Coal/Oil Boiler-Question About Domestic Hot Water

I'm brand new to this forum, and very glad I found it! I am hoping someone can help me with this(and from reading lots of previous posts, I think you all can!)
We have a Keystoker combination coal/oil burner, a KA-6, that was installed last October. We have the old water filled radiators for heat in most of the house, with baseboard heat in just the kitchen. Domestic hot water is heated through the boiler then pushed up to faucets.
First, let me say that I love the coal burner. It is in our basement, and helps to keep the basement warmer and drier, which is a plus, and even though the coal is stored in our garage right now, necessitating going up and down stairs to transfer coal and remove ashes, we are going to spend the summer building a coal bin in the basement. Of course, the money we have saved over the winter burning coal instead of oil is the best part of it all!
However, the one thing I really, really don't like is that we can have either heat or hot water, but not both at the same time. Because there are only 2 of us in the house, it has not been a huge problem, nonetheless it is a problem to me. I've had more cold showers over this past winter, than in my whole life..... my better half claims that we just need to know when the heat kicks on, finishes heating the house then use hot water. I, on the other hand, feel that there is something not quite right here.
I really think that the hot water system was not hooked up right to begin with, a valve maybe that isn't installed properly? Before we call someone to fix it(plumber?), I thought I would get some insight here!
Ask me any questions, and I will try to answer them, can anyone help?

I believe your wife is correct, BUT you need t do some checking and recording of water temperatures

It sounds like the water temp in the boiler drops way down when the large volume of cold water in the radiators is circulated to 'the boiler [when the thermostat calls for heat].
You can check this by turning the thermostat down a few degrees, let the house cool a bit, then go downstairs, boiler water temp should be about 180*. Have your wife turn the thermostat back up, watch the boiler's water temperature, if it drops below about 120*, this is too cool to heat your domestic hot water and feed hot water to the radiators.
Verify this by having your wife then turn on the hot water in the shower or tub, I'll bet the water temp in the boiler drops to 100* or less..Heating 50* well water to 115* takes more btus than heating your house on a normal day.

Now, there are several ways to 'fix ' this problem, one is follow what your wife said, I'd just turn the thermostat down a few degrees, take your shower and turn the thermostat back up once out of the shower. Easy, costs nothing.
Next would be to add a holding tank to the hot water system so that the cold water feeding the hot water coil in the boiler is 'tempered' by sitting in an uninsulated tank near the boiler, raising the well water temp to room temp.. this is far from a perfect solution but it will work, most of the time.. the idea is that the boiler's coil will see 75* water to heat for your shower instead of 50* water, this is a huge difference in BTUs needed and will draw down your boiler water temp a lot less.

Next would be to run some form of boiler mate hot water heater/tank, or to put your boiler DHW coil in the supply side of a normal oil or electric hot water tank, and let the oil or electric take up the slack when the boiler water temp falls too low.

Do some observation on the boiler water temps and let us know what you find.

Welcome to the forum!!
Greg L

Like Greg said, something isn't right- your high water content system may have something to do with it. Also, your low limit/circulator reverse settings may be wrong. If your installer wasn't familiar with domestic coil set-ups it could be anything. Coils are not common in this area of NYS so that could be it.

I think what Rob R. suggests is the first and easiest thing to check out. There has to be a reverse acting aquastat to stop the circulator when boiler temp. falls below a set value. Today everything is combined into one control which makes it easier to wire it wrong.

Welcome aboard bbecker. More system information would help find the answer to the problem. Did you ever look to see what temperature the boiler is operating at when your wife is running out of hot water ?

How about setting up a temper tank on a thermosiphon system to store 40 or 50 gallons of hot water in? Seems like this would effectively spread out the demand of heating the DHW so the boiler would better handle the home heating demand.

I use an old hot water tank. They are perfect since they are insulated and have connections at the top and bottom for the thermosiphon to work properly without another circulator.

Rob R. wrote:You are using the tankless coil in the Keystoker? If so, my guess is that the circulators are not wired to cut out when the boiler temperature drops below the low limit setting. That is what the ZR/ZC terminals are for, but most people don't wire the controls that way. You either need to change the way the controls are setup, or work on balancing the system so the boiler doesn't see so much variation in load.

Pictures of the piping and controls would be helpful.

Most likely he has it wired using C1+ C2 as per keystoker wiring diagram. bbecker what is your settings for Hi + Low on aquastat? What size is hot coal bed on grate after 40 mins, should be 2 inches of dead ash at end of grate. Are you trying to get hot shower after wife or call for dhw? You burning rice or buck? I'm using a electric hot water tank for storage on dhw. Welcome to the Board!

Thanks for the welcome, and the possible scenarios, I'll be checking them out one at a time....
Greg your experiment tells me a lot. I already know that when the heat is on, the water temp. drops to 120* and below, even down to 0 sometimes. I've watched it fall before, and it usually drops pretty quickly. It makes sense that the boiler is heating up all the water in the 8 separate radiators in the house, and so draws all the heat to there.
A holding tank- I don't believe there is one there, I will check that. There is a small, maybe 2 gallon tank set off to the side of the boiler, would that be one? Is it possible to have warmed water sitting in the existing hot water heater, or would it have to be a separate, newer tank?
I just added photos, let me know if I need different ones, closeups whatever, I don't have a great camera, but will do what I can.
I appreciate any and all help!
btw, I am the wife! I forgot to say that in my post! I am the half that has the mechanical mind in the family, but was hoping not to have to use it for this whole thing. I like it just fine, don't mind hauling coal and ashes, etc. but kind of hoped I wouldn't have to be the one to figure this out! lol!

Well I see the original heating system was a gravity type, meaning that it did not have a circulator. Hence you have 2" distribution pipes that hold LOTS of water. All that water in the pipes plus whats in the radiators cools down between cycles. Then when there is a demand for heat, all that cool water flows into the boiler dropping the temp quickly. From the photo it looks like your boiler water was about 200 degrees at the time that photo was taken. Plenty hot. With A system with 2" pipe, I would have had a bypass installed that would help keep the boiler temp from tanking on a demand for heat.

You at least need a system by-pass. Primary Secondary would be better.

I agree with oilman: a primary/secondary setup would be the best fix. But maybe you can get away with properly setting up the wiring on the aquastat to stop the heat circulator when the boiler water temp drops to far..

Greg L

bbecker wrote:Thanks for the welcome, and the possible scenarios, I'll be checking them out one at a time....
Greg your experiment tells me a lot. I already know that when the heat is on, the water temp. drops to 120* and below, even down to 0 sometimes. I've watched it fall before, and it usually drops pretty quickly. It makes sense that the boiler is heating up all the water in the 8 separate radiators in the house, and so draws all the heat to there.

As was mentioned, you need to wire the controls to stop the circulator once the temp drops below a certain level. This keeps the boiler temp from dropping too far and having to heat back up again. I had the same issue with my AA 260. I too got luke warm showers at times. And boy did I hear it when SHE did....... By changing the circulator cut off temp and increasing the boiler start temp, it kept the boiler warmer thereby keeping the showers warmer.

bbecker wrote:A holding tank- I don't believe there is one there, I will check that. There is a small, maybe 2 gallon tank set off to the side of the boiler, would that be one? Is it possible to have warmed water sitting in the existing hot water heater, or would it have to be a separate, newer tank?

That little tank in the pictures is your expansion tank. It's purpose is to maintain the pressure in the system to pump the water upstairs and allows a place for the increased pressure due to increased temps to go rather than blow off the pressure valve.

bbecker wrote:I just added photos, let me know if I need different ones, closeups whatever, I don't have a great camera, but will do what I can.
I appreciate any and all help!
btw, I am the wife! I forgot to say that in my post! I am the half that has the mechanical mind in the family, but was hoping not to have to use it for this whole thing. I like it just fine, don't mind hauling coal and ashes, etc. but kind of hoped I wouldn't have to be the one to figure this out! lol!

No problem "wife." In fact I like wifes....... Ask all the questions you want. My wife knows about our coal boiler system and can take care of it when I'm gone. She does not know a lot about it but enough to keep her warm and safe. I even trainer her to take out the ashes......Ooops now I'm in trouble.

Rick

Welcome to the Forum! You've been given a lot of good information. I was going to suggest a bypass line to keep the boiler from taking in so much cold water all at once. It's an added pipe and valves from top to bottom of the boiler. It will make the boiler water want to spin in a circle so not as much heat goes out to the radiators. The radiators will heat slow & steady, the boiler will stay up to temperature. In my opinion it's a necessity. Allowing the boiler to drop below 140* is not a good thing. The last thing a boiler wants to do is expand, contract, expand contact. It won't bother a steel boiler too much, but it can be bad for a cast iron boiler. Also, dropping below 140 can allow condensation to occur in the exhaust & that's a bad thing too. That might be more of an oil thing than a coal thing, but physics is physics.

That being said... all the ideas about changing the controls are good ideas. Hot water should have a priority over heat. Yours is an extreme example of why.

Of course, if you have an extra $1,500 to spend, an indirect hot water maker would be the answer. That is a separate tank of water that gets heated by the boiler. It does away with using the hot water coil in the boiler. Then you'd have 40 gallons of hot water at the ready all the time. Happy wife, happy life!

I had the same problem with an old Yellow Flame stoker hot water heating boiler we had. Our DHW was heated by a coil in the boiler just like your keystoker. Coal does not respond like oil or gas. It takes a slow and steady ramp to heat up your boiler or allow it to cool down. Your photo shows your already set to run around 180 - 200 degrees. This boiler can supply more than enough heat for what you want.

A very simple fix that does not involve cutting piping, adding valves has already been mentioned. 30 minutes or so before you want to take a shower or bath turn the room thermostat(s) back 10 degrees. That shuts off the pump(s) supplying the radiators and keeps the hot water in the boiler to heat the coil. Don't worry about stressing your Keystoker. It can take the temperature swings.

Shower or baths done? Turn the room thermostat back to normal setting.

No fuss no muss. No cutting, no system modifications. If the house starts getting cool then you forgot to turn the thermostat back up after your bath or shower.

It worked for my my wife and I. Try it, you might be surprised how simple the fix might be!

Rev. Larry