The guy from Coldzone emailed me this info.
Note where it says. Headmaster's fail closed. With very few exceptions. I hope mine is not the exception
I am gonna call the guy again and see about just recovering what gas is in there and weighing in charge. The customer is not gonna let me shut their box down overnight and let their Kegs get warm. I wanna change the TXV while I'm at it.
BASIC UNIT CHARGING PROCEDURE FOR FLOODED UNITS ONLY
Warning: Not to be used in Lieu of IOM Manuals included with the unit.
Specials units or construction may or may not differ.
Caution: Please verify if the unit, you are charging, is a Flooded or a Floating Head System. The following is meant for Flooded System with an 180psi Headmaster or 3-way valve (with a 180 marking) piped around the condenser coil. This procedure will not work on a floating head System (Like Sierra or High Sierra Units) and could damage equipment.
Basic Info
Tech note: You can speed read (not skip) this paragraph, the good stuff to follow.
Once the system has been energized for 24 hours and a proper vacuum has been accomplished, be sure the compressor discharge valve is open and the suction valve is open 2 or 3 turns with a valve stem wrench attached for quick throttle adjustments if needed (Valves are usually at mid-seat to accommodate brazing. but not all).
Compressor Start-up
Tech Note: Some little “ old school meets new school” stuff in here.
With gauges attached charge the unit with 50 to 60% of the system charge into the receiver (mandatory R-404A and R507 must be charged as liquid) before the start up of the compressor. Once started it may be necessary to throttle the compressor suction valve to keep suction pressure reasonable to prevent trip outs during charging and pull down. If necessary to add liquid refrigerant to the suction side, a full control ball valve must be used in the charging line to slowly meter refrigerant into the system.
Tech Note: You know to keep the L.P. switch from tripping or prevent slugging and stuff.
Tech Note: Here’s the meat and potato and gravy.
Flooded Systems Require Extra Winter Charge
When charging the unit it will be necessary to bring the head pressure to a minimum of 200 PSIG before just clearing the sight glass (a bubble or two is ok). In low ambient conditions it may be necessary to block off part of the condenser (or shut off the fans) to achieve the 200 PSIG minimums.
Tech Note: This is to insure the headmaster is closed and simulate a summer charge. If you’re a touchy-feely kind of tech: You can verify this, by feeling the condenser coil outlet drain line and the line feeding down to the receiver. These should be the same temperature or within a few degrees F. If the pipe leading to the receiver is “much hotter” then the headmaster is open and allowing hot discharge gas through. When you’re over 200# this could be because the pressure drop across the valve is two high (+12psi). You may need to shut the system down and let the pressure equalize or tap it with a rubber mallet. Headmasters’ fail closed. Therefore, having the entire refrigerant charge feed to the condenser coil, with very few exceptions. (See the Tech Note for Headmasters for more info.)
Extra Winter Charge Info
Now that you have achieved the summer charge, addition of the “winter charge is required for the “Flooded” System. Prior to this and if you blocked the coil to maintain the 200psig minimum head pressure, you can remove the block on the coil (to prevent nuisance High pressure switch tripping while adding the winter charge).
Tech Note: The winter charge is necessary, when the outside ambient starts getting below approx. 70degF, the headmaster will start opening and send hot discharge gas into the drain line to the receiver. This “hot discharge gas” will hit the liquid present and expand to maintain 180+/-10% PSIG. You can feel by touch, as mentioned above. (the purpose for this type of control can be found in the Tech Notes –Headmaster page.)
For Russell units get the “extra” winter charge weight from the tag on the coil or the IOM Manual the came with the unit.
For Multi-Compressor units only: you will need to add the extra charge required for winter conditions as follows, on Medium (+10sst or above) Temperature systems, you will need to add 3 lbs of refrigerant per compressor horse power and 4 Ibs of refrigerant per horsepower for Low Temperature.
Wait, your not done!!
The Last thing to do is set the superheat on your system and you can go home.
SUPERHEAT SETTING
Superheat setting at the compressor should be between 25 and 35 degrees F. Measured on the suction line six (6) to eight (8) inches from the compressor and subtracted from the suction pressure when converted to degree F. Make sure you leave at least four (4) to six (6) degF superheat at the evaporator minimum measured around the TXV bulb.
Tech Note: Superheat at the compressor has a direct effect to the life of the compressor. Frost line is an indicator, but not an exact science and your compressor needs you. At the same time we need to make sure that the “change of state” from liquid to gas is being done inside the evaporator coil, (plus a little additional superheat) hence the “4-6degF minimum” superheat, as noted above. I know, you were taught and in a perfect world the evaporator is “supposed to be adjusted for 10degF superheat but the piping in a building is rarely perfect or other addition loss is encountered. Also the compressor performance may not be an exact one to one match up to the evaporator design. Superheat for Low temp systems usually is around 6-12degF and med temp systems are usually 8-14degF. Some systems may have been designed for even higher superheat and TD setting to remove moisture from the box. Bottom line is; the compressor must be protected. (See Tech Note for TXV for more)
Final: This should provide years of trouble free performance, as long the employees don’t use the box to cool themselves off. Thanks for putting up with the humor. See our website for even more info
www.russellcoil.com under ”Products and Literature”.
Thank you for helping us, help, our Customer.
