solaniod valves I'm wondering if it should have been an MOP?. This 06E burnt out for the second time in less than three months (I was not involved in the first job) mainly due to short cycling. Strangely the rebuilders Recom advised to replace the element due to contaminants - I have not heard of this procedure before but did it to comply with the next warenty, the TEV was replace only three months prior.

Here the valves are not used as replacements, or well, lets say not as direct replacements. I mean, both of them are Alco TI-SWs which are rated for R404 and R507; but one serves for R23 and the other one for R14. Originally, the TI-SW is a liquid charge / no MOP.

Buying appropriate items would have been far more expensive than modifying existing products; so I'm doing a bit of experimentation.

I've had the time to test the TXV filled in with R23 today. Apparently, it works quite well with ~ 160kPa: tune to evaporate at about atmospheric pressure.

TXV's for low temperture application as R23 R503 and similar.

I have never experienced those used without MOP. It seems to be critical to hold the suction pressure pretty low to protect the compressor. To much gas return make wild discharge pressures which wear the compressors fast and often burn the valve plates.
The most common problem with the gas/liquid filling (MOP) I find on testchambers and ultralow temperature chillers is that the liquid migrate to the head on them and by that close the TXV for good/all time. The partially liquid filling must be a high boiling point type.
Just to recharge a valve with a singel gas, may be the same as the system use would be a thing I would avoid because of the lack of MOP function. The chiller brand use a heater cable around the head to prevent the head to be much colder than the bulb. Some testchambers start the cooling system with a bulb at +200c and the head at minus 40/45c. That made a lot of problems related to the migration occuring on MOP types as a drawback on them.