Pressure testing

[eggman08.2008]

Hi guys,

I've just been going throught a old book and got to a section on pressure testing procedures.
The book says;

"if necessary, remove or blank any low pressure components or sensitive equipment that might be damaged by the pressure test"

Can anyone tell me what they might be, how to blank or remove them and when is this necessary?

Also, the book says;

" the system should be tested to a pressure 10% above the systems maximum running pressure"

How do I find out the maximum running pressure?
Is it stated somewhere on the outdoor unit?

Oh, Brian.

I dont have any donuts but i do have jammy dodgers:D

[casstrig]

Well basicly study your equipment,low pressure device could be for example the rupsure disk on a r11 centrifugal chiller it will rupsure at 30psi and of course you shouldnt reach this pressure.For maximum pressures they will be diferent for each type of system and will be less than safety device setting's.

[The Viking]

First of all we have to define what type of system we are talking about.

As you have posted this under the A/C heading, one assumes that we are talking about splits or VRV/VRFs...

Most of these will be heatpumps nowadays and as such doesn't have a low pressure side. (As the indoor unit will be the condensor whilst in heat mode and the evaporator whilst in cooling)

Typical components on the LP side that needs isolating includes:
LP switch, OP switch and any LP pressure relief valves...
(all depending on what's fitted to the system you are looking at)

In the good old days, maximum working pressure were normally defined as the saturated pressure at 55 degrees C.
But if we are talking about A/C systems you should find all the relevant test pressures in the install manuals...

[GXMPLX]

Can anyone tell me what they might be, how to blank or remove them and when is this necessary?

No. The only person who can answer this is you or someone watching the system, all I can do is give you examples of what to look for:
- Vacuum gages connected will break at 15 psi
- Low pressure gages will break at 250 psi
- High pressure gages not prepared for R410a will break over 500 psi
- Schrader valves should have their caps on or you can have flying bullets depending on the valve position.
- Safety valves are set to a pressure. Be very careful not to go over the value of valves that burst open. Generally these give you the limits on how high you can go.

You need to check the whole system and see what is hooked to it and look for information on how much pressure it can withstand. In general you should be able to go up to 350 psi except for R410a systems but YOU HAVE TO CHECK THIS!



" the system should be tested to a pressure 10% above the systems maximum running pressure"

It depends if you have to stick to standards, follow the standard. Note that this is RUNNING PRESSURE, not the maximum pressures I mentioned.


How do I find out the maximum running pressure?

This question makes me doubt if you should do any of this at all!

Look for manufacturer's information. If you can't find check if you have record data on high pressure in hot days.

Check if the system has any sign of corrosion first!

Be very careful not to let anybody close to the system especially if it shows signs of corrosion.


Is it stated somewhere on the outdoor unit?

Generally NO. But some systems do have test pressure information.


I dont have any donuts but i do have jammy dodgers

Lucky you I don't even know what this is!

THINK ... SAFETY FIRST!

[eggman08.2008]

So if im pressure testing a heat pump system then I dont isolate any components as they are designed to withstand high pressure.

Is that right?

[NoNickName]

You shouldn't be pressure testing a system. It come already pressure tested by the manufacturer, as Directive in force.
You shall only leak test, when needed.

[2007eng]

Hi guys,

Also, the book says;

" the system should be tested to a pressure 10% above the systems maximum running pressure"

How do I find out the maximum running pressure?
Is it stated somewhere on the outdoor unit?

Oh, Brian.

I dont have any donuts but i do have jammy dodgers:D

I recommended that you most revise your AC manufacture manuals for the testing pressure (not 10% above the systems maximum running pressure) this 10% may destroy your devices.
Normally you can find out the maximum running pressure on the service manuals.

[GXMPLX]

Pressure test should be done under a strict policy of safety procedures.

If a system does not show signs of corrosion or suspected for some reason, or you have policies demanding it, I would not normally do it.

I think isolating componets is a bad idea except for the high pressure receiver, if you are using it to store refrigerant.

A system should withstand pressures as a whole.

[jason09]

dude if you dont know how you should leave it alone

[eggman08.2008]

dude if you dont know how you should leave it alone


I work below a fully qualified engineer. Any questions I ask are just for educational purposes.

The reason im asking here and not asking him is because i've recently found out he's a cowboy teaching me bad habits.

[Peter_1]

After assembling, you should do a pressure and a leaktest according to EN378/2008.

If a system contains less than 2,5 kg (5.5 lbs) of the L1 refrigerants (those we use the most) and we can't separate low pressure side from high pressure side, then we may test at max allowable pressure on the low pressure side if the components on the high pressure side were prior high pressure tested.

Minmium value for allowable pressure 'ps' will be at temperatures of 55°C (131°F) when ambient is at or lower then 32°C (89.6°F) and 63°C (145.4°F) at ambient at or lower then 43°C (109.4°F)
For teh LP are the temperatures the same as the ambient
Test pressure will be equal or less than 1.0 ps.

The highest temperatures are those temperatures that can be expected during normal operations. When defrosting, temperatures can be higher.

[BigJon3475]

I do three inspection minimal. I'm in the US so if your requirements are different then it is what it is.

After brazing I visually inspect all joints.

Then I pressure test with nitrogen. Since the nitrogen we use would be considered "wet" if you were testing a ref. circuit for moisture. I think 1500 ppm but don't quote me. If you have a sight glass that indicates moisture you will see the "cheap" nitrogen is not truly dry. Real dry nitro is available here but @ 4-5 times the cost of reg. nitro.

So since I'm using that nitrogen and I did not vacuum the system first before adding the nitro I take not of ambient temps before allowing to sit for at least 1 hour would prefer more. Ever come back and have more pressure than you started with?? Even being inert I didn't remove the non condensibles completely before "pressure testing"
Admittedly if your purging nitrogen while brazing the possibility of air being trapped in the system is minimized.

If I'm testing the evap only I test to 300 psi...sorry for not converting to SI.

If it's the condensing unit it comes factory charge so there isn't much need to do that....unless you turn that service valve and no rush of ref.....opps! Check those before installing :)


The finally I release the nitrogen and pull a vacuum. If the system was known to have moisture in it a triple evac is in order and maybe a very long hold test under 500 microns/mtorr.

I have done test to see what happens to microns when a vacuum is pulled very quickly.
http://s68.photobucket.com/albums/i25/BigJon3475/?action=view&current=Boilingwater3.flv
http://s68.photobucket.com/albums/i25/BigJon3475/?action=view&current=boilingwater2.flv


Basically if you have moisture in the system the microns will not drop below 1000 till the moisture freezes. If you continue to pull on the system without adding heat it will take a very long time to achieve <500 microns even with only a very few drops. When reaching 1100 or so microns the microns stop moving and the temp. starts dropping till it reaches freezing it actually does this fairly quickly depending on the heat load on the system.

The test I did was actually to simulate using to large of a pump on a system to see detrimental effects of having to large of a pump....it was up for discussion so a test was in order. Sorry the movies aren't longer.

[NoNickName]

After assembling, you should do a pressure and a leaktest according to EN378/2008.


Neither apply for packaged units, though.