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Electric water heater wiring

paul burrell

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Around here, most of those are wired with a 30 amp breaker and #10 wire. Wires are always fine, no excess heat on the breakers or wiring even after we've put the water heater through its paces.

4500 watts at 240 is going to pull between 18 and 19 amps and I don't think that both elements are kicking on at the same time or these would be tripping the 30 amp breakers.

My take. Of course, I'm stupid about electricity, so if I've got it wrong I know Jim or someone else will set me straight.



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According to my info - If you have a 5000 Watt element with a 240 Volts the minimum wire size should be #10 Copper or # 8 Aluminum, and a maximum 30 amp breaker. That's my info, I'm not sure about the IRC, or the NEC.

Ohm's Law says to figure out Amps - divide the Watts by the Volts.

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Originally posted by randynavarro

Mike, how do you put a water heater through its paces?

Hi Randy,

Interesting question. I've never really thought about how really, but if I had to spell it out I think I'd say I evaluate location first, installation second and operation third.

1. Location

a. If in a garage is there adequate clearance around it and is it the required height off the garage floor and is there at least one bollard to protect it if it's where a vehicle can strike it?

b. If inside in a utility closet, is the door wide enough to remove it, is there sufficient clearance around it and, if it's gas, is there good air supply into that room and how is the air supply configured?

c. Is the base clear of debris so that the air inlets aren't blocked and plenty of air can flow to the burner? Are there puff shields in place? If so, are the correctly installed?

d. Is it being used as a 'shelf' with a ton of stuff piled on top of it?

e. If it's in a laundry/utility room, whether it's gas or electric and, if gas, whether it's a gravity, direct or power vent and whether there a good air supply into that room with the door closed and how close is the nearest air suction source (furnace, clothes dryer or exhaust fan)?

f. If it's in a bedroom or bathroom, is it a direct-vent type?

g. Are the isolation valve(s), T & P valve and drain petcock readily accessible?

h. If gas, is it oriented so the homeowner can easily get to and remove the puff shields, see the pilot and burner and will be able to easily light it?

i. If gas, is the space shared with any other gas-burning appiances and, if so, is there an adequate volume of makeup air for combustion for both appliances to operate correctly? Are there any signs at either appliance that there have been problems with makeup air (rollout scorch marks, melted plastic insulators near the draft hood at the top of the tank, heavy mineral salt accumulations on pipe joints, etc.)?

2. Installation

a. Is it stabile and adequately braced against seismic activity with full-circumference straps in the top and bottom third of the tank, no closer than 4 inches to the controls, and, if so, are they secured with adequate fasteners to solid anchor points, and is there blocking filling any gaps between the tank and the wall to prevent it from bouncing around inside the straps during an 'event'?

b. Is there an expansion tank? If so, is it adequately secured to prevent it oscillating and becoming damaged during an event? If not, why not?

c. Are there heat trap nipples at the top of the tank or are the connectors configured as heat traps?

d. Are the nipples dielectric or brass? If dielectric has a jumper been installed between the hot and the cold pipes?

e. If it's electric, is there a disconnect within sight or a lockout in the panel and is the breaker and wiring adequately sized?

f. If gas, is there a shutoff valve within 3 to 6ft. of the appliance and ahead of any unions?

g. If electric, is the cable the correct type, protected from damage, adequately secured at both ends and is there an equipment grounding path?

h. If on a second floor or in an attic, is there a drain pan with drain?

i. Is there adequate working space around it?

j. If gas, has the right flue material been used, is it adequately sized and free of rust and holes?

k. If gas, is the flue baffle in place and/or is it sitting on the burner plate or is the plate covered with a pile of rust?

l. If gas and in an unheated location, has double-walled vent material been used? If not, is there any sign of condensate drainage/damage around flue joints, the draft hood or under the baffle tube or on the burner plate?

m. If gas, how many bends are there in the exhaust, how sharp are the bends and what's the ratio of horizontal to vertical vent length?

n. If gas, does it vent into a shared vent? If so, how is the transition done and is the shared vent adequately sized for both appliances and proper braced at required intervals?

o. Are the isolation valves full-bore types and are flexible connectors and nipples adequately sized and are there any dissimilar metal issues with them? Are they reversed? Are they insulated?

p. Are all the connections (gas and water) tight and leak free? Is there any sign of rust?

q. Is there a T & P valve? If so, is it in the top 6 inches of the tank, is the discharge pipe the right material, adequately sized, in constant drainage plane and terminates properly? If no T & P, is there a Watts 210 or equivalent installed on the system?

r. Is the draft hood in place and secured?

s. Is the temperature set at a safe level? If not, is there are mixing valve installed?

t. Is there sufficient clearance from combustibles around the flue and does it terminate the proper distance above the roof.

u. If venting into a masony chimney, is the masonry chimney lined and properly sized and are there any signs of condensate damage to the flue? Does the flue need cleaning?

v. Are there any odors of gas?

w. Are there any signs of leaks around the tank bosses where the heating elements screw into the tank?

x. Is the gas connector properly sized, the right type and is there a drip leg?

3. Operation

a. Does it work? If so, is it making any weird sounds? Does it seem to provide sufficient hot water? How's burner flame look?

b. Are there any odd odors around it when it's operating?

c. If signs of possible backdrafting or there seems to be insufficient makeup air, with the door closed, does a monoxir test indicate the thing is backdrafting any CO for more than a couple of minutes after cold startup?

That's all I can do off-the-cuff. Those are the observations that come readily to mind. I'm sure I've left something out that I'll think of later, but it's really a reflexive process anyway and can change from house to house, depending on what's there.

This is only for conventional tank-type water heaters and I didn't comment at all on oil-burning water heaters because 10+ years I've yet to encounter one.

Is this what you meant? If not, I guess I'll have to figure out how to make a water heater walk, trot, canter and gallop before I'm able to put it through its paces.



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Great list Mike. When you originally stated "put the water heater through its paces" I was visualizing some sort of testing methods other than the visual inspections you've described.

Its a good thread going next door about how to test the electrical elements of an electric tank. Maybe that's what I was curious about. How far does one go in testing an electric tank, if at all? It sounds like one can get pretty comprehensive with checking the heating elements, t-stat etc.

Me, I just do visuals on electric tanks. No tools or meters involved. But if there was a way to do a bit more diagnostic work on an electric tank without having to test all the terminals, then cool. Looks like there really isn't one though.

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Hi Randy,

Most folks just use a clamp meter around one of the wires at each element and run the water to push the tank to respond. Like you, I don't do that.

Yung goes through the home testing all of the fixtures and appliances and runs a ton of hot water. She's got a pretty good sense of when something isn't right - water's not hot enough, hot water doesn't last long enough, water doesn't re-heat fast enough, volume is weak etc. - and she'll always tell me when something just doesn't seem right. That's when I'll go back and look a little deeper into it and either figure out what it is and recommend appropriate repairs or recommend that a plumber or electrician, whichever is appropriate, check things out and fix it.

So far, I've only had one water heater callback in 10-1/2 years, and that was about one that was 17 years old and built into the corner of a kitchen beneath the countertop and had never been serviced. I'd told the lady not to be surprised if it failed as I was backing out of the driveway. It didn't and she didn't have it replaced. Instead, it failed a week after she moved in and then she called me up bellyaching. I gave her a refund of her fee because she was an unhappy customer, just to be a nice guy, and then had her sign a hold harmless agreement.

It didn't do any good. She was mad as a hornet anyway, because that wouldn't cover the total cost of tearing apart the kitchen counters, draining and removing the old tank, installing a new one and then rebuilding the counters and restoring the kitchen. Guess she thought I'd just fallen off a turnip truck and would roll over and pay for it anyway. Not a chance.

Yung wasn't working with me back then. Good thing, or, knowing her temper, that lady would have suffered a shiner.



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The older the heater, the more likely sediment and/or gunk are gonna catch in the valve and prevent it from closing properly. Those things should never be operated.

People ask me sometimes whether they should drain the water-heater tank once a year. It isn't a bad idea now that the drain cocks are brass. But when the cocks were plastic, they invariably gunked up and refused to close once the tank was emptied. And the homeowner had to pay a plumber $100.00 to install a replacement.

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I tested T & P valves on about the first 30 jobs I did. Then I got an old one full of sand and the damn valve stuck open and the homeowner began bellyaching about 'that damned inspector doesn't know his **s from a hole in the ground.' After the inspection, I drove down to Ace Hardware, picked up a new one, returned and installed the damned thing. I insisted that the homeowner watch me, so that he would know that it did not leak when I'd finished and left. Afte that, I decided that I wouldn't test them anymore.

Now I instruct every client to flush their tank of sediment once a year and then test their T & P valve. I also instruct them to change their anode rod about mid-way through service life (about 5 to 7-1/2 years into the life of a tank around here.), and advise them, if the tank isn't too old, to pay a plumber to replace the drain spigot with a longer nipple and full-bore valve, so they'll be able to more easily and quickly flush the tank and won't have to worry about the valve breaking off on them.

I doubt if many of them actually do any of this, but I'll credit that little bit of training with the fact that, other than one lady with unreasonable expectations about the life of a water heater, I've never had any complaints about water heaters in 10 years.



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TPR valves are a big safety item and should be tested especially if they are old and corroded and will not open. However if one is opened and will not re seat it is also defective and should be replaced. I will not open one unless I am alone or get the owners permission. The owner knows anything that proves defective when tested is the inspectors fault, just because the TPR is 10 years old and corroded has nothing to do with it. Not to test the TPR is a disservice to my clien't. However one must be cautious and do a lot of CYA.

Just my opinion.

Paul B.

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