Test Question on NY Fire Dept Exam

[coach411]

Hello, Im going for my refrigeration operators license and I was going over my test and cant get the answer to one question Im going to post it here hopefully Someone who knows can answer it.



A condenser is oprerating at a higher pressure than normal, the inlet water temperature is 85deg and the leaving water temperature is 88deg. What best explains this condition?

a)incorrect refrigerant charged into the system
b)overcharge
c)undercharge
d)excessive sub-cooling



Thanks, and if you answer it could you give an explenation not just pick a letter.

[highlimit]

By process of elimination A. wrong refer. or non condensibles
However ,wait for more responses.
an over charge would include high sub cool
a nunder charge would exclude high disharge

[ericnyc]

wow ...3 degrees is considered high? ill go with c.

[drsuperheat]

It could be one of two things not listed. First, the low delta T is the result of the condenser being dirty, thus causing poor transfer of heat to the condenser water and raising the head pressure. It could also be non-condensables like Highlimit said, similar symptoms.

A the wrong refrigerant could give you a higher head pressure, i.e. 404 in a 22 system, but you would still have roughly a 10° delta T across the condenser, assuming proper water flow.

B is possible if it a GROSS overcharge where the condenser is nearly 100% full of liquid.

C would give you lower head pressure, not higher.

D is the result or a symptom of being overcharged.

If I had to choose from the answers you have listed I would say B.

[madarius]

O.k. coach411 let me give you by theory the best answer for this problem. I am 90% sure of it. Let's take into consideration that there is an undercharge. An undercharge influences head pressure to also be low and so I'm ruling that out. It's definitely not wrong refrigerant because that is not practical in the feild. We are looking for practicality. Excessive subcooling will tell you that the water is extracting heat from the refrigerant which in this case is only a 3 degree delta, so not logical also this unit is operating at higher than normal head. The answer that best describes this symptom is an overcharge.

[coach411]

Thanks for the info guys, I passed the exam today, I have a practical scheduled for late October. I dont know if that was the right answer but I figured the same as some of you.