My Tankless Experiment

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GrumpyPlumber

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I have yet to try an electric tankless....so far I've only heard they don't perform very well...but your first-hand account prompts me to look into it more....comes in handy in condo's or hard to vent area's.
Keep us abreast of the bill...VERY curious on that one.
 

GrumpyPlumber

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Mark,
From memory...so I might be off...shower is 2.5 gpm...lav 1.25...toilet is either 1 or 1.25 (I forget) but thats irrelevant for hot (I usually go with factor values for sizing with the .05 residential demand factor unless it's commercial)
Let's say the KS is 2.5 for sake of argument, tack that on too.
(not up to wandering through the code book to verify...feel free to correct it)
3.75 potential hot GPM per bath....but...not too often is the lav & shower on at the same time.

easiest way to look at it....a 6.9 gpm Noritz will contend with 3 showers and a KS at once -
totalling 10 gpm(worse case scenario), thats 7.5 for the showers alone.
I'd guess that would be tapping it, I have only installed one tankless that was less than a whole home (6.5 gpm or better)
It was the Rheem 4.2 gpm...customer had a Roman tub spout with 3/4" feeds and it slowed down drastically when the hot was turned on, she'd opted for the less expensive model, though I suggested otherwise.
I'd gotten a call from her later that day...we'd initially checked the temp at the KS, and the flow wasn't bad, but later on when she went to pour a bath she noticed it.
I went back and looked at the screen, drained it out from both sides, checked the aerator...no sediment...called the MFG and they verified that it has a flow restriction device to ensure the temp stays where it's set when the demand can't keep up.
I have done one Bosch (Lowes carries them), the customer had already gotten it and I verified that it was state code approved before I installed.
It had a tendancy to jump in temperature wildy as it warmed up..Tankles do that a little, but this one took at least 30-45 seconds to level off.
 

Master Plumber Mark

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electric tankless heaters

Their is absoutely no demand for them here in
the mid-west...too hard a water content

I have not heard anything good about them....

I have heard stories about having to install a larger breaker panel......$$$

I have heard that they lime up really fast compaired to
the gas units too so you MUST have a water conditioner.
$$$..


perhaps it will work ok for a few years......

you are already in it pretty deep ....

now its really all just a question of pride as to how far
you are willing to go..... ....


 

Master Plumber Mark

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tankless----go big or stay home....???

The general feeling I am getting is it is better
to err on the side of overkill with a tankless heater

than to be left standing in a cold shower with
your monkey in your hand...
waiting for the hot water to arrive...

it that about correct???


If I ever sell them I certainly will oversize a system rather than undersize one.....

I dont need the greif.dealing with dis-satisfied customers....and if they dont like it,
they can calll somesone else....I doubt they can beat
my price anyway....even with the smaller unit....

I Got a call into my Takagi rep and I am gonna try
to haggle with them for about a 9-12 gallon
per minute unit.....


it really does not cost that much more to go big
and its basically an issue of wether you will lose efficinecy
with the bigger unit
but gain dependibality.....
 
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GrumpyPlumber

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master plumber mark said:
The general feeling I am getting is it is better
to err on the side of overkill with a tankless heater

than to be left standing in a cold shower with
your monkey in your hand...
waiting for the hot water to arrive...

it that about correct???


If I ever sell them I certainly will oversize a system rather than undersize one.....

I dont need the greif.dealing with dis-satisfied customers....and if they dont like it,
they can calll somesone else....I doubt they can beat
my price anyway....even with the smaller unit....

I Got a call into my Takagi rep and I am gonna try
to haggle with them for about a 9-12 gallon
per minute unit.....


it really does not cost that much more to go big
and its basically an issue of wether you will lose efficinecy
with the bigger unit
but gain dependibality.....
My thoughts on the overkill...YES, about $300 price difference from the "single bath" model to the "whole home"...I won't risk a bad name over catering to short-term budget..I tell them up front.
I'm hearing you LOUD n' clear on the electrics....not up to being a guinea pig here.
I'm "JONSING" to see how your experiment goes...big time.
 

Jadnashua

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The biggest factor in the midwest, especially in the northern parts, is the winter incoming water temperature. The things are usually designed for a 70-degree temperature rise at a certain flow. Change the input temperature, it can't raise it to the level it was in the summer at the same flow. Lower the flow, and it can be too hot. As a result, they usually spec them to be installed with a tempering valve to keep from scalding you. Some of them have a modulating heat output to help prevent that, but they are generally not stepless from what I've seen, so at some flows, it could be jumping between one level and another, causing the temperature to fluctuate.

Everyone seems so concerned about standby losses...these are important, but a good tank in a temperate room keeps the delta T losses down when it has good insulation.
 

GrumpyPlumber

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jadnashua said:
Everyone seems so concerned about standby losses...these are important, but a good tank in a temperate room keeps the delta T losses down when it has good insulation.

That alone wouldn't sell them...the avg water htr is 60-65% efficient...the tankless's get upwards of 84%...when running.
 

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Cass said:
The very best Model would be a between 1977-1980 and the size would be contunious 36-24-36 :D

With no mother-in-law.

I just now caught that...I really, really like those figures...thats an EXCELLENT model.
 

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I went with an indirect, since I had the boiler anyways...nominally 94% efficient.
 

GrumpyPlumber

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jadnashua said:
I went with an indirect, since I had the boiler anyways...nominally 94% efficient.

Another EXCELLENT alternative...done a few of those this year too....gas co offers the same rebate as tankless too.
The advantage is the two following have a lifetime warranty:
Superstor, Boilermate...I'd guess you did the Superstor...just a hunch
 

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GrumpyPlumber said:
That alone wouldn't sell them...the avg water htr is 60-65% efficient...the tankless's get upwards of 84%...when running.
I did a lot of research on HE direct-vents and tankless a few months ago when I was first scoping my renovation. The most consistent criticism of tankless was the risk of no heat/inconsistent heat at low flow. In your opinion, is this overstated?

I also ran across the AO Smith Vertex PV. They claim 90% efficiency (versus 67% for their own Promax line). My plumber checked with his distributor, and the price is nearly double the next highest model. Still, I'm wondering if anyone has any experience with the Vertex, or if their claim is even valid.

Great discussion, BTW. I like the idea of tankless, but was discouraged when I learned about low flow performance, as well as the calculated savings vs an HE direct vent gas-fueld storage model (apparently, the total OPEX of the storage is still lower over the long term than tankless, especially when factoring in the unit and installation cost differences). This is why I am also interested in seeing the results of the "noble experiment"; it would be nice to have some hard, real-world numbers to point to for reference.

With thanks,

Jay
 
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GrumpyPlumber

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jay_sfb said:
I did a lot of research on HE direct-vents and tankless a few months ago when I was first scoping my renovation. The most consistent criticism of tankless was the risk of no heat/inconsistent heat at low flow. In your opinion, is this overstated?
I have only seen one name with a noticeable problem, Bosch...I was startled by it's irratic temp changes for the first minute or two....luckily for me it was purchased by the customer. (I'm gunshy about pawning new nam4es on customers without experience orr research)
Most of them state they won't kick on till you have at least a .5 gpm flow rate give or take a few hundreths of a GPM.

I also ran across the AO Smith Vertex PV. They claim 90% efficiency (versus 67% for their own Promax line). My plumber checked with his distributor, and the price is nearly double the next highest model. Still, I'm wondering if anyone has any experience with the Vertex, or if their claim is even valid.

Great discussion, BTW. I like the idea of tankless, but was discouraged when I learned about low flow performance, as well as the calculated savings vs an HE direct vent gas-fueld storage model (apparently, the total OPEX of the storage is still lower over the long term than tankless, especially when factoring in the unit and installation cost differences). This is why I am also interested in seeing the results of the "noble experiment"; it would be nice to have some hard, real-world numbers to point to for reference.

With thanks,

Jay
If you have the budget for the best option for efficiency...go with a condensing boiler & DHW/indirect storage tank set-up.
If you're just on the market for an efficient water heater...tankless is the best. (Though A.O. Smith 90% does get my attention, your still paying to heat water that sits there)
You have to look at the ins and outs on each name...Paloma/Rheem for example max out at 120 (though I think that can be modified...but that effects the efficiency)
Sort through Rinnai, Takagi, Noritz, Rheem (same MFG as Paloma)...there are quite a few more, but those are the ones I know to be dependable...as for Bosch - they're the cheapest...but, er...let's give them a few years to fine tune things.
 

Master Plumber Mark

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the nobel experiment......

I apologise that my experimient
its certainly not on the fast track.

with a vacation comming up and being very
busy at work......


having a little difficulty with my pay pal
account and I cant seem to buy that damn
gas meter , without a dog fight......

installing it with a tee a couple of stops or a
bypass to check either the 75 or the tankless
is no big deal.....

its mostly finding the time to get motivated.

when you got a perfectly good 75 gal in place its
hard to explain to the wife why you are screwing up
the laundry room.....

probably will be monitoring the 75 gallon
unit by Aug1st...thats .no big deal

probably will have the tankless installed by
Sept 1 if I can obtain one at a discounted price.

that is the plan
 

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Talk about coincidence -- and I suspect this will make GP particularly itchy -- but DIYNetworks recently ran an episode on pulling an old tank heater and replacing it with an electric tankless. This is particularly interesting to me, since the old system was gas and the new one is electric (SETS). I seem to recall reading that an electric tankless is not as cost-effective as a modern HE gas tank; but I can't locate that reference now, and the program never really discussed the difference. They did indicate that the new system required an upgrade to the electrical to the tune of adding a -dedicated- 100A circuit. This is not the solution for me, though I am planning on upgrading from my current 70A shortly :eek:... jay
 

GrumpyPlumber

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Right...I already looked into a SETS (made by Noritz if I recall...tried looking it up and nothing for sets...may be discontinued?!) for a condo owner that couldn't add venting aside from the natural draft already in a closet through the roof.
The supplier told me he was better off with his draft type, weighing all costs and the fact that electric tankless's aren't nearly as good as the gas.
 

Molo

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There has been no discussion of how gas tankless units handle hard water. We have very hard water here. Someone told me that tankless can't handle that. Is that true for electric and gas tankless?

Molo
 
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