Conventional Hot Water Tank Off of a Coal Boiler?

EarthWindandFire wrote:Here's a great Youtube video about an old coal-fired water heater that I thought was interesting.

What language is he speaking?

I emailed Edson which is based in Australia, whether they have any info on these coal-fired water heaters. This must be a 40 year old unit?

I couldn't find out anything about them on the internet surprisingly.

Stoked wrote:I have a small Keystoker KAA-2 and the tankless coil in it provides me with virtually unlimited hot water. I use a Watts tempering valve so nobody gets scalded.

http://www.watts.com/pages/_products_details.asp?pid=6888

The only way I'll run out of hot water is if the fire goes out. Triple aquastat is set to 180* high 160* low therefore when my house is calling for heat the circulator stops pumping when the boiler gets to the low setting. That's the lowest the boiler water temp will go. Tempering valve set to 120*. I have old cast iron radiators and never have a problem maintaining 66*-74* in my 1600 sq. foot house with 3 zones. When a zone is unoccupied it gets set to 66* otherwise between 72*-74*. BTW we're a family of 5 with plenty of showers, laundry, and dishes to be washed.

I'm glad that the KAA-2 is working well for you, but I'm concerned that some readers of this may discount the amount of heat that it takes to make DHW, and the possible importance of the size of the boiler. On the back of an envelope, if I have the math right, imparting an 80 degree temperature rise to a 1 gpm stream of cold water requires about (8.4 lb/gallon x 1 gallon/minute x 60 minutes/hr x 80 deg x 1 btu/lb-deg =) 40,320 btu/hr. The KAA-2 has an advertised net output capability of about 76,000 btu/hr. Put another way, even if the KAA-2 were making only DHW (i.e., putting no heat into the radiators) its steady-state limit would be a little under 2 gpm.

That may work in some households but not in others. For example, those cast iron radiators probably are helping to moderate the temperature drop that otherwise might occur in the house when the capacity of the boiler is being utilized to satisfy DHW needs. I'm all in favor of relying on a coal boiler for DHW, but would suggest that people planning to do so consider boiler sizing carefully, since making DHW can consume a lot of btu's.

Mike

there have been a number of "things" neglected in this thread

none so important as load consideration

Often folks with stoves attempt to make DHW and wonder why the stove doesn't heat as it should. Usually not the case with a coal boiler

but this is a good point - one I have stood on my soap box about in the past -

Good Job Mike - picking up the slack with kind words and clear data

Like Scottie said on the Bridge of the new time line Enterprise

"I like this Ship!"

MontgomeryScottyScott5.jpg[/img]

When sizing a boiler for tankless DHW isn't it typical to add 20,000 btu/hr to your home's heat loss for a single family?

After all, an electric hot water heater with 4500w elements converts to about 15,400 btu/hr at 100% efficiency. At 80% efficiency, 20,000 btu/hr would be about right for coal, oil and gas.

Booth Mikes' data is interesting indeed.

Since my Kaa-2 is probably undersized for 3500 sq ft anyway, I'm glad that I have a normal tank. [although elec is switched off]

I'll assume that since I'm using a loop from tank to boiler's coil, and a low flow rate pump to circ the water through said loop, I don't see the large heat loss from the boiler that the numbers say would occur with a direct setup. I have checked pre and post long shower boiler temps and seen little drop. Although, it is on the 'stat and stoking.

Dave

Pacowy wrote: I'm glad that the KAA-2 is working well for you, but I'm concerned that some readers of this may discount the amount of heat that it takes to make DHW, and the possible importance of the size of the boiler. On the back of an envelope, if I have the math right, imparting an 80 degree temperature rise to a 1 gpm stream of cold water requires about (8.4 lb/gallon x 1 gallon/minute x 60 minutes/hr x 80 deg x 1 btu/lb-deg =) 40,320 btu/hr. The KAA-2 has an advertised net output capability of about 76,000 btu/hr. Put another way, even if the KAA-2 were making only DHW (i.e., putting no heat into the radiators) its steady-state limit would be a little under 2 gpm.

That may work in some households but not in others. For example, those cast iron radiators probably are helping to moderate the temperature drop that otherwise might occur in the house when the capacity of the boiler is being utilized to satisfy DHW needs. I'm all in favor of relying on a coal boiler for DHW, but would suggest that people planning to do so consider boiler sizing carefully, since making DHW can consume a lot of btu's.

Mike

You're right, I was merely saying it is possible to heat your DHW utilizing a tankless coil. I'd rather have a properly sized boiler (which I do) to take care of all my heating needs instead of a more complex setup for heat and DHW. It's simple and works for me. One thing with my house is we don't have a lot of water volume, therefore can only use once source of water at a time. I don't need enough hot water to run the dishwasher and shower at the same time because it's not going to happen.
I hope nobody is (misinformed?) enough to go buy a KAA-2 for their 2400 sq foot home and expect it to be adequate.

Stoked wrote: I hope nobody is (misinformed?) enough to go buy a KAA-2 for their 2400 sq foot home and expect it to be adequate.

This is why we all try to get folks to do a lucid heat loss calculation

THEN go look for the correct - matching appliance

And Not listen to the salesman trying to sell old stock that on the floor.

[quote="Stoked
You're right, I was merely saying it is possible to heat your DHW utilizing a tankless coil. I'd rather have a properly sized boiler (which I do) to take care of all my heating needs instead of a more complex setup for heat and DHW. It's simple and works for me. One thing with my house is we don't have a lot of water volume, therefore can only use once source of water at a time. I don't need enough hot water to run the dishwasher and shower at the same time because it's not going to happen.
I hope nobody is (misinformed?) enough to go buy a KAA-2 for their 2400 sq foot home and expect it to be adequate.[/quote]

You mentioned low water volume problem. The quick temp draw-down of the boiler [Kaa-2] issue aside with no tank, I have a well, which is one reason that I would not want to draw my DHW directly through the 1/2" coil. I believe that 3/4 piping from the 1" main to tank, and on to the showerhead makes a difference. No 1/2" with a well for me, thanks.

I agree that is is possible to heat the DHW with the boiler's coil alone. However, I believe that I made the right choice with a normal tank [switched off during coal season] and a simple loop from it to the boiler's coil. $50 worth of fittings and pipe and a $122 pump is much cheaper than a special tank, hardly complex, and I have 50 gallons of hot water sitting there when it's needed. None of the drawback of the "direct" setup. If there should ever be a problem with the coil [or the boiler itself], I shut two valves and switch the elec tank back on.

The Kaa-2 isn't adequate for 2400 sqft? Don't tell mine that it's not supposed to be heating 3500 sq feet of home, basement and garage to 70*, and making DHW for two. I might be in trouble at -20F, but single digits no problem.

Dave

You can use a candle to keep the dumper from freezing in a well insulated outhouse

or you can use a Transcontinental Intergalactic Nuclear fueled behemoth to heat a corn crib

is all about matching the APPLIANCE to the LOAD

Not the other way around because you bought what the salesman wanted to sell you

dave brode wrote: You mentioned low water volume problem. The quick temp draw-down of the boiler [Kaa-2] issue aside with no tank, I have a well, which is one reason that I would not want to draw my DHW directly through the 1/2" coil. I believe that 3/4 piping from the 1" main to tank, and on to the showerhead makes a difference. No 1/2" with a well for me, thanks.

I agree that is is possible to heat the DHW with the boiler's coil alone. However, I believe that I made the right choice with a normal tank [switched off during coal season] and a simple loop from it to the boiler's coil. $50 worth of fittings and pipe and a $122 pump is much cheaper than a special tank, hardly complex, and I have 50 gallons of hot water sitting there when it's needed. None of the drawback of the "direct" setup. If there should ever be a problem with the coil [or the boiler itself], I shut two valves and switch the elec tank back on.

The Kaa-2 isn't adequate for 2400 sqft? Don't tell mine that it's not supposed to be heating 3500 sq feet of home, basement and garage to 70*, and making DHW for two. I might be in trouble at -20F, but single digits no problem.

Dave

In no way am I trying to insult your setup. I would agree that you made the right choice because you already have the electric water heater for summer use. If that was my DHW source I would definitely utilize it just like you. Alas, I use my oil boiler during the summer. I've put extensive thought into getting an electric water heater just to store hot water but I really have no need for it.

Man, you must have some serious insulation in your home for the KAA-2 to perform well in 3500 sq feet!?

Stoked,

No offense taken here, and I hope none was seen from me about your setup. Honestly, I missed the fact that you heated DHW with an oil boiler in off-coal season. I hope that we may have helped others to see different options from different angles.

No gas here, and I didn't want oil or propane. So, elec was my only choice for warm weather DHW. I'll say that my elec bill goes WAY down in winter with it off though. Fwiw, running the boiler all year for DHW doesn't appeal to me. I'll have an add on heat-pump water heater for next year [non heating season]. [6000 BTU of cooling and dehumidification when it runs, said to run for 40% of cost of operating a normal elec tank]

My 20 yr old house is 2x6 wall, but ceiling insulation is lacking, need to improve that. I didn't think that my Kaa2 was doing anything that others here aren't doing with theirs. Imo, K-S under-rates it. I chose the Kaa2, nobody sold me on it. The fact that the K6 was another $900 did play in.

Perhaps if there were 5-6-8 people living in the house, the DHW would be more of a load? I'm no expert, but although some may say that I should have bought a K6, others here say that my Kaa2 running hard is a good thing as far as efficiency. It rarely gets below zero here [although I've seen it -20*]. I do have a heat pump for cooling and maybe a week or two of heating spring/fall, and the toasters in it could make the meter go around if I ever did get in trouble with sub zero temps.

That said, I must admit that I am extremely happy with the results from my pumped DHW loop.

Dave

Watching that Youtube video about the coal-fired water heater from Australia was interesting.

I've thought about getting a square stainless steel pressure vessel welded together and tapped with the required fittings and a flue. The most important piece would be the center section containing the combustion fan and stoker motor. A hopper would be attached to the tank and then a base fabricated with a door for the ash pan.

Here's a very basic sketch.

Hi guys.
For 18 years I used a side arm heater I rebuilt off an old hand fired unit. How I did it was as follows:
1) The side arm was mounted to the boiler with 1½ iron pipe. The top went into a tee coming off the top of the boiler. The bottom was hooked into the return in a similar manner downstream from the circulator pump. Natural convection kept the sidearm heater hot.
2) The cold water heading to the water heater tank first ran through this sidearm heater from bottom to top (cold enter in the bottom and hot out the top). From there the water passed to the base of my hot water tank and was tee'ed in with the tank drain.
3) The usual cold water "IN" tap on the tank was plugged off.
4) From the "HOT" outlet tapping of the tank I had a TEE. One side went to the house system of piping. The leg went into a circulator pump. The outlet side of this pump had a check valve and then entered the cold water line feeding into the sidearm heater.
5) When the t-stat called for heat ( the old lower stat from the electric element) it turned on the pump which then circulated water from the tank, through the sidearm, and back into the bottom of the tank.
This system worked perfectly for 18 years until our local water shed source changed and became extremely hard. I opted to install a seperate water heater tank by Amtrol when the price came up right on Craig's List. I have the side arm for sale too.
This can be used for any boiler no matter what fuel and can further be enhanced by adding a circulator pump to the boiler water side to operate when the domestic circ pump comes on. I never need to though as this system gave us more hot water than 3 daughters, one wife and one son could use in a morning.
The attachment should clarify a few things for you.