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1 or 2 hot water heaters?

SimonThompson's picture

having a debate with my plumber/hvac guy.

i am building a 3500sqft house and was thinking of using an 80gal steibel eltron hybrid unit for dhw,

i know people who have them and love them.

he said stebel what? thats a bad idea, and insisted the only way to go is to instal 2 ao smith 60gal hybrid units for the same price.

has anyone done this? not sure if two is always better.

any advice/input would be great!

thanks simon

"...not sure if two is always (post #209306, reply #1 of 3)

"...not sure if two is always better."

Well that's what makes building so interesting, NOTHING is ALWAYS better.

People, and I would go so far as to say "tradespeople" except the only reason I would say that is because that's who I generally get into these disagreements with due to my line of work (as a tradesman myself) often have a certain way of doing things, a certain way of approaching this very question.

But regarding the question of a single DHW source vrs multiple units to serve the same house, I think a lot depends on how spread out the baths/kitchen/laundry areas are.  When you open the hot valve, you want hot water there as soon as possible, and you don't want to heat then let water cool in long supply lines until you open  that valve again, wait for hot water to chase out the cold, only to have another batch of already hot water go cold awaiting the next time you open that valve.

Obviously, right?  Thus the concept of "point of use", or even tankless DHW units.

So as a rule, I'd say this - if you have that 3500sq' spread out over a single story, I'd consider multiple, smaller HW heaters distributed appropriately for short runs.

If that same 3500sq' is stacked 4 floors tall, it might be smarter to use a larger single HW heater as centrally located as possible.

Again, obviously, right?

I have the same opinion  about centralized vrs zone heating.  There just aren't many times when I think a single source for heating the house makes as much sense to me as the ability to heat various rooms/areas to varying comfort levels. 

But it continues to amaze me every time I bring it up to a potential subcontractor and their first reaction is resistance.  I think a lot of people are thinking about what's EASIEST for them, or MOST PROFITABLE, or maybe even thinking more about the weekend ahead than what the BEST solution is (for any given problem).

People use hot water not (post #209306, reply #2 of 3)

People use hot water not houses.  Your square footage is meaningless in the equation.  A 3500 sq ft house for empty nesters who take showers and an occasional bath will demand less hot water than a 1000 sq ft home with 5 teenage girls that all take baths to shave their legs and then follow that up with a shower.  The occupants and their personal habits are the variables that need to be know.


How many people?  Do they all take baths/showers everyday at the same time of the day and or same time span such as morning or evening?  Does the designated laundry person insist hot water is the only way to wash clothes and insist on doing laundry at the same time people are bathing or do they use primarily cold water and wash laundry when no one else is using hot water.  Do you run the dishwasher at the same time as people as showering?  Do you plan on restricted flow shower heads or are you going to install a rain forest shower with 52 heads to pummel your most intimate places?  Are you putting in a mini swimming pool and will you actually use it beyond the week you move in?  How stubborn and inconsiderate are the people who will live there?

My personal home operates well but not perfectly on a 60 gallon natural gas traditional tank system.....Thats with 8 people five of them female.  5 teenagers.  Almost all take baths at night with the parents in the morning.  Our washer runs every day mostly at night at the same time baths are being taken and our dishwasher runs at the same time as well.  It wouldn't work at all if everyone insisted on taking a bath at the same time or they all insisted on filling the tub up until it hits the overflow. 

Know the people (and be honest about it) and it will go a long way to knowing what you need to install.  For some people, running out of hot water is the only way they know when they should be done so installing a point of use system will solve the problem of running out of hot water but aggrevate the issue of someone setting up shop in the bathroom for hours.

Respect the Tradesman (post #209306, reply #3 of 3)

I have the greatest respect for tradesmen, and their advice ought to be ignored with great hesitation. They know what works, what they need, and how to make it happen. That said ....

We're all creatures of habit. Plumbing houses are limited in the brands they carry, and that's usally what is pproven to work well in your area.

Case in point: In Reno my plumber swore by Bradford-White water heaters. This brand is not readily available in the Missouri bootheel area, and the houses here carry AO Smith. They're both fine products, and it's not worth making a fuss over it.

A contrasting case: A university insisted on the specified HVAC unit. I do not know why they were set on that product - it did not match any other equipment they had - but that's what they wanted. Bringing in a factory tech to certify and maintain the unit will forever involve long waits, airfare, and hotel rooms. The unit operates in a significantly different manner than the brands available locally, so local servicemen are at  disadvantage. IMO, the customer et his academics get in the way.

I suggest you aproach other plumbers, and see what they say. If they echo what your usual guy says, it's worth reconsidering your plans.