York E1FB240A25B

[tinkertech]

Was asked at work to look at this 20 ton two-stage system that is very unfamiliar to me,so I need some help. The first stage system only runs for about 30 sec. before the head pressure reaches it's cut-out pressure of 398 lbs. I replaced all filters and checked the fire damper to make sure it hadn't closed. Still does the same thing.

Found a bad leak on the second stage system(no freon in system) and fixed it. It will only run for a few seconds even though the discharge pressure never goes higher than 250 lbs. Also, it's started something new today. One of the 3.2 amp circuit breakers started tripping though I bothered no wiring for it. One of the wires comes from a transformer and the other two are connected to relays. I have 24 v. coming from transformer to C.B. and 24 v. coming to C.B. from one of the relays. I put my meter on one of the wires and read over 7 amps before breaker tripped. Is power supposed to be coming from relay to breaker as well or do I have a bad relay?

[dkpd1581]

Start with the basics...what metering device do you have Fixed or TXV. 

What is the return air, what is the supply air, whats the ambient temp? 

Is the condensor fan(s) running, if so is it in the right direction with the blades correctly faced up.  Is it on a fan cycling switch, are the coils clean inside and out.

Do you have a restriction in the lines, kinked copper, bad filter drier.  Are you simply grossly over charged with refrigerant?

You may have to recover enough refrigerant to get the thing to run long enough to watch it, get your super heat and/or sub cool. 

Just start with the basics. The big machine is just like the little ones - just with a little more "Wow!" factor.  It all is the same principle albeit RTU split, one stage/multi stage.

As to the relays you may have some fire alarm shut down system, some building automation system.  Again the basics...where do the contacts go, are they NO or NC, are they passing HV or LV? What is feeding the coils HV or LV, where is the feed coming from. 

Grab a diagram and start cutting wire ties and start following wires by hand if necessary.