high pressure protection

[karimihassan]

Hi,

i want to get information about selecting discharge high pressure switch.
for attract more attention i will explane more.
-one air condition system has max discharge operation pressure that system works properly,for protecting the system from riseing discharge pressure we should install a high pressure switch .i want to know how we select the reng of it.

tanks all friends.

[The Viking]

Normally you would look at the designed maximum ambient temperature, use that as the refrigerant's saturated temperature (on your gauges for example) and translate that to a pressure.
BUT, will the system cope with the pressure??
I would ask the manufacturer what the design pressure is for the specific unit..

[Lowrider]

In Holland we use the following:

Aircooled condensor, ambiant 32dgrC, HP at 63dgrC
Watercooled condensor, ambient 32 dgrC, HP at 55dgrC

Aircooled condensor, ambiant 42 dgrC, HP at 68dgrC
Watercooled condensor, ambiant 42 dgrC, HP at 63dgrC

But if it's a split unit the supplier is suppost to put maximal operating pressures and maximal allowed pressure on the unit!

Should look like the attachment or something similar!

[karimihassan]

thanks for your attention.

if possible give us regular formula to be able to calculate HP seting for different refrigeration gas at different ambiant temprature.

[Lowrider]

Just take the temperature and read off the pressure in a p-t diagram or your ruler! It's that simple!

[lana]

Hi there,

In your area the ambient temperature is very high during summer.

First of all you have to know your condenser design temperature difference.
If this difference is 10°C then you have to add 10°C to your highest ambient temperature and convert it to pressure with refrigerant temperature and pressure table. This pressure is your working pressure at highest ambient temperature. You pressure switch setting must be higher than this working pressure.

Example : Your condenser design temperature difference is 10°C. Your highest ambient temperature is 45°C. Then your condensing temperature will be 10 + 45 = 55°C
Find the pressure for this temperature : R22 --- 305 Psi(g)
You have to set the pressure switch above this pressure.

If the air cooled condenser is not designed for proper temperature difference then you will have high pressure problem.

Cheers

[karimihassan]

Hi there,

In your area the ambient temperature is very high during summer.

First of all you have to know your condenser design temperature difference.
If this difference is 10°C then you have to add 10°C to your highest ambient temperature and convert it to pressure with refrigerant temperature and pressure table. This pressure is your working pressure at highest ambient temperature. You pressure switch setting must be higher than this working pressure.

Example : Your condenser design temperature difference is 10°C. Your highest ambient temperature is 45°C. Then your condensing temperature will be 10 + 45 = 55°C
Find the pressure for this temperature : R22 --- 305 Psi(g)
You have to set the pressure switch above this pressure.

If the air cooled condenser is not designed for proper temperature difference then you will have high pressure problem.

Cheers

---------------------------------------------
Dear Sir.

Thanks for your explanation.
you mentioned that the setting is higher than the pressure corresponding to 10c above the maximum ambient temperature but i would like to know the amount of HIGHER according to HVAC standards.
does it have any formula.

[lana]

HIGHER [/U]according to HVAC standards.
does it have any formula.

Hi,

I have not seen any formula.
It must be higher than maximum working pressure. If you set it too high then there will be no safety. If you set it too close then you might get annoying cut outs during summer.
Cheers

[karimihassan]

Yes Sir.

we need the regular formula becuse evry body say evrything.

[The MG Pony]

Well he gave you the regular formula! 10c Above max ambient temp!

[paul_h]

Well he gave you the regular formula! 10c Above max ambient temp!

Not all condensers are rated for 10K though, it depends on the application, evap pressure etc.

You need to work at what that temp difference should be for your application, then what the design ambient is in your location to get the max temp you expect to see in your condenser.
Then use a P-T chart to get the pressure for your refrigerant, then set a HP slightly higher than that, like 100-200kpa higher

[The MG Pony]

Not all condensers are rated for 10K though, it depends on the application, evap pressure etc.

You need to work at what that temp difference should be for your application, then what the design ambient is in your location to get the max temp you expect to see in your condenser.
Then use a P-T chart to get the pressure for your refrigerant, then set a HP slightly higher than that, like 100-200kpa higher

Lol, I have no problem sizing them, my methode is propriatery, I take the refrigerant and system, figure the max pressur test then use an average of 300psi for R-22 down, as there is no way the system should ever get that high properly running, but it is still well within safe limmits of material.