Bock water heater or boiler for radiant floors

Steve Eayrs

since I don't have the time to talk about all the differences..........

- Lower AFUE efficiency in the Bock that most boilers.
- Large stack loss on standard installs on Bock.
- Warranty is shorter than most boilers on the Bock.
- Cost of Bock is not that much less than some boilers.
- I like Buderus, Veissman, but both are higher priced. Also have install a number of Ultimate (Dunkirk) and EK oil fired boilers with good results.
- The Bock will also most likely make more noise.


Your best bet is to look at the whole picture. A lot of factors will need to be considered, when deciding which you use. You will need to either hire someone who can help you with these choices, or spend a fair amount of time learning how to do this yourself, w/ all the right parts included, and in the right places. I won't tell you its as involved as building your own car, but either system involves a lot of parts and pieces, which are not included with either a boiler or oil fired water heater.
Lots of books out there, (look at Dans on this site). Find out what is sold and serviced easy in your area.


Steve

Bob Krauss

Bock water heater or boiler for radiant floors

Hi,
Just got the therma-floor poured in my house. Trying to decide on a heat source. I am limited to oil as the fuel. I have a calculated heat load of 47,000 Btu/hr, supply temp 115 Deg F, and 9.9 USGPM calculated by the Wirsbo Design Program. I used a 9in tube spacing with 1/2 PEX to keep supply temps down. Low R value floor coverings are planned.

Since my supply temps are so low can I use an industrial water heater like a BOCK?? The Btu seem to be more then enough to handle the load. Will the standby losses be too great, or will the storage tank increase efficency by limiting short circuting?? Will the maintance costs for a Bock be more then a traditional boiler?? It seems like an obvious choice but since not many people use them I might be missing something. By the way it is a closed system dedicated to heating, no DHW in mind.

Please help explain the pros and cons.
If you think a boiler is better what is a good brand??
Thanks for everything
Bob

DaveGateway

With radiant jobs

that also need DHW, I would rather use a WH with a built in heat exchanger. Ususally cheaper, but lower AFUE and life expectancy is only 10-12 yrs or so. Take a look at Bradford White's oil fired Combi-core. Triangle tube's delte-elite offers the seperate stainless steel inner tank for DHW, at the price of a boiler. If you still want to go with a seperate boiler, Dinkirk's EV series has a small 56K CI boiler, the smallest oil fired boiler I've seen.

Dale

Crown Freeport

Take a look at a Crown Freeport with a megastore domestic hot water. The 92 K output should be right if the domestic is added. Fuel isn't ever going to be cheap again, China is just adding too much demand.

George_10

You are certainly right about China

When I was flying into ISH, the fellow sitting next to me was on his way to China. He spends 3 weeks a month there and told me that every major US company has a presence there trying to get into China's fantastic expansion.

They want to have our standard of living and they are spending the money to acquire it.

The result is, these prices will seem low in a few years.

Welcome to the world modernization of the 21st century.

Our grain prices will be rising soon also.

hr

If you use a WH

you will need to use a 3 way mix valve if your temperatures are low, say 120 or less.

A water heater, with it's purposly inefficient HX can handle low return temperatures for periods of time. They will not tolerate low operating temperatures on a continous basis.

That HX, in a tank type water heater, at some point needs to get above the fuels dew point to dry out and prevent corrosion in the passage, and that cork screw looking baffle arrangement. Those baffels will rust, corrode, and flake down onto the burner. Then you add a CO issue to the corroding tank problem!

A small boiler would be a better match, ideally a small wall hung condensor!

If not several manufacures offer external HX packages for water heaters. And AO Smith showed a HW tank with an external HX at the ISH show.

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Unknown

I agree with the WH, but the dual use units are more prone to failure than a WH with external flat plate heat exchanger. Plus, if either the WH or the HE goes, you're replacing both instead of one.

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Unknown

HR, I'm not sure what you're talking about. Bocks don't have internal heat exchangers. Is that a general comment about dual use water heaters?

With an external HE and a variable speed injection pump, we've had very good results.

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Unknown

Bob , what are you using for hot water ?

In the oil fired water heater category , the Bock is tops in efficiency . In longevity , used for hot water , they do not last any longer than the other brands we replace . I'm not sure how the Bock would be affected by using it on a closed loop heating system , but I would guess it would not last longer than the cheapest tin can boiler .

With the price of the Bock , I know of a few dry based steel boilers that might be cheaper to buy , and the AFUE would certainly be higher . Some mid range cast boilers might be within a few hundred dollars of the Bock . Almost all of the oil boilers have a provision for a coil , if the demand for hot water is not too high gpm wise .

Bob Krauss

Thanks for the help
I thought the Bock would give me more fuel savings due to the large storage tank. I'm really not looking for a cheap way out. I want to get as close to the best as I can afford. Think I'll go the boiler route. I like the Monitor Condensing boiler buy, my only concern with a condensing boiler is the condensate. I have an onsite septic (sand mound) and I don't want the acidity to mess anything up. Any thoughts on this??? Is this boiler worth the extra money over a cast iron model???
Thanks Again

Unknown

You can get the most efficient thing out there, a modern condensing boiler. However, whether it's worth it or not depends on what kind of heat load you have and what kind of prices you're looking at, as well as fuel cost of course.

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Mark Eatherton1

I used to heat my home with a water heater...

a fourty gallon gas fired water heater. I realize you're talking oil instead of gas, but allow me to tell you of my experience. It wasn't just a "regular" water heater. I'd installed a solenoid gas valve between the Unitrol gas valve and the burner so I could do a full reset on the heater with a tekmar controller. I thought it was the bees knees. The ultimate in cheap heat. Then I installed a Munchkin T50 wall hung boiler, and I reduced my gas consumption by 30 to 40 percent, even with cooler temperatures this year versus last.

As for the condensate, I use a 5 gallon bucket filled with chipped marble as my neutralizer. I also dropped some copper sulfate into the bucket so I continually dose my yard sewer with copper sulfate to keep the tree roots at bay. You might not want to do the sulphate thing because you're on a septic system, and you don't want to kill the anerobes. I'm on a city sewage system.

Water heaters are not all their cracked up to be as it pertains to energy efficiency. If they were REAL good, and efficient, the rest of the world would be using them, and they aren't. Only the wasteful Americans would think of keeping their water at a constant temperature with a 3 or 4 inch hole (larger in some cases) running RIGHT through the middle of all that stored energy, losing energy dollar$ right into outer $pace for the 22 hours they're on standby...

THere are some real good small oil boilers availble that will meet your loads nicely. Spend your money wisely now, and it will come back to pay you in the near future. As oil becomes more scarce (and it is) it's price will continue to climb.

ME

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Unknown

They aren't the most efficient thing you can do, no doubt. I am suspicious that your reset jury rig was inhibiting your fuel efficiency, not helping it, however. Just a hunch. Sipping bits of water out of a standing tank that is "cruising" has got to be lower impact than continually trying to change the temperature of a large tank of water. I'm not promoting that as fact, just a hunch. Real interesting experiment in any case Mark!

I can easily swallow that switching to a condensing boiler saves energy. expecting 30-40% in most situations seems a bit extreme however.

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hr

Rob

Guess that doesn't read well. Point I was trying to make is a water heater IS a HX. But a very inefficient one.

This is due to the fact, as Mark mentioned, that it is a tank with a 4" hole in the center. Really the only HX transfer is the burner heat and flue gases touching the wall of that 4" tube as it goes up through the tank.

As you know most tanks have a cork screw looking baffle to maximize the heat exchange as the energy goes up the inner pipe. This is what I meant by a sloppy HX. A tank with a hoile in the center and the burner placed directly under that hole

Over the years manufactures have tried to improve WH efficiency. Remember the American Nautalis and AO Smith submerged chamber water heaters? Or the Reem/ Rudd tri flue design. These were all attempts at improving the efficiencies. Although they are no longer around Some large commercial tanks still se multiple tubes, however.

The basic center flue gas fired water heater is designed to be simple and inexpensive. But is does so at a low efficiency when compared to fin tube of cast iron pin type HXers. And way behind high efficiency condensing models, as ME's, and many others, actual experiences proved

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