Boiler/Tankless Water Heater

Any thoughts on using a natural gas tankless water heater to replace a boiler in a shop heating system? If anyone has experience in this area a basic piping diagram and any thoughts would be appreciated.
Thank You
Jerry Whitaker
[email protected]

JLW Tankless water heaters do not care where the heat goes.

If you pump clean enough water through, at appropriate rate, tankless heaters do a fine job of transferring heat (at the burner rate) into it.
For good reason, they usually have a safety interlock below about 1/2 or 3/4 gpm.

If you keep minerals and crud out of the water, they will go for years.
Make sure your expansion system remains functional.

Hth Ag

Jerry,

I don't know if they still make them, but I heat with a Paloma Pak gas boiler. It is made from a Paloma tankless water heater with a NEGEA (New England Gas and Electric Assn., I think it was.)

Installed it in 1980 and replaced the heating unit of it this past Winter, just because I had a spare on hand from a couple years ago when I thought it went bad.

My house is well insulated 1900 SF and it has never failed to keep it up to the thermostat setting, at least to the 13 below that I do remember, the Winter I got my upstairs plastered and was told by the plasterer to leave the windows open to let the water from the plaster go out the windows. He called me a couple days later to ask how all was, told em to JEEZ, close the windows, I didn't mean at that temperature.

I said I don't know if they still make the boiler. I know they still make the tankless water heater. As I said I bought 1, 2 years ago. 43 thou BTU, 36 thou net, and heats my house. I have about 75% of my exterior walls run with baseboard, so think I get more heat input than with the "correct" footage for that 36 thou.

Contrary to Ag, I don't think you have to worry about your flow rate. This unit, at least, requires water to be flowing, and in a boiler scenario, that flow is a suction on the output side of the gas control valve. If there is no pressure differential, the burner will not light.

Also, you will have a closed loop so all the lime and the like will line the tubing and only make up water from leaks that you might have will enter. Minimal scaling. As a water heater, it would need to be descaled on a regular basis because every gallon you heat will be new water, new scale.

You might try tanklesswaterheaters.ca
I emailed them at "sales@ the above.

Cheers,

George
Man, I don't know what my home made wine comes in at, but just went out to smoke one and drink a glass and gotta squint to type the last of this.

New batch to come in about 2 weeks, this year's squeezings. I don't know what to make. Barolo, Pinot Noir, Sauvignon Blanc, last season. Year and a half old dandelion still not bottled. Kick in the ass wine, last time I tasted, kinda like a hay mow. POTENT!!

I'm building a shop right now using a tankless for heating

My architect and his radiant heating associate who have been doing hydronic since the mid 80's spec'd out this design. It's a 2400 sq ft shop with hydronics in the floor, and a 195k btu Rinnai tankless. I heard tankless have smaller orifices, and can erode quicker than true boilers like the Munchkins, but after showing this design to my very experienced plumber/heating contractor, he admitted it is a good scheme. So I'm going ahead with this-

edit- No bubble wrap insulation. At least not on it's own. I'm using 2 inch extruded insulation board under the slab. I will probably use bub ble wrap insulation over that for the house. But not on it's own. It reflects, but doesn't have an r value when smushed under the weight of a slab. And remember, perimeter insulation is crucial.

Greeg K:

195 KBtu/Hr for a 2400 sf shop in CA??? Is it a greenhouse?

You might want to do your Handbook J analysis again, paying particular attention to the location of the decimal points

FYI, my 5000 sf shop's max design rate is 96KBtu/Hr. My neighbor has a 2400 sf shop with two of the three bays being drive-through, with 14x14 doors on each end...and his shop is 8 ton as well...due to the doors. Both of these structures use 65F as the design max T. (Seattle)

Not meaning to cast aspersions, but second only to concrete contractors, there are fewer qualified contractors in the radiant heat industry than in any other field. There are virtually no optimized systems available for the home consumer, which results in huge inefficiency due to over sized heat sources, or systems that don't work at all due to undersized water heaters.

Let the buyer beware.

I've got a Baxi wallhung boiler. It works great except it still has to run on propane.

Breezy, thanks for the heads up.

I studied mechanical engineering in college, and did energy modeling and calculations. But I'm lazy now, and have other things to be doing, so I didn't double check on the common sense of the design. Now I will do some checking. I think people avoid problems and work by simply oversizing things.

Also specify Grundfoss pumps instead of those nasty Taco units.

Gregg K said:

Breezy, thanks for the heads up.

I studied mechanical engineering in college, and did energy modeling and calculations. But I'm lazy now, and have other things to be doing, so I didn't double check on the common sense of the design. Now I will do some checking. I think people avoid problems and work by simply oversizing things.

Click to expand...

You are most welcome, Sir. Thanks for not yelling at me for sticking my nose in where it doesn't belong

As an engineer with zero construction experience, I was amazed to see the broad spectrum of 'bids' for my geothermal heating system with radiant floors for my new home and shop. The more questions I asked, the less these so-called professionals knew. Eventually, as is always the case these days, I was forced to become my own expert. Fortunately, the internet is all about assisting dufusses like me learn anything they want, so I did. Obviously, you can too.

It sounds like you already know this, but in case you don't, there are all sort of heat-loss calculators on the market, designed to assist you in accurately determining the heat-load for your structure, they are all based upon the HVAC industry standard, known as Handbook J. It's a trivial process to tabulate the losses in your structure. Even if all you do is verify that your 'Pro' is correct you will, literally, have a warm feeling for years to come knowing that you made sure it was right...not to mention how you will feel if you discover that he is wrong.

You are absolutely correct with your comment on people's tendency to be lazy and compensate by overbuilding. I know because I have difficulty fighting that tendency in myself all the time Its almost never a smart way to go, and compensating for less-than-optimal design with excess capacity is a particularly brutal mistake in a heating system. You'll pay for that mistake for years.

If you find you are interested, you may PM me at your convenience to pick what's left of my brain on the issue.

Aha!

I'm using my boiler for domestic hot water in the shop. I have a temporary shower until the house is finished. Therefore, 195k Btu boiler.

But thank you for prompting me to double check things.

JLW said:

Any thoughts on using a natural gas tankless water heater to replace a boiler in a shop heating system?

Click to expand...

Okey dokey

I thought from the post above that you were using it for your shop heating system.

Now, just in case, based upon your last post, you are planning on using your tankless heater for an open system in your shop, i.e. radiant heat including potable water, you will find that that is not a good (read healthy) way to go. You will, however, find HVAC contractors that will tell you it is ok.

Google will set you free, should that concern you.

Best of luck with your new design.

Glad to run across this thread....

I just installed a Takagi brand T-K Jr. natural gas tankless in a rental house of mine. I wanted to help lower their gas bill a bit (12 year old that takes hour long showers!!!)

Been in service 3 days and they report no lack of hot water. My biggest problem was having to go under the house and replace the ancient 3/8" gas line with 3/4" to meet Takagis'r requirement of a large gas supply line.

My big question is with the Governments income tax credit for using this type of thing- which is another reason I bought it. Part of the sales pitch when I was reading up on these things was that, supposedly, you were allowed to deduct 30% of the cost of the item and it's installation up to 1500 dollars for "2009 Tankless Water Heater Credit" for income tax purposes.

I downloaded form 5695 off the IRS website and that is what it is all about- income tax credits for energy saving devices. I read absolutely nothing on that form about these heaters- there is solar and geothermal and a couple of other things, but nothing about tankless water heaters.....

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ON EDIT- I just looked at that 5695 form and it is for 2008 so maybe the 2009 form will have it included!!!!
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Plus, in the sales literature I read, they explained that to claim this credit the heater you bought had to be, I think, 82% efficient and blah blah blah.

The page with my particular heater, the T-K Jr.- it says right there "this item qualifies for the 2009 tankless water heater credit", but now that I bought it and installed it and read a little more, turns out that the Natural Gas version only is 81% efficient versus 82% for the propane version. My fricking luck will be that there is no deduction for the darn natural gas version and I get screwed out of a little relief on income tax.

I am planning on buying one for my own house and just did the rental house first to see how easy it would be. I bought this one from PexSupply.com off the internet. I have bought lots of pex tubing and fittings from there for my plumbing and hydronic heating projects and I would recommend them for their service and prices.

Tax savings

JoeE.,
If it is a rental house your accountant should be able to deduct the whole cost. I can't speak for now, but years ago that was the case. Then all repairs on a rental house were deductible.

Can't do that on a house you live in.

I say "accountant" for the same reason you use a lawyer. They are way better at finding deductions and figuring out the forms. At least they are around here. Way less headaches with an accountant then do it yourself.

Thanks,
Paul

gunbuilder said:

JoeE.,
If it is a rental house your accountant should be able to deduct the whole cost. I can't speak for now, but years ago that was the case. Then all repairs on a rental house were deductible.

Way less headaches with an accountant then do it yourself. Thanks, Paul

Click to expand...

Well, I used an accountant for a while, but I discovered Turbo Tax and have been using that. You can get on there and type in questions so maybe I will do that. It is a headache for me to do it because I get so overwhelmed and make it way more complicated than it probably is, but I soldier on.

A tankless water heater requires the exhaust ducting to be stainless steel. It will not do to use zinc plated exhaust.

Rons,


I beg to differ. Mine, 29 years old, now, called for AL in and out.

OIL calls for SS, because oil is high in acidic content, so the gases will be acidic.

Cheers,

George

gmatov,
Every supplier I have visited has a stainless steel venting system. The reason
is the high temperatures in the tankless unit. Your installation may be outdated
and not considered up to code today.

Just got a Bosch system for my addition; 195K BTU, it calls for 3 inch PVC exaust pipe.

Yours must be a high efficiency model!!! I heat my house with hot water and I have a "Munchkin" brand natural gas boiler. It exhausts thru PVC. It is 92% efficient.

My Takagi is only 81%. The flue doesn't get too hot. It is single wall stainless with a sealing gasket on one end of each piece. I don't think there will be much condensate to corrode the pipe even if it wasn't stainless, but I don't know for sure. The higher the efficiency, the more likely the chance of condensate in the flue. Munchkin boiler=Low flue temp=PVC flue pipe.

I did some reading and there are some of these tankless with efficiencies up in the 90's! I read on and one of the better ones had two heating coils to extract as much heat out of the flue gas as possible. They also extract more money from your billfold.

rons,

Oh, TEMP is the equater. I can put my hand on MY flue after it has fired for 15 minutes, and keep it there. Not hot, at ALL. NOT Al destructive.

Now, the WATER heater fires up, forget it.

Cheers,

George