Rs 44 ref

[Darrenp]

Hi guys , need a bit of info , been on the most horrendous job the last 3 days , had an Airedale unit attached to a ahu (dx) had to change comp drier as a retro fit , this unit had rs44 and I was changing to r407c as requested , now I changed everything and once up and running the discharge was going through the roof at 350 psi , suction wasn't too bad at 60 psi..

But the standard charge on this old Airedale said 2kg and additional said 6 kg of rs44 , now it was only 10 m pipe run to ahu and the ahu coil was only small . So not entirely sure what's going on ,, the only thing that wasn't changed was the expansion valve at ahu which was still r22 , not sure wether this should be changed as well ?

But should the same amount of r407c have been added ?

Could do with some brains on this chaps , comp also getting hot at 117 degrees ..

[Rob White]

.

How much did you remove?

That would give you a guide to start from.

Rob

.

[Darrenp]

Nothing as it was empty , lost gas !! Airedale couldn't help either

[monkey spanners]

R407C is pretty similar to R22 (think sporlan use the same valve) though the TEV may need adjusting if it has been optimised for RS44 previously.

Haven't a clue charge wise, i'd probably go by subcooling or full sight glass and a squirt more, but keep an eye on things incase it was getting silly.

[Darrenp]

No sight glass ,

[Darrenp]

Just trying to work out why head pressure so high , coils clean , new drier on system , vacced well , so ruling out non condensables , txv ?? Mmm

[Darrenp]

But defo getting ref through the txv as it was 6c , adjusted , I did condemn it before buy typical management know better , system is 16 years old

[monkey spanners]

If liquid line subcooling is high, system could be overcharged which would go with the high head pressure.

[passandscore]

Perhaps this will be helpful.

[chemi-cool]

Replace TXV and add a sight glass before.
Forget whats written as for the original charge.
[I know it is dumb to say] make sure you charge liquid.

There is a blockage somewhere and the TXV sounds like a good spot to start from.

[Darrenp]

Yeah iv orderd a new 407 txv and sight glass so will try this ... Cheers

[aircontony]

RS44 was a replacement for R22, i would of charged your system with R417A.R407c you will be prone to leaks in places you never had before !
Think you may be overcharged. What tempereature is your liquid line? is it cold to touch? if so its overcharged.
Decant slowly if so until your head pressures drop.

[Darrenp]

It was charged with 407 .. That's what I replaced with , only had 2kg in , this is what Airedale said the base charge was for this particular unit , so 2kg still head pressure of 350 psi ??

[Darrenp]

Liquid line was warm , only cold once through the txv , which I expect ..

[moondawn]

Liquid line was warm , only cold once through the txv , which I expect ..

hi there are you able to measure the subcooling? if so is it excessive. if high hp amd high subcooling would seem it would be overcharged.

[passandscore]

What charging method did you use?

407c is a blended gas so even if you added 2kgs exactly you can end up with high discharge pressure if added to the system incorrectly. You have to add it as a liquid form! If you add as a vapor you will cause fractionization to occur. The vapor sits on top of the liquid and has a higher pressure to it then the liquid. Charging with high pressure fractionized gas will most certain result in high discharge pressure. Was the bottle of 407c new? If you charge incorrectly with blended gas it compromises the remaining gas in the bottle, leaving others who use that bottle to have potentially similar issues.

If you did charge with vapor I recommend reclaiming, evacuating and recharging with a new bottle.

http://www.refrigerants.com/faqs.aspx

[Darrenp]

New bottle .. Done the job last week , changed txv , put sight glass in , new comp and drier in .. Still doing same thing ??? High discharge .. Liquide charged .. Everything was done correctly

[passandscore]

I recommend reclaiming, evacuating and recharging again with the new bottle. As part of general procedure, Honeywell recommends initially charging the system with 85 percent by weight of the original system charge and then adding refrigerant as necessary in 5% increments to obtain equal baseline performance.

You may simply be overcharged. As mentioned earlier.



http://www.honeywell-refrigerants.com/americas/?document=guide-to-retrofitting-ac-systems-from-r-22-to-r-422d-or-r-407c&download=1

secondary info
http://www.tecumseh.com/ta/canada/library/~/media/North%20America/Files/Guidelines%20and%20Manuals/Refrigerant%20Documentation_North%20America/Tecumseh%20Service%20Guidelines%20HCFC%20R22%20to%20HFC%20Blends.ashx

[Darrenp]

No .. As the base charge for unit is 2kg .. I put 1.5 .. Then slowly added .. Upto 2 still high pressure

[Darrenp]

Anything over 2 would of taken the whole thing on a high pressure trip

[passandscore]

Were the pressures stable at 1.5kg? What were the pressures? Was it necessary to add the remaining .5kg? If you are not sure, then my recommendations are the same but this time stop at 1.5kg and monitor the system pressures?

[monkey spanners]

Just thinking outside the box as it were, is the condenser clean and fans going round the right way? Is the condenser piped correctly? (read about one that was piped up wrong from new and effectively trapped liquid in it) Was the old drier a reciever drier or a normal drier? (some have a smaller core and a space for liquid to go when not needed in the evap etc)