I just want to ask before I wire it up and turn on the circuit breaker.


20 Amp dedicated circuit for A/C unit, adding relay to control hot lead for 24V ac adaptor which controls the contactor. I have another thread if you would like to discuss the why, I have all the components and am wiring the box and just want to make sure I can close the circuit for the 24V ac adaptor by tying back to the neutral on the main leg of the circuit.

Specifics:
12/2 feed from dedicated 20amp breaker

Essex/Steveco 90-180 30A3P contactor 24VAC coil

NTE R04-11A30-120 DPDT 2 Form "C" Relay

Timer runs on NC throw of relay, engages coil, operates fixed window 6:45a - 10:45p

Thermostat runs on NO throw of relay, monitors room temperature and enables A/C unit if threshold reached (to keep A/C fan from running constantly as it does not cut off on its own)

 

Would it work? Yes, I believe it would. Is it legit? I really don't know. I can't see why not. After all, all the neutrals are electrically tied to the same point, so I don't see why it would matter where you connect the AC adaptor.

Why are you using a 20A breaker if your outlet is 15A?

 

Thanks mossman Unfortunately I'm not a licensed electrician. My cousin who helped me run the circuits is, but he's busy packing and moving out of his house so he isn't able to help me at the moment. He glanced at it on his smart phone and thought the same thing since it's all on the same neutral anyways it should work.

I 99% certain but since I only had a DPDT and not a 4P4T relay I wanted to make 100% sure.

 

Neither am I, I'm just looking at it from a functional standpoint. Only other feedback I have is that you may want to put a fuse inline with the timer and the thermostat .

 

That doesn't look like a workable configuration. It also looks over-engineered.

At work we sometimes install environmental controls for server farms. These systems read indoor and outdoor temperature, humidity and air flow, constantly adjust the HVAC units for optimum, create a continuous record and allow for offsite monitoring, troubleshooting and override, among other things.

Here at home we don't get quite that precise. We just build plenty of cooling into our servers and turn them on. My wife's main frame, for example, has five powerful but quiet fans. It sits next to her chair in the living room, which is where guests also stay occasionally, and visitors aren't even aware it's there unless the ask where her "computer" is. If they do, we point to the tower and let it go. There's no need to get into all of the peripherals it's connected to and using and controlling.

Back to the server farm model. Those use external cooling. The servers themselves are mounted in open racks which sit on a raised floor. The air from the cooling units is fed under the floor to rise through the racks and return above the ceiling to the condensing units.

You want the air on the over-clocking CPUs to be cool enough anytime they need it. Time of day is of no importance. Forget the timer. Replace the cabinet with a rack that air can flow through. Feed the air in one end and out the other. Control the A/C unit with a simple thermostat mounted on the wall, not an internal one. Insulate the closet, including the door, so that the expensive chilled air and the annoying noise stay inside it.

Or just build more air flow into the cabinet/tower.

 

Thanks for your input Nashkat1, but I'm wondering if you read that I was looking for information regarding the function of the electrical circuit.

I have the cooling handled already. If you'd like to discuss the why/why not to do what I'm doing, as I mentioned I have another thread for that discussion (here's a link: http://www.doityourself.com/forum/el...tacts-b-b.html) There's a pic of my cabinet in that thread.

I'm going forward with my plan I just need to make sure the circuit logic is sound. It took me some time to figure out the DPDT relay because I've never worked with anything other than SPST in the past. All of my past experience was with HVAC / Lighting automation controls and had a computer controlling multiple braincenters in various buildings all on a 24V dc system. Because the actuators were pneumatic and the light ballasts were already installed I'd never dealt with higher voltage or more complex relays.

 

I did. Did you miss my reply to it?Sticking with just the electrical circuit question, you show the 120V ungrounded potential from a line voltage timer connected to two of the four (presumably) input terminals on a device that may be a DPDT line voltage relay. You show the grounded potential from the timer connected to a third (input?) terminal and the ungrounded 120V potential from a (presumably line voltage) thermostat connected to the fourth (input) terminal. There is no grounded conductor run with the ungrounded conductor from the thermostat.

There is no indication of which pair of terminals should be connected to control power and which pair to the power to be controlled.

On the output side you show what appear to be one lead from a NO contact and one from a NC contact spliced together to supply the ungrounded input to a small 120V/24VAC transformer which is connected to grounded potential from a separate location. The 24VAC output from that xfmr is fed to a (NO?) coil that closes to connect 120V ungrounded potential to a standard 15A receptacle.

Have I got it so far?

If so, your diagram doesn't show how this setup would work, or if it would. It may be workable, but not be comprehensible due to the lack of labeling. I don't think that's the case, based on the two splice points on each side of the relay for one thing, but I could be wrong.

Let's say I'm wrong and this series of gizmos will do exactly what you have in mind. Then I either don't see how that will happen or it won't happen. How will this prevent overheating the CPUs between 10:45 pm and 6:45 am?

You can hook up all the devices you want. That doesn't mean you'll get what you're looking for at the end of them. Right now, as I'm looking at a timer, a thermostat, a DPDT relay, a transformer and a coil all wired together to control the ungrounded potential to a single 15A receptacle to turn a fan on and off, I doubt that you're on the most efficient track.

 

I saw that thread before I wrote my first reply here. That's the only clue I had to what you were doing.

If you're interested, you can transpose my comments on the overall design to that thread.

 

I'm not sure if you meant the reply where you said nothing about the correct/incorrect nature of the circuit (other than it doesn't look workable, & it was over engineered), and talked about your wife's main frame? or some other reply which I didn't see?

I saw that reply first reply though, yep.

Yep I think you have it. Up to the part about the ungrounded potential to a standard 15A receptacle. (the ground is just layered behind it on my visio diagram, my apologies)

I was having the same trouble figuring out the relay myself since they don't have markings and assume the installer knows how to operate it.

Also I wasn't aware ground was a necessary component in order for AC to function. I'll look into that and see how I can properly ground everything. Right now there's no ground terminals on either my DPDT relay or my Contactor so I've based the diagram on the information I had physically in front of me.

As it is now the Timer has a hot and neutral leading to the DPDT relay, neutral hooks up to one side of the coil, the hot I have hooked up to the other side of the coil & one of the poles.

The Thermostat only has a hot hooked up because I have only two poles and one is already in use for the Timer.

On the Throw side I have one lead connected to the NO throw, and another to the NC throw. There are four terminals on the throw side, 2 for Normally Open, and 2 for Normally Closed. The normally closed are connected when the coil is activated, normally open are connected when the coil is inactive. The wires are connected from the Left NC (my relay diagram is upside down) and the Right NO throws, together to the outlet for the 24v transformer. (Timer=L, Thermostat=R)

As far as working, I've individually tested the relay coil, and the contactor coil and both work fine, what I was uncertain of was creating the circuit by connecting the neutral of the outlet for the 24v transformer back to the main leg via a pigtail. Path of least resistance predicts it will work.

The Thermostat on the NO throw.

I never claimed to be doing this the most efficient way. I'm doing this as cheap as I can.

If I wanted efficiency I would have bought this: Digital Environmental Controller - Rakuten.com Shopping

and hooked up a separate dehumidifier, CO2 I'm not so worried about because I'm not growing pot.

I'm not overclocking, I do have virtual systems doing grid computing work when I'm at work and not using my home systems, and they do use more CPU but the heat is a constant buildup issue rather than a overclocking watt/output issue.

I'm aware of how data centers are operated and cooled, I work on the team which supports them at my employers multiple co-located data centers.

I've admitted I built the cabinet for quiet, and unfortunately did not give it enough airflow for my newer equipment. It worked perfectly fine on it's own before in my living room at my old condo with my old systems in it.

There are fans in the cabinet which move air just not efficiently enough when enclosed in the closet and only 14"sq supply/return passive ventilation. I don't have my actual BTU calculations and I'm too tired to figure it out right now but suffice to say the solution was I could install a bunch of fans in the door and attic space to ventilate (landlord would certainly not appreciate that, and I'm sure she won't like that I've cut holes in the door and ceiling) OR go with a less invasive active cooling method (ie. Tankless Portable Air Conditioner)

My apologies again that the diagram wasn't fully labeled to make it comprehensible, I had hoped there was enough information from the coloring, and information I provided in the initial post under "Specifics" below the diagram to determine what the devices were and how it would operate. I assume you read it since you asked which I've answered again above.

Let me know if there's any additional information I need to provide to determine if the circuit is complete or has a specific point of failure.

Thanks

 

WAY TOO MUCH to read thru here

The circuit as you have it drawn will work fine. You show a receptacle supplying power to the timer and T'stat. I would fuse that receptacle at maybe 5amps. Then your secondary wiring and relays wiring is protected. I just added contact lettering to your drawing. The wiring is shown correctly but the terminals aren't labeled correctly.


At rest... the thermostat will control the load.
When the timer is activated it will bypass thermostat control.

 

Thanks PJmax! Someone else had suggested the same thing to me on facebook I actually picked up some 5A fuses and housings last night at an electrical store. Not sure I need that much my transformer only pulls 430mA but it was such a similar price to a 1.25A fuse that I got the 5A.

Sorry for the long discussion, I had hoped to avert that stuff but I needed to be certain.

I was looking for a DIAC? or diode for AC and found something online from NTE a 4970 which I thought about hooking up before the poles on the DPDT but my local mom&pop electrical store and Fry's Electronics didn't have them. I'll likely order online. I'm not sure if they're necessary unless voltage somehow arc'd at the relay? I'm not 100% certain I'll even need them but the possibility exists if the timer deactivates the room could be at high enough temperature in the summer that the thermostat lead is already hot. Does that make sense? Again I'm not used to working with multiple pole relays. Most everything I've done in the past was just a coil making a single contact close.

Thanks again for your response

 

That relay is handling a minimum of current. I wouldn't worry about arcing being a problem.

If you wanted to use something you would use a MOV (metal oxide varistor)

MOV (Metal Oxide Varistors) - Allied Electronics

 

Awesome thanks so much for your help PJmax

 

I seem to have lost you at that point. I regret that I wasn't clearer there.

What I originally said was:That's what I meant to say, but I can see how it might not be as clear as I would like to someone not familiar with electrical terms.

To clarify, ungrounded potential is hot power, ungrounded from the source, and the "hot wire" is technically the ungrounded conductor. Grounded potential is the neutral phase, and the "neutral wire" is technically the grounded conductor. In a branch circuit, what we commonly refer to as the "ground wire" is actually the grounding conductor, which is shorthand for the equipment grounding conductor.

While your diagram would have been clearer if you had just assumed the grounds and left them out of the drawing, what I said had nothing to do with grounds, grounding or bonding. It wasn't affected by whether one of the grounding conductors was visible or not.

Here's what I said in less technical language (I hope): On the output side [of the relay] you show what appear to be one lead from a NO contact and one from a NC contact spliced together to supply 120V power to a small 120V/24VAC transformer which is connected to neutral from a separate location. The 24VAC output from that xfmr is fed to a (NO?) coil that closes to connect 120V power to a standard 15A receptacle.

Clear as mud? OK, glad we got that resolved.

Now, here's my real question about that part of your design: Why do you have the mini transformer and the coil, or contactor? It seems to me that you have what the receptacle needs coming out of your DPDT relay -- that is, 120V power that's on when you want the load plugged into that receptacle to be energized and off when you don't want it to be energized. Why not just connect that power -- that conductor -- straight to the receptacle? You could feed the neutral from the connection in the relay and have the set of conductors running in the same raceway (which is a code requirement) and you could eliminate the inefficiency and the additional potential failure points introduced by adding the xfmr and the contactor.

Or am I missing something here?

Note: Before I forget, thanks for expanding and labeling the relay diagram, PJ. That made this a lot clearer to me and, I'm guessing, to some others too.

 

10A load capacity on the thermostat contact.

15A draw on a/c unit

 

Hey now, I suggested using fuses in my second response

 

Sorry, my bad I should have also given you credit

My cousin's father in law emailed me and suggested the same 5A fuses since he didn't know the operational information on the transformer.

 

Thanks again to all who had positive input, I feel more assured having other sets of eyes go over what I believed to be accurate but being an unskilled hobbyist wouldn't want to burn down my landlords condo and have to actually use my renters insurance LOL

for all
:No Beer 4U: for any non-drinkers