Conventional Hot Water Tank Off of a Coal Boiler?

Isayre,
I merged your new topic about DHW from a coal boiler with the thread that you'd previously started on this subject, we can continue the discussion here.
Thanks.

Also, I run a tankless coil in the EFM, we never run out of hot water.

You should have no problems making your domestic water directly from the coil (unless you have a dozen kids). I have an indirect hwh, the one bonus with this for me once was when the fire went out( my fault, making adjustments when I was on the learning curve ) I was able to take a shower ,and the misses came home and took a shower. I thought I would hear about this one ,but she never new it,their was plenty of hot water left. If you have high calcium,that may block the coil,but could do the same on an indirect heater.

What is a highly recommended brand/model of 3/4" mixing valve for tankless hot water from a DHW coil? I.E., if you were going to shower knowing that 180 degree F. and 60 degree F. water were mixing through a valve to deliver the nice comfortable and safe 110-115 degrees F. that you like for a shower, which mixing valve would you trust to be up to the task of not scalding of freezing you?

**Broken Link(s) Removed**

Sting, would you be confident enough to shower using one of these Honeywell mixing valves?

I did tonight

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 have a watts 1170-m2 on my indirect, set it from 90-160 , it has an allen head bolt in the end to prevent young /and old fingers from making adjustments. Back out the bolt, turn the knob, and retighten the bolt.

Great news here! I was looking at a Taco 5003. Are the Honeywell and Watts mixing valves considered superior to the Taco version, or should they all be considered about equivalent?

lsayre wrote:Have any of you been able to successfully supply hot water to your household exclusively from a DHW coil, without the use a hot water tank (either direct or indirect)? If so, how did you accomplish it? How well is it working out for you?

Yes, you should be able to do that with any coal, oil or gas boiler if it was designed for dhw. My system is an AA130. The boiler vessel is about 20 gallons. The coil is very long, probably 20-30 ft or more and resides in that vessel. The tubing is 1/2" finned. I keep the boiler at between 170 and 190 degF for heating purposes. I have a tempering valve for the dhw. I have a tank installed in-line but it is bypassed except during the summer months when I shut down my boiler. I store zero domestic hot water and I have never run out of hot water. My family uses hot water for the dishwasher, the laundry, two adults showering, and one teen showering for 30 minutes, sometimes twice a day! I have never run out of hot water except once....when the coal fire went out!

The AA130 system is rated to deliver 3.5GPM of dhw through the coil continuously. That is assuming 40 degF input water and 140degF output water with an average boiler temp of 180degF. That is with the old style coil. I do not know if my "new style" coil is rated higher or lower. My input water is about 50 and the output is mixed to a temp of 120-130. The boiler averages 180 degF.

http://www.axeman-anderson.com/pdf/anthratube.pdf (see page 3 at the bottom)

My home is 1986 construction, split entry, with r-19 walls, heat loss of 80k BTUs/hr at -20 design temp, 2400 sq ft heated space to 71degF. I consume 5 tons of pea coal per year (beg oct through end of may).

The subject has switched to true tankless mode, but the OP asked about using the boiler coil to heat the water in a conventional tank.

Since mid Oct, We [wife and I] have been getting by on a gravity [syphon] loop from the Kaa2's coil keeping the water hot in the switched off 50 gallon elec tank sitting next to it. With boiler 'stat set on apx 170 high, might spike to 180 once in a while. My system is air over water, and I pump the boiler water 24/7. So, my temps stay quite consistant, and the guage on the return water rarely reads below 150.

Even at only 170 high boiler temp, with the syphon loop, the water at the faucet was hotter than with the factory setting on the tank in elec mode. Recovery was slow, however. Last night, I plumbed in a small #500800 Watts circ pump. They are sold for recirculating hot water. One end will take a 3/4" npt female adapter, and the other end has a rubber gasket, and the nut swivels, and will take a 3/4" npt male adapter. The pump is small, low draw. The pump has a timer, but I'm running it 24/7 for now. It does move enough water to make recovery much faster, and the water at the faucet is hotter, but not quite hot enough to have both hot and cold on wide open in the shower [for max pressure]. More like hot full, cold 1/2. I realize that running the boiler hotter would make the water hotter.

Here is the pump that I bought for $122 shipped; As luck would have it, there's one on there now for $80.
**Broken Link(s) Removed**Here is a pic of my loop. The pump was installed in the lower verticle section between the valve and the 45. Yes, close to the flue, but surprisingly, the por-15 coated 14ga flue does not reflect much heat. Ignore the block of wood. No, it's not a hanger LOL.

I should mention, the specs state 140* max.

Dave

On the subject of heating DHW;

While stating the performance of a non pumped gravity loop, I should mention that I have "sidearm" style heaters that pre-heat my well water prior to the DHW tank recieving it. I did not have them working until a few weeks ago [long story about a paper towel stuck in a pipe]. They do make a difference, but surprisingly, the water entering the DHW tank from them isn't really all that hot. Although, the shower would go cold a little quicker without them and just the gravity loop heating the water. Then again, the well water is 57F or so.

Fwiw, here's a pic if the side arms. One on return water, one on supply water, going and coming from boiler room. Side arms are fashioned by running the 1.5" boiler mains inside of 2", with tees on each end.

The 1" coming along the wall is from well. Water goes to sidearm on return side near tank and travels away from boiler. Water jumps over from the other end of it into the other side arm, then travels back toward boiler, out of that sidearm and down to tank.

During no fire season, I valve them off, and run the well water right to the tank.

Edit: Also noteable [again] is what has been said about deposits in coils, piping etc. I suppose that it depends on the water, and Ph. My well has some hardness, but is softened, so not much disolved mineral gets through. Ph is a tad low. I don't *seem to* have any problems with deposits.

Dave

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

While searching for the make and model of the coal-fired water heater as shown in the above posted video I came across this article.

http://www.libraries.psu.edu/content/dam/psul/up/ ... etin37.pdf

Here's an excerpt from page 1.

"The heating of domestic service water for the home is a problem that confronts the major portion of our population at one time or another; yet surprisingly little helpful information has been published on this subject. Not only is this problem important to the householder, but it is also of definite concern to the coal industry because so frequently it is allied with the heating of the home. The primary sources of heat used in the production of service hot water are electricity, gas, oil, coal, coke, wood, and the sun; while the indirect sources are steam, hot water, and waste flue gases. For domestic purposes, electricity, gas, oil, and coal are the most popular, with the choice depending on a number of factors such as availability and cost of the fuel, degree of automatic operation desired, fuel used for heating the home, cleanliness, cost of equipment, wealth of individual, safety, and the amount of water required.
From the viewpoint of the bituminous coal industry, the domestic water heating problem is of considerable importance. Not only could the yearly coal tonnage used for this purpose amount to a substantial item in itself, but frequently, especially in new installations, the choice of fuel used for heating the service water is a deciding factor in the choice of fuel for heating the home. The majority of home owners now heating their homes with bituminous coal use a different source of energy for heating service water because, in general, as much attention is required for the bituminous coal hot water heaters as for the regular heating system. Where a different fuel is used, duplicate equipment is required and with oil or anthracite duplicate storage facilities. Because they are completely automatic and practically trouble-free, gas, oil, and electric water heaters appeal to the public despite the fact that they are usually costly methods of heating water. All too frequently this leads to the installation of similarly fired automatic heating systems."