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hem057
14-01-2007, 10:54 PM
let me try to explain this as briefly as I can; this is a hussman 4 compressor rack, has been used in supermarket, now customer wants to use it in their processing plant, discharge header is 2 inch by 8 ft. goes into oil seperator, from the top of the oil seperator discharge goes into a 4 way heat reclaim valve (which I think I can remove, no heat reclaim anymore) then goes to 3 way split condenser valve, (also just above the oil seperator it t's off and goes back to the receiver through an A9 Parker valve) then it has the Press Reg A8 (parker) on the liquid line before the receiver, the 4 evaps are reverse flow 2 pipe system, so one evap can be defrosted at a time and liquid can flow back into the liquid header, I will have to install solenoids on the suction lines and
T them so the hot gas can be routed in that direction, check valves are already on the evap to allow flow around the txv, do I T into the discharge header and route it up to the suction line through soleniod valve? do I need a solenoid to close off the condenser, or how do I do that part of it, by pass the condenser? with solenoid or if I need to use differential where do that get tied in?
hope I've given enough to give a visual image of what is going on

zerodegreec
15-01-2007, 05:16 AM
Sounds like a Huss KG setup. First you will need a DDR (defrost diff valve) and that is installed after the Oil sep. Cut out the line from your rec to the KG defrost header and tie the header into a line BEFORE the DDR. You will need a suction stop, either a sol or a SORIT will do. This will give you reverse flow back into the liquid header. Some systems dump the return gas into another header and this ties back into the disch line going up to the cond after the DDR. This method is used to ensure the gas gets condensed and is used in applications where liquid subcooling is required. This also will improve the feed of liquid to the rest of the systems on the rack when one is on defrost since they will always have a full liquid feed from the rec.

Clear as mud?

joe magee
15-01-2007, 05:54 AM
Sounds like zerodegreec has you going in the right direction. Curious to know what type of controller your using. Superplus rack? How do you plan on terminating defrost? What are they cooling?

Regards.
Joe Magee

taz24
15-01-2007, 05:36 PM
First you will need a DDR (defrost diff valve) and that is installed after the Oil sep.

This also will improve the feed of liquid to the rest of the systems on the rack when one is on defrost since they will always have a full liquid feed from the rec.

Clear as mud?

I have worked on many, many packs / racks with hot gas defrost. All have the pressure differential valve in the liquid line. I have not seen them in the discharge line. In the UK hot gas defrost has gone out of fashion and there has not been many built by the regular pack manufactures since he nineties. I understand the reasoning behind this set up but does it acctualy improve the quality of the liquid in the liquid line because in my experience the liquid is spoiled by uncondensesd saturated liquid entering it from the defrosted evap coil. Does the positioning of the pressure reduceing valve mater that much.

Positioning aside I would recomend the fitting of service valve at all stages in the pipe work because with the introduction of hot gas you will be required to service solenoid valves and the like more often. If service valves are not fitted then future work becomes a nightmare.

Cheers taz.

hem057
16-01-2007, 12:59 AM
great information, will need to look over the details of all that has been offered, (just got in from a busy day) I just wanted to post (zerodegree) that this hussman rack is a Model no CSO4SLK; if that helps any? or makes any difference....
(joe magee) it has a reflecs cpc, will upgrade to cpc E2 controller, any thoughts on this.

zerodegreec
16-01-2007, 02:29 AM
The model sounds farmiliar but I cant picture it in my head. The upgrade from the RMCC to the E2 will be a nice change to the rack, although the RMCC is a VERY good control. Very stable. Not much goes wrong with them. The E2 is more user friendly and can do allot more than the RMCC.

Why do you want to convert the rack exactly? the Kool Gas system works well and gives you the ability to have more than 1 system on defrost at a time (without losses in available heat) plus you are not subjecting the equipment to the larger TD associated with Hot gas.



As for a reason for having the DDR in the disc rather than the liquid I cannot say why they do this other than the advantage to dump the return gas back into the discharge after the DDR to enable you to ensure the remaining systems will get a full colum of liquid. For example we use allot of Hybrid critical charge racks that esentually have no reciever, we run very low head pressure and maintain 20 degree subcooling 3/4 of the year, with the return going to the disc we can keep control of our subcooling and feed the systems properly.

Over the years I have not noticed a problem with valves on a HG system leaking at all, the only valves that I have seen that can start to cause problems is the Sporlan slide valves (3 way defrost valves found just before your EPR) Other than that I have not seen much for problems. I have seen major issues when a change of refrigerant has been done, example a 502 rack to a 507 ect. The POE likes to find all the holes the Mineral oil would not go through.

hem057
16-01-2007, 03:40 AM
the sporlan web site, they show the defrost differential pressure reg valve, piping daig on page 5 and 6 they show the defrost header tieing in just after the oil seperator, this wouldn't be cool gas though, my understanding has been that cool gas comes off the top of the receiver?

zerodegreec
16-01-2007, 05:16 AM
KG is from the top of the rec... you have a link to that page?

hem057
16-01-2007, 01:36 PM
I tried but it won't let me post url, so
www sporlan dot com back slash, 90-50 dot pdf
will get you there if you follow that

Josip
16-01-2007, 01:45 PM
Hi, Hem057 :)

Welcome to RE


I tried but it won't let me post url, so
www sporlan dot com back slash, 90-50 dot pdf
will get you there if you follow that

Maybe this will help;)

http://www.sporlan.com/90-50.pdf

Nice document...

Best regards, Josip

Mark
17-01-2007, 08:40 PM
The set up you may be reffering to is a ORI / ORD set up often used on Kool gas defrost packs.
The Condenser pressure regulator or ORI (between condenser liquid return and reciever) works in parallel with the ORD valve.(Situated inbetween the discharge line and the reciever).

When the ambient temperature and discharge pressure drops, The ORI regulator restricts the flow causing the liquid to back up in the condenser.
This raises the condensing pressure, the ORD pressure differential valve opens at a 20 psi diff between discharge and reciever pressure.

Kind regards

Mark

Peter_1
19-01-2007, 10:46 PM
Hellllllooooooo, Zerodegreec, this was some time we've seen you here.
Still walking with my dream.
How's K...rin and the kid?
We're leaving within 4 weeks for a week skiiing in Valle d'Aosta, Italy, not that far from France and...Switserland.

zerodegreec
20-01-2007, 02:42 AM
Hello Peter. Good to hear from you. Switzerland and parts of France were really struggling with the amount of snow on the mountains. Not much snow. I hope Italy will have enough for you.

Katrin and my Daughter are doing great. In fact we decided to go for another. (Half way through the baking ;))

I actually just found this site again, We had our old PC crash fatally and we decided to buy a MAC... forgot about this site for some time.

Peter_1
20-01-2007, 12:36 PM
Zerodegreec, may I wish you, Katrin and your daughter a perhaps late happy Newyear but let me know via my regular email when the new baby has arrived.
If I look on the webcam of La Thuile in Italy, then for the moment, snow isn't a problem.