Electrical Challenge! Can YOU Solve It?

Codywookman

I'm trying to build a cooling unit that involves the following:
*24V AC Thermostat (2; one in each chamber)
*110V AC Cooling Unit
*12V DC or 110V AC Fan
*12V DC Linear Actuator (no limit switches installed)
*110V AC Limit Switch (2; 1 for extending, 1 for retracting)
*12V DC LED Indicators (2; 1 to indicate cooling unit running, 1 to indicate fan running)

It is a dual chambered cooling unit; when the thermostat located in the non-cooling unit chamber "trips" the linear actuator opens a door and allows the fan to blow cold air into the chamber. Once the fan shuts off the linear actuator should return to the closed position. The other thermostat is located in the cooling unit chamber and trips at a certain temperature.

The first question I have is how to wire DC and AC in the same system? Do I need a set of relays, and if so what type (ie 24VDC controlled or does it matter)?

The second question is how to set it up so the limit switch stops the linear actuator when it is fully open, but the fan keeps running until the thermostat kicks it back off.

I appreciate any attempt at helping as my electrical knowledge is quite limited.

wirenut1110

Pretty simple to do but I don't feel like drawing or designing it for free

Personally, i prefer to use programmable relays for things like this than using several relays.

You'll need a 24 VAC (coil) relay or contactor to turn your cooling unit on, and the fan. This can also power your LED's.

I'm thinking 12 VDC magnetic limit switches in series with forward/reverse relays/contactors to "open/close" the actuator.

On the 24 volt relay, have one normally closed contact on it so when it's not running, it energizes the reversing relay till the limit switch cuts it off.

BCSparkyGirl

this is for sure not a basic DIY question................you may have to shell out a couple of buck for this info I am afraid....

Codywookman

Thanks for getting me on the right track wirenut1110,
I'll get to work on this and probably ask for additional advice soon...that is if you are willing to lend a hand. I might have to give you some of the homebrew I will be fermentin in this super chiller.
And don't worry BSCparkyGirl...I'm not looking for a full out electrical plan in front of me. I just need some pointers here and there to find the components that will be easiest to use. I thought about the programmable unit and thought for the price I could figure something better out.
Anyone else have advice that should be taken?

wirenut1110

If you want to get fancy and make sure the fan is on and blowing cold air, I would have a "klixon" on the cooling coil that will lock out the fan until the coil gets to a set temperature and a pressure switch on the fan.

wirenut1110

Ok, I was bored. This should get you started. Hope it helps. If you use an 11 pin relay you can eliminate R2.

Attached Thumbnails

 

Yoyizit

Draw your prelim. schematic with all components hooked up; it's easier to
critique a candidate than
design from scratch.

It seems like the fan shutting off is supposed to turn on the actuator reversing voltage. . .?

Magnettica

Oh boy, I think my heads about to explode!

Reminds me of my days in school.

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wirenut1110

Yeah mine too, and I'm out of alcohol.

nap

nut, do you want the LS's to be momentary NC?

and how did you copy that and post it here?

scan and upload to a photo hosting site?

and not picking on the work but the OP said something about 2 t-stats. Just figured you missed that.

wirenut1110

[quote]nut, do you want the LS's to be momentary NC?[quote]

Yes they need to be NC. I'm thinking he can add something to his actuator like some micro switches with a worm gear or something so when it hits in whatever direction it'll shut off but allow it in the other direction.

On this site, you can add as an attachment using the little paper clip and upload from your computer

[quote]and not picking on the work but the OP said something about 2 t-stats. Just figured you missed that.[quote]Yes I did, I was wondering because he said something about dual chambers.

Glad I did it with pencil

Codywookman

Ok I finally had time to start building today. I can't seem to find anyone who carries the 24VAC relays I need. Any certain products you would recommend or suppliers to go through? I appreciate the help.

Stubbie

Try Graingers


http://www.grainger.com/Grainger/wwg/start.shtml

__________________
" One nice thing about the NEC articles ... you have lots of choices"

Stubbie

wirenut1110

You can also look at http://www.newark.com/. or http://www.automationdirect.com/adc/Home/Home. Grainger prices can be a little high sometimes.

P.S. That drawing i gave you is fairly generic. I need a little more info on what exactly you have. Of course pictures always help.

Codywookman

Supplies on hand:
(2) 120VAC / 12VDC 1.2amp Inverters
(1) 120VAC Window Air Conditioner
(1) 12VDC Linear Actuator http://www.mpja.com/prodinfo.asp?number=17265+MD
(1) 12VDC Computer Fan http://www.goldmine-elec-products.co...6399&variation=
(5) 12VDC LEDs http://www.mpja.com/prodinfo.asp?number=15109+OP
(2) 120VAC LEDs
(2) Thermostats http://www.usaindustrialsupply.com/s...ammable/Detail

Haven't purchased limit switches, transformer, or relays yet.
This thermostat is rated for 24VAC. I'm not very knowledgable about AC vs DC but would it be possible to run the thermostat in the 12VDC loop? This would save a transformer and would be much easier to wire. If not then I need help finding a relay rated for 24VAC contact and 12VDC load.
Thanks for the help!