Low ambient Temps & Outside Air Cooled Condensers!

[Grizzly]

Hi Guys.
Because of the abnormally prolonged cold spell we have been having.
We have been getting a large amount of issues with plant. That is directly related to the system pressures being lower in the Condenser than the evaporator.
For instance, causing Liquid migration into the condenser with the subsequent L.P. issues upon start-up etc.
I was just wondering how for those of us that work in more extreme Cold climates get over this problem?
Grizzly

[taz24]

Hi Guys.
Because of the abnormally prolonged cold spell we have been having.
We have been getting a large amount of issues with plant. That is directly related to the system pressures being lower in the Condenser than the evaporator.
For instance, causing Liquid migration into the condenser with the subsequent L.P. issues upon start-up etc.
I was just wondering how for those of us that work in more extreme Cold climates get over this problem?
Grizzly


Just open the fridge door and let the heat out :p

taz

.

[monkey spanners]

I used to get problems with ice bank milk tanks in the winter, especially when they had heat recovery tanks on them.
Farmer would use all the hot water to wash the milking parlour, which would then be replaced by cold which would result in the refrigerant sitting in the heat recover, condenser and reciever and the unit going off on LP.

Bucket of hot water over the TXV and bulb to get some refrigerant into the evap, sack on the condenser, and away she went :D

Once it had been running for a while and got some heat in the system it would be ok.

[US Iceman]

Is the liquid draining back to the receiver, or is it stacking up in the condenser?

This is a common problem since you can't build discharge pressure to push liquid to the evaporators, right?

About the only to get the system running is to shut down the fans and valve off all of the coils except for one, and hope that works.

[chemi-cool]

I'd go with monkey spanners,

hot water will do the trick.

You can also operate it with a SV which is controlled by low discharge and a spraying nozzle.

[M.Nadeem]

Hi Guys.
Because of the abnormally prolonged cold spell we have been having.
We have been getting a large amount of issues with plant. That is directly related to the system pressures being lower in the Condenser than the evaporator.
For instance, causing Liquid migration into the condenser with the subsequent L.P. issues upon start-up etc.
I was just wondering how for those of us that work in more extreme Cold climates get over this problem?
Grizzly
Hi:- if condensor is air forced then u can use one fan cycling switch to mantain the discharge pressure . hope it will help you.
Nadeem

[Grizzly]

Thanks for all the input guys.

Taz.
I love your humour! Sadly the type of equipment I am talking about doesn't normally have Doors!
MS and Iceman you are both spot on with ways of getting around this problem.
I have used a variety of the above options to good effect and yes Iceman.
I was basically refering to the problem of lack of lift across the comp. Low Suction Pressures etc upon start up once the refrigerant has migrated into the Condenser.
Mike and M.Nadeem thank you also!
Basically I know how we have gotten around it this time!
But where it would happen more frequently has anyone developed a remedy?
Just wondered that was all!
Cheers Grizzly

[monkey spanners]

On another site, this time with a DX milk tank, compressors mounted on the tank but with remote condensers and no recievers and on pumpdown cut out.
This used to trip the LP switch on frosty mornings but by the time we had got to site the sun had been on the condensers and it would fire up ok (often they will start milking at 4-4.30am :rolleyes:

I did toy with the idea of fitting a three minute time delay to the LP switch (linked in with the solenoid so it only worked when it was open) but the problem went away with the warm weather, and the customer has now retired.

[haree]

all ideas good!

[HallsEngineer]

Condenser fans on VFD. Install a small dry cooler with pump.

[123-steve909]

i was working on a 20kw water chiller yesterday with the same problem. i ended up putting a fan speed controller on the condenser. not cheap as it was 3 phase but has sorted the problem

[Magoo]

Drain the water from basin and cycle fans only. A Russian trick I learnt, don;t forget to isloate the spray pump.

[lowcool]

whack a fan heater in it and cycle cond fan

[coolhibby1875]

Condenser fans on VFD. Install a small dry cooler with pump.


im sure tescos would pay for this! good idea all the same!

[fowlie]

ive had a few problems with the cold spell one store ambient temp was -16 during the day those searle cond units are a real pain as the fan speed controllers wont stop,had to go around fitting hp switches to cut out when hp dropped below 9br.had one store where the condensors had sucked in that much snow that they had iced up.

[Peter_1]

Drain the water from basin and cycle fans only. A Russian trick I learnt, don;t forget to isloate the spray pump.

Water from the aircooled condenser?:p

[Peter_1]

Refac used to bridge the LP for some time ( +/-20 seconds) after startup to allow pressure buildup on the high side.
With extreme cold conditions, how I should do it?
Install an additional condenser inside the building because I suppose this waste heat can be used usefully inside the building if it's really that cold. And then bypass proportionally the additional excess heat to the outside condenser.

[coelhinho78]

yep thats it, you can use a themoetactic tree way valve to control it

[Paul J]

This is a common problem in the south island of new zealand during winter, putting the condenser fans on a pressure switch helps but wont aid you during start up, Danfoss manufacture a wintering valve which maintains pressure in the high side keeping it high enough for start ups, bridging the LP helps but you don't really want it to run in a vacuum to long either.:cool: