Indirect tank vs. true tankless DHW

Steve M

1) Not sure about water being more corrosive, maybe it's harder than it is in Europe. We sell Rinnai brand and have sold them in areas where the water is hard and the pH level is around 6-6.5. Rinnai suggests putting a set of valves in the piping so the unit can be de-limed if it needs it. The controller will tell the homeowner when this situation exists. So far there have been no problems that were caused by the water. If there is low pH water, a neutralizer can be installed to bring it back up.
2)How can firing a boiler to heat your domestic water when no one is home to use it be cheaper??

Roy Jonker

Indirect DHW tank vs tankless: general views

Answers to two questions would be appreciated.

(1) My contractor is trying to talk me out of a tankless HW heater (Rinnai or Tagaki) using the arugument 'they work well in Europe, but here the water is much more corrosive'. Disregarding that both Rinnai and Tagaki are from Japan: is there any truth in this 'more corrosive' story?

(2) he also claims that adding an indirect tank to a new Vitodens will work out cheaper over time that a seperate tankless DHW heater. Any views? What I found so far indicates that a Rinnai Or Tagaki would be cheaper over time.

The cost of both options are similar, and tankless would be fine from a flow rate point-of-view (we are from Europe, and used to checking if someone else is already taking a shower).

Thanks, RJ

Uni R

Hey Roy

I'd listen to your contractor. When he says cheaper I think what he should say is that it will be better finanically. I think it is better for resale just in case the potential buyer is worried about capacity issues of a tankless or has had a bad experience with one and also you are keeping only one burner working and using it more contstantly. The Vitodens is a well insulated efficient water heater. I'm sure he'll insulate the indirect piping well. I think it also helps a burner to have a job in the off season. One of the big reasons people use tankless and wall hungs in Europes is that space is much more expensive than it is in North America. As for your choice, I think that as far as water heating efficency goes, the difference is very marginal but for system life and maintenance the simpler and bigger the better, especially since you aren't losing anything.

Jack_23

Go with tankless...it's cheaper

Water quality is definitely an issue with tankless units. If you are on city water call the water dept to get an analysis of the town water. If it is a well system you should have your own done. You should know this info becuase it can affect a lot of other equip in your house too. I have a Buderus G220 with and indirect and it heated my water fine, but when I put in my Rinnai my summer gas bills declined from 36-44 therms /mo to 10-15 therms/ mo. Same appliances, same # of people and I only use gas for HW in the summerso I know it is right. The US is the last tank type market in the world. Look at any market where people spend 4-5 times what we pay for fuel and they all use on demand...because it makes sense. The newest on demand units now have the capacity to handle the American markets flow rates too. Does storing hot water make sense? Pay attention to how long you actually have a hot water tap open. Why store hot water? Another thing, when you get home from work in the evening do you let your car idle all night so it is ready to go in the morning? Why not? I'm biased because I represent Rinnai in New England...but my gas consumption figures also make me an informed consumer!

kevin coppinger_4

I gotta ask...

what make & model was the indirect? was /is your basement unusually cool? What is the flow rate for your tankless? kpc

Jack_23

My indirect is a 40 gallon Buderus

Ecomatic control. full off cycle damper. The basement is not "unusually cool". The Rinnai will fire from 15,000-180,000btu. Flow rates from .5gpm -8,3gpm. Flow rate is totally based upon temp rise. 70f temp rise output is 4.8gpm. Rinnai 2532FFU.

Unknown

Tankless=Temp. rise

I think tankless options should ALLWAYS be considered EXCEPT where corrosive water is present. The heat transfer geometry of the tankless units I have used (Takagi) are superior to anything you will find in a boiler.

Why store hot water? Pay as you go. Unless you've got a Vitodens;-)



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ScottMP

Jack

We have installed the Rinnai in a pool house and its works fine. I spoke to you about this job last summer.

My question is there appears to be a "pulsing" of the unit during hot water production. Is this normal ?

My bigest concern with the tankless units has been the flow rates. Most would not put out the flow rates that Americans are used to. Customers with open minds and a slant towards conserving will do fine with this style.

I can't imagine that heating only what is needed would not be more effiecent over storing gallons of water. Now add in a whirlpool and four teenagers ????? How many of these things do you want .

Scott

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Unknown

Pulsing

I ALSO HAD A CUSTOMER COMPLAINT reGARDING PULSING. tURNED OUT HE WAS ON A WELL AND THE DIAPHRAM EXPANSION TANK WAS NOT CHARGED PROPERLY. After charging up the tank, the surging evened out. However the temperature would not maintain constantly the same throughout the well's cycles.

OOPS.. I had the SHOUT key on. sorry.

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ScottMP

Gary

ssshhhhhhh don't yell its to early

This is not on a well.

Scott

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Jack_23

Pulsing?

On the controller, with the water running, pushand hold the H (red)button and then push the green button. controller will read GPM. so 8=.8gpm, 44=4.4gpm. Once flow is known, push C (blue) button and hold and poush green. this will give output temp of hot water sensor leaving the unit. Connect manometer and monitor gas pressure. Check it at max flow to see if it is holding. Nationwide the biggest mistake with these is to low gas pressure. Not sure if I understand "pulsing". Where are you? I'm off to Maine this am and will be off line for a couple days. Call my cell if you would like to discuss. 617 834-8751. Or call 800 621-9419 x 207 or call both. They work.Let's get to the bottom of it!

Roy Jonker

Tankless, or hook up to Vitodens?

Gary, you may ;-) when you wrote 'Unless you have a Vitodens', but, yes, that is what we will get.

Normally tankless is the way to go, but typical Tagaki efficiency at 85% should be compared to the 94-or-so% of the Vitodens. Calculating lower standby losses against somewhat lower efficiency is too tricky ...

One more point against getting a tankless is that there will be one more machine.

Still, it looks like a Tagaki.

Thanks for the comments. RJ

Unknown

I WAS'NT KIDDING. Hook it up to Vitodeens.

That is one honkin fine piece of equipment. Now if it were me, I would utalize the high efficency of that boiler coupled indirrectly and store the water in one of their Verticells. Not a whole lot of runaway BTU's there.
Either way you can't go wrong with these two fine very fine systems. Bolth are best at what they do. IMHO

The venting requirments will usually decides the issue for you.

Hope this helps you decide:-)

Gary Wallace AIM; Radiantfloors

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