240VAC water heater wiring?

The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.

ranger58sb

Guru
Joined
Aug 21, 2013
Messages
7,097
Location
USA
Vessel Name
Ranger
Vessel Make
58' Sedan Bridge
I think our Atwood E20-220 (17.9 gallon) water heater has begun leaking... and it might be the tank or it might be the seal around the heating element. Or both. I reckon to hope for leaks around the element, and I finally have the parts (hopefully) to replace the heating element and the mounting gasket(s).

But... this is a 240VAC unit... and I'm a little hazy on how that wiring works. The replacement 240VAC/1500W (clearly marked) heating element only has two wiring posts, similar to a 120VAC unit... and I'd have expected four. I haven't uncovered the original element yet, but online pics of it also suggest there are only two wires to connect.

Ummm.... what's up with that? Do these only use 1 leg of a 240VAC system, with amperage to match? 12.5A instead of 6.25?

Or... ?

In the meantime, the original water heater is working (knock wood)... but I'm not holding my breath for longevity. Actually replacing the whole tank, if I can band-aid something better that works for a while, will be a PITA; might have to remove some engine parts to get a new one in. So far, a Torrid 17-gallon tube-shaped replacement looks to be best option, and closest to maybe installing without engine surgery. I'm hoping to put replacment off until we get back home, though...

-Chris
 
In a typical US 120/240 split phase system, you have 4 wires. Ground, L1, Neutral, L2. From L1 or L2 to Neutral you get 120V. From L1 to L2 you get 240V. So if the unit only uses 240V and doesn't use 120V for any control circuits, it would be wired to L1 and L2 (and presumably ground), but wouldn't use the neutral wire.
 
In a typical US 120/240 split phase system, you have 4 wires. Ground, L1, Neutral, L2. From L1 or L2 to Neutral you get 120V. From L1 to L2 you get 240V. So if the unit only uses 240V and doesn't use 120V for any control circuits, it would be wired to L1 and L2 (and presumably ground), but wouldn't use the neutral wire.

And the ground wire will likely connect to the tank somewhere, not to the heating element. All the 240V heating elements that I've seen only accept two wires. How to wire it should become clear when you remove the access panel and see how the existing element is wired.
 
Chris....no manufacturer install book or online install instructions? Sometimes the wiring diagram is on the inside of the panel where the thermostat is located.

The next question is it a single or dual heating element water heater?

Otherwise my guess is it is a simple 2 wire from the thermostat to the heating element....no neutral...and green ground to the case/shell of the heater if metal or interior metal framing if exterior plastic.

Usually the amp requirement for the 240V is 1/2 of the 120V if the appliance is of equal wattage... but the typical recommendation for 240 appliances is 10ga wire...then again many of those are very high wattage appliances. If only a single element heater the normal amperage for the given wattage would apply for the wire size.
 
Open the cover to the element. Take a picture of it. It will be a 4 bolt or a screw in style There will only be 2 posts/screws on either version for wires. Verify your voltage on the heater. Make sure you get the 220 v version. Very simple to install. You can pick up at lowes or home depot. or plumbing supply yard. No need to order anything special. You may have 1 or 2 elements. TURN POWER OFF BEFORE SERVICING. LOL Refer to your picture and re install wires . on 22o there will be no difference which post the wires go on.
 
Ah. Thanks, guys. Two wires to the element, ground probably elsewhere on the tank. 220 only, so no neutral required. And all 240V elements only have two posts too. All that gets me squared away.

Yes, I have the manual with diagram, and it's the 4-bolt style, but the diagram is for a 120V "example unit" with no mention of any changes in wiring for the 220V version. Single element. Fairly straightforward, I'd think. I've changed the element in a 120V water heater before, no issues... but thought better to check about this one, since I'm sorta new to 220V stuff.

In this case, trying to get my mind around it before I open it up... so I know what to expect and how to sort it while I'm there. I'd thought all along it should be pretty straightforward to just duplicate however the original is wired... but understanding why is even better!

I'm actually expecting it's probably the tank that's leaking, though, with maybe no way to get some temporary sealant on the failure point... <sigh>...

-Chris
 
Last edited:
If you pull the element cover you should be able to tell if it is the element seal that's leaking just by visual check.
 
When you guys refer to a 4-bolt style heating element, I have never seen/heard of that. I have only seen the screw-in type. Anyone happen to have a picture of one?
 
here you go
 

Attachments

  • 04643_out.jpg
    04643_out.jpg
    32.4 KB · Views: 10
Dont really know. Run into both styles. The thread in style are most common that i see.
 
If you pull the element cover you should be able to tell if it is the element seal that's leaking just by visual check.

Yeah, now that I have all the parts I might need if it's element/seal related, I'm about ready to get down there... after our current guests hit the bricks. Hoping it's that, actually, and not a leak in the tank somewhere.


Thanks. Are they more common in marine water heaters, in Europe, or other?

I've only ever seen the 4-bolt version, first in our 2002 11G water heater, and now in a 2006 20G model... both from Atwood. (One "t")

-Chris
 
Make sure the wattage of the new element is correct for your wiring and circuit breaker size. Also, make sure the tank is completely full before turning power back on. If your tank has a replaceable anode, this is a good time to replace that too.

Daniel
 
As it's turned out... the water heater isn't leaking at the element/gasket... and it's way too old to invest any more time/money in repairing or even troubleshooting it.

We're now hoping it'll last long another month or so... and then we'll replace it after we return home. Looks like we might be able to get a horizontal Torrid 17 into place without having to temporarily remove any engine parts. The original "E20" is actually 17.9 gallons, so a 17-gallon Torrid should give us same capabilities.

-Chris
 
Figures no easy fix
 
Figures no easy fix

But good you figured it out before replacing the heating element

Yeah... and I expected it'd turn out like this...

Got the parts (new element, gaskets...) in advance, and I even got some Flex Seal Liquid (says OK for up to 350F degrees) just in case a tank leak might be visible/accessible... just in case a Band-aid approach might work for a while...

(And when I had eyeballs on, the wiring became obvious.)

But I also did the shopping for complete replacement at the same time.

I'll make up some kind of mock-up of the target replacement, just to be sure I know what'll be involved in getting the new one into place...

And then I'll hope availability isn't a problem, once we get back to where we could place an order.

-Chris
 
For horizontal tanks, look at the Isotemp options as well. I've been happy with the one I installed and it seems to be far better insulated than my old Raritan unit was.
 
For horizontal tanks, look at the Isotemp options as well. I've been happy with the one I installed and it seems to be far better insulated than my old Raritan unit was.
Agree!
 
I put in the 17 Gal. horizontal Torrid about 6 years ago and am happy with it's performance. They sure have gone up in price.

Here in the PNW with our 45º F. supply water, it takes about 1.5 hours to raise the water temperature 90º F. using the 240V. 3kW element. I would not go with a lower rated element.

The Torrids, along with the Raritans are glass lined tanks, which many consider a step up in durability compared to a Stainless or Alum. tank.
 
Thanks for recommendations!

I had checked Kuuma (a clone for the original Atwood with one "t" clone), Whale/Seaward/Attwood (two ''t"s)/Seaward (similar to original but not identical), Isotemp, Quick, and Torrid.

I think I'll probably have to remove the original Atwood cubic version with a Sawz-All, so replacing with a Kuuma or Whale model would almost certainly mean removing engine parts to get the new one in, intact. (Those pesky V-8 engines...)

Near as I can tell, Isotemp only has 115V and 230V/50Hz models, nothing for 240V/60Hz US power. Ditto for Quick.

The Isotemp 20-gallon model is pretty fat, and I'd almost certainly need to remove engine parts first to get the rascal into place, if they had a 240V version.

-Chris
 
Thanks for recommendations!

I had checked Kuuma (a clone for the original Atwood with one "t" clone), Whale/Seaward/Attwood (two ''t"s)/Seaward (similar to original but not identical), Isotemp, Quick, and Torrid.

I think I'll probably have to remove the original Atwood cubic version with a Sawz-All, so replacing with a Kuuma or Whale model would almost certainly mean removing engine parts to get the new one in, intact. (Those pesky V-8 engines...)

Near as I can tell, Isotemp only has 115V and 230V/50Hz models, nothing for 240V/60Hz US power. Ditto for Quick.

The Isotemp 20-gallon model is pretty fat, and I'd almost certainly need to remove engine parts first to get the rascal into place, if they had a 240V version.

-Chris

It might be worth checking with Isotemp if there's any issue using the 230V/50hz model on 240/60. I don't think there are any components in the unit that are frequency sensitive, so it's likely fine on 60hz power.
 
My read of the Isotemp Basic series water heater info. is that they are all 16" in diameter with the 20 Gal. model being 42" long. The 17 Gal. Torrid is also 16" in diameter and is only 31" long. The Isotemp may well have a smaller diameter water tank inside, which would allow for some increased insulation thickness while keeping the 16"OD. Perhaps this saves some energy.

I doubt the Frequency of the input power has any part to play in the heater's performance, resistance elements generally don't care.

The Isotemp with it's standard 750W element will take about 7 hours to raise the 20 Gal. of water by 90º F. Even with the optional 2kW element it will still take about 2.7 hours.

The 17 Gal. Torrid with it's 3kW element, makes Temp. in 1.5 hours. That and the glass tank cinched it for me.

Your needs may be different.
 
My Isotemp Spa 11 gallon was nearly 2X the gallons that my Seaward cheapo was and was much better at regulating and keeping water hot. It was also superior in time to hrat because of the superior insulation.

For 2 people it never ran out of hot water even with back to back normal showers. When it was very cold out, We would use tank water that would be warmer than dock fed city water....I think that helped.
 
Real world user experience is usually useful, however without some kind of indication of the capabilities of the units that you are comparing, the "ya that's reasonable" conclusion is somewhat hard to make.

Fortunately, the power needed to heat water over a given period of time is pretty well known and can be found all over the internet.

I don't think any of the calculations include the losses incurred while heating as you would need to know the specifics of the tank, the plumbing and the surrounding air to get an accurate read on that.
 
OK....so you made my point...a poorly insulated tank takes longer to heat than a well insulated tank....right? The shear construction between the two units I discussed could leave no questions which unit is most likely superior. Also... what water source temp you use would affect it (or any water heater) too....right?

I am not saying my Isotherm was the best or performs magic...just saying by doubling the gallons of hot water and the quicker recovery over other lesser water heaters was quite noticeable.

I have had enough experience in real world operation testing of systems/equipment to know the difference between physics, engineering expectations and what my body feels while living. Also knowing how to help your systems perform to their best is sound judgement....right?

Sometimes real world experience by someone you trust is all is needed to make a wise decision.
 
Last edited:
No, quite the opposite. What I said was you need a lot more specifics to make the statement that those real world experiences are reasonable.

For example, if we have two tanks each filled with the 50º F. water, with the poorly insulated one half the capacity and half the power consumption of the highly insulated one, the poorly insulated one will make temperature, say 130º F. quicker provided it is situated in a 120º F. ER, while the highly insulated one is in the 50º F. bilge.

You could get the same result, that is, the poorly insulated tank could make Temp. quicker, even if they were the same volume and in the same conditions provided the heating element of the poorly insulated one was of sufficient size.

To make the blanket statement that "the poorly insulated tank takes longer to heat than a well insulated tank" is just not reasonable unless you know all of the other conditions.

Likewise, your statement that the Isotemp "was also superior in time to heat because of the insulation" may not be valid unless you were to also state that all other conditions were the same, leaving only the insulation different.

I have no appetite to argue with you further and firmly believe that an Isotemp water heater is a reasonably well insulated unit. Their issues in my mind are their pathetically small heating element (750 W is standard for 20 Gal.) and their stainless tank.

Torrid or Raritan both with glass lined tanks and 3kW elements, when compared with the standard 750 W Isotemp will heat much quicker provided the capacity and input Temps. (there, see how easy that was) are the same.
Given regular maintenance, they will likely last longer as well.
 
The Isotemp can be had with a bigger element (mine has a 1200w element in an 11 gal tank, not much different than my previous Raritan). But the only time heating speed really matters is when heating on generator power. Otherwise, staying hot for longer is more important.
 
If your 11 Gal. water heater has a 1200 W element and you don't consider passive gains or losses during the heating period then it will take about 2 hours to raise the water temperature 90º F.

Using a 750 W element the time goes to over 3.25 hours.

Using the 20 Gal tank and the 750 W element you are now are at about 6 hours to make temp.

I don't know about your use patterns but if my boat is in the house unused for a few days the water heater is not energized.
I would not consider it acceptable to have to be at the dock for more than at most a couple of hours for the water to heat. I always leave with a full tank of hot water and by choice do not heat water using waste heat from the engines.

Further, we often have 6 or so people overnight and the recovery time using a 3 kW element speeds the morning shower process, regardless as to whether we are on the dock plugged in or on the hook.

Recovery time for us is important.
 
I also included Raritan on my shopping list; forgot to include that in my note above. Looked decent, too fat.


It might be worth checking with Isotemp if there's any issue using the 230V/50hz model on 240/60. I don't think there are any components in the unit that are frequency sensitive, so it's likely fine on 60hz power.

I agree probably not frequency sensitive, but I think too much trouble to change the whole electrical system given the Torrid 240VAC version would be a straightforward connection mirroring our original. (And I haven't a clue how to get 3-wire 230VAC from a 4-wire 240VAC system.)


My read of the Isotemp Basic series water heater info. is that they are all 16" in diameter with the 20 Gal. model being 42" long. The 17 Gal. Torrid is also 16" in diameter and is only 31" long. The Isotemp may well have a smaller diameter water tank inside, which would allow for some increased insulation thickness while keeping the 16"OD. Perhaps this saves some energy.

The 17 Gal. Torrid with it's 3kW element, makes Temp. in 1.5 hours. That and the glass tank cinched it for me.

Your needs may be different.

The 20-gallon Isotemp is 23" diameter, next smaller is a 13 in either 16" or 23" diameter.


Here in the PNW with our 45º F. supply water, it takes about 1.5 hours to raise the water temperature 90º F. using the 240V. 3kW element. I would not go with a lower rated element.

The 240VAC Torrid 17 with the entry-level 1500W element would have been my target, closest to what we have now (17.9G, 1500W)... but a member on another forum (who has one) suggested getting it with the 2000W element instead. I was surprised by your 3000W recommendation... I think our breaker on that circuit might be 15A and I'd probably not like to push that limit too closely. Have to do some more research on that...

-Chris
 
Last edited:

Latest posts

Back
Top Bottom