Installation of NRVS check valves

[Josip]

Hi,

Need your opinion...suggestion.. regarding installation of check valve type NRVS (installation direct to solenoid valve flange) in liquid lines in front of evaporator...

on suction lines will be installed PM-3 pressure regulator valves ... double temperature rooms

electrical heaters for defrosting - not hot gas..

refrigerant ammonia

from one Danfoss representative came an offer with suggestion to install above mentioned check valves .... .... what do you mean about check valve installation?

...this valve is flanged type and for me only increases installation costs and creates opportunities for leaks ... it is possible to use it only with new type of EVRA/EVRAT solenoid valves GGG 40.3 having direct flange mounting ( - of course, usually much more expensive

Best regards, Josip

[RANGER1]

Josip ,
Are you asking if check valve is actually needed at all because of it being electric defrost ?
To me its 50/50 as it not like hot gas which you do not want it backfeeding down liquid line .
You could also consider SCH stop check after solonoid so as less chance of leak .

[Josip]

Hi, RANGER1

thanks for answer...

Josip ,
Are you asking if check valve is actually needed at all because of it being electric defrost ?

..... SCH stop check after solonoid so as less chance of leak...... .

....exactly.... maybe I miss something...but without hot gas defrosting we never install check valve in liquid line...

.... what is SCH stop check valve ... maybe to post a link...

Best regards, Josip

[RANGER1]

Josip ,
Its a danfoss stop/check valve but you can use any type . Thought you would have a stop valve after solonoid anyway , so why not use a stop check valve instead !
During defrost it would help to increase pressure/temp in evaporator for more efficientcy .

[Josip]

Hi, RANGER1

Josip ,
Its a danfoss stop/check valve but you can use any type . Thought you would have a stop valve after solonoid anyway , so why not use a stop check valve instead !
During defrost it would help to increase pressure/temp in evaporator for more efficiency .

... why to use it at all sorry, I do not see any positive purpose, ....only can have a problem with ammonia pump because to open check valve need additional pressure .... and having many rooms...no..no...

...defrosting will be electrical with timer - both solenoid valves liquid and suction closed and pressure/temp will increase ... overpressure will go back to suction ....PM3+CVP+EVM...

...SCH is not applicable ... seems to me like valve for compressor discharge valve ....

... we never ever install check valves on liquid line on evaporators without Hot gas defrosting ... working without any problem ... I think this is only to make extra money and causing problems as I mention before ... nothing else..

Best regards, Josip

[US Iceman]

Hi Josip,

If the evaporators are electric defrost I do not think you need the check valves after the liquid line solenoid. When the coils go into defrost all you need is a pump down to remove the liquid. After a pump down for a few minutes, close the suction valve and then energize the heaters.

Will the suction valve be able to relieve the pressure in the coil as it increases during defrost?

The only possible reason I could see using a check valve in the liquid line with electric defrost is if the coil pressure rises and might cause the solenoid valve to lift (back flow). If the liquid solenoid will remain closed, then the check valve is not needed.

The only place I have seen stop-check valves used s on compressor discharge lines or refrigerant pump discharge lines. And, I have seen problems with these valves if they are not properly adjusted. It is hard to beat a wafer style check or a disc type check valve! No adjustments and they always work.

[BESC5240]

The only possible reason I could see using a check valve in the liquid line with electric defrost is if the coil pressure rises and might cause the solenoid valve to lift (back flow). If the liquid solenoid will remain closed, then the check valve is not needed.

I agree with US Iceman : the only reason to install a check valve after the solenoid in the liquid line is to prevent the solenoid been lifted (or damaged) due to the pressure in the coil being higher (during defrost) then the liquid pressure in front of the solenoid.

Usually standard solenoid valve can only handle little to no back pressure. (EVRA10 : 0,1 bar , bigger valves even less).

About " new type of EVRA/EVRAT solenoid valves GGG 40.3 " : These are made from 1998 . Do you still use GG-25 valves ?

About the pressure drop in NRVS: typical pressure drops would be 0,05 to 0,1 bar... depending on the application and the choosen combination of course ...

Best regards

[Josip]

Hi, BESC5240

I agree with US Iceman : the only reason to install a check valve after the solenoid in the liquid line is to prevent the solenoid been lifted (or damaged) due to the pressure in the coil being higher (during defrost) then the liquid pressure in front of the solenoid.

Usually standard solenoid valve can only handle little to no back pressure. (EVRA10 : 0,1 bar , bigger valves even less).

About " new type of EVRA/EVRAT solenoid valves GGG 40.3 " : These are made from 1998 . Do you still use GG-25 valves ?

About the pressure drop in NRVS: typical pressure drops would be 0,05 to 0,1 bar... depending on the application and the choosen combination of course ...

Best regards

thanks for answer... I agree too with US Iceman and you...

I was speaking about this valve ... old one I am not sure if possible to find ...

www.mark-off.ru/fam/eqpmnt/other%20eqpmnt/danfoss/Danfoss%20Cat%202000/02English/rd6na102.pdf

installation definitely increase costs .... anyhow ... for our application with pump down check valve is not needed ...

Best regards, Josip

[US Iceman]

...for our application with pump down check valve is not needed...

The gas pressure could still rise in the coil during defrost even if all of the liquid is pumped out. The suction valve keeps the coil isolated from the suction pressure. You need the gas pressure to increase in the coil so that the coil can defrost well.

Imagine what happens if the outlet connection from the coil was open to suction pressure (if the saturation temperature is below 0°C). If the gas pressure is open to the lower suction pressure this slows down the coil defrost...

[BESC5240]

Hi Josip,

www.mark-off.ru/fam/eqpmnt/other%20eqpmnt/danfoss/Danfoss%20Cat%202000/02English/rd6na102.pdf

This is also the valve (NRVS) I'm talking about. An old one (from 1999 ?), but still applicable on PM and EVRA.

As I see it, the need for it is independent of what kind of defrost you apply. The only thing you need to check is : will the pressure after the solenoid (in the coil) become higher then before the solenoid (in the pumped liquid line)?
If you can make sure it doesn't, you don't need a check valve.

[US Iceman]

The only thing you need to check is : will the pressure after the solenoid (in the coil) become higher then before the solenoid (in the pumped liquid line)?
If you can make sure it doesn't, you don't need a check valve.

I agree completely...