Connecting a 240v Water Heater to a Timer/Switch

[osiris12]

Hello,

I have a 240v water heater with a machincal timer which went bye-bye after I installed it over 15 years ageo. Those darn plastic gears finnaly broke. So I bought a Intermatic EH40.

The line is 240v with 3 wires (white, black, and ground) which matches the water heater wires.

But because the EH40 is a DPST and my old switch was a SPST, I'm having a brain freeze about how to connect it. I'd rather not return the unit.

How do I connect my water heater to the new timer/switch?

 

[Danger]

Welcome to PF, Osiris.
If I understand the question correctly, you can just leave the neutral (white) line intact, and splice one side of your DPST into the hot (black) line.
Better wait for an electrical expert such as Berkeman to respond before taking my word for it, though. If in doubt, the best thing is to have a professional electrician or appliance repairman come in and do it for you. There's no point in taking chances.

 

[osiris12]

Welcome to PF, Osiris.
If I understand the question correctly, you can just leave the neutral (white) line intact, and splice one side of your DPDT into the hot (black) line.
Better wait for an electrical expert such as Berkeman to respond before taking my word for it, though. If in doubt, the best thing is to have a professional electrician or appliance repairman come in and do it for you. There's no point in taking chances.

Thanks for responding so quickly. I've done this before years ago but I'm a little rusty. I think your suggestion sounds right. I have some friends who do this but they are hard to get a hold of.

 

[Danger]

Bye the by, your illustration didn't appear when I first read this. Even now, though, I can't quite understand it. The combination of a foreign language and incomplete circuitry is really confusing me. What the hell is a 'charge area'?

 

[osiris12]

Bye the by, your illustration didn't appear when I first read this. Even now, though, I can't quite understand it. The combination of a foreign language and incomplete circuitry is really confusing me. What the hell is a 'charge area'?

Yeah I know. There is English on other pages but when it comes to the circuit layout, it goes foreign. Nowhere in the box does it show an English representation.

But here is the full PDF http://www.intermatic.com/~/media/files/intermatic/products/instructions/timers/eh10%20-%20english.ashx

 

[dlgoff]

The switch in your attachment is a DPST. Is this the one you are wanting to replace? As shown, it will work correctly. The two poles are terminals 3 & 5 with a single throw to terminals 4 & 6 respectively.

 

[negitron]

What the hell is a 'charge area'?

It doesn't say "charge area" it says:

CHARGE
CARGA

That's the French/Spanish, respectively, for the power supply/mains voltage.

 

[Danger]

It doesn't say "charge area" it says:

CHARGE
CARGA

That's the French/Spanish, respectively, for the power supply/mains voltage.

Oops...
Once again, my brain misinterpreted something that my eyes saw just fine. I run into that problem a lot, and have gotten into some serious trouble due to it upon a couple of occasions. (Honestly, I didn't see the wedding ring...)

 

[osiris12]

The switch in your attachment is a DPST. Is this the one you are wanting to replace? As shown, it will work correctly. The two poles are terminals 3 & 5 with a single throw to terminals 4 & 6 respectively.

Ok, so I attach the load to 4 & 6 and do the jumpers too? Thats where I'm getting a little confused. With the old SPST box there were just 3 pins. So on the DPST each pin is not tied to anything else. So the jumpers is what bridges them, right?

 

[dlgoff]

Where are you located? In the US, black is the source (115volt), white is the return/neutral, and green is the safety ground. In this case you only need to switch the source wire. So you could do this with just a SPSP switch. If you are using a 230volt source, then you would have two sources (Line 1=115volts and Line 2-115volts) and would need the DPST switch. However if you are in Europe then you will have a single source of 230volts I think and would not want to advice you without seeing what you have.

 

[negitron]

If you are using a 230volt source, then you would have two sources (Line 1=115volts and Line 2-115volts) and would need the DPST switch

In this case, one line should be black and the other red. The neutral, if present, will still be white and the ground will be green or bare copper.

 

[dlgoff]

In this case, one line should be black and the other red. The neutral, if present, will still be white and the ground will be green or bare copper.

Yes. I failed to mention the colors for two lines. Thanks for the catch.

 

[vk6kro]

The load is the circle on the bottom right.

The timer is the rectangular box on the top left. This switches the two contacts shown.

Incoming power is the lines marked "Ligne 1 and Ligne 2".

The timer gets its own power from the unswitched lines, of course.

Switching both power lines is a safety feature, but follow your local code.

 

[Danger]

In this case, one line should be black and the other red. The neutral, if present, will still be white and the ground will be green or bare copper.

Osiris did, though, in the original post, specify that the 3 wires were white, black and ground.

 

[negitron]

Then he's probably not in the US. My post specified the US color code for 240 V split-phase wiring.

 

[belliott4488]

The diagram seems to make sense for a 240 system with two sides at +/- 120 V, but I'm wondering how the OP's original circuit was wired with only a SPST switch. Are there any locations where there is a single-sided 240 V supply voltage?

If the original circuit was somehow simple enough to use an SPST switch, then I would think recreating the same connections on one side of the new switch should be equivalent, since a DPDT switch is just two SPST switches ganged together.

By the way, for those who couldn't read it, the text in the lower left says "To interrupt the two sides of a charge of 240 V" (I'm guessing "charge" is better translated as "voltage", but I can't say for sure.) The box at the top left is roughly "timer feed". "Ligne 1/2" are simply "Line 1/2".

 

[vk6kro]

Yes, a lot of countries (including Australia) have a line that is one phase of a 3 phase system and the neutral of the 3 phase system brought into houses. The neutral is approximately at Earth potential, but may have a few volts on it relative to Earth. An Earth wire is also used and all exposed metal on appliances is attached to Earth.

So this may be 240 volts rms relative to Earth on only one line. It is, however, traditional to switch the neutral line as well as the active line for appliances. Lighting is usually only switched in the active line.

There is no 120 volt line.

Higher power is available if all 3 phases of the 3 phase line are brought into the house (or factory). In this case, the voltages are all 240 volts relative to Earth but about 400 volts relative to each other. This costs extra for the wiring and more expensive power meter.

The American system is actually unusual, but makes perfect sense.

Incidentally, I fed "charge" into Google language translator and got the following:
1. burden
2. load
3. loading
4. cargo
5. office
6. charge
7. onus
8. trust
9. onslaught
So, it can mean something different in French to the same English word. I'd pick "load".

 

[Danger]

That PDF gave me a headache.

 

[osiris12]

Then he's probably not in the US. My post specified the US color code for 240 V split-phase wiring.

Thanks everyone for responding. I really appreciate it.

I'm in the Northeast US and my house was built in 1969. The line is 240v (238 really) coming from the romex, White, Black and Green ground. I orignally bought a SPST 15 years ago and it was easy to wire. In fact I have done a lot of electrical work like replacing bad throw fuses, adding digitial thermostats for my electric baseboard heaters which are also 240v to wiring recessed lighting, but I'm not a licensed electrican, just an enthausiast with common sense.

I got the new DPST at a great price and it was about half the price of the SPST from the same company. It is strange that the wiring diagram was not in English thought...

So in wiring up the new DPST switch I would use pins (screw contacts) 4 and 6 as dlgoff suggested?

 

[vk6kro]

Yes, input on 3 and 5 and output from 4 and 6.

 

[dlgoff]

The line is 240v (238 really) coming from the romex, White, Black and Green ground.

This bothers me. If you have a 240volt split-phase line in the US that is up to code, you would need two wires for line1 and line2, one wire for the return, and one wire for the safety ground as negitron posted.

In this case, one line should be black and the other red. The neutral, if present, will still be white and the ground will be green or bare copper.

What I think you have is, and this is the type of thing that can get your killed, is line one on the black and one line on the white with the return on the ground wire. And I don't see how you could have used a SPST switch to break both lines. You must have only been breaking one of the lines keeping the other connected to the heaters elements.

I think you should have an electrician come in and replace the wiring from you service panel to the heater with the correct up to code wire. And while you are at it, have him to install the switch.

 

[osiris12]

This bothers me. If you have a 240volt split-phase line in the US that is up to code, you would need two wires for line1 and line2, one wire for the return, and one wire for the safety ground as negitron posted.

What I think you have is, and this is the type of thing that can get your killed, is line one on the black and one line on the white with the return on the ground wire. And I don't see how you could have used a SPST switch to break both lines. You must have only been breaking one of the lines keeping the other connected to the heaters elements.

I think you should have an electrician come in and replace the wiring from you service panel to the heater with the correct up to code wire. And while you are at it, have him to install the switch.

When i put the volt meter between the black and white lines I get a 238 reading. With the old SPST, yes, i was breaking only one of the lines while keeping the other connect. I get no reading from the volt meter from the green ground wire.

 

[dlgoff]

I get no reading from the volt meter from the green ground wire.

What do you get for the black to green measurement and the white to green measurement? 115 volts on each I bet. Not safe to supply power to a water heater without a safety ground.

 

[vk6kro]

The new timer gives you double pole switching, so that is safer than the old setup. However a water heater is a closed system, so accidental contact with the heating element would be very unlikely. Anyone replacing it should know to turn off the power at the switchboard.

The US 240 volt supply is really two 120 volt lines that are 180 degrees out of phase with each other.
So, you can put a heater across the two 120 volt lines to get 240 volts on it without any need for a neutral. The ground wire is to ground the metal parts of the heater, not to normally carry any current.

 

[dlgoff]

... a water heater is a closed system, so accidental contact with the heating element would be very unlikely. Anyone replacing it should know to turn off the power at the switchboard.

Until you are leaning against the tank in all that leaking water and one of the elements shorts to the tank. You can't depend to the plumbing to take the fault current. The man needs to get the wire replace with a proper ground.

The new timer gives you double pole switching, so that is safer than the old setup.

Yes. That's why I advised him to get the electrician to install it.

 

[vk6kro]

So, why is that different to leaning against the water heater when the timer is turned on?


There is a grounded outer casing on the heater element and this is connected to a ground wire.
If there is any leakage to the casing, the Earth leakage detector (RCD?) should pick it up and cut off the power. The fuses or contact breaker should do it if there was no RCD.

The plumbing should not be involved but it should certainly be grounded if it isn't already.

Are you saying there should be a neutral line? Where would it go if the heater element wasn't centertapped?

 

[dlgoff]

If there are two 115 volt elements supplied by L1 and L2 they might be connected together with the return. In this case you would need a ground should one element fail by opening from the return and make contact with the tank. There needs to be a route back to a GOOD ground. You can't rely on the piping to shunt the power around you body. What if there is plastic pipe somewhere in the system?

You are correct that you don't need a neutral if there is just one 230volt element and the ground is really a ground connected back at the fuse box.

 

[vk6kro]

But he said there were just 3 wires. Two line and one ground. No neutral because the system doesn't need one.

These heating elements always have an outer casing which is grounded. Otherwise, the water would contact mains voltage.

So, it doesn't matter if there are ten heating elements, if they all have a grounded covering on them and this ground goes back to the control board, the elements can short to the frame of the water heater and nothing will happen because the covering is grounded and so is the water heater frame. The water joins the two all the time anyway.

We agree, though, that an electrician should do this and we agree that the new DPST switch arrangement is better than the old one.

 

[Danger]

I'm starting to be even more glad that I have all gas appliances.

 

[vk6kro]

:)

Yes, it is hard to decide between getting electrocuted and poisoned with gas or blown apart with a gas explosion.

We have gas for water heating, cooking and some room heating but electric air con and electric lighting and electric computers.

I came across this from about 5 years ago:
https://www.physicsforums.com/showthread.php?t=7262&pp=15&page=97
see item 1454.
I see by your avatar there has been some deterioration since then. :)

 

[Danger]

I see by your avatar there has been some deterioration since then. :)

Actually, the avatar came before the member photo. A lot of people don't realize that the avatar is a photo of me in one of my Hallowe'en outfits. It took quite some time for me to get comfortable enough to post a real one.
Only my furnace, stove and water heater are gas appliances. My lights run on wax and fire, the fridge, freezer and main computer are water-powered, and my laptop has a gerbil on a treadmill turning a generator.