relays on heaters

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  #1  
Old 10-27-06, 06:57 PM
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relays on heaters

I have a nice sized room that is heated in the winter by 4 220 volt 20 amp heaters that are set in the wall. The problem is that all they have for controlling them is low, medium, and, high. I would like to put them all on a thermostat. I was think about perhaps installing 4 relays or 1 relay if they make one big enough for this at the circuit breaker box and then running a low volage wire into the room from there and connecting on it a heat only thermostat. Any help. Thanks
 
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  #2  
Old 10-27-06, 08:01 PM
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Here's something to chew on.

http://www.white-rodgers.com/wrdhom/pdfs/04_Cat_pages/04_Cat_pg_111.pdf

I suspect the C25ENF440T is fairly close to what you need, with a 24 VAC coil, although at 40A per pole it's overkill. I am assuming your four heaters are on four separate circuits and therefore you need four poles. If code requires that both poles of each circuit are disconnected, you would need eight poles, and therefore two contactors like this.

I am not saying that you can or should do this codewise, but this might give you the means.

Also you are probably aware that you can get all kinds of thermostats for individual heaters. If that's news, just google cadet heaters.
 
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Old 10-27-06, 08:28 PM
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Why not buy a thermostat for a 240 volt heater? They are wired directly from line voltage.
 
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Old 10-27-06, 09:13 PM
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That would work but since I beleive the heaters are on multiple circuits, the OP would need a t-stat for each circuit. A relay situation would allow one t-state to control multiple circuits.
 
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Old 10-27-06, 09:36 PM
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These are typically what is used when a lo-vo T-stat is needed/wanted to control line-volt electric heat.

The lo-vo control side can be wired in parallel so one T-stat can control multiple relays and therefore multiple heaters.

http://www.heatersplus.com/24a06g-1.htm
 
  #6  
Old 10-27-06, 11:22 PM
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Originally Posted by nap
That would work but since I beleive the heaters are on multiple circuits, the OP would need a t-stat for each circuit. A relay situation would allow one t-state to control multiple circuits.
All of them coming on at once?? That would be quite a surge. Some sort of staging would be nice.
 
  #7  
Old 10-28-06, 12:09 AM
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Yes, they are all on there own circuit. oops I have 3 heaters not 4. I was thinking 4 cause there is a total of 4 heaters in the circuit breaker box but one of them is in another room. I suppose I should get c25dnd325t instead of the C25ENF440T.

I went online to http://www.heatersplus.com/24a06g-1.htm. Looks nice, not too sure if I fully understand how to connect it up though.

Very good replies. Not too sure if I know what exactly to get and how to hook it up yet. Thanks
 
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Old 10-28-06, 05:51 AM
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Ok petey. Tell me what purpose the unit you linked serves.
(I'm not an hvac guy)

Can you explain the purpose of the bi-met heaters. It would seem it itself serves some sort of thermostatic control but over what? Possibly something to do with the delays the specs speak of? Why would that be neccessary ?(possibly staged energizing of multiple units?)



JimmieDee:All of them coming on at once?? That would be quite a surge. Some sort of staging would be nice.

using multiple contactors and utilizing a delay on make timer would remedy that situation if desired.
If using independant contactor for each unit a delay on make timer could be used on 2 set to different times so they would sequentially energize.
 
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Old 10-28-06, 06:18 AM
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"Can you explain the purpose of the bi-met heaters. It would seem it itself serves some sort of thermostatic control but over what? Possibly something to do with the delays the specs speak of? Why would that be neccessary ?(possibly staged energizing of multiple units?)"

Go back to that page if you will. Scroll down to "Features" and read. It will explain everything.
Basically it is a relay to control line volt heat with a typical lo-volt t-stat.
I have installed many of them myself and there are hundreds of them in use in my area.
 
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Old 10-28-06, 06:40 AM
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That is a great link speedy. I will work on a wiring diagram for using three of those to control three heaters, using one thermostat.

The only thing I do not see is how this could be used with a programable thermostat, unless the t stat were battery powered.

Nap, there is no inrush on resistive loads.
The time delay is probably to prevent short cycling if this were used on a compressor, or other motor load.
 
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Old 10-28-06, 06:48 AM
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>Nap, there is no inrush on resistive loads.
>The time delay is probably to prevent short cycling if this were used on a compressor,
> or other motor load.
Not as such, but heating elements generally have lower resistance at colder temperatures and will draw more power until they've warmed up to design temperature. So you get an effect not unlike inrush.
 
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Old 10-28-06, 07:41 AM
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This is a pretty cool box - Looks like it would allow me to use my zone controller and a programmable stat to run my electric heat, too. Is this correct:

White + Red to stat 1
White/Stripes + Red to stat 2
OR
White & White/Stripes jumpered + Red to stat

Black - From breaker x, pole A in panel
Blue - From breaker x, pole B in panel
Red - to heater 1, pole A
Black/Stripes - from breaker y, pole A in panel
Red/Stripes - to heater 2, pole A

Heater 1 pole B fed directly from breaker x pole B
Heater 2 pole B fed directly from breaker y pole B
 
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Old 10-28-06, 08:37 AM
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I am surprised you guys have never seen those W-R boxes. Like I said before, they are very common around here.
 
  #14  
Old 10-28-06, 08:47 AM
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Originally Posted by grover
>Nap, there is no inrush on resistive loads.
>The time delay is probably to prevent short cycling if this were used on a compressor,
> or other motor load.
Not as such, but heating elements generally have lower resistance at colder temperatures and will draw more power until they've warmed up to design temperature. So you get an effect not unlike inrush.
True, but this will not create a situation where a dangerous level of current could be forced on the main wires the way a bunch of inrush from motor loads could, if they all start at the same time. My point was not that there would be no extra current, just that it would be safe, and therefore not a concern to the OP.
 
  #15  
Old 10-28-06, 09:06 AM
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I made this drawing.

I hope it helps.

http://i128.photobucket.com/albums/p175/jwhite480/3BBHeatTStat.jpg
 
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Old 10-28-06, 01:45 PM
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It is a very good drawing. Forgive me for not understanding how this works completely and I am sure it's purpose is there but I don't really understand the full purpose of the White Rodgers 24A06G-1. Couldn't you get it done with the thermostat, 3 pole single throw relay, and the transformer. I am sure I will get a lesson in electricity from this but I put this drawing up to help me understand more. http://adt-web.com/construct/3BBHeatTStat1.jpg Thanks
 
  #17  
Old 10-28-06, 02:25 PM
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I prefer to switch both legs on a 240 volt circuit.

You could use three two pole power relays, the transformer and t-stat, and wire the coils of the relays in parallel.

You would either need to get a junction box for installing all the relays, or ones that have the coils and contacts seperated.
 
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Old 10-28-06, 02:57 PM
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So now we are back to what I had suggested awhile back. A delay on make timer(actually 2) can be used in addition if one desires to avoid all heaters starting together.

Hopefully petey will return and explain what the WR mystery box does that this set-up doesn't. I am curious.
 
  #19  
Old 10-28-06, 03:49 PM
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How does this drawing look http://adt-web.com/construct/3BBHeatTStat2.jpg . Hopefully I didn't slop it together too badly and you can understand it well. So many wires I had to choose alot of colors so you can see what goes where. Don't know if I need additional equipment for a delay though. Thank you all for helping .
 
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Old 10-28-06, 04:28 PM
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Looks like what I envisioned. Note tat each heater is controlled by 1, 2 pole contactor (or shoudl be)

I don;t know if a delay is actually needed or not. If all else fails a smoke test would give you the answer without any damage. If a breaker trips (like the main of the house) then I would time them to start independantly.

something like this little guy (there are dozens of different ones available wired in series with the contactor coil would do ya.

http://www.artisancontrols.com/pdf/438up.pdf
 
  #21  
Old 10-28-06, 05:09 PM
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"smoke test" what does that mean. Alright can anybody here recommend the equipment that I will need for this. 1 transformer, three 2 pole 20 amp 240 volt contactors with a 24 volt coil, and 1 programmable thermostat. Thanks
 

Last edited by robj; 10-28-06 at 05:21 PM.
  #22  
Old 10-28-06, 05:15 PM
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basically turn things on and load them and see if they smoke or fail to function as intended.

Not as bad as it sounds. Things are meant to be correct before actually turning them on but things have been known to smoke if an error was made or there was defective equipment.
 
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Old 10-28-06, 06:02 PM
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Nap, I am not sure what you are looking for, or what you think I am hiding. This REALLY is no mystery.

I pretty much explained what these relay boxes do and their site explains the rest.
The bi-metal heater's function is to flex with an applied current so it activates the internal switch. Similar to line volt thermostats.

In a nutshell this is what it does, as I have said several times before:
"Level-Temp allows low voltage 2-wire thermostat to control line voltage loads such as baseboard heaters."

Pretty basic stuff.
 
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Old 10-28-06, 06:21 PM
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I didn;t mean that to come across as offensive in any way.

when I posted this:

Hopefully petey will return and explain what the WR mystery box does that this set-up doesn't. I am curious.

It was meant to be taken as a bit of levity. I was wanting you to add your input as to why which of the two designs talked of within this post is better. Your input is very informative and generally on point. I actually was looking to you for your wisdom, not meaning to offend.


I believe the drawing floating around here by Jeff are incorrecty placing a relay within a system using the box.

I believe the box is used instead of the relay that Jeff has added within his diagrams with the t-state simply wired into the low voltage side and the load in the other end with the apparent ability to utilize 2 t-stats, one to contol each load.

The thing is that it controls only two loads so the OP would need 2 of the things. This then presents the problem of being able to contol 2 of these things with 1 stat. How would you remedy this situation?
 
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Old 10-28-06, 07:11 PM
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Four heaters can be controlled by two of these relays.
One leg of each heater can be broken by one set of contacts as seen in this diagram on page 2:
http://www.white-rodgers.com/wrdhom/pdfs/instruction_sheets/0037-4165.pdf

The thermostat would be wired in parallel to both relays.
 
  #26  
Old 10-28-06, 10:37 PM
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. When I think of it more if I can get this single unit to control 2 240 volt heaters rated at 20 amps then I wouldn't even bother with the third heater. One of the heaters is in a bad location anyway and I usually don't have to have all three of them on during the winter to properly heat the room. It looks like the unit has its own built in transformer so I don't really have to worry about that and it has 2 poles rated at 240 volt 25 amps each. I could only switch one leg of each though if I put this thing on two 240 volt 20 amp heaters. Correct? How does this diagram look http://adt-web.com/construct/IMG123.jpg. If this works all I need is a programmable thermostat. What programmable heat only thermomostat would work in this situation. I think that anyone would but I better ask before I make a mistake. Thank you
 
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Old 10-29-06, 05:13 AM
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That looks good robj
you will need a stat that is battery operated if you want it to be programable. Hunter makes one and they are available at the big box stores.
 
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Old 10-29-06, 07:07 AM
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Originally Posted by nap
I believe the drawing floating around here by Jeff are incorrecty placing a relay within a system using the box.
I placed the relay for two resons. One is so that more than two heaters could be controlled by one thermostat. The second was so that I could provide power for the thermostat from our control system, which requires isololating one system transformer from another.
 
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Old 10-29-06, 08:22 AM
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Originally Posted by jwhite
I placed the relay for two resons. One is so that more than two heaters could be controlled by one thermostat. The second was so that I could provide power for the thermostat from our control system, which requires isololating one system transformer from another.
If using the seperate relay idea, the WR unit becomes redundant and is unneccessary.

When strictly using the WR unit as designed, a relay would be unneccessary. It didn;t offer what I woul want in this system control (both leg disconnect, and more than 2 unit control) so I personally would make my own without using the WR unit at all.

I simply saw no need to use both.
---------------------
Too bad you can't pick up the other leg from the low voltage side of the x-former in the WR unit (and have it be 24 volt) so a programmable t-stat would fit into the system without the concern of batteries. From all the diagrams I have seen, it looks like it is not designed to be utilized.
 
  #30  
Old 10-29-06, 09:50 AM
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It seems that hunter makes 6 of them http://www.hunterfan.com/sort.php?pType=thermo&type=4

This is the one I choose http://www.hunterfan.com/prodSum.php?pid=15&pType=thermo&sType=4 . I think I am good to go. Thanks
 
  #31  
Old 11-25-06, 02:34 PM
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Hi all posting back that all went well and thank you for the help.

I have another project going and it has to do with this one. In the same room is a in the wall air conditioner. I was thinking about using the same thermostat and the same White Rodgers 24A06G-1 unit to control a relay that is for the 120 volt air conditioner. Might be kinda hard to explain so I made this drawing. http://www.adt-web.com/construct/relayimg.JPG

I don't even know if this is possible though. Thanks
 
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