Need help re: schematic class

[Triggerman]

Greetings y'all!

I am preparing material for a general familiarization class in schematics reading for HVAC/R technicians. The basic plan is one night per week for four weeks. Here is the general outline:

1) Low voltage alternating current
2) High voltage single phase AC
3) Three phase AC
4) DC

Any ideas, graphs, clip art, etc. greatly appreciated.

Thanks

[Electrocoolman]

Hi Triggerman,

A lot of US drawings take form of Ladder diagrams (I believe). ie. Start at top left with power and work down and to the right.

There is a logic associated with these.
Need to know symbols for the various components in order to be able to read and work out what is meant to be happening.

Motor types and methods of starting and protection. Direction of rotation. Changing motor speed.

More and more HVAC using inverter technology including VSD.

Hope this helps.

[Dan]

I agree, Ladder diagrams are extremely important for troubleshooting. Also, don't forget the basics: All switches are shown in refrigeration mode, no power applied. You cannot have 2 loads in series. Open switches, fuses, etc are found with a voltage indication across them, closed switches and fuses are found with no voltage indication across them. Always disconnect any wires to circuits that you intend to ohm out. Don't read your circuits to ground unless you are simply looking for ground faults.

I am surprised how many experienced technicians have to be vetted out on these sorts of basics. Once they get a good grasp on the simple things, they become amazingly more proficient.

[expat]

Hi Dan, we've never spoken, I agree with your statement but in my training the work we did on schematics did not help me to cipher the things I later came across, and I often find myself stumped.

What to do?

Here's an example I posted in the eletrical forum, that Brian_Uk kindly helped with
http://www.refrigeration-engineer.co...3&d=1183566477

any comments gratefully received

[Brian_UK]

Triggerman and perhaps Expat...

I've just been looking for info on the Carrier site and came across a section where you can download wiring diagrams.

http://www.commercial.carrier.com/co...MID165,00.html

You need a rough idea of the Carrier model numbers so I would start with '30' and go from there.

[US Iceman]

If you do a Google search on ladder diagrams you should come up with some fairly basic information on developing ladder diagrams.

It's important to know and realize there is a structure used for these and not a haphazard approach. Certain things like knowing the difference between rails and rungs, what the rung numbers mean on the right hand side of the rails, what the underlined numbers indicate, and so on.

Schematics I view as something completely different from ladder diagrams.

Besides the actual layout and use of the ladder diagram, knowing the symbols and how they operate in real life is just as important as knowing their powered and un-powered state.

Dan touched on some of this and I fully agree.

[Dan]

Hi, Expat. Not sure what you wanted from me on the wiring diagram, but I fiddled and muddled with it without really understanding the equipment.

Brian probably did a much better job of sorting it out, but perhaps my thought process provides a different view. Let's remember that a wiring diagram is not going to substitute for an operation or service manual, but will guide a technician with his meters to find opens and shorts in the equipment. Hope my musings help.

[Triggerman]

More and more HVAC using inverter technology including VSD.

Hope this helps.

Thanks. I am including VFDs in the material.

I am surprised how many experienced technicians have to be vetted out on these sorts of basics.

After a statement like that you should change your name to Ed Zachary. Because you are edzachary correct! My course is being developed for all skill levels to gain some knowledge. Thanks.

I've just been looking for info on the Carrier site and came across a section where you can download wiring diagrams.

Thanks. I have already downloaded diagrams from Carrier, Trane, York and a few others.

Schematics I view as something completely different from ladder diagrams.

How true. And, I'm finding more these days, there are no pure drawings. They all seem to be a blend of schematic, wiring diagram and component layout.

I fiddled and muddled with it without really understanding the equipment.

Dan, you hit it out of the park on most everything. HR is for Holding Relay. Carrier engineers' retirement plans were heavily invested in relay manufacturers, I'm sure of it.

Thanks y'all for all the great help. I will let y'all know how it came off.

[Lowrider]

If needed I can provide some wiring diagrams in Dutch standard!

[Triggerman]

Thanks to everyone for their replies. We have decided to table the idea until next year.

[TXiceman]

Something that you need to consider is that most A/c and small packaged equipment have a point to point wiring diagram rather than a ladder diagram. Seems most service techs prefer a point to point, but I do prefer a ladder diagram for trouble shooting.

Ken

[sapper]

i agree with Triggerman it is becoming more and more difficult to locate pure schematic diagrams. seems to be more common to find a schematic/ component layout than a pure schematic. However these are just as usefull