Headmaster valve

[Justin Stone]

I am having problems with a Scotsman Model CME1056. What is the best way to trouble shoot the H.M. Valve. Not looked at it much yet,I am scheduled to do so tomorrow. The system is less than 3 years old (+/- 1 year) always have the tolerance factor. As far as I can tell by just playing with it what little bit I did today the system seems to be charged right ( FLA on the compressor is right on the money ) didn't have a chance to put gauges on it will do so tomorrow. Some where, at some point in time, someone at McDonalds thought that it would be a good idea to tie the condensor of the ice maker in the same cond unit as the walk in freezer and walk in cooler (called a mac ? mack ? system) although I dont like this design, this one is done the same way. anyways I will have some more info tomorrow, if anyone wants to help with the original question now that I have put all of this other useless info down I would appreciate it. (Just venting please excuse)

Thanks guys
Justin

[Temprite]

G'day Justin.

Try this.

http://www.scotsman-ice.com/general....ldownloads.xml

[Justin Stone]

Took a look at this today and come to find out it was a low charge

However 2 hours after I returned home to the wife and kids after a 10 hour work day + travel I got called out to the other side of the state for a walk in freezer. The compressor is bad in this one

A hard working man's job is never done

Well off to bed for 4 hours and back at again tomorrow.

Regards,

Justin

[Peter_1]

Sorry I ahve to ask but what's a headmaster valve?

[Justin Stone]

A valve that is to maintain head pressure during cold weather months. located at the condenser on the high side of the system, (tricks the unit into thinking that the head pressure is higher than it actually is depending on the ambient temp)

[herefishy]

Actually, the Flooded Condenser Control valve (headmaster is a tradename), serves to short-circuit compressor discharge gas around (by-pass) teh condenser coil. This serves to slow the refrigerant flow in the condenser coil.

The decreased velocity of the refrigerant in the condenser causes the coil to start filling with liquid refrigerant - decreasing the effective area of the condenser and thus maintaining the temperature/pressure of the "high side".

The process doesn't "fool" anything. It actually does maintain (higher) adequate high pressure by making the condenser less effective during low ambient conditions.

Advertantly, the discharge gas by-passing the condenser also serves to warm the receiver.


Cheers!

[Justin Stone]

Much better said. If I knew everything about them I would not have been on the troubleshooting forum asking how to test them

The info I provided was given to me by a ref tech as a short explination, I haven't had that much dealing with them as my experience is limited with ice mach.

Thanks for the explination

Justin

[Temprite]

Good to see you posting again herefishy.

[sanchezbond007]

hello every body this my first day in the forum.

well about the head master The way that I check if the headmaster is working properly is feeligng or taking the tempeture on the three tubes of the head master if I feel that the three tubes are on the same temp then is bypassing is the weather is hot the head master is faulty. because is not supposed to be bybassing to raise the presure.

[Dan]

Good to see Herefishy again. Hello to Justin and Sanchezbond007.

Herefishy's explanation of a headmaster is one of many that is perfectly correct. I have my own explanation that helps me to understand it. The headmaster is a form of winter condensing pressure control. It is a single valve system that behaves as two valves. A flooding valve, and a receiver pressure regulating valve.

The flooding valve closes off liquid return from the condenser, and the receiver pressure regulating valve opens a pathway to increase pressure on the receiver.

So the result is we increase discharge pressure by filling the lower tubes with liquid refrigerant, and we communicate that pressure to the receiver to insure sufficient pressure drop across the TEV and liquid quality to the TEV's.

The way that I check if the headmaster is working properly is feeligng or taking the tempeture on the three tubes of the head master if I feel that the three tubes are on the same temp then is bypassing is the weather is hot the head master is faulty. because is not supposed to be bybassing to raise the presure.

The head master has a refrigerant charged dome on it that reacts to the ambient temperature. If the temperature drops, the pressure in the dome drops and permits more refrigerant flow into the receiver and less into the condenser.

If you lost the charge in the dome, it will tend to bypass the condenser entirely and cause high discharge pressures.

If you ffeel that the line going into the receiver is as hot as the line going to the condenser when it is warm outside, you can suspect the head master is not working properly. I have known mechanics to take a good knock at the powerhead with a ball peen hammer to get things working correctly again. I am sure that is a loss of powerhead charge temporary solution. I have also seen Schrader valves replacing the charging tube on the dome.. I swear, I did not do it and I promise that I will never do it again.

I think you understand how it works, from what you said. I just had to rethink all of this for my own benefit.

[CBreeze_2004]

This is interesting. I've never heard of these valves referred to by any name other than "the headmaster" (often followed by a string of expletives!) -- I was not aware this began life as a trade name!

What is the general opinion regarding fan cycle control vs. headmasters for maintaining head pressure on txv systems (outdoor condensing units/cold weather ops)? I'm occasionally asked by clients to relocate condensing systems from hot kitchen environments to the roof and always pick the fan cycle option because it's easy. Does anyone think the headmaster is a superior enough pressure control method to warrant the extra time and effort?

[FEISTY]

I've recently learned that condenser manufacturers who use a headmaster valve sometimes do it as a design point. They feel the constant supply of condenser fan airflow is required to control compressor body cooling. They do not suggest changing an original design to a fan control except in a temporary " get out of trouble " situation. I have found more valves with clipped tubes, releasing the charge and opening the valve 100%, this year than ever before. I think it is from techs not knowing how to verify if it works or not. They just cut and run. I install quite a few outdoor units and when ordering the condenser, order a headmaster valve along with a PRV safety from the factory. Here in Chicago, they are code and not worth the violation.

[Toosh]

Hi Fiesty the originator of this post made this many years ago and has never been back