H/p L/P switch settings

[bernard]

When setting up switches is there is there a method for working out the settings including differential. At present I normally set up H.P. at 300 LP at 10. should this alter depending on the gas.

Regards to the wise ones.

Bernard

[Latte]

HP/LP Settings should be different depending on gas.

Take R12/R409(FX56) Head pressure should be about 120psi therefore when the system was pressure/strength tested is was probably put upto 150psi max. A HP switch set at 350 would be useless because the system whould blow well before then. Also if these gases were used in a low temp application (Unlikely i know) but the system would stop because the suction pressure would be if anything in a vac.

R404 Head pressure should be about 240psi running so an HP at 350psi would be higher than i would put it (Prob 325 at most)

R22 runs about 190-200 so 350psi also well excessive.

Let us know what kind of equipment and gases you are woking on and i am sure someone will post the OFFICIAL HP Guidelines.


Regards

Raymond

[bernard]

Raymond

Thankyou for your reply:

The one I am most concerned about is R407c.But what you say makes sence there must be a guide or % to set these switches above the hp running pressure.

Thankyou

Bernard

[Latte]

Sorry Bernard,
Got me on that one, never used the stuff yet & my HRP sliderule doesnt show it. If anyone has a list of HP switch settings or wants to put one together i would like to see it

regards

Raymond

[Brian_UK]

One way of deciding on the settings is to work out the condensing temperature at maximum design ambient then add a small overshoot allowance.

The differential should be quite wide to reduce compressor cycling; remember everytime the compressor starts it pumps a bit of oil out, if it doesn't run for long enough then the oil doesn't return.

End result - dry compressor - bang

If there is a continual head pressure problem then it should be investigated and rectified.

[Latte]

Hello Brian,
Maximum design ambient, now there is a subject that could take up a lot of space within the forum.

Anyone out there know the head pressures of R407 & R410 & what the HPCO's should be.

Regards

Raymond

[chemi-cool]

hi raymond,

there is no such thing,

what you said before is right for the uk.

over here, R22 works around 250 and more in the summer.
so the settings will be different.

I guess the setting depend on the working conditions.

chemi

[leonmartinharms]

1.you take the max avarage ambient for the region,say 35 deg.
2.take condensor td,say 15k.
3.add 5psi for safety
add 1,2 and 3 =35+15+5=55 degrees. this temp should match the pressure on hp gauge.
That applies to all gasses