Temp. Controller

[RAVWARD]

Hi,
I am not an instrumentation guy but have to do a temp on and off control for three heaters rated at 720 W at 240 V AC each. I selected Honeywell T775C1009 controller

http://customer.honeywell.com/Techlit/pdf/63-0000s/63-2489.pdf

On Page 14, is the model I selected. It has a 4 relay output. If you clearly the input to controller is
240 AC with RED and BLACK wires, where RED is fed to Common and BLACK to line side but on four contacts, RED is fed to NO contacts and BLACK is fed to COM. Why it is different for contacts. The other confusion I have is
about the breaker rating feeding the controller. On page 2, the electrical rating for four stage controller is 13 VA at 60 Hz .
The total current for three heaters is 9 AMP at 240V. Can I use a 15 Amp breaker for both controller and heater ?

Last question, I am having a hard time to put this thing on to a drawings so that a HVAC contractor could understand it. I just need some advise on how to represent instrumentation schematic. Could you please advise any link on web where I can get a start for this. I would honestly appreciate a word.

Thanks

 

[itsmoked]

RED and BLACK wires, where RED is fed to Common and BLACK to line side but on four contacts, RED is fed to NO contacts and BLACK is fed to COM. Why it is different for contacts.

It does not matter as the 'upper common' is just the power into the actual controller(to run it). Do not confuse the two even though the maker sorta has.

Can I use a 15 Amp breaker for both controller and heater ?

Yes as long as the wire can handle 15A. If the controller does not have it's own internal fuse for an internal failure then you might want to include a fuse in the red wire AFTER the point where it Tees off to the loads. (But without reading it I would expect the unit to be internally protected.)

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[danw2]

1) For 240Vac in the US, both red and black are "hot" wires. The drawing on page 14 is OK. Follow the drawing and you'll be OK.

2) The controllers power consumption, 13VA at 240Vac, is sligthly more than 1/20 of an amp. 1/20 of an amp is very little additional load on top of the heater load, which you pointed out to be 9 maps.

I'll have to leave the answer about using the same breaker for both controller and heaters to an electrician who's familiar with the code.

3) Drawing for a contractor? What about the using the drawing on page 14? The heaters are the loads. You can white out the other boxes if need be. The document was meant to be used by installers and contractors.

You do know you bought a controller capable of staged control (first heater on at 70°, 2nd on at 68°, 3rd on at 66°). Did you intend to do that or do you really want to turn all 3 heaters on and off at once?

Dan

 

[wareagle]

RAVWARD
In this installation red and black are both energized. Therefore it does not matter which conductor(red or black)
goes to the common terminal.

 

[RAVWARD]

Thanks Everybody.

It is 416/240 V AC and I am choosing single phase pnly 240 V(Not like domestic, single phase split neutral). That means, one is supposed to be Neutral and other Line. I understand it does not make difference but that is the reason that out of three prongs for sockets, neutral prong is bigger than line prong.

Danw2:
I did not selected this controller for staged control. I selected it for simultaneous turn on and off. Am I missing some thing here? I hope I can do this with this controller.
Please advise me, If I am losing it at this point.
Thanks

 

[waross]

Your neutral, or white wire should be used in place of the red wire.
Repeating in different words, what has already been said.
The controller is a load.
The relays are switches controlling external loads. That is why the wiring is different.
Talk to the contractor and give him the diagram that you posted.
One of the reasons for the bigger neutral prong on a plug is to maintain polarity on two wire plugs. The other reson is to prevent heavier equipment from being used on light gauge extension cords.
You will notice that light grade extension cords have both slots the same size so as to reject the plugs with the wider neutral prong that are used on heavier appliances.

 

[danw2]

>I did not selected this controller for staged control. I selected it for simultaneous turn on and off. Am I missing some thing here? I hope I can do this with this controller.
Please advise me, If I am losing it at this point.

If you wanted all heaters to turn on and off simultaneously, another approach is use a controller with a single output which then drives multiple contactors, where you have one contactor for each heater.
But that takes more footprint in the enclosure, more wiring, and for all I know, the cost is a break-even proposition.

Dan

 

[danw2]

Make sure you switch the line, not the neutral.
Run the line to the common, not the neutral. The neutral gets connected to the unswitched side of the load.

Dan

 

[RAVWARD]

Thanks Dawn. I am drafting this drawing my self then asking a drafter to do it for me. So, that i feel my self comfortable my self. I will be posting the link for drawing image in few minutes. I honestly appreciate your time.
I asked honeywell people about this red and blk thing but some times you dont get right people on tech support to answer. I am just in dilemna that this supply can be a 240 V single phase(416/240 V) and we can also use 240 V split phase neutral like in domestic stuff, in that case both red and black will be lines. But in single phase 240 V will be one line and one neutral. then all common on supply and relay contacts will be connected to neutral and NO will be connected to line oppposite to as shown in Page 13 of the link in my first post. I am not sure, if I am making sense. I will be posting my link soon. Please advise me, if It is good for a contractor to understand.
Thanks

 

[RAVWARD]

Hi Everybody,
Here is my final circuit not complete though as I need a lot of notes and stuff but for you guys comments.Please copy paste the link

http://img169.imageshack.us/my.php?image=controllerfy8.jpg

here is the link to contactor used:

http://customer.honeywell.com/Techlit/pdf/69-0000s/69-0874.pdf

I would appreciate a comment.
Thanks

 

[danw2]

If I got the diagram I wouldn't know how to wire it.

It isn't clear where the heaters or controller are fused.

You really need some local design help. There are times when internet advice is just too remote and too awkward.

My experience with licensed electricians has been that they are a capable lot and can make their own sketch and wire a circuit of this magnitude.

And since you've already bought it, there's no reason not to use the control relays in the controller. Why complicate with a contactor when you already have multiple relays?

Find a local electrician who can help with this.

Dan