Water heater element problem.

CJW8 wrote:

Old-Biscuit wrote:
And yes.they will also weep when heating water if the air pocket at top of tank has been lost

It may weep but if it does it should be replaced as they are inexpensive and not really worth servicing. Relief valves are not supposed to weep, no if's and's or buts about it.

IF the air pocket is there then the PRV shouldn't weep.....they weep when the air pocket is lost due to the increase in pressure from the water swelling when it is heated. Expanding water (which can't be compressed) causes the increase in pressure. The air pocket (which can be compressed) allows for the water to swell when heated without the increase in pressure which is what causes the PRV to weep.

YES...a defective PRV should be replaced.
Just because it weeps doesn't mean it is defective.
Establish air pocket and then IF PRV weeps replace.

Here's the reply I got from a electrican site but that doesn't mean I understand it.
(There is no separation inside the element, it is a resistive load, when dealing with 240, each leg is 180 degrees apart.)

Dusty R wrote:
120 volt element uses 2 screws 1 hot, 1 neutral.
240 volt element uses 2 screws 2 hot, one from each leg.

Dusty

I can't understand how on 220 volt the two hots are not touching each other are there 2 smaller rods inside the bigger one ?

120 volt element uses 2 screws 1 hot, 1 neutral.
240 volt element uses 2 screws 2 hot, one from each leg.

Dusty

Removed the relief valve and soaked in vinegar for about 3 hours with it open blew it out and the spring plunger worked a lot better reinstalled and no drip.

I still don't understand why it's called a 240 volt element with only 2 screws you couldn't just hook the two hot wires. I'm going to have to to do some thinking and that's dangerous. It's working with the 110 but I don't think you could hook it for 240 if you wanted to.

Old-Biscuit wrote:
And yes.they will also weep when heating water if the air pocket at top of tank has been lost

It may weep but if it does it should be replaced as they are inexpensive and not really worth servicing. Relief valves are not supposed to weep, no if's and's or buts about it.

Thanks everybody. I've got the relief valve soaking in the vinegar I drained out of the tank. I'll try the air pocket trick.

Well now you know the 220V one will work just at a much lower wattage then the 120V element

You did a small vinegar treatment and got a lot of scaling out......that is probably what is wrong with your PRV. It most likely has scale built up on valve seat/disc and weeps.
You can try cleaning it up with vinegar or CLR
You can try to dislodge the scaling by opening and letting it snap closed several time with tank full and water pressure on
You can replace it......

And yes.they will also weep when heating water if the air pocket at top of tank has been lost

The element will work okay on 120 volts but the watts will be 750 instead of 3000.
The resistance of the element will be about 19.2 ohms. At 240 volts it will draw 12.5 amps and the power will be 3000 watts.
At 120 volts it will draw 6.25 amps and the power will be 750 watts.

At 240 volts

W = VxA
A = W/V = 3000/240 = 12.5 amps
R = V/I = 240/12.5 amps = 19.2 ohms

At 120 volts
I = V/R = 120/19.2 = 6.25 amps
W = VxA = 120 x 6.25 = 750 watts.

As far as the leaking relief valve this is what the Atwood manual says to do to replace the air pocket that can help prevent drips.

"To replace the air pocket start by turning off the water
heater, shut off the incoming water supply
and open the closest hot water faucet. Pull the
handle on the pressure-temperature relief valve
straight out to allow the water to flow from the top
part of the tank. Once the water has stopped
flowing allow the handle on the valve to snap shut,
close the faucet and re-engage the water supply. "