Thermostat wiring advice needed

[Pete Kurki]

I heat my workshop with a 5600 W electric heater that has its own simple thermostat. My unit is exactly like this one:
http://www.air-n-water.com/product/L5600.html

Since I only work in the shop during weekends and a some nights during the week, I usually set the thermostat to the lowest level at about 45F when I leave the shop. I figure this saves me a bucket of money vs maintaining a working temperature at all times. Then when I come back to the shop I increase the temperature to about 55-60F, but waiting for glue and lumber to warm up can be frustrating.

So I figure my shop life would become much more convenient if I could somehow add a simple programmable thermostat to the heater. Or actually I am guessing it might be easier to add the thermostat to the power line just before the 240V/30A outlet that is dedicated to this heater.

I have done a few wiring jobs in my life including my shop (and passed the state inspection), but I have no idea how to add a thermostat to a power line like this, and have not find any really clear directions from the web either. So - my two questions are:

1. Where could I find good directions for what components to buy in addition to the thermostat, and how to do the wiring? Or maybe someone could try to just explain it to me here.
2. Is there anything non-code about this? We only have state inspection here and they use the NEC, no local codes that I am aware of. I have a NEC 2005 handbook but could not find anything about thermostats there.

Appreciate any constructive help.

Pete

[Chris Padilla]

Pete,

I'm not sure I'm too much help because I don't know exactly how a 'wall' thermostat works other than I've wired them up at my house following the directions and they work fine. There are only 4 wires, I think...maybe 6.

I do know how you can control that outlet, however, and that is with an appropriate sized contactor. You'd want a 30a/240V contactor with the appropriate coil that matches what your thermostat will need.

An example:

I have a pool and two water pumps on it. One is the main one for the pool and the other is for the little leaf sucker that runs around the bottom of the pool. I have two very cheap sprinkler timers running these "massive" 2-3 hp pumps. How'd I do it? I used two contactors. Both contactors are rated at 30A and 240 V so that matches what the pumps require. The sprinkler timers output a 24 V DC signal and so I found a contactor that has that particular input on it and viola, I can use a pair of cheap sprinkler timers (7-day timers, important to me because I only want to run the pool pumps every other day).

Contactors come in all shape and sized and with all kinds of inputs. Folks here use 30A/240V contactors with 120V coil (input) so they can remotely switch (or, heck, even use a cheap-o light switch) to turn their dust collectors off and on.

[Scott Loven]

Replacing a regular thermostat with a programmable thermostat is very easy, much more easy then what I think you are contemplating. Mine was two low voltage wires, easy on, easy off.
Scott

[Ken Baker]

This is definitely something you can do, I'm really good with electrical - but this requires no skill at all, and like 10 minutes time.

You can pick one up for like $20 if I remember - no special wiring, unscrew the existing, screw the existing to the new unit - and you're done.

Here is a video:

http://www.thisoldhouse.com/toh/video/0,,20053916,00.html

[Chris Padilla]

Uhm, did either of you look at the link provided? Here is a photo of the back of the portable heater.

It is probalby a rheostat of some kind but I dunno.

If I am following what the OP is looking for, he wants to control this portable heater with a programmable thermostat normally meant to wire to a furnace/boiler.

Am I all wet here? :confused:

[Tom Leasure]

Pete,
If you have access to a Grainger's outlet try the Honeywell thermostat
Honeywell model # is TL8230A1003 & Graingers # is 6WY24 - around $58.00 bucks - http://www.sawmillcreek.org/images/icons/icon4.gif a word of CAUTION - this will only handle 15 amps at 240 volts - If this wont work Chris's advice would be the way to go.

[David G Baker]

Chris,
Ain't a drop of water on you.
I would get a line voltage 240 volt 30 amp thermostat that is more than likely sold by Grainger. At best it would be a jury rigged device not designed for a plug in type portable heater.

[Tom Leasure]

Pete,
I forgot to mention the thermostat from Grainger's is programmable as well as a line voltage - look up Grainger on the web, punch inn the stock number & you can get all the info on it there

Tom

[Pete Kurki]

Wow that's lots of responses in short time. Thanks alot for all the advice. Unfortunately I realize I was not quite clear enough about what I am looking for. Anyway:

Chris, your latest guess was exactly on the money for what I was thinking. I just want to buy a cheap low voltage programmable house thermostat and use it to control the 240V/30A power line going to the plug where the heater is plugged. I would just max out the unit's own thermostat and let the wall thermostat switch the power on and off whenever needed based on the room temperature. Obviously there is something that needs to go in between the low voltage thermostat and 240V/30A power line. Chris, I think you are on the right track in your first note when you bring up this contactor. I think wall thermostats use 24V and I need a contactor relay that matches that kind of input.

So, if I am on the right track here, if I find this kind of contactor relay, how easy is it going to be to do the wiring? Eh, I'm sure pretty easy if I know exactly what goes where but that's the whole point...

Pete

[Rollie Meyers]

Pete,

I'm not sure I'm too much help because I don't know exactly how a 'wall' thermostat works other than I've wired them up at my house following the directions and they work fine. There are only 4 wires, I think...maybe 6.

I do know how you can control that outlet, however, and that is with an appropriate sized contactor. You'd want a 30a/240V contactor with the appropriate coil that matches what your thermostat will need.

An example:

I have a pool and two water pumps on it. One is the main one for the pool and the other is for the little leaf sucker that runs around the bottom of the pool. I have two very cheap sprinkler timers running these "massive" 2-3 hp pumps. How'd I do it? I used two contactors. Both contactors are rated at 30A and 240 V so that matches what the pumps require. The sprinkler timers output a 24 V DC signal and so I found a contactor that has that particular input on it and viola, I can use a pair of cheap sprinkler timers (7-day timers, important to me because I only want to run the pool pumps every other day).

Contactors come in all shape and sized and with all kinds of inputs. Folks here use 30A/240V contactors with 120V coil (input) so they can remotely switch (or, heck, even use a cheap-o light switch) to turn their dust collectors off and on.

Sprinklers are 24 volt Alternating Current not DC...:D

[Chuck Gregg]

You will also need a 240/24 volt transformer to power your contactor.
Here is a quick sketch of how to wire it.
A line voltage thermostat to handle 30 amps would be very expensive if it's even available.
Sorry about the sloppy drawing.

[Derek Tuchscherer]

I know of some woodworkers here that did exactly as you are wanting to do. You need to find a thermostat designed for an electric baseboard heater. Then you put this thermostat on the line going to the plug for your heater and leave the thermostat on the heater itself turned to max.

[Chris Padilla]

Sprinklers are 24 volt Alternating Current not DC...:D

AC...DC...why quibble about a letter?! :p

Yes, of course, you are correct...the 'a' and 'd' are kinda close on the keyboard, right?! :o

[Chris Padilla]

You will also need a 240/24 volt transformer to power your contactor.
Here is a quick sketch of how to wire it.
A line voltage thermostat to handle 30 amps would be very expensive if it's even available.
Sorry about the sloppy drawing.

Nice drawing, Chuck. The contactors I'm familiar with already have the input coil built in but I suppose they could come separate.

Cutler-Hammer is a good brand to look into. I bought my contactor off of eBay but do some searching on the web and you'll learn a few things.

[Pete Kurki]

You will also need a 240/24 volt transformer to power your contactor.


Transformer too? I thought I might be missing something. The drawing will be very helpful too. Thanks Chuck.


I know of some woodworkers here that did exactly as you are wanting to do. You need to find a thermostat designed for an electric baseboard heater. Then you put this thermostat on the line going to the plug for your heater and leave the thermostat on the heater itself turned to max.

I was initially looking into an inline option like this, but could not really find anything for 30A. But if you have an idea where to find a safe unit like that I am interested.

Thanks,

Pete

[Chris Padilla]

Pete,

Check out this post (http://www.sawmillcreek.org/showpost.php?p=205663&postcount=74) in a longer thread (I was building a cyclone DC).

There are a couple of pics of the setup I used to remotely control the operation of my DC.

The last pic is a close-up of the contactor in its own box. You can see the LINE-IN coming from the wall encased in flex conduit (240V/30A) as well as some smaller wire that comes from a 120V/20A circuit that connects to the coil on the contactor so that I can use an ordinary remote-control lamp control module. The lamp control module turns on the coil and that in turn connects the LINE-IN to the load (which will be my 5 hp DC motor).

[Derek Tuchscherer]

Wouldn't the max amperage draw be 20 amps? 4800watts/240 volts=20 amps? Or is this not correct?

[Pete Kurki]

Wouldn't the max amperage draw be 20 amps? 4800watts/240 volts=20 amps? Or is this not correct?

Derek, according to the specs my heater pulls 23.3 amps at 240V. Its max 5600 W unit. I have a link to the specs in my first post in this thread.

Pete

[Rob Russell]

I think this is being made more complicated than it needs to be. I bought a line level thermostat at our local Home Depot. Wire that in series to the receptacle you plug the heater into. Simple and straightforward - no contactor needed.

[Pete Kurki]

I think this is being made more complicated than it needs to be. I bought a line level thermostat at our local Home Depot. Wire that in series to the receptacle you plug the heater into. Simple and straightforward - no contactor needed.

Serious? You actually found a line level thermostat that can handle 23.3 amps? I was in a HD close to me just today and they only had one for 110V/5A rating?

Pete

[Chuck Gregg]

Just another thought, purchase another heater and put a 40 amp. time clock on the one with the higher setting. Kinda looks like the price would be comparable.

[Rob Russell]

Serious? You actually found a line level thermostat that can handle 23.3 amps? I was in a HD close to me just today and they only had one for 110V/5A rating?

Pete

I just checked with our local HD. They have a line level thermostat - although it's not programmable - that can handle 22 amps at 220/240. I hadn't really looked closely at the heater unit, although I'm surprised it used more current at the higher voltage - that's backwards from normal applications. I suppose this is a resistive load though, not a motor.

Looks like you're stuck with the contactor route.

[Al Willits]

Most programmable stats control the 5 day week and 2 day weekend, if your going to use the shop on a sporadic time frame, the stat might not be what ya want, may want to read what the stat will control before you buy one.
Also if the stat will function in the range you want it to, some may not go cool enough to work for what you want.

fwiw, I'd use a 110v to 24v standard 40ma furnace transformer and a 24v stat, remember most need to be powered to keep their program, the batteries are usually only for back up.
Wire the transformer to the stat then a AC contractor, check to be sure but most should have a 220 amp rating that would be high enough to handle the load you have.
Easier to deal with 24v than 110 and the choice of thermostats is quite higher.

Just a thought..

Al

[Pete Kurki]

I just checked with our local HD. They have a line level thermostat - although it's not programmable - that can handle 22 amps at 220/240. I hadn't really looked closely at the heater unit, although I'm surprised it used more current at the higher voltage - that's backwards from normal applications. I suppose this is a resistive load though, not a motor.

Looks like you're stuck with the contactor route.

Yup. Really no point in adding another thermostat to a unit that already has one. I am looking for a programmable one so that I have a warm shop waiting when I come back from work.

[James A. Wolfe]

You could go with the thermostat, relay, transformer etc but you might want to look at this option:
http://www.amazon.com/Honeywell-RLV430-Programmable-Baseboard-Thermostat/dp/B000IN00JK
It's a line voltage, programmable thermostat designed to do exactly what you're trying to accomplish. I got mine at the borg but they don't show it on the website. Just over $50 and very clear instructions.
Good luck,
Jim

[Pete Kurki]

You could go with the thermostat, relay, transformer etc but you might want to look at this option:
http://www.amazon.com/Honeywell-RLV430-Programmable-Baseboard-Thermostat/dp/B000IN00JK
It's a line voltage, programmable thermostat designed to do exactly what you're trying to accomplish.

Good lead Jim but not quite enough for my heater. According to the Honeywell sales sheet I found elsewhere this unit is rated for max 3500W. I need 5600W. Otherwise I would love this kind of an easy option. Maybe I just need to go ahead and buy two smaller heaters and I would have lots of nice and easy solutions like this one. :(:(

[Rob Russell]

Pete,

A thermostat and contactor is an easy solution. You just leave your heater on "high" or set the heater's thermostat to something like 80 degrees.

You could do the thermostat, transformer and contactor for under $150 - under $100 if you're patient and don't mind buying on Ebay.

Rob

[John Gornall]

Low voltage relay with transformer kit for baseboard heaters - an all in one unit that mounts through the hole in a junction box. 220 switch wires enter the box - low voltage wires outside go to a low voltage thermostat. The ones I have in my home are rated 25 amps. My shop is warm when I come home from work. My house is warm when I get up in the morning.

[John Gornall]

A little fun here - the 60's hippy version of auto thermostat that actually works well.

A cord, socket and a 15 watt light bulb. Duct tape the bulb to the heater's existing thermostat. Plug the cord into a cheap timer. When the bulb is on it warms the thermostat and the heater is off. When the bulb is off the thermostat is cold and turns the heater on.

[Chip Lindley]

The fact that this is a 220V heater which needs a 30A circuit complicates most of the solutions offered in this thread. At least a 30A contactor, 24V coil and 220V/24V transformer would be needed. This is the same configuration as a LVC motor control like Delta used to make, contained in one metal box. (Line In/Load out) But instead of push buttons to start/stop, you will be using the programmable thermostat. The programmable wall thermostat would be wired between the 24V transformer output and the 24V coil of the contactor. This is the same configuration as your home heating systems thermostat.

I have all the junk parts out in the garage to build you one (scrounged off old central A/C units...but it's more fun if you do it!