AO Smith Water Heater Hissing & Element Replacement

[Aztarac]

I'm probably overthinking all this, but would love some advise. We had our electric water heater replaced (tank was leaking) in February 2023 with an AO Smith LTE-80. This is a light duty commercial water heater that came from the factory wired for 277V and includes 2 dual rated elements (6100W 277V - 4500W 240V). The plumber did a factory authorized conversion which consisted of moving 1 wire on the distribution block in the heater to convert that system to residential voltage of 240V. So the elements are running at 4500W 240V (and verified by the conversion sticker applied to the water heater). I also verified with a meter the incoming voltage to the upper thermostat is indeed 240V.

About 2 weeks ago the heater started making a hissing noise. I was able to determine its the lower element that makes the noise when its heating. I flushed/drained the tank and didn't notice any visible sediment coming out in the water when it was draining. Filled the tank and the hissing noise persists when the lower element is energized and heating. I called the plumber who installed it and he said "Oh, water heaters start making that noise after awhile. Don't worry about it"

I don't think it's "normal", so at this point I'm just going to replace the elements. But here's the issue: when I look up the replacement elements (AO Smith 100347979) the description states they are 6100W 277V and doesn't mention anything about them being dual rated like the originals. Obviously 6100W 277V won't work since the heater is running on 240V. I don't want to order these in the hopes they are dual rated like the ones currently installed. Am I ok with just ordering/buying standard 4500W 240V elements? Like these: https://www.supplyhouse.com/AO-Smit...d-Copper-Mid-Line-Screw-In-Element-240v-4500w

Again, maybe I'm overthinking all this and those 4500W 240V elements will be fine, but I don't want to screw anything up.

 

[GReynolds929]

Should be fine either way. They should be the same 12-13 ohm resistance element, when 277v is applied they are approx 6100w, when 240 is applied they are approx 4500w. You could always double check with AO Smith.

 

[sarg]

I've had good luck with Camco elements from Amazon .... but I change them every six months during maintenance.
https://www.amazon.com/dp/B0006IX89G?ref=ppx_yo2ov_dt_b_fed_asin_title

When I remove the elements I vacuum out the tank with a wet vac through the bottom element hole and inspect the anode rod as well. I put a LED flashlight ( also from Amazon ) in the top element hole that makes the job easier.

 

[Twowaxhack]

Turn the power off and use a water heater element wrench to attempt to tighten the lower element just a little.

This can quiet them down some. High density water heater elements can “ sing “ when heating and this is normal. It’s actually a vibration. Tightening then slightly CAN change the vibration and quiet them sometimes.

Also mineral build up can also cause noises like popping or sizzling.

Personally I would ignore if I could.

 

[Aztarac]

Thanks for the responses everyone - I really appreciate it.

@Twowaxhack - I did read about the element "sing" and did try to tighten the element. It was already pretty tight and moved a little, but I didn't want to bear down and crack it. Unfortunately it didn't help. I suppose to really reposition the element I would need to remove it. Since I'd have to drain the tank to do that, I might as well just replace it with a new one. I'd love to ignore it, but my OCD has kicked in and now that I know it's making noise I can't forget about it.

I'll get new elements ordered and report back.