ISO Recommendations RHEEM ELECTRIC Tankless Hot Water Heater

NBF

Member
Good morning all. For those snowed in I'd like to ask a question concerning RHEEM ELECTRIC Tankless Hot Water Heaters. I capitalized 'electric' as it seems no one wants to install an electric tankless water heater. I purchased the unit through Home Depot (HD) and even their contractors declined to install it. Has anyone successfully had one installed in their home? So, my RHEEM has been sitting in an unopened box since September 2018 as I cannot find anyone to set it up.

Can anyone provide me with their experience of having it installed? Or, not installed (LOL)...

Thank you in advance.

NBF
 

PeoplesElbow

Well-Known Member
Can't help you on who might install it, but the biggest question is do you have the required electric service to operate it? A whole house electric on demand heater would require some pretty stout capacity.
 

Chris0nllyn

Well-Known Member
Have you confirmed your service size and panelboard space yet? That thing needs 3-40A/2 pole breakers (Or 4-40A breakers if you got the 36kW model).
 

PeoplesElbow

Well-Known Member
Installing it shouldn't be that big of a deal IF you have the required electric service.

If not, then you need to find an electrician, maybe contact SMECO to see if you have the service from them to cover it. It is quite possible you will need to upgrade your outside lines, then we are talking big money, if SMECO will even do it to a residence.
 

NBF

Member
OMG. Never, ever thought about the good points you all brought out. Man, if I had ever thought that I might need to upgrade outside lines I would've never purchased it. Would be great if SMECO had a program for us consumers in helping us to upgrade to more efficient water heaters. I guess I'll have to call them up now. In the meanwhile, pile on with the comments. I hope this helps others that are thinking about "upgrading" their water heaters. I know I am tired of waiting for hot water when I need it.

NBF
 

Chris0nllyn

Well-Known Member
OMG. Never, ever thought about the good points you all brought out. Man, if I had ever thought that I might need to upgrade outside lines I would've never purchased it. Would be great if SMECO had a program for us consumers in helping us to upgrade to more efficient water heaters. I guess I'll have to call them up now. In the meanwhile, pile on with the comments. I hope this helps others that are thinking about "upgrading" their water heaters. I know I am tired of waiting for hot water when I need it.

NBF
You likely have a 150 or 200A service. The service should be okay to run it. The issue is running it with your electric stove and electric dryer or running it with your emergency heat (heat pump) on may trip the main breaker.

What model did you get?

Let's assume it's the 26kW model. That's 108A @ 240V. An electric oven with 2 burners and the oven on is about 9400W or about 40A @ 240V. So, with JUST those two things running you're at 148A. A circuit breaker will trip at apbout 80% of its rating so if you have a 150A main breaker, it'll trip around 120A. Long story long, you may have to be careful with what you're running at the same time. Obviously the example above is sort of worst case, but something to keep in mind.
 

itsbob

I bowl overhand
Have you considered Gas? Seems in your case gas would be the much simpler and much cheaper install.. and in the long run much more efficient after install.

We had Taylor gas install ours (they did the gas, I did the exhaust and the electric).

Simple and straight forward install even if you don't have a tank now.

We've had a Noritz for about 12 years now. NO issues.
 

LightRoasted

If I may ...
If I may ...

Good morning all. For those snowed in I'd like to ask a question concerning RHEEM ELECTRIC Tankless Hot Water Heaters. I capitalized 'electric' as it seems no one wants to install an electric tankless water heater. I purchased the unit through Home Depot (HD) and even their contractors declined to install it. Has anyone successfully had one installed in their home? So, my RHEEM has been sitting in an unopened box since September 2018 as I cannot find anyone to set it up. Can anyone provide me with their experience of having it installed? Or, not installed (LOL)... Thank you in advance. NBF
We ... need ... the ... model ... of ... the ... heater. Without the proper information we all are shooting in the dark. There may be a very good reason why no one wants to install it. Heck, you may be able to do it yourself, but we need information. Like did you call a plumber or an electrician to install? Because you will need both if you have someone else do it rather than yourself.
 

PeoplesElbow

Well-Known Member
OMG. Never, ever thought about the good points you all brought out. Man, if I had ever thought that I might need to upgrade outside lines I would've never purchased it. Would be great if SMECO had a program for us consumers in helping us to upgrade to more efficient water heaters. I guess I'll have to call them up now. In the meanwhile, pile on with the comments. I hope this helps others that are thinking about "upgrading" their water heaters. I know I am tired of waiting for hot water when I need it.

NBF
I've always viewed the on demand electric water heaters only as good for a single sink etc and not a whole house due to the amount of electric required for one. They are great for something like a garage bathroom that you don't need hot water for very often.
 

NBF

Member
SPECS:

RHEEM PERFORMANCE 36KW SELF-MODULATING 6GPM ELECTRIC TANKLESS WATER

RHEEM
RETEX-36

* This water heater provides instant and continuous hot water for up to 5 showers and 2 faucets (based on geographic location)

* Rheem Performance Tankless Electric Water Heaters help reduce energy usage, save on energy costs, and are small so they will be a perfect match for installations under a cabinet or sink in your home, office, boat or RV

* 5-year heat exchanger and 1-year parts limited warranty

* Energy and cost savings: heats water only when it is needed for savings of up to 50% on water heating costs when used in a point-of-use application or 34% when used as a whole-home solution

*Instant, continuous hot water: instantly provides ample hot water for up to 5 showers and 2 faucets (review selection guide below to confirm this water heater will provide the hot water needed based on your geographic location)

* Up to 8.8 Gallons Per Minute

*Space savings: small, compact design fits perfectly in tight places like under cabinets and sinks

* Energy cost savings and a 5-year heat exchanger and 1-year parts limited warranty

*Easy to adjust: electronic temperature control adjustable in 1° increments from 80°-140°F with easy-to-read display (Celsius and Fahrenheit compatible)

* Easy installation: compatible with 3/4 in. water connectors for flex hose installation and no venting or T and P valve required for Easy installation (professional installation recommended)

* Easy to maintain: durable, easy-to-replace heating elements

* A reliable hot water solution from Rheem, the global leader in water heating
 
Last edited:

DoWhat

Sexy Stud
PREMO Member
I've always viewed the on demand electric water heaters only as good for a single sink etc and not a whole house due to the amount of electric required for one. They are great for something like a garage bathroom that you don't need hot water for very often.
We have a propane one and love it.
Thank you Taylor Gas.
 

Chris0nllyn

Well-Known Member
SPECS:

RHEEM PERFORMANCE 36KW SELF-MODULATING 6GPM ELECTRIC TANKLESS WATER

RHEEM
RETEX-36

* This water heater provides instant and continuous hot water for up to 5 showers and 2 faucets (based on geographic location)

* Rheem Performance Tankless Electric Water Heaters help reduce energy usage, save on energy costs, and are small so they will be a perfect match for installations under a cabinet or sink in your home, office, boat or RV

* 5-year heat exchanger and 1-year parts limited warranty

* Energy and cost savings: heats water only when it is needed for savings of up to 50% on water heating costs when used in a point-of-use application or 34% when used as a whole-home solution

*Instant, continuous hot water: instantly provides ample hot water for up to 5 showers and 2 faucets (review selection guide below to confirm this water heater will provide the hot water needed based on your geographic location)

* Up to 8.8 Gallons Per Minute

*Space savings: small, compact design fits perfectly in tight places like under cabinets and sinks

* Energy cost savings and a 5-year heat exchanger and 1-year parts limited warranty

*Easy to adjust: electronic temperature control adjustable in 1° increments from 80°-140°F with easy-to-read display (Celsius and Fahrenheit compatible)

* Easy installation: compatible with 3/4 in. water connectors for flex hose installation and no venting or T and P valve required for Easy installation (professional installation recommended)

* Easy to maintain: durable, easy-to-replace heating elements

* A reliable hot water solution from Rheem, the global leader in water heating
Ah, the 36kW model.

Your 3-40A breakers just went to 4. 150 amps to power the heater at max load.

I'd go with gas if you really want tankless.
 

spr1975wshs

Mostly settled in...
PREMO Member
I worked in the Plumbing Department at Lowe's for 4 years, selling water heaters was part of the job.

I researched tankless water heaters, to have better answers for customers.

Most true whole house units need 300 Amp service to the house as they can take up to 3 60 Amp breakers.

Most state environmental departments where you get freezing temps in the winter do not recommend tankless electric, save as a point of use, because of the difference in ground water temperature versus temperature rise to comfort level (usually 125F).

Last time I priced out a retro-fit to a gas model, price was in the $2500 - $2700 range, including heater, exhaust, intake, plumbing fittings, all hardware and labor.

They are most cost effective when you can make it part of new home construction or a major remodel/renovation.

We have a Noritz Natural Gas tankless that was installed when the house was built in 2012.
It works well, time lag for hot water in the 2nd floor bath or laundry is no worse than drawing water from a tanked heater.

You save because fuel use is on demand.

If you decide on getting an LPG tankless, keep this in mind for a ballpark on fuel use.
Think of a regular water heater like a burner on a gas stove in the kitchen.
Think of the tankless as a high output turkey fryer burner.
 
Last edited:

Blister

Member
You likely have a 150 or 200A service. The service should be okay to run it. The issue is running it with your electric stove and electric dryer or running it with your emergency heat (heat pump) on may trip the main breaker.

What model did you get?

Let's assume it's the 26kW model. That's 108A @ 240V. An electric oven with 2 burners and the oven on is about 9400W or about 40A @ 240V. So, with JUST those two things running you're at 148A. A circuit breaker will trip at apbout 80% of its rating so if you have a 150A main breaker, it'll trip around 120A. Long story long, you may have to be careful with what you're running at the same time. Obviously the example above is sort of worst case, but something to keep in mind.
You are right that their service probably won't be sufficient to run a 36kw load. However you are way off on molded case circuit breaker trip current. A properly functioning circuit breaker will carry 100% of rated current almost indefinitely. A typical home panel Square D QO 200A breaker is designed to trip somewhere between 9 & 50 seconds at 200% rated (400 Amps). They are not a high precision device.
 

LightRoasted

If I may ...
If I may ...

You probably could get away with using your most likely current service of 200 amps. This thing is rated at 150 amps. 75% of your 200 amp service. I'd up your service to 300 amps. But do you have space in your breaker box for four 40amp breakers? Plus you'll have to use 8 awg wire. You might have to schedule showers and whatnot so other high power load devises are not being used at the same time. Depending on how many bathrooms, sinks etc you have using hot water, and the length of run for the pipes, and if they are insulated. Looking at the ROI, if you have to go to 300 amp service, it will be a long time before you realize any savings. And with 200 amps, it will still be a long time before you realize any savings. From installation costs etc.
 

Chris0nllyn

Well-Known Member
You are right that their service probably won't be sufficient to run a 36kw load. However you are way off on molded case circuit breaker trip current. A properly functioning circuit breaker will carry 100% of rated current almost indefinitely. A typical home panel Square D QO 200A breaker is designed to trip somewhere between 9 & 50 seconds at 200% rated (400 Amps). They are not a high precision device.
I misspoke when I said "trip at 80%" (though I've seen some old Square D breakers trip at 80%).

Only 100% rated molded case breakers can carry 100% of a "continous" load. 100% breakers are marked as such. Standard breakers are rated at 80% to limit nuisance tripping due to the breakers being grouped in an enclosed panel (heat).



Hence why Article 210 of the NEC says:
“Where a branch circuit supplies continuous loads or any combination of continuous and non-continuous loads, the rating of the overcurrent device shall not be less than the non-continuous load plus 125 percent of the continuous load.”

“Exception: Where the assembly, including the overcurrent devices protecting the branch circuit(s), is listed for operation at 100 percent of its rating, the ampere rating of the overcurrent device shall be permitted to be not less than the sum of the continuous load plus the non-continuous load.”
If this heater will run for over 3 hours, the NEC considers it a continuous load.
 
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