Industrial Chiller question

[Firebrick43]

So the other night at work they had an a chiller that cools on open glycol tank that cools a 1.5KW laser. There is a glycol loop from an outside water evaporator tower that runs through a plate type heat exchanger (condenser) and then the glycol tank/loop to the laser runs through another heat exchanger(evaporator) Excellent flows on both loops. It is a 20 ton compressor, R407C gas and TXV valve system and it was throwing low pressure faults on the proprietary PID controller. Checked most everything elese first, nothing else was malfunctioning. Any way I was charging it by sub cooling, only had about 1 degree as found. It stopped faulting almost immediately as I added freon.. It was a german machine, with a german manual, that as best as my google translation could surmise, If any faults, problems, or even a fart, call the manufacture.

Any who, for the actual question. This system had a 6mm pressure line coming off the directly after the output of the compressor and down through a solenoid valve(controlled) by the PID and dumped between the TXV and the heat exchanger the heat exchanger (evaporator). It had an odd capped off ball valve to regulate flow. If I pulled the DIN connector off the solinoid (Normally Closed) I actually had cooling(before adding a charge) but with it open it added enough heat to cancel out any cooling, hence the 1 degree of sub cooling.

Having no specs I was going to originally shoot for 10 degrees of sub cooling, and things were cooling real well even with that solenoid valve open at about 8.5 degrees but when that valve would close(for what ever reason????) it would jump up to 15 degrees of sub cooling for 30 seconds or so before settling down.
What is the purpose of adding hot freon out of the pump to after the TXV Valve???? Would you take the measurement while it was open(most of the time) or closed?

Thank you

 

[fitter30]

Hotgas bypass to either reduce compressor capacity and or raise suction pressure. Sounds like package chiller like this is a package chiller which i be looking at flows through the plate heat exchangers and temp drops. Being a package this chiller more than likely has the the amount of refrigerant on the label and could be critical charge.
Because if flows vary, loading varies theres only so much volume of refrigerant for it to go in all.the right places or not.

 

[Firebrick43]

Hotgas bypass to either reduce compressor capacity and or raise suction pressure. Sounds like package chiller like this is a package chiller which i be looking at flows through the plate heat exchangers and temp drops. Being a package this chiller more than likely has the the amount of refrigerant on the label and could be critical charge.
Because if flows vary, loading varies theres only so much volume of refrigerant for it to go in all.the right places or not.

Unfortunately the label on list the type of refrigerant and the manual only had a generic temperature equivalent chart for the 407c

 

[fitter30]

407c pt chart

https://www.google.com/url?q=https://www.igasusa.com/pt-charts/R407C-PT-Chart.pdf&sa=U&ved=2ahUKEwiop4yYqLL4AhXAKkQIHV-SDHYQFnoECAcQAg&usg=AOvVaw1Cxj41uIC7QfsLY49lgrla

Chiller a built up system not a package? There should be a manual and start up sheet showing charge, flows, superheat, subcooling ,amp draws of pumps, compressor and design info. Call or email the manufacture they should have some design criteria ask for tech also might have some info on the mechanical drawing. Hot gas tee is between the expansion valve and distributor. There is usally a sized orfice in the inlet of distributor and a pressure regulator in the hot gas line set at a certain pressure not a ball valve. Google Sporland hot gas tees and pressure regulators. How long has it been that the plate hx have had the glycol checked for % and inhibitors?

 

[American Locomotive]

I'm guessing it's a KLH or Riedel packaged chiller?

That solenoid is a hot gas bypass, and it's used to "stage" the chiller. If the hot gas bypass is on, it reduces system capacity. The idea is that you regulate temperature a bit better. So instead of just cycling the compressor on/off above and below setpoint with a large hysteresis, it will just reduce system capacity near the setpoint and keep the temperature more stable.

So if the valve was open, the chiller was likely under low load or near the set point.

 

[Firebrick43]

407c pt chart

https://www.google.com/url?q=https://www.igasusa.com/pt-charts/R407C-PT-Chart.pdf&sa=U&ved=2ahUKEwiop4yYqLL4AhXAKkQIHV-SDHYQFnoECAcQAg&usg=AOvVaw1Cxj41uIC7QfsLY49lgrla

Chiller a built up system not a package? There should be a manual and start up sheet showing charge, flows, superheat, subcooling ,amp draws of pumps, compressor and design info. Call or email the manufacture they should have some design criteria ask for tech also might have some info on the mechanical drawing. Hot gas tee is between the expansion valve and distributor. There is usally a sized orfice in the inlet of distributor and a pressure regulator in the hot gas line set at a certain pressure not a ball valve. Google Sporland hot gas tees and pressure regulators. How long has it been that the plate hx have had the glycol checked for % and inhibitors?

The glycol is tested every month I believe and has a filter on it was well that is changed every two months. We cant find anything other than the manual which has a schematic, all the electrical info, and it being 407c but none of the other stuff.

The schematic states that its a ball valve? I would have to look it up monday for manufacture/part number but unless the translation was bad its a ball valve on the schematic and parts list.

I looked up the hot gas tees and thank you for that. I have a much better understanding now of what is going on.

I'm guessing it's a KLH or Riedel packaged chiller?

That solenoid is a hot gas bypass, and it's used to "stage" the chiller. If the hot gas bypass is on, it reduces system capacity. The idea is that you regulate temperature a bit better. So instead of just cycling the compressor on/off above and below setpoint with a large hysteresis, it will just reduce system capacity near the setpoint and keep the temperature more stable.

So if the valve was open, the chiller was likely under low load or near the set point.

It actually is a Riedel chiller. We finally found the leak, and made it worse. It was at the johnsons controls thermostatic control valve for the condenser glycol loop. The when we finally got a HVAC guru there, he was adjusting it and freon started spraying out. So we have one on order. He said my charge was spot on but he did think we needed more through the condenser as the delta T across the glycol inlet/outlet was to great.

When the charge was low, when it opened/closed didn't seem to have any rhyme or reason, but acting correctly it does open towards the end of its cycle as its coming close to the set point.

 

[fitter30]

Does anyone take readings on this chiller, pumps, pressures and ir thermometer being a process chiller?

 

[Firebrick43]

I assume as a pm you mean. If so, no

The glycol pump pressures and temp is constantly monitored but the refrigerant side of the system never has been and its bit them hard now.

 

[fitter30]

Worked on many process chillers and boilers logging equipment can be beneficial to spotting a problem before theres a failure. Never could understand why business will spend $ million or more to upgrade computer equipment but not spend anything on backup or preventative maintenance.