120v water heater questions

[Sbas]

Hi guys, I live in a small house with a 50 amp breaker. My breaker box has a two pole 20 amp (40 amps total) for my 30 gallon electric water heater I was planning to use.


Being in a small space, I have been thinking about exchanging it and using and electric tankless water heater instead.


Because I only have 50 amps, one of the only tankless water heaters that will work is the ECO8. It’s 8 Kw and requires a 40 amp breaker. It shows more info on it if you click on the link.


I have a few questions on whether or not I should make the change.

1) Will a 2 pole 20 amp breaker be ok for this? If not, is it any easy fix for an electrician to change to single 40 amp?

2) Besides taking up less space and heating on demand, are there any other pros of tankless? Are they easier to install or less prone to leaking (both important reasons for me)?

3) I do not have anywhere where I can run a drain hose in the event of a leak. Would it be ok just to have a drain hose ran in a bucket? Leaks are usually just drips right so wouldn’t fill up that fast?

4) I am only concerned about a 5-10 minute hot shower. I live in Fallbrook California where I believe the city water is quite warm (charts online show san Diego county is one of the warmest in the county). Do you guys think this water heater will be sufficient for that? And is there any online sources to find out the average water temperature where I live?

Thank you so much for your help!

 

[Jadnashua]

A two-pole 20A breaker does not equal 40A when dealing with 240vac...you get 20A going out on one wire, and 20A returning. Power = volts * amps...so because you have 240vac, you get double the power. If you plug in a 120vac device on a 20A circuit, you'd get half of the power. To get 40A, you'd have to have 40A going in one and back on the other.

You CANNOT plug that electric tankless into your 20A, 240vac circuit. The first time it tried to turn on, it would trip the breaker and never work. With your existing power panel, forget a tankless that needs to make hot water as used. A tank could take all day to reheat the water you stored up in it so you could take your shower (it wouldn't need that long, but you get my point - I hope!). Most WH want more than 20A, but there are some you can buy that will work with that low power but they will have a fairly slow recovery rate.

 

[Sponsor]

 

[Dana]

An electric tankless would a pretty lousy solution at even if you had a 100A 240AC service.

The average incoming water temp in your area would be about 70F, perhaps 60-65F during the coldest weeks of the year.

A 40F rise (65F in, 105F at the shower head) at a low-flow 2 gpm is 40,000 BTU/hr, or about 11.7 kw. That's almost 50A of 240VAC, just for the shower. (At 120V it would take 100A.) Any additional draws would bump it even higher. The smallest "reasonable" tankless solution would e on the order 20kw.

An intermittent heavy load like that is really abusive of the grid infrastructure, which adds to the fixed costs of everybody's residential power bill. In some places they are experimenting with residential rate structures with a "demand charge", usually a flat charge per kilowatt of the largest power use during any 15 minute period during the billing period, independent of the energy use to cover infrastructure costs. At $8/kw an 8 minute 12 kw shower adds 6kw to the background load, adding $48 to the power bill. As more behind the meter solar goes onto the grid proposals like this are coming up in rate cases at increasing frequency, which would make a tankless water heater a real liability if t increases your demand charge from $20-25/month to $50/month.