cheapest way to drop 480vac to 240vac

[mramos1]

So, it needs 240 VAC power and access to the 24 VAC line that controls the contactor AND the power company has to have a place to mount their gizmo close to a disconnect, Probably 3 feet, but check with codes in your area.

It was explained to me, they have a 240 or 208 input (two style units) and a contact relay that ties to the yellow thermostat line (to open and kill the unit). Explained to me by the installer. He said get him 240 or 208 and the thermostat wire and he would install it and we would get the credits.

So were do I fine a 480 to 240 OR 208 transformer that can handle say 2 amps of a load (their box and relay) on the 240 output side. That's the magic box I'm looking for. Ot a way to do the ground to 277 with output of 240 ot 208. Wish it was a Microchip, Atmel, Intel, moto, etc I was dealing with, or analog/digital circuit, but electrical is not my bag.

Thanks for all the help guys. If I ask the electrician he will have an $800 giant transformer for me. And I would like to put the unit inside the AC unit, but not required.

 

[circuitspecialists]

You can use a capacitor to drop AC voltage....you use the capacitive reactance of the cap at the frequency of use 50 or 60 Hz.

 

[KeepItSimpleStupid]

You weren't paying attention: I'll take a finder's fee: https://www.automationdirect.com

Type "transfomer" in the search box and take your pick.

Here you go, $40 for 50 VA. Other values are available. I don't think you need 500 Watts or 2 * 240. That's 1/3 the wattage of a toaster. You might even be able to get the integral fuse holders and accessory kits. That was a tough one!!!

 

[Reloadron]

I may be off base with this but all you need is a common control transformer like for example a Hammond PT25QP and here is the data sheet. Scroll down to the part number PT25QP which should be more than adequate for your needs. They run about $35 USD depending on the vendor. I use Allied Electronics for stuff like this but there are others. Transformers like this include the fuse mounting hardware.

You have as mentioned 480 VAC WYE power where each leg to ground is 277 VAC and additionally in many manufacturing facilities that 277 between any phase and ground (Neutral) is used for lighting applications.

The transformer primary is wired phase to phase and your secondary is 240 VAC which is what you want for the power company gizmo box. If an enclosure is needed you can get one from McMaster Carr that meets your requirements be it NEMA 1 or whatever. Matter of fact you can likely buy the transformer from McMaster Carr now that I think about it. The Hammond Manufacture I called out is just an example, these transformers are very, very common hardware.

Ron

 

[strantor]

please forget about this notion:

a way to do the ground to 277 with output of 240 ot 208.

The link provided by KeepItSimpleStupid is exactly what you need. If you really think you need 2A, then this 500VA model is available from the same site for 109$. I doubt you will find a better deal.

 

[KeepItSimpleStupid]

Ron: Welcome back
Stantor: KISS will work

I suspect 40 VA is enough.

 

[strantor]

Stantor: KISS will work

good. That will make things easier

I suspect 40 VA is enough.

As do I.

 

[mramos1]

Thank you guys for the input. All what I needed to know. Cap idea if I had a value/rating I would try it, but power folks said transformer only.

Unless I find it cheaper from the KISS link, will be going with a PT50QP and probably all from McMaster Carr if they have it all. Allied is 50/50 for me. Like Digikey and Mouser

Once again thanks.

 

[mramos1]

automationdirect $41.50

temcoindustrialpower.com $30.01

Guess I need to call on any free shipping offers. They were a couple lbs each.

 

[KG4MXV]

Sorry to be the barer of bad news, but I am familiar with these devices and using a transformer will not work.
The system is made for residential use not commercial.
You need a system that will work with 3 phase 480.
The residential system only cuts the power to the compressor and not the entire system so you can still have air circulation
in the home.
Progress energy use to have the same system here in NC and my home had one but the program got 86'ed years ago.
I had to remove mine because it started to actup and cut the power to my compressor randomly and caused a lot of problems.
even putting it on one phase will be too high of a voltage for it.
You need to get one that is for commercial HVAC systems.
I wish I could have a 3 phase 480 feed to my home.
I could have had SG300kva UPS for free with two strings of batteries that were less than a year old.
My load on that UPS it could run for 24hrs before the batteries would be depleted to the stop operation limit.
Now I would have had to put in a 8' X 10' shed with its own hvac system.
wishfull thinking.

 

[KeepItSimpleStupid]

The residential system only cuts the power to the compressor and not the entire system so you can still have air circulation
in the home.

So, cutting the 24 VAC power going to the outside unit will do that. In fact, it is the C and Y lead, specifically the Y.

Now, if this were a heat pump you might have a few more wires to deal with, but nothing serious.

There is NO reason, I can think of, why you need to put two contractors in series. The boxes and the one internal to the compressor. Furthermore, the neighbor's only has a Thermostat loop (enter/exit) and a 240 entry.

I can see where cutting the power to the compressor would not be a good idea, because the anti-short cycling that is now built into most electronic thermostats would not be present. I had to install an anti-short cycle relay on a mechanical thermostat system that was installed in 1968 after it obliterated a couple of fuse blocks from starting after a brief power failure or a quick flick of the t-stat.

 

[KeepItSimpleStupid]

mramos1: Do get the fuseholder and the fingergaurd option for your transformer.

 

[KG4MXV]

KISS is 100% correct, Now if the power co. equipment doesn't sense the current consumption of the hvac system and only uses utility power to run the communications and microprocessor in their equipment then a step down transformer would work
but you have to consider how are they connecting to the equipment.

data over the power-lines or a RF link, if it is a data over the power lines then you will need a way to pass that signal around the transformer.
another thing to consider the control wiring on a commercial HVAC unit might be completely different than the standard home or consumer hvac unit.

 

[KG4MXV]

BTW I have a step down transformer and din-rail mounted safety fuse holders all new. and din rail.
I think I even have some 5A fuses. I will sell the entire kit for $100.00 The transformer is a bit larger what you need so if you want jus the fuses, holders and din rail. $40.00 free shipping inside the upper 48.
Now if you want the transformer I will have to see what the shipping would be for it since it weighs
15lbs or so.
The transformer was part of a install kit of a battery charger on a generator. I didn't need the trans former.
And the transformer is a GE unit.
I will dig everything out of the shop Saturday and take pictures.
I woud do it tomorrow but I am having a stint removed from a kidney stone removal operation I had last week.

I am going to be doped up on oxycodone before and after the procedure. So I am not going to be doing much.
friday. ;-)

 

[johansen]

Sorry to be the barer of bad news, but I am familiar with these devices and using a transformer will not work.
The system is made for residential use not commercial.
You need a system that will work with 3 phase 480. .

that's what this entire thread is about, converting the 480/277 into 24.

since it drives a relay it won't matter if its single phase 240 or three phase 1200vac.

 

[Reloadron]

Back to the beginnings:

The power company here will install a small unit that monitors your AC (208 unit and 240 unit, assume single phase) line and certain times (emergencies) flip off your AC to the air conditioner for 15 minutes with a credit each month.

They said it will only work on 208 or 240vac and we have a 480vac 3 phase AC units. If I can get it to 240 and show them the thermostat wires they will install it for me.

Power companies are starting to offer "smart grid controllers" for industrial as well as residential power consumers. During times of peak demand on their grid it allows them to reduce the load. For example here in the greater Cleveland, Ohio area our power is primarily nuclear generated and provided by First Energy. When demand on the grid really increases they occasionally need more power and fire up their coal burning plants. This obviously increases their operating cost. Thus, they offer smart grid controllers and pass some of the savings along to the customers.

All that is required is single phase 240 VAC which is typically obtained from a simple little transformer. Their smart grid controller is a very low current device wired into the customers Air Conditioning thermostat. That is all they care about. The fact that the thermostat may use 24 VAC or any other control voltage for the system really matters not. The VA rating of the transformer used isn't much of an issue, my best guesstimate would be a few hundred mA.

Me thinks India should be looking at smart grid control systems.

Ron

 

[KeepItSimpleStupid]

Carrier can throw off the simple break the Y wire. If you put Carrier's ABCD bus to the outside unit then there is no "Y" wire and the POCO can just say "Sorry, your system is not compatable".

With a Building automation system, you probably already have energy savings built-in from outside air control, CO sensors, variable speed drives, occupancy sensors and even air pressure control, staging chillers and you name it. Nope, won't work.