Only one shrader valve in unit - will vaccum be good ?

[piotres]

Hello

I want to know Your opinion about service ports . I've been curious if I braze only one shrader valve on suction side of unit (near compressor, unit with rotary compressor) will vaccum in whole unit be good enought ?

What is You opinion ?

I use 1/5 HP one stage vaccum pump .

Thanks
Best Regards
Peter

[{.bLanK} GoD]

If you vacume long enough, sure.
If you get a micron gauge, you can be 100% sure of your vacume.

[Patrickclouds]

i would always use two shrader valve. they aren´t that expensive :D

[DagoDuck]

I don't believe that this is a good idea. You need an additional service port for a good vacuum. Especially for such strong units. It saves a lot of time. A piece costs about 1-2 euro.

[[N@irolF]]

On top of that it's possible to check the low-side pressure

gr33tz

[Duniek]

no problem with use only one shrader ;)

I made rotary unit with one valve, and I made vac by 12k btu rotary
and I have 900-1000 microns after 1,5-2hour
in theory its sucks but works very good (-55@ 235W @r22)

when I made vac by profesional 2 stage vacuum pump I achieve about 100 microns after 20 minutes ;) and perfomarance is the same ;) maybe better -0,5*C :p:

in "our" very small units it doesnt matter, in bigger (industrial) maybe but not sure

[star882]

For something large like a central A/C unit, you'll want to vacuum from both sides as well as remove the valve cores or it would take longer than necessary.

[piotres]

OK, thanks for Yours opinions . :)

[Moc]

If you evac only in the lowside area, the highside will only evac through the captube... an that really takes LOT of time.
Use two schraders, definatly the better way.

@Duniek
A Rotary will NEVER make a vacuum with 1000micron!

[tim-]

more schraders = more possible places for leaks.

I don't use schrader on regular SS units when i do what I've done before and know it works good since they are potential leakspots, especially over time.
on next unit i will proberbly not have any schradervalves after charge and tuning, just braze it of.

[Moc]

Why don't you just screw the end"caps" on the schraders? Should solve the possible leak.

[piotres]

more schraders = more possible places for leaks.


That's what I'm afraid too :( ...not about costs, please don't be funny, one shrader cost around 1.5 eur so peanuts ;) .

[DagoDuck]

Then you have to wait only a little longer so that the whole humidity disappears. At least one valve is required. You can determine the pressure also with the help of the temperature.

[[XC] gomeler]

I agree with you piotres. I've stopped using high-side shraeder valves as whenever I remove them I typically lose a small portion of the charge as I quickly try to remove the hoses. I was talking with NoL about this same issue, far easier to braze in a gauge with a cap-tube connection and when done simply crimp and braze shut. I won't be using high-side valves in my upcoming cascade either, I blew out the entire CO2 charge on the last unit when I pulled the hose and the valve got stuck. Even with my thick gloves I could get a hand in there with a tool to try and wiggle the valve and save some of the charge.

[Clemmaster]

If your using a high pressure manometer you don't need two valves. The time needed may be longer but anyway you don't know how long you have to vaccum even with 2 schrader valves...

That's just a good solution to prevent from pipe cutting when the captube is block for instance, to remove gas in the discharge line but if you trust your brazing job you don't need it.

@Gomeler : don't tune a unit with the high side flexhose, when you remove the hose, more gas remains in than what you tuned for.

[august123]

http://kaeltetechnik-shop.at/index.php?a=5673&

use this and you wont have much leck when remove the hoses.

[[XC] gomeler]

Do those quick couplers let you depress the valve stem on demand? That'd be ideal, haven't found any of those in my local shop. Kind of like pneumatic quick disconnects.

[DagoDuck]

See below.

[piotres]

@DagoDuck : :eek: Shrader valve in not expansion valve :eek: .

gomeler;2813121']I agree with you piotres. I've stopped using high-side shraeder valves as whenever I remove them I typically lose a small portion of the charge as I quickly try to remove the hoses. I was talking with NoL about this same issue, far easier to braze in a gauge with a cap-tube connection and when done simply crimp and braze shut. I won't be using high-side valves in my upcoming cascade either, I blew out the entire CO2 charge on the last unit when I pulled the hose and the valve got stuck. Even with my thick gloves I could get a hand in there with a tool to try and wiggle the valve and save some of the charge.


Gomeler, we have been talking about leaks after finishing unit ...You know in LONG time term (more than one year) .

About losing refrigerant when we are unscrewing service hoses from shraders - that's why most times I put hi-side gauge on unit - and I just tune it without service hose from manifold connected to discharge side shrader :) .

Anyway in unit which I braze today I decide not to put hi-side shraders . Vaccum on hi-pressure side in going down much slower than in case we have shrader there, but it's going down :) (I see that on gauge built-in unit) .

[DagoDuck]

@piotres

I'm not so stupid. You have not understood me. I know that of course. We have just said that the high side will only evac trough the capillary tube. But what happens now with an expansion valve? I don't know how such a part is built, because I have never used it before.
If you evac only in the lowside area, the highside will only evac through the captube... an that really takes LOT of time.
I would like to know only if I can evac the high side also with an expansion valve by _one_ shrader valve in low side. Is my English that bad?

[Moc]

Ah... now I understand your question.
The high and lowside in a "expansion valve" unit is connected through the nozzle.
And because of this connecting, it will be evac'd too...
@Piotres
Vacuum on a gauge means NOTHING. Its important to evaporate water there (you know that for sure) and that really won't with just one schrader and normal vacuum times.

[DagoDuck]

And because of this connecting, it will be evac'd too...
That's what I wanted to hear. Thank you very much. :)

[DetroitAC]

it's a valid concern, DagoDuck has raised in my opinion.

When pulling a vacuum the txv is as closed as it can be. Normally it is not able to seal off since the valve is not designed to do that. However it can, and occasionally does completely close. I am an automotive refrigeration engineer, and in my experience its ~1 txv in 20 that will do this (auto txv). I only know because when testing I only evac from the low side port (complicated reasons for this), and I will once every year or so find a txv that is able to completly close (I have pressure tranducers at every point in the system so I can see it happen).

Commercial refrigeration txvs are not so different, but I can't say for sure if they would ever seal off like that. :shrug:

[{.bLanK} GoD]

For something large like a central A/C unit, you'll want to vacuum from both sides as well as remove the valve cores or it would take longer than necessary.

For commercial VRV systems we remove valve cores, vac from all three pipes (Liquid, suction and discharge) we vac through Cu pipes not hoses and use a 3/8" common pipe to the vac pump.

[[XC] 2long4u]

Auto ac somtimes comes without the high side schrader. I don't like these systems because it limits the diagnosis. The greatest fringe bennifit of the high side is when evacuating without a dedicated machine you can turn on the compressor to push most of the refrigerent into a seperate tank.