Just like pink insulation... every article about heat pump water heaters is a marketing article written by industry in my opinion.

Anyone want to prove to me how in upstate NY... someone can take inside air... cool it... to make hot water... and save money????????

What about the need to now warm up the cooled air with the heat system????????

Sorry... I just don't get it... not for my climate... yes for any place South... and warm.

Same thing hear with geothermal heat... my ground temp is 45degrees... Electric is at .17cent a KW.. nope... not too good hear... oh... and gotta love the air temp coming out of the air registers with geo... 80-90 degrees... might as well go sit on the snow bank out front in the sun at those temps. 

my city water... hears a good one... comes in right now... end of winter... at 34 degrees... now try running that thru a tankless water heater... another silly thing to buy where I reside.

Anyone... chime in a straighten me out... would love to hear...
aj

Depends on what your other options are. In the winter, it will heat water at something in between the cost of your room heat and electric heat (closer to the former, will never exceed the latter). When not using interior heat (spring/fall), it is about 3x more efficient than electric hot water heat. During the summer when using AC, it is "free" or close too it. How that all adds up depends on your situation and propane/nat gas/elec/etc costs.

There is lots of material available about geothermal (basically the same thing as a heat pump water heater). It may not be the best choice at $.17/kwh.

at that price geo likely only makes sense for very large heat demands. geo air or hydronic systems can be properly designed for comfort with cool air coming out of the register though. solution is simply, put the registers such that they do not blow on people.

and how about tankless water heaters... and 34 degree incoming water? Any takers?

output of the water heater divided by (8.4 x 75 x 60) = GPM it will deliver at 110 deg F.

Ok... formulas... neat...now real life... I asked around to see what owners of tankless say around here...

for people who do not want to know about the math involved to take a hot shower... they suck.

for the dentist type... who knows more about math than I do and loves to fiddle with everything
within reach of his priceless mitts... oh they are great... why let me just tell you exactly how much money we are saving now...

oh and one more end result... yaa... we now have endless water and... now all my kids take three hour showers twice a day too! So our fuel bil is now double instead of half... thanks so much!!!!

OK.. now I guess you all really know how I feel about tankless... oops... just let that cat out of the bag didn't I!!

aj
the lobsterman/antimarketingpinkguy

Heat pumps can't make "useable" domestic hot water without using electric resistance backup a.k.a. electric water heater. For some this represents 25% of there total fuel bills. In Minnesota this could be higher than the cooling bill.

if people don't know the math involved to take a shower, all heat sources can suck. not being able to size a heat source is a problem, when you need to size a heat source.

I'm not a fan of tankless heaters in most cases, and they are definitely oversold. but you can find bad uses for every technology in existence... that doesn't prove much of anything really. Your incoming water being 34 degrees is kind of irrelevant to whether on demands "suck" or not. It just means they need more ooomph to deliver the flow you need.

Rob... ????

1- I don't do math to take a shower.
2- Nor would I ever ask a customer to do math... to take a shower. That is just plain silly talk.
3- As to bad use of technology.. put it this way... some technology may just be stupid. The unintended consequences of so much we dream up in the last 50 years is huge and amazing. IE... this subject...

tankless vs. tank:

a tanked water heater... puts out hot water very predictably. starts with hot with no sandwich to be designed around.. and then with no technology or cost or intervention at all.. none... no tricks up anyone's sleaves, no rabbits being pulled from hats or amazing new over hyped and marketed water heater... yup it amazingly runs out of hot water to limit your teen showers length to a sane 15 minutes... and there by... keeps you from having to kill and eat your young.

I see you and I are also types that need to persuade till we win our arguments...

If you don't concede now with this last post... why... I will have to find you and buy you your beer tonight. But I will then miss volleyball... and that is not a pretty picture either!
aj
winnerofallfightstobuyaworthyadversaryaSamAdams

Posted By adkjacUpstateNY on 15 Mar 2010 01:14 PM
Rob... ????

1- I don't do math to take a shower.
2- Nor would I ever ask a customer to do math... to take a shower. That is just plain silly talk.
3- As to bad use of technology.. put it this way... some technology may just be stupid. The unintended consequences of so much we dream up in the last 50 years is huge and amazing. IE... this subject...

tankless vs. tank:

a tanked water heater... puts out hot water very predictably. starts with hot with no sandwich to be designed around.. and then with no technology or cost or intervention at all.. none... no tricks up anyone's sleaves, no rabbits being pulled from hats or amazing new over hyped and marketed water heater... yup it amazingly runs out of hot water to limit your teen showers length to a sane 15 minutes... and there by... keeps you from having to kill and eat your young.

I see you and I are also types that need to persuade till we win our arguments...

If you don't concede now with this last post... why... I will have to find you and buy you your beer tonight. But I will then miss volleyball... and that is not a pretty picture either!
aj
winnerofallfightstobuyaworthyadversaryaSamAdams

A tankless (or tank heater) combined with a 50%+ recovery drainwater heat exchanger provides more than ample capacity at half the fuel use that yer kid can dawdle in the shower and you still don't have to kill & eat 'em.

An indirect running off your boiler with a drainwater heat recovery heat exchanger, same story.

DWHR is like having an extra 30-35K burner on while the shower is running, but it's a "burner" that uses no fuel- every body wins (unless water is very expensive too.) If you're heating water with propane or $0.10+/kwh electricity it's usually cost effective for a 30minutes of 2.5gpm shower time/day.  At 2gpm a typical tank heater will keep up for over an hour, even at 35F incoming water and the recovery time would be shorter since it's 75F not 35F water coming in at the bottom of the dip tube.

Standalone tanks have lousy standby loss characteristics- they're FAR lossier than an indirect.  If you don't have an indirect, a tankless would be a "next best" from an efficiency & convenience point of view, but don't hold your breath on any "payback" on it beyond the space savings unless fuel prices soar again.  But for less than the installed price of a tankless most household installations would get similar showering capacity and better fuel economy going with a middle-of-the road tank & drainwater heat recovery.  The short-cycling losses of a tankless on small draws are significant- in typical household use patterns they hit efficiencies 5-15% lower than their EF test numbers, an artifact of the EF test being 10.2 gallons/draw, never 0.5-2 gallons as in "real life".  They're still significantly more efficient than standalone tanks though, especially for intermittent or low-volume use. ( See this. ) But it takes decades to pay back in fuel savings unless you have expensive fuel. Propane, yes, natural gas, not so much.

Still I've yet to meet anyone who has gone the on-demand route for fuel savings as their primary or even secondary goal.  Most peops I know who went either thought the space savings was worth it or had some monster soaking-tub to fill, or needed/wanted the "endless shower" feature.  

My first on-demand tankless (installed in the early 1990s, retired working last year) I bought for the space savings and capacity for 4 serial showers without recovery time.  My more recent one I'm treating as a cheap disposable modulating copper tube boiler, using an indirect to heat water & buffer the micro-zoned heating system.  With a 4-foot x 4" drainwater heat recovery unit the output of the tankless never exceeds 60KBTU/hr during showers (though it's capable of more than twice that), but it'll hit that when all zones are calling for heat during a shower.  It'll keep up with a combined shower + space heating load 24/7, but as installed & tweaked it's possible to run tepid at the end of a rapid large tub fill with all zones calling for heat. (Dialing back the fill rate somewhat still results in a plenty-hot bath.)  I could crank up the baseline burn rate if I needed/wanted higher hot water output, but only at the expense of some modulation savings foregone in space-heating mode.   As-is this Rube-Goldberg contraption is suiting our needs, and it's tweakable if our needs change.  (Of course Rob & Morgan figure I've spent too much for too little here, but they're discounting the entertainment value it's provided. )

As for tank-top heat pump water heaters, they're great for cooling dominated climates where the incoming water is north of 60F, but they're not more efficient than desuperheater DHW solutions, and kinda suck in heating dominated climates with 40F incoming water.  The recovery time on 'em is atrocious, and the efficiency less than the heating system it's drawing from 6-9 months/year.

I still say if the person choosing the heat source can't do the shower math, any heat source can suck. and there are a lot of demands out there not feasibly met with tanked water heaters. If you can't figure out what the BTU load of a shower is, you have no business selecting a water heater. People who do so often end up with less capacity than they want.

for the majority of cases I prefer tanks, definitely. Indirect or not... cast iron indirects are only about 30% efficient so Dana should be careful to note that only low mass boilers with indirects are significantly better than direct fire water heaters

plenty of arguments out there against tankless. they just don't have anything to do with incoming water temp, which is what started this line of conversation.

all players.... here yee here yee... how would you all like to teach me some game theory... ala...

like... the Nash equilibrium ....????

Me thinks we are at such a point... no? yes? what say all?

aj aye

OK... if we agree that we are basically sinking into some kind of lowest common denominator... Nash equilibrium ...

then what shall we do... accept such a fate? Hell no... we is thinking Mericans.... we can do better...

I say... after my litltle time at wik... that we form a cartel. yes... a cartel

for the benefit of all us Mericans... us bord ludites.... air breathin bio puters...

aj? aye

If you can back up assertions with facts or substance, please do so. If you can't, no need to fill the void with pointless babble.

How about posting your bias in the open like the rest of us with commercial interest around here do?

Not sure what my bias is...

what is it?

Posted By NRT.Rob on 15 Mar 2010 08:28 PM
I still say if the person choosing the heat source can't do the shower math, any heat source can suck. and there are a lot of demands out there not feasibly met with tanked water heaters. If you can't figure out what the BTU load of a shower is, you have no business selecting a water heater. People who do so often end up with less capacity than they want.

for the majority of cases I prefer tanks, definitely. Indirect or not... cast iron indirects are only about 30% efficient so Dana should be careful to note that only low mass boilers with indirects are significantly better than direct fire water heaters

plenty of arguments out there against tankless. they just don't have anything to do with incoming water temp, which is what started this line of conversation.

Cast iron+ indirect efficiencies go down with size, relative to the size of the load (be it space heating OR hot water), and go up in proportion to their steady state efficiency.   A 2-plate 40-50KBTU 83% AFUE cast iron beast + indirect won't be much outperformed by a 35KBTU 78-80% combustion efficiency tank heater during the summer, but a 300KBTU 83% beast will suffer greatly.

An aging atmospheric-drafted ~104K cast iron beast with a 72% steady-state thermal efficiency scores about 37% (more than 30%, but nothing to write home about) in water heating only mode according to this test document , whereas a 160K mod-con with a 4/1 turndown only scores a whopping 58% in water-heating-only mode (which can be matched or beaten by pretty-good non-condensing noo-skool tank heaters, and just about every tankless.)

But by increasing the duty cycle for hot water heating during the heating season the water heating runs at pretty much the AFUE of the boiler. If the boiler is right-sized for the heating load AVERAGE annual efficiency of an indirect is much closer to the heating AFUE than it's water-heating only mode. But they all take a hit in the summer.  If the boiler is an utter piece o' junk (like that 72 percenter in the test) and 3x oversized for the peak loads it won't beat a standalone tank on an annualized basis, but almost any new equipment reasonably sized will.  Of course, lower mass=lower cycling losses, and a lower overall efficiency hit from being way oversized for a water-heating-only load.

Non-monster sized cast iron boilers with internal water heating coils run 25-40% typical efficiencies in water heating only mode, mostly a function of their relative insulation.  The same boilers operated as cold-start with indirects do significantly better, since the tanks tend to be much better insulated than the boilers themselves, and suffer less standby.  The cycling losses are higher than low mass boilers though, due to the greater mass of hot water abandoned in the boiler on each cycle, but this loss can be minimized with heat purging control.

Assuming it's inside of conditioned space, during the heating season some portion of the tank heater's standby is going into reducting the heating load.  But it's standby flue losses are still a net increase in total standby loss related to the heating appliances. And tank heater combustion efficiencies run 78-80% to a cast iron boiler's low-mid-80s.  Even power-vented tanks rarely have draft dampers, most don't have direct-vent/sealed combustion. All post 1990 cast iron boilers come fitted with flue dampers, and many mid-efficiency cast iron boilers are now direct-vented, presenting zero induced infiltration to the heating load.  Even though it's summertime water heating efficiency is low, the heating season benefits of higher combustion efficiency and lowered total standby loss usually outweighs the comparatively higher summertime fuel use by the high-mass oversized burner.

But when it comes to indugent splendor of the 4gpm showerhead with 8gpm of sidespray, nothing quite beats a 400-500kbtu burner and an indirect with a heat exchanger capable of delivering the full output, efficiencies be damned!    (They're out there!)  But with a decent sized drainwater heat recovery heat exchanger you might be able to run that ridiculous shower with a 250K mod-con with only modestly-ridiculous fuel use.

Your "bias" is your professional interest in the subject adk. More bluntly, what company are you associated with?

dana, a local company I know datalogging systems indicates that the 30% efficiency is very common in the field for cast iron on indirects, in the summer (domestic only). Now, they sell solar systems, but still I have little reason to doubt their integrity on the matter. Good design or the right product selection can significantly improve that, but most cast iron is still installed with no additional control at all, so the cycling losses are significant.

it's worth noting that a few hundred bucks on a reset boiler control with post purge should have pretty good payback though on such a system, even if all it did was improve your DHW efficiency. So the fix is not necessarily expensive or complicated.

Posted By NRT.Rob on 17 Mar 2010 08:31 AM
Your "bias" is your professional interest in the subject adk. More bluntly, what company are you associated with?

dana, a local company I know datalogging systems indicates that the 30% efficiency is very common in the field for cast iron on indirects, in the summer (domestic only). Now, they sell solar systems, but still I have little reason to doubt their integrity on the matter. Good design or the right product selection can significantly improve that, but most cast iron is still installed with no additional control at all, so the cycling losses are significant.

it's worth noting that a few hundred bucks on a reset boiler control with post purge should have pretty good payback though on such a system, even if all it did was improve your DHW efficiency. So the fix is not necessarily expensive or complicated.

Datalogging and measuring stuff is good! Are they going to publish?

The fact that many states & utilities are subsidizing indirect retrofits at the same dollar level as 0.82EF tankless makes me believe that somebody has done both the science & economics on this, but the politics of such policy decisions aren't always reality based, to be sure.  It wouldn't surprise me to see 30% water-heating-mode efficiency on a 200KBTU 80% atmospheric drafted boiler, but I'd be VERY surprised to see it measure that low on it's 50KBTU sibling.

It's surprising that heat purge control is still so rare, given it's a no-brainer in anybody's cost/benefit analysis.  Then again, the economics of insulating the hot water and near-boiler plumbing is also a no brainer, commonly left as an exercise for the home owner.

If we paid $8/gallon for fuel oil all would make sense. Since a conventional NG atmospheric boiler for a family of four may cost $300.00/ year to operate, payback is a no-brainer. In fact it isn't there.

A cast iron boiler at 82% AFUE will run at steady state most during most of a DHW call, ODR has no effect on this. Standby losses in cold climate are nearly zero for the indirect and are not considered in a conditioned space (drying the basement out in summer and heat the building in winter). Post purging a 400# boiler makes sense in summer perhaps but can't be justified with NG a .98/therm.

If you have a ModCon with ODR and post-purge built-in ( I find half the boilers with these features unused) you are all set and make more usable water at less cost than a conventional "tankless". The low-mass nature of the ModCon and improved pre-mix burn make steady state achievable in a matter of minutes.

I have never tested a ModCon (9 manufacturers so far) while making DHW while operating at less than 86% combustion efficiency. In short, I don't believe their numbers.

around here badger, if you have a cast iron boiler doing domestic, you are guaranteed to spend $200 over a summer for DHW, minimum. It's fuel oil up here in the northeast though, which is not as cheap as NG. Post purge is a cheap feature and would have significantly better payback. for NG fired cast iron though, sure, I'd agree with you.

as for mod/cons and DHW: combustion efficiency is not the whole story though, as you know, I believe, better than most should. I think you would be wise to pay a little more heed to brookhaven on this.

It is no surprise to find discounted numbers for the condensing propane boiler in the Oil- Industry- sponsered- study, as the propane ModCon is the bane of all oil salesman.