View Full Version : How much OFN...?

01-06-2012, 06:00 PM
Hi all,

Given the current climate (financial..), i've been asked to carry out the fitting of new PRV's to a couple of chillers. Whilst i have no problem undertaking the work, my main background is on the commercial side. The chiller has 2 circuits with 87/80kg of gas. The only problem i do have is estimating the ammount of OFN that would be required to pressure test the system.

Would anyone know an appoximate figure of OFN required to pressure test a circuit containing 87kg..?

With thanks,


01-06-2012, 06:13 PM
What are you proposing to do to the PRV's.
You state pressure test, surely you mean leak test your joint onto the system?
It is not a requirement to actually lift a newly fitted PRV.
In fact doing so may well cause that prv to fail.

If I am reading you wrong and you are wondering how much to leak check.

I would try and isolate the High side to reduce the amount required. because on a chiller that size you would logically need at least a large size K or W (BOC sizes).

01-06-2012, 06:30 PM

Thanks for your reply. Yes, sorry, I meant leak-test.

Just looking for a ballpark figure for an estimated amount of OFN to undertake the leaktest. As I have 2 chillers (four circuits) to fit new PRV's too. As part of the written scheme for the chiller, we are required to change the low-side PRV also. Point taken and already considered about isolating the high-side.

My background is mainly light to medium commercial so a small 10L OFN normall does me just fine.

For general interest the manufacturer (York) quoted 6,700 to fit new certified valves which were a further 800. Nice work if you can get it....

01-06-2012, 07:15 PM
I am always surprised as to what differing Insurance surveyors expect, especially as they apply pressure regs to all prv's on chillers.
When some are fitted to comply with en378.
As a rule lp does not require changing.
In fact if it's worth questioning upon what basis the lp side is being changed.
Some written schemes as I say are applied incorrectly.

01-06-2012, 07:23 PM
Hard to say how much, if in doubt give them an open price if quoting and be honest...tell them you cant estimate!

I normally just go on experience for a rough guide, and if in doubt i ask at a local supplier..climate etc if i can bring some of the cylinders back if i dont need them. Normally if your nice they can be ok with it.


01-06-2012, 07:25 PM
2 W size bottles from Boc should be ample remember to check the MWP Of the evap and stay 2 bar below (per circuit)

01-06-2012, 07:41 PM
I usually use a big bottle(size N I think) per system, should be plenty...