Diagrams

[IrishJoe]

Hey fella's,

First post here! I'm in a HVAC-R college program - 1st term, tech school.

First I want to thank you guys for all the good info & debates (tips & tricks-rocks). I'm getting an "edge" in class for sure. I'm work as a lab tech. (min. wage-do-it guy!) on campus for the program while in school. They get a lot of old & new A/C units, furnaces, walk-ins, etc. donated. They have about 20 a/c units in the lab, and about 50+ stashed behind the building! How do I get spec for these? Most diagrams are weathered away and unreadable. Can I just write the manufacturers? Mostly, wiring is the big concern. They even have a unit from China. That's a whole different problem!

[cem-bsee]

you need a schematic for one --
learn it & rest will be quite simular --

schematics show how devices work together
diagrams show how devices are wired together

start thinking about what controls what
what must happen before the unit starts,
what will cause unit to stop
what will cause poor preformance

[davefr]

You're likely to face the exact same problems out in the field. (i.e. missing documentation, unreadable/worn schematics, old systems, etc - "Sorry Mr. Customer, it's 20 below zero and I know you have no heat but I have to write a letter to the manufacturer since I can't read the schematic on your unit.")

What books are you using in school? I'd highly recommend you get hold of a book called Modern Refrigeration. They go into a lot of depth describing common refrigeration and control circuits. Once you understand "theory of operation" you'll be able to sketch out your own schematics.

It sounds like a good school project for the instructor to drag out one of these old "boat anchors" and have the class reverse engineer it and produce a schematic/wiring diagram and theory of operation.

If I were the instructor I'd also jumble up some wiring and tell the class to fix it.

[Shophound]

It sounds like a good school project for the instructor to drag out one of these old "boat anchors" and have the class reverse engineer it and produce a schematic/wiring diagram and theory of operation.

If I were the instructor I'd also jumble up some wiring and tell the class to fix it.

My thoughts exactly.

If I had to write to a manufacturer each time I came across a unit with a missing schematic (especially when I ran service) I'd be dead meat. Truth be told, an accomplished tech can strip a unit's electrical control box down to nothing (pull all wires off components, etc.) and be able to put it back together and it works again. He may or may not need to draw out a schematic...doesn't matter. Point is he knows how electrical control circuits work and has a good grounding in electrical theory.

Me? When I was younger I might've been able to wire up certain components out of my head, but these days with CRS setting in I like to draw it out on paper. Make the mistakes there vs. at the breaker box. :D

[cem-bsee]

"and has a good grounding in electrical theory"

not only in theory, but for the chassis!

[totaleclipse]

Hey fella's,

First post here! I'm in a HVAC-R college program - 1st term, tech school.

I'm getting an "edge" in class for sure. I'm work as a lab tech. (min. wage-do-it guy!) on campus for the program while in school.

On a side note, I am glad to see that you are working at the school in your spare time. When I was in school(for a different trade) I did the same thing and I picked as much if not more from that than I did the classes. I know what you mean about the min. wage guy, but the knowledge you will pick up is worth more than your time invested IMO. Keep it up, you wont be disappointed!

[IrishJoe]

Thanks for the replies.....and yes, i have to agree about learning more working on campus. Our lab time is limited, and we work in groups of three, so alot of the "hands-on" is watching someone elses hands. While I'm working, I get to tinker around with the units by my self, I have the super heat & subcool thing down from adjusting the equiptment after class labs. looks like i'll be getting a jump on electrical class as well trying to put spec packets together for the untis. My instructor agreed that most units have the same general wireing principles, so I guess I can just start on the ones that have the diagrams, and learn from there.

Thanks again.

[IrishJoe]

Double post! Oops!

[cem-bsee]

see if you can get a copy of a diagram --
then get some color pencils | pens | highliter
or use X | o | dot | slash | dbl slash to Identify :

the 24v common
24v hot
etc

now make a schematic to learn how the stuf works!

BTW, I just use a box for a circuit board --
ID signal in
ID signal out

remember, "signal in" may be a switch, or a relay contact
"signal out" may be power to activate a relay coil, or a solenoid coil or ___

[HPuser]

Seer 10 HP is pretty simple, I don't know about higher numbers. Just get diagram for any seer 10 HP, it will help. There are many diagrams in Langley book. It is hard to diagnose capacitors but if you have couple good ones in your bag you will just switch them. Have fun with old AC, it will be great practice. You can probably even sell them if you give warranty