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SimonBrown
23-10-2006, 05:39 PM
Hi

Could any of our experienced members suggest me a good, reliable and simple controller which can do the basic function of controlling the evaporator fan and liquid line solenoid (on/off) according to the thermostat reading i.e. higher or lower than the set point temperature (say for eg. the temperature of a cold room). The system is an ammonia recirculated type.

I believe there are ones with integrated defrost control as well. Info on a reliable controller is also welcome.

simon

Brian_UK
23-10-2006, 06:53 PM
Have a look at Eliwell, LAE etc.

Andy
23-10-2006, 08:12 PM
Hi

Could any of our experienced members suggest me a good, reliable and simple controller which can do the basic function of controlling the evaporator fan and liquid line solenoid (on/off) according to the thermostat reading i.e. higher or lower than the set point temperature (say for eg. the temperature of a cold room). The system is an ammonia recirculated type.

I believe there are ones with integrated defrost control as well. Info on a reliable controller is also welcome.

simon

Simon:)
we use Danfoss:)
EKC201 is the basic control. Others are available if you are using a suction and vent solinoide.
www.danfoss.com

I will try to get you an exact model for pump circ.

Kind Regards Andy:)

NH3LVR
23-10-2006, 11:07 PM
Could you tell us a bit about the system you wish to apply this to? Number of evaps and room temps? I will not presume to recommend Controlers as we usually use different equipment here than you folks on the other side of the pond.
The reason I am asking is because I have seen troubles with controling tempertures with solonids on Recirculated NH3 systems under some conditions.

SimonBrown
24-10-2006, 01:16 AM
Thank you Andy, Brian and NH3LVR.

There are four or five evaporators in this cold room (each of about 25 kW), which maintains an inside temperature of about +4 oC. The evaporators are fed by NH3 using pumps.

Separate defrost controller (Hansen frost master) is available for hot gas defrosting. The controller I am looking for is one, which switches off the fan/liquid line solenoid when the desired room temp is achieved, and vice versa.

simon

NH3LVR
24-10-2006, 02:00 AM
I think you will escape the problems I was thinking of. A system I was working on recently was a Cold storage operating at -10F (-24C), with a single Evaporate. The operator wanted to raise the Temp so he used the thermostat. It caused havoc in the engine room when the booster was constantly loading and unloading.
We use Hansen's and they work well. But they are programed to leave the fans on except during the defrost cycle. This could be worked around with a relay or two.
Is there a good reason to turn the fans off when the Temperature need is met? We usually leave them on.
Nh3 coils of the bottom feed style take a good bit of time to pump out. This can cause some temp variation.The best system I have seen is to control the Evap pressure with a motorized valve and a temperature sensor. It is an expensive setup however.
One thing you might consider is the availability of sufficient hot gas for defrosting. On a cold day without the fans running you might have a insufficient amount for defrosting. Unless there are other rooms tied into this system as well, which I suspect there are.
On a completely different note I visited your fair city 4 years ago. I stayed at the Ruben's by the Palace. Spent 4 nights in London and went to Scotland and Wales. I truly love the Underground as a way to get around. As soon as I got to London I E-Mailed the Boss a short message, "There are 7000 Pubs in London, this may take longer than I thought".