New cooler has high head and won't cool below 50 f.

[kengineering]

Our open grab and go display cases are very basic. A Condensing unit, TXV, 2-circuit evaporator and a couple of fans. We've built a hundred over the years we know they work. I got a service call and the mechanic has us scratching our heads. It's a 404a system head pressure 350 suction 90. Superheat 8 f, discharge temp 50 f . The ambient temp is 72f- 76f. there are no outside air currents affecting it. Nothing is blocking return or supply grills. The discharge velocity is 260 fpm (normal). the delta T is 15 degrees f over the condenser. The mechanic has changed the TXV and drier, recovered the refrigerant , evacuated and recharged to the proper levels. He has changed the condensing unit and still no change.

The service manager the mechanic and myself are at an im-pass so I thought I'd toss it up to this group.

Thanks for taking the time...

[al]

Is it being charged by superheat or do you have a weight that it takes? 10c discharge temp, would suggest it's pumping liquid, at a guess I'd say way overcharged, but given the only component you haven't changed is the evaporator, is it piped right? both circuits feeding ok, any chance it's installed upside down, backwards, blocked?

What subcool have you at the TXV? What is delta T over evaporator?

[Glenn Moore]

How do you charge your systems. Do you charge using a sight glass, or degree of liquid subcooling or weigh some charge in ? . What is the design temperature of the cabinet ? What type of txv are you using ?

[kengineering]

Is it being charged by superheat or do you have a weight that it takes? 10c discharge temp, would suggest it's pumping liquid, at a guess I'd say way overcharged, but given the only component you haven't changed is the evaporator, is it piped right? both circuits feeding ok, any chance it's installed upside down, backwards, blocked?

What subcool have you at the TXV? What is delta T over evaporator?

One issue is not being on-site. Everything done via phone.
1) I don't have condenser sub-cool, data.
2) Delta -T over condenser is ; entering 85F (29C), leaving air 100F (38C)
3) Not overcharged , sight glass just clear, Amp draw OK and Sh 8f.
4) Installed correctly.
5) the service guy even took out the orifice checked the distributor tubes for restriction/ blockage.


The only that hasn't been changed is the Evap and the line set inside the case, but I can't wrap my head around doing that. If there was a restriction my suction pressure would be low.

[kengineering]

How do you charge your systems. Do you charge using a sight glass, or degree of liquid subcooling or weigh some charge in ? . What is the design temperature of the cabinet ? What type of txv are you using ?

We charge by weight, but we install a sight glass as well. A sporlan TXV ,size A, which is always use on this size case. Design temperature for 38*f (3*C) product.

Thing is we ran / tested this case before shipping.

[cadwaladr]

Has it been charged with liquid out of the bottle not vapour?

[Glenn Moore]

What is the condensing unit model details and the sporlan Tev type details

[mikeref]

We charge by weight, but we install a sight glass as well. A sporlan TXV ,size A, which is always use on this size case. Design temperature for 38*f (3*C) product.

Thing is we ran / tested this case before shipping.

Possibly two problems as figures obviously don't add up. ( Specific Values taken at one point in time won't necessarily solve this problem.)
1. Compressor is cycling with an extended off cycle. No Liquid line Solenoid Valve might explain the +10 C discharge temperature. A data logger should be set up with the sensor in the supply air duct.

2. Contaminated Refrigerant.... not by Moisture. Pull the Gas, change the Drier, Vac it and fill with another R404a bottle.

[RusBuka]

So high dicharge pressure tell us, overcharge or small condenser. 350 PSI = 24 Bar, Your condenser is full of liquid.
Do you try fully close TXV?

[kengineering]

Thanks to those who helped to sort this out...As it turned out I was getting bad information from the tech which clouded any chance of diagnosis. He never really measured air over coil properly. Wrong fan blades

[Magoo]

Hi Ken.
thanks for feed back on problem, I have been watching post with interest.