Lets talk about water heaters!

Fabrik8

Fabrik8

Overcomplicator
Joined
May 27, 2015
Location
Huntersville
Need some good advice.

My short/lowboy crawlspace water heater has a bad lower element I suspect.

Me and my multimeter need to venture into the crawlspace and troubleshoot, but I’m just going to assume the worst and figure it likely needs replacing, like everything else in the house since we bought it. It probably choked from too much sediment and decided life was too difficult.

Current unit is electric, and is in a strange spot. Could ideally be moved closer to the things that actually use hot water, so installing a new one probably won’t be a direct drop-in replacement if it gets moved. Plus, the entire house is gray polybutylene water lines, which will be incrementally replaced as we remodel the house.


So, let's assume I need a replacement:

Debating between a tankless heater, or another storage heater.

Storage heater will likely be something in the AO Smith ProLine …er… line (Proline/Master/XE), and a tankless would be Takagi/Noritz/Rinnai most likely.

Storage heater would remain electric, with minor re-plumbing to move it closer to the baths/kitchen. It would move closer to the breaker box, so existing wiring would be re-used/re-routed. Just need to figure how to make a new pedestal in an encapsulated crawlspace.

Tankless would go on the outside of the house. Gas line is available, and would need to be extended from the kitchen area so there is some cost there. Also the cost of some minor crawlspace plumbing reroute to T into the hot/cold trunk at a different spot. It would be very well located at that point, and very close to both bathrooms and much closer to the kitchen.

I understand (from my trusted internet sources of level-headed green building information) that the tankless don’t usually deliver the promised cost payoff from energy savings, and that the cost payoff (versus a storage unit) is measured in decades depending on climate zone. This means that I wouldn’t be doing it to save money, because the up-front purchase and installation costs are obviously higher as well. So there needs to benefits to hot water delivery, etc.

Keep in mind that I wouldn’t be replacing the cheap storage unit with another cheap storage unit, and a good quality storage unit will be decently expensive as well.



Anyone want to weigh in on real world experiences with tankless units, and whether they are actually a good functional replacement for a storage unit? I'm willing to spend the extra money if it makes sense.
 
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I have a tank-less Rinnai, it works great. I have no idea if it would really save any money but I never run out of hot water. I have two hot\cold outside hose spigots, works great for washing cars on a cold day.

There are a few other threads on this subject.

Tankless Water Heater for Home???
 
@CasterTroy let's fight about it! And while we're at it, does NCMC allow you to vent a gas WH out under a 2nd story deck below 2nd story windows and doors? I'm thinking not, but it's a convenient time to ask the question.

Oh, on another related note, I still haven't replaced our WH, but I'm entertaining the idea of doing an old-school gravity loop on the hot side in lieu of a pump. The water heater is at the bottom of the system, so it should work fine in theory.
 
shawn said:
@CasterTroy let's fight about it! And while we're at it, does NCMC allow you to vent a gas WH out under a 2nd story deck below 2nd story windows and doors? I'm thinking not, but it's a convenient time to ask the question.

Oh, on another related note, I still haven't replaced our WH, but I'm entertaining the idea of doing an old-school gravity loop on the hot side in lieu of a pump. The water heater is at the bottom of the system, so it should work fine in theory.
Click to expand...

I didn't finish the other thread yet, is there a grudge match going on here?


I replied to that other thread when it was fresh, and I didn't even remember it existed.
 
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My house had a conventional electric 50 gal water heater. As most water heaters do, it failed from the inside out. Ruined all my carpet when it leaked out, and then I went and put hardwood floors down in the house.

To ensure that I wouldn't potentially have another 50+ gallons of stored water ready to leak out into my home, I opted for an Eemax 18kW electric tankless unit.

Shop Eemax 240-Volt 18-kW 7-GPM Tankless Electric Water Heater at Lowes.com

I ran two runs of 8/2 wire from my panel (its wired with 2 hots and a ground, no neutral), landing on (2) 40A double pole breakers. It's a beast when it's heating water, but also pulls nothing when not being used, unlike a conventional storage water heater.

My house gets its water from a spring box in Boone (very cold water), and I can achieve an instant 80 degree rise over the incoming water temp, with both a shower and hot sink tap on. It's pretty impressive. Endless hot water!
 
336wheeler said:
My house had a conventional electric 50 gal water heater. As most water heaters do, it failed from the inside out. Ruined all my carpet when it leaked out, and then I went and put hardwood floors down in the house.

To ensure that I wouldn't potentially have another 50+ gallons of stored water ready to leak out into my home, I opted for an Eemax 18kW electric tankless unit.

Shop Eemax 240-Volt 18-kW 7-GPM Tankless Electric Water Heater at Lowes.com

I ran two runs of 8/2 wire from my panel (its wired with 2 hots and a ground, no neutral), landing on (2) 40A double pole breakers. It's a beast when it's heating water, but also pulls nothing when not being used, unlike a conventional storage water heater.

My house gets its water from a spring box in Boone (very cold water), and I can achieve an instant 80 degree rise over the incoming water temp, with both a shower and hot sink tap on. It's pretty impressive. Endless hot water!
Click to expand...

I have thought about this.... The real question is: Does it consume less energy overall vs a storage unit? I have a 40 gal now, and will likely step upto a 60 or 80 if i do another storage unit. Not so much worried about payback vs monthly costs.
 
You can't vent below "operable windows"

Deck would be "combustibles" and you have to maintain Min 18" clearance side to side and nothing above, but the special note of "As determined by code official" means you get to hear the inspectors opinion.



Fabrik8 said:
I didn't finish the other thread yet, is there a grudge match going on here?
Click to expand...

It's been my experience that instantaneous heaters last about as long as a contractors warranty (12-18 months) depending on the hardness of water. Forsyth county upped it's scale to line it's decrepit old underground piping to aid in winter ruptures, so we have to treat most water in commercial applications because the boilers will scale and corrode in a matter of years as opposed to decades.

Most instantaneous heaters need drained, and descaled every year around here, or it starts taking it's toll on the capacity. Within a few years an instantaneous heater can lose up to 30% of it's heating due to scale. However....treat the exchanger and keep it clean and you MAY have a good experience.

336wheeler said:
My house gets its water from a spring box in Boone
Click to expand...


You may likely never see issue, as spring water (typically) has very low scaling potential (YRMV)

Water source is everything.

Whatever replacement you choose, instead of moving the source of your hot water........if it were me, I'd add a fractional hp circ pump and a 1/2" pex line from the furthest point back to the CW supply on the water heater. Install a check valve on the incoming water side, and wire the circ pump for continual use day/night. I wouldn't even bother with a time clock, as I've run the cost analysis on a 1/20hp circ pump and it's almost 12 whole dollars to run a pump of that size all year. Mere pennies to have how water instantly at any fixture of your home.

Given your situation though I'd go back electric with something that's good but not better/best as you will likely be doing this again, as lowboys in crawlspaces do not usually have a stellar life span (nothing in crawlspaces lasts long)
 
CasterTroy said:
You can't vent below "operable windows"

Deck would be "combustibles" and you have to maintain Min 18" clearance side to side and nothing above, but the special note of "As determined by code official" means you get to hear the inspectors opinion.
Click to expand...
Dammit.
 
A little over 3 yrs with a Rinnai tankless in our new house. We have been very happy with it. The only negative is that it takes a little while before you get hot water. I have not found that to be a problem though. I just turn on the shower before I start getting undressed/go to the bathroom etc. By the time I am ready to get in, the water is hot.
 
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CasterTroy said:
You can't vent below "operable windows"

Deck would be "combustibles" and you have to maintain Min 18" clearance side to side and nothing above, but the special note of "As determined by code official" means you get to hear the inspectors opinion.
Click to expand...

There's a 3 foot radius in any direction from an operable opening to a combustion vent too, isn't there (is it more than 3 feet)? I need to go find that again in the NCMC, that's the biggest thing that will impact where a tankless would mount on the outside of the house.
There's a laundry room/mudroom door that is stupidly useless and horrible quality, and might get turned into a window, or just some blank wall. There's an upstairs operable window nearby, but it's offset so won't be directly above the tankless. That window could turn into a fixed window as well, because the bathroom is blown apart for remodel and is already getting a window retrofit. Choices....


CasterTroy said:
Given your situation though I'd go back electric with something that's good but not better/best as you will likely be doing this again, as lowboys in crawlspaces do not usually have a stellar life span (nothing in crawlspaces lasts long)
Click to expand...

That was my first thought. The existing unit has spend all of its life (except for the last year-ish) in a vented crawlspace, which is why I'm expecting it to need replaced. The new unit will live a much more pampered life with a nearby dehu and a fairly constant temperature year round.

The mid line for AO Smith Proline (Proline Master) appears to be the best blend of commercial-ish parts (if you believe the marketing literature) and price. Good anodes and Inconel heater elements and all that stuff.
There's no lowboy unit in that particular range, but I'm going to measure and see if a short might fit.
The lower range ProLine is similar but with shorter warranty and a copper upper element instead of Inconel. Lowboy available in that range.

I'm still not sure how they stack against the Big Box units, but for the price and features they should be better quality. Again, marketing literature. They make a very clear point that they aren't sold in Big Box stores.



But yeah, doing a gas tankless is still an attractive option it seems.
 
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336wheeler said:
My house had a conventional electric 50 gal water heater. As most water heaters do, it failed from the inside out. Ruined all my carpet when it leaked out, and then I went and put hardwood floors down in the house.

To ensure that I wouldn't potentially have another 50+ gallons of stored water ready to leak out into my home, I opted for an Eemax 18kW electric tankless unit.

Shop Eemax 240-Volt 18-kW 7-GPM Tankless Electric Water Heater at Lowes.com

I ran two runs of 8/2 wire from my panel (its wired with 2 hots and a ground, no neutral), landing on (2) 40A double pole breakers. It's a beast when it's heating water, but also pulls nothing when not being used, unlike a conventional storage water heater.

My house gets its water from a spring box in Boone (very cold water), and I can achieve an instant 80 degree rise over the incoming water temp, with both a shower and hot sink tap on. It's pretty impressive. Endless hot water!
Click to expand...


Specs call for 75amps at 240 volts! Holy crap! I couldn't imagine what the power bill is to run that thing versus gas!
 
Fabrik8 said:
I'm still not sure how they stack against the Big Box units, but for the price and features they should be better quality. Again, marketing literature. They make a very clear point that they aren't sold in Big Box stores.
Click to expand...


Not a lot useful to add here except the following.
My dad and step-om have both been in the plumbing/mechanical supply distribution/rep business for 35 years.
In fact that's how they met :D

Step mom, who is like mom #2 25 years later, is... (some title) of the local rep firm for AO Smith. So...I know where you can buy the proline and get good pricing :D
 
Ron said:
Not a lot useful to add here except the following.
My dad and step-om have both been in the plumbing/mechanical supply distribution/rep business for 35 years.
In fact that's how they met :D

Step mom, who is like mom #2 25 years later, is... (some title) of the local rep firm for AO Smith. So...I know where you can buy the proline and get good pricing :D
Click to expand...

Very good to know. ;)
 
rockcity said:
Specs call for 75amps at 240 volts! Holy crap! I couldn't imagine what the power bill is to run that thing versus gas!
Click to expand...

Like I said, it pulls a lot when it's being used, but none while it is sitting idle (unlike a conventional water heater that keeps 50 gallons of water heated to 120-130F, all the time).

My power bills are cheap. Granted it's just 2 people using the thing... but let's do some math...

18kW-instantaneous @ 30 minutes (or 6 kWh) X twice a day.. 12 kWh/day or $1.20 per day for 2 (very hot, non-diminishing) showers. That's assuming you'll use 1 full hour of hot water every day, which you likely won't unless your wife washes clothes a lot (then you really need to be more concerned about how much it's costing to run the dryer - not the water heater).

My options were electric and propane. I considered a Rinnai propane unit, but having to futz with installing the gas vent through my roof, I just ran a couple of 8/2 runs in my attic from my load panel and called it a day. All in all I have about $600 in my electric tankless unit, compared to closer to $1000 for the big Rinnai units.

My kWh cost is approx 10 cent/kWh, while propane is more like $2.40-2.50/gallon.
 
paradisePWoffrd said:
I have thought about this.... The real question is: Does it consume less energy overall vs a storage unit? I have a 40 gal now, and will likely step upto a 60 or 80 if i do another storage unit. Not so much worried about payback vs monthly costs.
Click to expand...

The tankless unit would probably be close in operating cost to a 40 gallon, depending on how often you use hot water. The less you use it, the more it saves over a conventional storage tank. Never running out of hot water is pretty bad ass, too.
 
336wheeler said:
Like I said, it pulls a lot when it's being used, but none while it is sitting idle (unlike a conventional water heater that keeps 50 gallons of water heated to 120-130F, all the time).
Click to expand...

You do realize that conventional storage water heaters don't run all the time either, right?
 
Ron said:
You do realize that conventional storage water heaters don't run all the time either, right?
Click to expand...

Yeah sure, they only run when the water needs heating. And said heat gets lost at the rate of the tank insulation. R-8 or so without a tank wrap. I could make you a CFD TRNSYS model of that heat transfer problem if you wanted to visualize the heat being lost. :flipoff2:

My tankless WH has 0% standby loss. The flow-activation they use is actually pretty neat. It turns on at something like 0.1 GPM, very sensitive.

That, and I freed up an entire closet now for storage.
 
One other note and added expense is the gas line. We did this several years ago and have been happy. We had to switch to a 2psi gas meter and get the lines inspected again. If yo have other appliances running on gas you'll need to install new regulators. Ours is a Rheem unit. Like this. Rheem RTGH-95DVLN 9.5 GPM Indoor Direct Vent Tankless Natural Gas Water Heater - Water Heater Parts - Amazon.com
But ours is a outdoor unit. We have a window above it, but it's 6' above and follows the manufactures guideline for install. Psnc installs rinnai but I've had their guys comment on how nice the rheem is laid out. Operation cost is apples to oranges. Can't fill wife's 80gallon soaker tub with a tank unit and wash dishes and cloths and take a shower. Soaker tub nights usually end well. [emoji3] I've installed the electric units as point of use heaters. If your trying to supply multiple points with a single electric unit you'll be disappointed. Temp will fluctuate hot/cold. It's a hassle going tankless but I'm glad I did. If you install yourself. Keep the install handy whe inspector comes around. Here they've never seen anything but rinnai and need to reference your material to sign off on it.


Sent from my iPhone using Tapatalk
 
336wheeler said:
Yeah sure, they only run when the water needs heating. And said heat gets lost at the rate of the tank insulation. R-8 or so without a tank wrap. I could make you a CFD TRNSYS model of that heat transfer problem if you wanted to visualize the heat being lost. :flipoff2:

My tankless WH has 0% standby loss. The flow-activation they use is actually pretty neat. It turns on at something like 0.1 GPM, very sensitive.

That, and I freed up an entire closet now for storage.
Click to expand...

Ok...so which is greater, the energy required to heat 80 gallons of 50F water to (pick a number) 190F in a period of 20 minutes and then maintain it or....the energy required to heat 50F water to 190F in a period of 8 seconds and maintain it until shut off.

Of course heater ambient, temp setting, input temp, demand duration etc etc etc alter the curve. Ive tried like hell to justify a tankless. But you just cant make the numbers work on an electric tankless. Ive tried. Now if you want to value space and showers longer than 45 minutes (how long my daughter can go on our 80 gallon) then sure. Filling up a hot tub? Maybe. But if you re a high demand user you also have to worry about Duke reclassifying you. 35kW for a period of 10 seconds 3 times in a given month is typically enough to get you bumped up to high use/light business class rates. Then you $/kwh goes 1.72x...
 
shawn said:
Nope. Tank unit with a mixing valve.
Click to expand...

Ok I'll bite. I'm not familiar with this setup. How's it work? Have a 80 gallon tank that maintains a 190degree temp 24/7 and mixes cold water in to give you 200 gallons of 120degree water? Seems like it'd work but why heat water then cool it down when you can heat only the water you need at the time you need it. I'm sure it's probably cheaper than tankless. Could probably over insulate it to cut down on maintaining the temp the other 22hrs a day you don't need it.
 
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