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Higher wattage elements for 208v water heater?

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Number21

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I have a 40 gallon electric water heater in my shop. It spends most of it's time just sitting, so I think I'm going to start shutting off the breaker when I leave the shop and turn it back on when I get there.

Problem is the water heater heats up really slow. It's a standard 240v model, rated at 4500w x2, but my shop has 208v 3 phase power, which results in more like 3300w x2. That's around 22,000 BTU vs 30,600 BTU which it is designed to have.

Anyway, is it possible for me to find heating elements that are rated for a full 4500w at 208v? Or, can I find even higher than 4500w, in a 240v model?
 
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Torque1st

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Wrap a lot more insulation around it. Also insulate the pipes going in and out. This will help it hold the heat and also help it heat marginally faster.
 
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nate379

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I'd imagine you would use less juice maintaining it at a temp vs cold to hot.. I could see if you don't use it for a couple weeks at a time though.
 
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Number21

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A demand heater would be best, but I doubt the electric savings will ever outweigh the initial investment.

It is also an issue of not much hot water if I'm using out of the hose...the recovery time is terrible with the elements being "under driven".

I'm going to set up a little loop of pipe around my wood stove to heat the water when I happen to have a fire burning...
 
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Number21

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Now that I think about it, my water heater is in the corner of my brick shop and on top of the bathroom in a space about 4' from the ceiling. If I built a wall around the two remaining sides with 2x6 and insulate it with fiberglass, and an access panel, am I going to have any problem with the codes?

Right now it's about 50 degrees in there since nobody's home, but the water heater is still keeping up with 125. Probably won't be back for a day or two. I keep seeing that "$417 estimated yearly useage" sticker on it calculated with 1995 electric rates and roll my eyes...
 
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Keep in mind that most electric water heaters have the two elements interlocked so that only one can operate at a time... so you are probably only getting 11,000 BTU/hr! This is so they can be installed on a 30A breaker and not tax the electrical system of older houses.

Some manufacturers permit rewiring for simultaneous operation for faster recovery, but you need to have a larger breaker and wiring than is typical.

Tankless electric water heaters commonly use a 9.5KW element and come in 1, 2, 3, and 4 element models. Around $400 for a typical 2-element model, which requires two 50A double breakers at 240V. With the reduced output at 208V, you would probably need at least a 3-element model--yes, that's 3 double pole breakers to feed it! Nice thing is no standby loss when not in use and doesn't take up floor space, plus no waiting for hot water when you want it.

However, new high-efficeny electric tank units with 2" of foam insulation have much lower standby losses than old units, so you aren't paying much to leave it on. Better yet is a Marathon with plastic tank surrounded by 4" of foam insulation. I have a 50 gallon Marathon in my house. I switched it off when I went on vacation. Came home a week later and the water was still warm!

Be very careful with that wood stove loop... I think its a great idea, but you need to be very careful not to have a steam explosion! If you use a circulating pump, what will happen if the power fails while the wood stove is going full bore? With a thermosiphon system that isn't a worry, but the tank must be several feet higher but not very far away horizontally. I've read that you should have a swing check valve in the "cold" line just before the wood stove--the theory is that if a steam bubble forms it will be forced the other way and drive a self-pumping action. In either case, put a PTRV in the "hot" line just after the stove--in addition to the PTRV at the tank.
 
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Number21

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VHF said:
Keep in mind that most electric water heaters have the two elements interlocked so that only one can operate at a time... so you are probably only getting 11,000 BTU/hr! This is so they can be installed on a 30A breaker and not tax the electrical system of older houses.
Click to expand...

Wow, I didn't realize that. Don't know much about electric water heaters, I've been using gas at home for years. My gas heater is rated at like 40k BTU. Mine is on a 30 amp breaker, so that's only 6,240 watts max. Didn't even think about calculating that out LOL! They must be on only one at at time...or it's overloading the circuit...

I do have another 30 amp circuit that's not being used and really close to the water heater - I could extend it a little ways and use two seperate 2 pole 30A breakers. If I did that maybe I could get one 4500w element and one 3300w element and simply turn off the 4500 when I leave.

VHF said:
Be very careful with that wood stove loop... I think its a great idea, but you need to be very careful not to have a steam explosion! If you use a circulating pump, what will happen if the power fails while the wood stove is going full bore? With a thermosiphon system that isn't a worry, but the tank must be several feet higher but not very far away horizontally. I've read that you should have a swing check valve in the "cold" line just before the wood stove--the theory is that if a steam bubble forms it will be forced the other way and drive a self-pumping action. In either case, put a PTRV in the "hot" line just after the stove--in addition to the PTRV at the tank.
Click to expand...
Yeah, I haven't really penciled out the plumbing yet, but I want to setup a small thermosyphon, with some kind of thermostat to turn it off at like 180 degrees or something. Also plan to have one or more pressure/steam blow off valves, I want to design it so it can burn with no water in it or no circulation and not blow up. :)
 
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VHF

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It is pretty easy to follow the wiring with the water heater acess panels removed. Both hot legs first go to a thermal cutout (typically with red reset button.) This breaks all the current to the elements if the tank reaches 180F. The current then goes to the upper thermostat, which feeds the upper element if the top of the tank is below the set point temperature. If the top thermostat is satisfied, the current is then allow to go to the bottom thermostat and feed the bottom element if needed.

The theorey is that the top element will heat the top 1/3 or so of the tank to give you some hot water sooner rather than have to wait for the whole tank to come up to temperature. In normal residental use, the bottom element does most of the work. It is only when you use all (or almost all) of the hot water that the top element kicks in.

To run both elements simultaneously, it would be preferable to feed a single 50A circuit to the water heater. That way both elements are still protected by the thermal cutout. If you want to feed separate circuits for each element, you would need to figure out how to add a second thermal cutout near the top of the tank--and I suspect that level of modificiation would void any UL listing. Under no circumstances provide power to an element that does not go through both a thermal cutout and a thermostat!

MythBusters disabled the various saftey devices on an electric water heater to see what would happen, and the results were pretty spectacular. The bottom burst out and the water heater shot straight up through the roof into the air about 100 feet. Think steam-powered rocket! The steam explosion demoslished the little "house" the water heater was in. You do not want this to happen in your house or shop! :shocking:
 
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Number21

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VHF said:
MythBusters disabled the various saftey devices on an electric water heater to see what would happen, and the results were pretty spectacular. The bottom burst out and the water heater shot straight up through the roof into the air about 100 feet. Think steam-powered rocket! The steam explosion demoslished the little "house" the water heater was in. You do not want this to happen in your house or shop! :shocking:
Click to expand...
Yeah, I saw that...pretty amazing, you'd think you would hear about that more often on the news. I will DEFINATELY make sure the pressure relief valve on the water heater is working correctly. Maybe replace it just to be safe.

PS - are you supposed to replace the anode in an electric tank every so often? I doubt anybody has ever touched my water heater since it was installed around 1995...
 
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VHF said:
To run both elements simultaneously, it would be preferable to feed a single 50A circuit to the water heater. That way both elements are still protected by the thermal cutout. If you want to feed separate circuits for each element, you would need to figure out how to add a second thermal cutout near the top of the tank--and I suspect that level of modificiation would void any UL listing. Under no circumstances provide power to an element that does not go through both a thermal cutout and a thermostat!
Click to expand...

You think a 50 amp circuit is preferable......:wtf: On top of that you think the UL listing would only get voided once he added a second thermal cutout, I'll clue you in on something, once he ran a 50 amp circuit to it he voided the UL listing and violated the NEC.

It just amazes me people post this kind of **** advice and think it's the preferable way to do it?? Who are you really helping?

He needs to live with what he's got or go with a different type of water heater if he needs faster recovery. That's all there is to it.
 
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Number21

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Aceman said:
He needs to live with what he's got or go with a different type of water heater if he needs faster recovery. That's all there is to it.
Click to expand...
Oh yeah, you're real helpful. :rolleyes: No, I'm not going to spend $500+ on a new water heater. I will modify the one I have however I like. As noted in the original post the water heater is already under powered significantly for what it was designed for. I should have plenty of hot water if it was working at design spec.

**** the NEC, more or less. I know how to be safe, I don't care what they *think* is safe for me.
 
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Number21

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Aceman said:
It is working at design spec for 208 volt.
Click to expand...
No, it wasn't designed for 208v, period. Not "spec'ed" for it. Somebody just cheaped out and put a household water heater in an industrial building.

It's like plugging a lamp into a socket that only has 100v...you'd need a brighter bulb. (but it's not dangerous if you do it right, whether or not the NEC agrees)
 
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Number21

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Jaguar Fan said:
Isn't there a type of thermostat controller where you "phone in" to turn on the water heater?
Click to expand...

Actually I was thinking about getting some sort of X10 setup, so that I can control most everything in my shop over the internet.:D I'm not sure if they have stuff heavy duty enough for a water heater or not, but I could always use relays....
 
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