Tankless water heater educate me!?!?!?

[338sniper]

I have an all electric home. With 3 kids and my wife and I sometimes hot water is no longer an option when I go to shower at night. I am considering an electric tankless water heater. Can someone educate me in how to determine the size (kW) I need and if it's worth doing. I do HVAC for a living so I would guess I could install it myself.

here is what I was looking at...
i have 2 bathrooms, dishwasher, and washing machine.

Stiebel Eltron Tempra 36 Plus 36.0 kW Whole House Tankless Electric Water Heater at Menards

 

[PeaShooter]

you need to figure out what the maximum flow through the heater will be, along with what water temperature rise is desired. Start with your incoming water temp, usually 45-55deg, figure out where you want to be in terms of output temp. Figure out how many fixtures you want to keep hot water at the same time and calculate their flow rates (low flow showers 2gal/min, sinks 2gal/min, tubs ?). Look at the sizing curve on the technical details from the website. Follow the curve for your model until it intersects with the desired flow-rate and then determine if it will have sufficient temperature rise capacity at that flow for your application and adjust sizing accordingly.

BTW, I am not a plumber, just an electrical engineer who likes to do-it-myself, also. YMMV

 

[IndyGunworks]

Only major issue i have had with them (we have them at the fire stations) is if you like to use the sink at a slow flow with warm water it will not be enough to get the hot water to fire... you can go from freezing to super hot real quick. the solution is just to increase the flow of the stream but with the way i cook and do the dishes that leads to a mess and alot of wasted water.... aside from that i like them, although i doubt you will really see a whole lot of savings on the bottom line. they WILL fix your current problem but make sure you are not created another problem by fixing the first one.

 

[Lectric102002]

I have an all electric home. With 3 kids and my wife and I sometimes hot water is no longer an option when I go to shower at night. I am considering an electric tankless water heater. Can someone educate me in how to determine the size (kW) I need and if it's worth doing. I do HVAC for a living so I would guess I could install it myself.

here is what I was looking at...
i have 2 bathrooms, dishwasher, and washing machine.

Stiebel Eltron Tempra 36 Plus 36.0 kW Whole House Tankless Electric Water Heater at Menards

36 kW is 156 amps at 230 volts, single phase. Do you have that much available service in your house ? If you are total electric and using a heat pump with resistance heat as emergency heat, you had better have at least a 400 amp service.

 

[Mr Evilwrench]

A little hot water discipline will go a long way; set your dishwasher up and don't start it until you're leaving in the morning, do the laundry off shower time. Maybe you need a bit bigger heater, I put a 40 in place of the 30 that came with the house. We don't run out with 4 people.

 

[sig-guy]

You might want to take a look at Seisco. They have a RA-28/RA32 whole house water heater. The 28's minimum is 150A service, while the 32's minimum is 200A service.

They take standard elements and are variable under use (think modulating furnace).

They seem to be a reliable company that has a top-end product. There's a supplier selling them on e-bay cheaper than you can purchase them as a contractor. Seisco will still do the support and warranty for such products. You just want to check the serial, as that will effect the warranty expiration date.

 

[Kernal1984]

Electric tankless units suck in my opinion, my uncle installed one for his wifes in house salon and the temp fluctuates a lot and the electric use is obscene.
Ones I have seen installed require 2 60 amp breakers and a 70-80 amp breaker which is more juice than a dryer, electric range, A/C unit, and an electric furnace(of average capacity) combined.

 

[churchmouse]

A little hot water discipline will go a long way; set your dishwasher up and don't start it until you're leaving in the morning, do the laundry off shower time. Maybe you need a bit bigger heater, I put a 40 in place of the 30 that came with the house. We don't run out with 4 people.

Totally this^^^^^^^^^^^^^^^^^^^^

also, check the elements in you heater for amp draw. If you are a tech as you state this is simple easy-peasey. You could be limed up in the bottm. If so, clean out the lime and change the anode rod.

 

[mrjarrell]

OP, you may want to do a search for "tankless" here. There are a number of threads on tankless water heaters and you'll get even more info.

 

[Arm America]

Is natural gas available at your location?

The gas units work great and only require a 110volt outlet with little amp draw.
Depending on you location, most gas utilities will bring service up to the house.
(provided your in a neighbor hood with gas)
Just a thought.

 

[Mr. Habib]

I have a gas tankless unit and really like it. When I was having it installed, I ask my plumber about the electric units. He told me that he had installed one and would never do it again.
The installation cost was ridiculous since it required three 60A, 240V circuits, and it was not reliable at all. He had made several service calls for it already in just the first year. IMO,
go with gas if you can or don't go tankless.

 

[x10]

In our area the lime and calcium in the water even after a water softener (when salt is low) cakes up the heaters and people end up choking up their system.

Here's my 2Cents, I've seen many people go from Tankless to standard but never seen someone go the other way.

 

[JettaKnight]

Is natural gas available at your location?

The gas units work great and only require a 110volt outlet with little amp draw.
Depending on you location, most gas utilities will bring service up to the house.
(provided your in a neighbor hood with gas)
Just a thought.

I thought about switching to a tankless gas, but the requirement for a larger gas pipe, stainless steel exhaust, etc. was too much. They may use less energy (depends on the user), but the impulse is way more.

Plus, with tankless there's no way to run it during off-peak hours. Not a big deal in the Midwest, but other energy conscious places...

 

[sig-guy]

stainless steel exhaust.

There's units that vent with PVC.

 

[SMiller]

I researched and wanted one and everything I read said to run from them and use a water heater, must be a reason everyone is not j mping on them...

 

[slimplmbr]

I'm not a fan of the tank less water heaters myself, gas or electric. Never really bought into the hype. The startup cost of having to buy one and then if you ever have problems the repair cost is more. Newer higher efficiency gas heaters are cheaper and just as cheap, if not cheaper to run. I've had people want me to install one and I recommend a high efficiency tank every time. That's my opinion and to each their own.

 

[shibumiseeker]

I'm not a fan of the tank less water heaters myself, gas or electric. Never really bought into the hype. The startup cost of having to buy one and then if you ever have problems the repair cost is more.

That's because it's a tankless job!




(badump bum!)

I'll be here all week folks...

 

[rkwhyte2]

You might want to take a look at Seisco. They have a RA-28/RA32 whole house water heater. The 28's minimum is 150A service, while the 32's minimum is 200A service.

They take standard elements and are variable under use (think modulating furnace).

They seem to be a reliable company that has a top-end product. There's a supplier selling them on e-bay cheaper than you can purchase them as a contractor. Seisco will still do the support and warranty for such products. You just want to check the serial, as that will effect the warranty expiration date.

^^^^+1 for the Seisco. We have the RA-28 in our house ( 3 bathrooms, washer, dishwasher). It came with the house when new. It's been over 10 years and the only thing I've done is change a few elements. It is nice to take as long a shower as you like but I'd swear I can hear the meter spinning when that happens. It will need quite a bit of power. If I lived in an area where I could get gas I think I would go with the gas option but overall we have been very happy.