neslab chiller merlin33

[linbill]

Hi all,

I am having one unit of neslab chiller is failing for temperature setpoint.The unit model is Merlin 33,power supply is 115Vac,50Hz and single phase.
The problem is can't maintain the temp: setpoint.
Let say, example we desire temp: is +20 'C but the chiller run go through max: temperature and afterthat get back to min temperature, this cycle is repeatly.
Mostly, we want to know which part is may be faulty.
So anyone can help me about this problem.

Thks & Best Regards,
Bill

[DVaider]

Hi,Linbill. Maybe the temperature operation limits is lower than +20 deg. C and the "brains" of your chiller couldn't understand your request?

[weeksy]

Hi Linbill,

I realise this answer may be a little late, but here goes:


Check the condenser is not blocked & the fan motor is running & drawing good air flow through the unit.
(Its possible the compressor is running & then tripping out on its thermal protection for a while before re-starting...this may cause the drifting temps you've seen.
Check the fluid strainer is clean & that the pump runs continuously...the RTD sensor is located in the fluid lines, so if you have poor or interupted flow, this may also result in "drift".

If all the above is OK, then its almost certainly the PWM valve thats failed. (Its similar to a solenoid valve)
The older M33 chillers contained valves with a floating teflon washer that became mangled & made the valve stick.
The PWM valves are from Parker, but believe me, it will be quicker buying the valve direct from your local ThermoFisher Scientific agent....although they're not cheap!!

Regards

weeksy.