Wiring up a zone valve

[Eric Johnson]

I'm hoping keyman or elk or one of you other wiring wizzards can walk me through the process of wiring up a three-way zone valve. I have a spec sheet for the valve, but nothing for the Honeywell Class 2 transformer, other than a sticker on the side listing the load capacities for the various wires. I can probably dope this out on my own, but figure it doesn't hurt to check with somebody who actually knows what they're talking about.

OK, so all I want to do is take 120v current from an aquastat and use it to activate the zone valve. On the transformer, it identifies the wires as follows:

Primary:
BLK (com)
WHT 120V
RED 208V
ORG 240V 60HZ

Secondary
BLUE-YEL 24VAC 40VA

Since the aquastat is just a switch, I'll have a 120V black wire running from it to the transformer. I'll have a 120V white wire going directly back to the breaker panel. Do I connect the black wire on the thermostat to the black wire feed coming from the aquastat and the white to the white?

Presumably, the blue and orange 24V wires connect to the zone valve. Let's tackle that connection once I'm clear on the 120V side.

 

[keyman512us]

I'm hoping keyman or elk or one of you other wiring wizzards can walk me through the process of wiring up a three-way zone valve. I have a spec sheet for the valve, but nothing for the Honeywell Class 2 transformer, other than a sticker on the side listing the load capacities for the various wires. I can probably dope this out on my own, but figure it doesn't hurt to check with somebody who actually knows what they're talking about.

OK, so all I want to do is take 120v current from an aquastat and use it to activate the zone valve. On the transformer, it identifies the wires as follows:

Primary:
BLK (com)
WHT 120V
RED 208V
ORG 240V 60HZ

Secondary
BLUE-YEL 24VAC 40VA

Since the aquastat is just a switch, I'll have a 120V black wire running from it to the transformer. I'll have a 120V white wire going directly back to the breaker panel. Do I connect the black wire on the thermostat to the black wire feed coming from the aquastat and the white to the white?

Presumably, the blue and orange 24V wires connect to the zone valve. Let's tackle that connection once I'm clear on the 120V side.

Eric... Sounds easy enough.

Ok... First thing, what you have is what is called a "Multi Tap Transformer" that will work on a variety of voltages. You don't need to worry about the red or orange wire. If the transformer is "new right out of the box" then chances are the white, red and orange are "unstripped" and have a "yellowish plastic/wax dipped covering on them". If so no need to worry any farther....if not cut the exposed portion of conductor (wire) off flush with the insulation and either tape or wire nut the end of the red and do the same to the orange...they are unused and don't apply for your particular setup. As long as they are insulated and separate from one another, you are ready to hook up the transformer.

Depending upon how your boiler is setup...find an un-switched 120volt "hot lead". Should be taken from a point protected by a "service switch". Verify the aquastat terminals are rated for at least 120volts. If so...run the "hot lead" to one side of the aquastat switch then come off the other side of the aquastat to the Black wire on the transformer. Even though you might question it is marked (COMmon...to one side of the windings in the trasnsformer the other wires are 'taps')
The white wire marked 120 volts will then be connected to the white (grounded conductor....or as people like to incorectly refer to it as "the neutral").

The blue/yellow from the secondary side of the transformer goes to the zone valve... (two terminal or three on the zone valve eric??).

The only thing I would add is to check the VA (volt-amp) rating of the zone valve.

The VA rating on the transformer is what it will produce. The VA rating on the zone valve is what it will consume. Just make sure the VA consumption on the zone valve is less than what the transformer will be able to produce.

To wire in a thermostat "cut into" the circuit on the secondary side (low voltage side) of the transformer. All you have to do is place the thermostat in between one wire on the secondary side between the transformer and the zone valve.

Will that get you started Eric??

 

[Eric Johnson]

Yes, thanks so much. Let me digest what you are saying, check everything out, and then see where I'm at. Everything is new. And yes, I have three wires coming out of the valve actuator, so that's a tad confusing, too.

Right now I'm getting the valve body soldered into place. I'll check back with you later.

 

[Eric Johnson]

OK, as we know, the transformer is rated at 40VA. The valve actuator head says 6VA. So that sounds alright.

I'm going to be using this zone as a diverter valve. In other words, when the temp. at the aquastat drops to 160, I want the valve to close and divert the water back into the house, instead of going back to the boiler. Basically, I'm creating two loops out of one big one when the boiler temp gets too low. This allows the boiler to catch up because circulation to it stops as soon as the valve isolates the loop. The circulator is on the house side of the zone valve, so it will continue circulating water from the storage tank and into the house zones, even when the boiler is playing catchup.

Or, to put it a lot more simply, I want the zone valve positioned one way when it's getting current from the aquastat, and I want it in the other position when the current stops.

Attached is a link to what I'm talking about.

http://www.nefpexpo.net/thewholeshebang.pdf

Also attached is a scan of the part of the zone valve documentation that I think indicates how to connect the wires to the transformer. I just can't figure it out. I have the "cable" version, not the "Molex."

 

[Eric Johnson]

As I look this over again, maybe I'm thinking about it wrong. The aquastat I'm using is a Honeywell with SPDT switching. For this valve to work the way I want it to, should I run wires from both connectors on the stat, so that I basically have two alternatively energized wires controlling the zone valve, instead of an on/off arrangement with one wire?

 

[keyman512us]

As I look this over again, maybe I'm thinking about it wrong. The aquastat I'm using is a Honeywell with SPDT switching. For this valve to work the way I want it to, should I run wires from both connectors on the stat, so that I basically have two alternatively energized wires controlling the zone valve, instead of an on/off arrangement with one wire?

Eric...You are "on the right track" from what you are saying above. Does the aquastat have two terminals or three??? If it is a SPDT then it should have three terminals. One should be COMmon, One NO(normally open), one NC(normally closed) Yes???

If the aquastat has three terminals you can do it either way...

This is where things can get tricky... Anytime someone asks "How the circuit" should work I like to try to put it in as simple terms as possible "Think of wiring like a 'choo choo train'...the electricity goes from point A to point Z (making a loop). Each time a switch "opens" is like a red light telling the train to stop and wait... A SPDT or DPDT is like switching the train to a different track" might sound a little off the wall but to the average person...an electrician is the train dispatcher...he keeps all the trains moving and headed where they need to go(the whole big picture) so for someone that doesn't do wiring everyday... follow the wire one action at a time back to the start...then switch the switch to follow all the way through the next 'trip' and you will get a better understanding of how the thing is suppose to work"

Back to proper terminology... Simple and easiest way to make it work: Follow the diagram on the bottom of the connection chart labeled "2+COM (For SPST Controller) Run two wires from the secondary side transformer wires (blue and yellow) to the Blue and brown wires on the zone valve...the unit now has power and is using the brown and black as a "switch leg". Run two more wires (to extend the brown and black wires from the zone valve to the next station..the aquastat) if you have 3 terminals....place one wire on the COMmon terminal and the other on either the NO or NC (will particulary depend on how the valve is plumbed to determine NO or NC terminal)... Which is which will also depend on whether the particular aquastat is an "Open on temperature rise or close on temperature rise"...

Having said all that...have fun! (Any dilemas just ask)...

 

[keyman512us]

Eric..One other thing to make it easier for your setup... Keep in mind with the 24 volts applied (and if the other two wires are not connected to anything at all) then the valve should be "In a state where Port A is closed and Port B will be open"...

Like I said...the easiest way to figure out wiring is to "break it down to the simplest view"...Once you know how each part works...you can get it to do exactly what you want it to do.

Even if the aquastat had only two terminals...you could still make it work.

Just out of curiousity Eric?? How many different zone valves and circulators are you going to have in your system???

Depending on how many you are looking at (now or in the future) you might want to look into geting a Taco "SR-503 or 506". They are a little pricey (but if you consider how many items need to be switched) it might be worth it...

In addition, if your system (has or will have) a 'Superstore' ('Indirect' DHW heater) the SR series has a "Priority Zone Function" built right into it...

Just giving you options...

 

[keyman512us]

Eric (or anyone else following this thread that may be interested).

Just for reference:
http://taco-hvac.com/en/products/Sw...List&current_category=139&selected_infotype=2

Good price guide:
http://www.pexsupply.com/categories.asp?cID=195&brandid;=

On the surface...heating with hydronics might sound complicated and expensive...but it is definatley worth it when you consider the true "bang for the buck".

Ebay...Not bad:
http://cgi.ebay.com/TACO-SR506-SWIT...IORITY-ZONE_W0QQitemZ7625194992QQcmdZViewItem

 

[BrotherBart]

On the surface...heating with hydronics might sound complicated and expensive...but it is definatley worth it when you consider the true "bang for the buck".

I read the thread and thought "Wow. I have trouble just deciding how far in to push the primary air control on a stove.". Eric's setup looks like the International Space Station to me.

 

[Eric Johnson]

Yes, the aquastat has three terminals. I've always used this type as an "either/or" aquastat that can be made to make or break on rise. But now I see that you can use both hot terminals to control a valve like this.

I'm not sure if it's "normally open" or "normally closed." I don't think it matters. It's not really opening or closing--just acting as a gate to allow the flow to go one way or the other. If I get it hooked and it's doing the opposite of what I want, I think I can just swap the connectors on the aquastat and it will be right. At first I couldn't figure out how the motor was supposed to change the valve's position if the power was cut, since there's no solenoid in this valve. That's what got me thinking about the SPDT switching.

Anyway, as before, keyman, let me look over your posts and see if I understand. Given your talent for explanation, I bet it will become clear. Then I have to figure out how much more wire to run out to the boiler. I'll fill you in on that later and see if you can help me figure out what I need.

BB--making it all work right is half the satisfaction. Staying warm for free is the other half.

 

[keyman512us]

On the surface...heating with hydronics might sound complicated and expensive...but it is definatley worth it when you consider the true "bang for the buck".

I read the thread and thought "Wow. I have trouble just deciding how far in to push the primary air control on a stove.". Eric's setup looks like the International Space Station to me.

BB...That was how I felt at first. "Way too complicated"(when I was first installing mine).

Regular boiler wiring can be tricky enough...now put an "add on boiler" into the picture and it really gets fun.

We have burned wood ever since I can remember. After years with a stove and then moving to a wood boiler tied right into the central (hydronic) heating system... there ain't no turning back! Once you have a wood fired boiler "stoves are out of the picture".

Actually from everything I've seen of Eric's setup...he has"really done his homework" and I might be talking with him down the road (Grrrr...you got me pondering a new wood fired boiler Eric)... I'll definately be watching (and helping) from the sidelines Eric.

It's nice to have exact, even heat...and know it's coming from a wood fire.

 

[BrotherBart]

I have never had the pleasure of experiencing hydronic in any form. From my first house in 1977 to today my houses have had electric forced air. Well, installed anyway. I had the wood stove installed in that first house while we were at the lawyers office signing the closing papers. The one here was delivered the month after closing.

 

[keyman512us]

I have never had the pleasure of experiencing hydronic in any form. From my first house in 1977 to today my houses have had electric forced air. Well, installed anyway. I had the wood stove installed in that first house while we were at the lawyers office signing the closing papers. The one here was delivered the month after closing.

If I had $2500.00 "burning a hole in my pocket" I would be taking a drive to NY... :
http://cgi.ebay.com/ws/eBayISAPI.dl...Sell_LogicX&refwidgettype=cross_promot_widget

I know "You boys' down in the other Commonwealth" don't have to much to do with oil fired furnaces... but this one is a sweet deal. A Buderus coldstart boiler and INDIRECT (Superstore) DHW heater for $2595.00???

Can't beat that...especially if you have to pay through the nose for hot water...

 

[Eric Johnson]

Thanks for your encouragement, keyman. As I recall from my school days, however, you can do your homework and still fail the exam.

No indirect on this system. Instead I have a 1.5-inch sidearm heat exchange hooked up to my elecric water heater. I used a 1.25-inch sidearm on my old system and it worked great. I built the new one because I wanted 1-inch supply and return connections, instead of the 3/4 inchers on the old one. So DHW is not going to be an issue.

Actually, I have one of those Taco boxes controlling the 4 zone circulators on my gas-fired boiler. I'm putting another 4 pumps on to the wood-fired side, but nothing too fancy. Two of the new pumps are pretty much wired to be on all the time. The other two are directly wired to aquastats or thermostats. I've done a fair amount of direct-wiring aquastats with 120v current. But this stepping down to 24v has me confused.

So I'm obviously missing something. Here's the deal: I've got a 120v Honeywell L6006C SPDT aquastat hooked up to the boiler. Its job is to position the zone valve. I have three terminals on the stat. One completes the circuit when the boiler water is below 160. The other completes the circuit when the water is above 160. The third one is where the current is supplied, so it's always energized. Downstream I have a transformer with a white and black wire going in to the 120v side, and a blue and yellow wire coming out of the 24v side. The white wire connects to the white wire on the circuit. The black wire connects to one of the wires from the aquastat.

If I connect both wires from the aquastat to the black wire, then it will be energized at all times. If I only connect one of the wires from the aqastat to the black wire on the transformer, then it will only receive current at one setting. And even if I could put two different "signals" into the transformer, I've only got one hot wire (presumably the yellow) coming out of the other side of the transformer. But the zone valve actuator has three wires--three if you count the common one, which presumably connects to the blue wire coming out of the transformer. The other two position the valve. But I've only got one wire (the yellow one) coming out of the transformer to connect them to.

So while I have three terminals on the aquastat and three on the zone valve, it seems to me that the transformer creates a bottleneck in getting from 120v to 24v that reduces my options.

What am I missing?

 

[keyman512us]

Thanks for your encouragement, keyman. As I recall from my school days, however, you can do your homework and still fail the exam.

I've done a fair amount of direct-wiring aquastats with 120v current. But this stepping down to 24v has me confused.

So I'm obviously missing something. Here's the deal: I've got a 120v Honeywell L6006C SPDT aquastat hooked up to the boiler. Its job is to position the zone valve. I have three terminals on the stat. One completes the circuit when the boiler water is below 160. The other completes the circuit when the water is above 160. The third one is where the current is supplied, so it's always energized. Downstream I have a transformer with a white and black wire going in to the 120v side, and a blue and yellow wire coming out of the 24v side. The white wire connects to the white wire on the circuit. The black wire connects to one of the wires from the aquastat.

If I connect both wires from the aquastat to the black wire, then it will be energized at all times. If I only connect one of the wires from the aqastat to the black wire on the transformer, then it will only receive current at one setting. And even if I could put two different "signals" into the transformer, I've only got one hot wire (presumably the yellow) coming out of the other side of the transformer. But the zone valve actuator has three wires--three if you count the common one, which presumably connects to the blue wire coming out of the transformer. The other two position the valve. But I've only got one wire (the yellow one) coming out of the transformer to connect them to.

So while I have three terminals on the aquastat and three on the zone valve, it seems to me that the transformer creates a bottleneck in getting from 120v to 24v that reduces my options.

What am I missing?

Eric...I've drawn a diagram that should make things easier to understand to help you out

 

[keyman512us]

I've done a fair amount of direct-wiring aquastats with 120v current. But this stepping down to 24v has me confused.

So I'm obviously missing something. Here's the deal: I've got a 120v Honeywell L6006C SPDT aquastat hooked up to the boiler. Its job is to position the zone valve. I have three terminals on the stat. One completes the circuit when the boiler water is below 160. The other completes the circuit when the water is above 160. But the zone valve actuator has three wires--three if you count the common one, which presumably connects to the blue wire coming out of the transformer. The other two position the valve. But I've only got one wire (the yellow one) coming out of the transformer to connect them to.

So while I have three terminals on the aquastat and three on the zone valve, it seems to me that the transformer creates a bottleneck in getting from 120v to 24v that reduces my options.

What am I missing?

"Just keep it simple". The easiest way to do that is to "Take the transformer out of the equation for a moment". What you have to work with:The "supply" is 120volts...wire the transformer so that it has power all the time....okay that is standard. Having done that we take the 120Volt out of the picture. The zone valve is the key factor...it needs to be controlled with 24 volts. Anything electrical needs to "complete a circuit to operate" In the ladder diagram above... all the switching is done on the 24Volt side... If you wire your setup like in the diagram above and the Zone valve "functions in the opposite manner" that you intended it to...all you have to do is switch one wire on the aquastat: Move the wire connected from the "B" terminal to the "W" terminal.

I would do it the way I just described...that way there in the future should you decide to add components you have a 24volt source already available. Also if you decide to "modify" it...you can add relays into the existing wiring a lot more easily on 24volts...than with 120volts.

The way this will be wired will simplify your runs of wire too. Everything should be able to be done with standard 18-2 "thermostat wire".

 

[keyman512us]

Eric...Don't know how much literature came with the aquastat...but I found and used this 'cut sheet' for reference:
http://www.bmed.mcgill.ca/REKLAB/manual/Common/Hydraulics/Pump/L6006.pdf

 

[Eric Johnson]

Keyman, you're de man!

Thanks. That makes things a lot more flexible. I didn't realize that you could run a 120v aquastat at 24 volts, but it makes sense the way you show it. You also saved me some money on Romex. It's quite a run from the barn to the basement.

I spent most of the day running Pex tubing. I'm using 3/4-inch pex-al-pex, which has an aluminum shield sandwiched between two layers of plastic. It's pretty stiff, so I was worried that it would be hard to work with, but it proved to be a lot easier than I expected. The aluminum allows you to bend it and have it stay bent. Since it comes in a big, 300-foot roll, you have to straighten it out before snaking it into place. A lot like soft copper. You have to do some planning, of course, since there are few or no joints, so everything has to be snaked right the first time. More like wiring than plumbing, I think, since you spend a lot of time pulling pipe and then stapling it up into place. Actually, I'm using fencing staples and those plastic zip-zip fasteners. Works really well.

I already have a one-inch copper line running from the boiler room to the gas boiler and tank in the basement, but I need more capacity for the new boiler, so that's why the pex is going in. Eight-eight cents a foot beats two bucks any day. Plus very few fittings. Ideally, an adapter at each end of the run.

 

[Eric Johnson]

Thanks for your encouragement, keyman. As I recall from my school days, however, you can do your homework and still fail the exam.

I've done a fair amount of direct-wiring aquastats with 120v current. But this stepping down to 24v has me confused.

So I'm obviously missing something. Here's the deal: I've got a 120v Honeywell L6006C SPDT aquastat hooked up to the boiler. Its job is to position the zone valve. I have three terminals on the stat. One completes the circuit when the boiler water is below 160. The other completes the circuit when the water is above 160. The third one is where the current is supplied, so it's always energized. Downstream I have a transformer with a white and black wire going in to the 120v side, and a blue and yellow wire coming out of the 24v side. The white wire connects to the white wire on the circuit. The black wire connects to one of the wires from the aquastat.

If I connect both wires from the aquastat to the black wire, then it will be energized at all times. If I only connect one of the wires from the aqastat to the black wire on the transformer, then it will only receive current at one setting. And even if I could put two different "signals" into the transformer, I've only got one hot wire (presumably the yellow) coming out of the other side of the transformer. But the zone valve actuator has three wires--three if you count the common one, which presumably connects to the blue wire coming out of the transformer. The other two position the valve. But I've only got one wire (the yellow one) coming out of the transformer to connect them to.

So while I have three terminals on the aquastat and three on the zone valve, it seems to me that the transformer creates a bottleneck in getting from 120v to 24v that reduces my options.

What am I missing?

Eric...I've drawn a diagram that should make things easier to understand to help you out

Keyman--can you post a higher res version of that diagram? I can almost read it, but it gets a little blurry in places. Thanks!

 

[keyman512us]

Thanks for your encouragement, keyman. As I recall from my school days, however, you can do your homework and still fail the exam.

I've done a fair amount of direct-wiring aquastats with 120v current. But this stepping down to 24v has me confused.

So I'm obviously missing something. Here's the deal: I've got a 120v Honeywell L6006C SPDT aquastat hooked up to the boiler. Its job is to position the zone valve. I have three terminals on the stat. One completes the circuit when the boiler water is below 160. The other completes the circuit when the water is above 160. The third one is where the current is supplied, so it's always energized. Downstream I have a transformer with a white and black wire going in to the 120v side, and a blue and yellow wire coming out of the 24v side. The white wire connects to the white wire on the circuit. The black wire connects to one of the wires from the aquastat.

If I connect both wires from the aquastat to the black wire, then it will be energized at all times. If I only connect one of the wires from the aqastat to the black wire on the transformer, then it will only receive current at one setting. And even if I could put two different "signals" into the transformer, I've only got one hot wire (presumably the yellow) coming out of the other side of the transformer. But the zone valve actuator has three wires--three if you count the common one, which presumably connects to the blue wire coming out of the transformer. The other two position the valve. But I've only got one wire (the yellow one) coming out of the transformer to connect them to.

So while I have three terminals on the aquastat and three on the zone valve, it seems to me that the transformer creates a bottleneck in getting from 120v to 24v that reduces my options.

What am I missing?

Eric...I've drawn a diagram that should make things easier to understand to help you out

Keyman--can you post a higher res version of that diagram? I can almost read it, but it gets a little blurry in places. Thanks!

Eric, I re-worked/re-sized the diagram it should be a little sharper in detail. If not PM me your e-mail addy and I'll send it to you.

BTW?? You still trying to make a regular thermostat shut off a circulator when the temp. drop (Can't remember the thread)....but I remember the question.

 

[Eric Johnson]

Much better--thanks.

The old 30-gallon expansion tank I was going to use as an emergency heat dump turned out to be full of holes. So I'm basically at buying a new, 50-gallon electric water heater and using that instead. I think a standard SPDT aquastat set at its lowest setting (40 degrees, I believe) will accomplish what I'm trying to do.

Here's the deal: My boiler is in an insulated cinderblock room in my unheated barn. Above the boiler room, I have a 3/4-inch copper supply and return line piped into the boiler. On that line is an AutoMag zone valve, which works on a solenoid and opens when the power is cut. So when there's a power failure of any kind on that circuit, the valve opens up and the hot boiler water is replaced with cooler water from the water heater through convection. Pretty simple/pretty effective.

My problem is that the tank is sitting in unheated space. How do I keep it from freezing? Well, one option would be to run the water heater so that it stays above freezing. But since I don't have a 240V line out into the barn, wiring it up would be a pain in the ass and a few bucks down the drain, not to mention a minimal--but ongoing--expense.

Instead, what I'm thinking is simply to wire the AutoMag up to an aquastat that makes the connection on rise. That way the valve will open up when the water gets down near freezing, and presumably keep it in a liquid state. The fact that the water heater is realitively well insulated to begin with (I'll put a shroud on it, too), makes the $250 bite a bit less painful. I've been looking around for scratch & dent sales, but so far, no water heaters.

That's what that was all about. I can get the boiler going before doing that. The dump zone from the old system is just a couple of old cast iron radiators piped into the line. Since I ran glycol in the old boiler, they just sat up there exposed, waiting to serve. But I have other uses for those cast iron rads, and they need to come out of there before the weather gets too cold. One of them I'm going to use to hang the expansion tank, air scoop t/p gauge and pressure relief valve off of in the greenhouse, which will be a glycol loop (hopefully) heated with my old sidearm heat exchanger. That's all piped up, by the way--all I need to do is put in 30 feet of finned tube baseboard, the ci radiator and all the junk mentioned earlier. The pump will run directly off an old single-pole electric baseboard thermostat in the greenhouse.

 

[Eric Johnson]

I got it wired up and it works just like you said, Keyman. Thanks--I couldn't have done it without your help and the diagram. As it was, I did a fair amount of head scratching (different colored wires, etc.), but it works. All the rest of the wiring is working, too. I had it all working on Sunday. Then I drained the boiler and tried to power it back up yesterday. And when I hit the breaker I got nothing--nada. After poking around for a few minutes, I took a look at the low water cut-off. No water in the boiler means no connection, which means no power.

So it's all good.

Let you know on Saturday how it all works out.

 

[Eric Johnson]

Now I need to go the other way. There's a pump that I want to shut off when the aquastat is at a certain point. The aquastat and transformer are about 100 feet away from the pump and the zone valve. Is there a way to power the (120V) pump on and off with the 24-volt circuit? Do I need another transformer or a relay to "step it back up" or however you would describe it? Or do I need to run a 120v line directly from the aquastat on the boiler to the pump in the basement?

 

[keyman512us]

Now I need to go the other way. There's a pump that I want to shut off when the aquastat is at a certain point. The aquastat and transformer are about 100 feet away from the pump and the zone valve. Is there a way to power the (120V) pump on and off with the 24-volt circuit? Do I need another transformer or a relay to "step it back up" or however you would describe it? Or do I need to run a 120v line directly from the aquastat on the boiler to the pump in the basement?

Okay... A couple of questions. First one: Do you want to use the same aquastat that you just installed to control this 'new circulator'??? (Can be done very easily).

If so... All you need is a 24volt 'relay'....and a run of 18-2 wire from the aquastat to the circulator location (where you will install a 24volt relay.) Will cost about $9.00 at radio shack. Or if you want really simple (but a little more $$$...like around $50, but it's just connect a few wires):
Air Products & Controls MR100:
http://www.ap-c.com/products/relays_n_accessories/MR100_200.asp

Gonna go "hunting around on the net BRB"...

 

[keyman512us]

Found this on EBAY...

Would work for what you want:
http://cgi.ebay.com/Air-Products-Co...ryZ78205QQrdZ1QQssPageNameZWD1VQQcmdZViewItem