Coalpail.com Forum

Good day!

If I add a coal boiler to my existing system, would I do it as "A" or "B"?

draw a picture of "C" where each boiler can be run completely independent and isolated of each other, or used in tandem.

Picture "A" I saw on line. I made "B". In "B" both boilers stay hot when either is running. The idea is to set the boiler aquastat 20 degrees lower than the coal boiler. If the coal stops heating, the oil cuts in automatically. I don't know the idea behind "A". It seems in "A" the hot water by passes the oil boiler. I think you'd have to manually turn on the oil if the coal stopped heating.

Right now either "A" or "B" could be run in unison as long as the chimney can handle the output, or two seperate chimenys.

"C" would be add valves to segregate one totally from the other. If you feared running them in one chimney or your laws don't allow it you could swap valves and chimney pipes.

I guess my original question should have been "What's the advantage of "A"?

Picture A is the way I have my stove. It circulates hot water from the stove to the boiler pump #1(Blue) then when there is a call for heat pump #2 (Red) will send it to the zone that called for it. Works good!

Freddy wrote: I guess my original question should have been "What's the advantage of "A"?

A will heat the domestic hot water in the oil burner off the coal burner if the unit is equipped with a tankless coil. B risks firing the oil on a DHW demand when there have been no calls for heat. It will require that the SFB's circulator runs once up to minimum temp.

With B, the oil boiler will have a continuous heat loss to the coal boiler's chimney when the coal is down.

A will cost more to install and B will cost more to run.

e.alleg wrote:draw a picture of "C" where each boiler can be run completely independent and isolated of each other, or used in tandem.

curious.... could you draw a pic of what you're talking about

with the addition of 6 valves, another pump, and expansion tank you now have the option of running oil only, coal only, or coal and oil together. This setup will pretty much eliminate any kind of no heat "emergency" and adds flexibility. My drawing could be better but I just did it quick and I like extra pipes. Note the bypass loop for the coal boiler, that is critical for summer DHW use.

Ok sorry for the bad post here.

I asked a question that I essentially answered myself. feel free to remove this post!

e.alleg wrote:with the addition of 6 valves, another pump, and expansion tank you now have the option of running oil only, coal only, or coal and oil together. This setup will pretty much eliminate any kind of no heat "emergency" and adds flexibility. My drawing could be better but I just did it quick and I like extra pipes. Note the bypass loop for the coal boiler, that is critical for summer DHW use.

OK, let me see if I understand this.

1. When the coal pump is one and the oil pump is off, the water takes the path of least resistance and goes through the by-pass for the oil boiler.
2. When the oil boiler pump is on and the coal pump is off the water takes the path of least resistance and goes through the by-pass for the coal boiler.
3. If both the coal and oil are running, then neither bypass loop is used and the boilers appear to be in series.

Here's where I need some more clarification. When you get a call for heat, how does the coal or oil boiler know when to fire up.

i.e. If my house calls for heat and the coal boiler is up and running how does the oil boiler know enough to stay off?

or use a 261 control
**Broken Link(s) Removed**http://www.tekmarcontrols.com/design/apps.html

With a Effical draft control on the oil boiler to control heat loss

It's been a long day & I'm a bit fuzzy.... but I think 3 valves and you could segregate the two, having one or the other. Both? I guess just open all 3 valves. As e.alleg showed, to segregate them you have to add another expansion tank.

in the diagram are flowchecks as in the second picture.

beatle78 wrote: Here's where I need some more clarification. When you get a call for heat, how does the coal or oil boiler know when to fire up.
i.e. If my house calls for heat and the coal boiler is up and running how does the oil boiler know enough to stay off?

This would apply to Razzlers drawing A.
Typically, both boilers fire from the aquastat's reading of the water temperature it is immersed in, it will fire until it reaches the maximum set point and go off until it falls to the minimum. The thermostat's call for heat to the aquastat runs the blower once the water temperature falls below the maximum setting. The oil boiler is set at a slightly lower min/max temps and heated by the coal boiler when it is operating. This is why it won't fire. Once the coal reaches minimum temp on the aquastat, the coal circulator starts and heats the oil boiler in a loop with no call for heat. On a call for heat, the zone will open and the other circulator will complete a loop through the zone's radiation and back to the coal boiler. It can be totally auto with no electrical connections between the two boilers. It does however require flow check valves that are not shown.

Freddy's drawing C appears like the oil will fire to maintain temperature if it is left on.

e.alleg wrote:with the addition of 6 valves, another pump, and expansion tank you now have the option of running oil only, coal only, or coal and oil together. This setup will pretty much eliminate any kind of no heat "emergency" and adds flexibility. My drawing could be better but I just did it quick and I like extra pipes. Note the bypass loop for the coal boiler, that is critical for summer DHW use.

I like extra pipes too

He said under his breath

but if you simply move the connection you drew in on the top of the loop from the right to the left of the existing air scoop - you remove the need for the extra one you drew in below - and keep all the functionality that you designed.

I'm a bit confused myself. I think until I actually start plumbing I won't get it. LOL My boiler is a "cold start" boiler. It doesn't run unless something calls for heat. I have an indirect water heater. Now that I think of it, I don't think I can make it work to automatically take over if the coal stops heating. I think I'll end up with something similar to my "C". Open & close valves, flip a couple of switches & I'm back to oil.

Right, like I said I drew it quick and didn't feel like scanning another drawing. The easiest way to get it right is to draw it out and then trace it with a pencil pretending the pencil is the water. Or just start fitting pipes The bypass loop is just for the coal boiler, it's so the water can circulate naturally and prevent hot spots when the circulator pump is off. Honeywell has a catalog full of variously priced controls that can do everything including calling your cell phone based on different parameters. You can get a L6006 strap on aquastat to start the oil boiler if the coal boiler cools off. Plumb it with all copper pipe and solder joints and it won't leak and it will go quick, although fairly expensive. They say that ball valves are just as good as gate valves, you be the judge. Use full flow valves in any case. I used "leftovers" - all iron pipe - and I cut and threaded it myself. I saved money but it wasn't worth it. I'll guarantee you that you won't use the oil boiler regularly once you start burning coal, it's like paying $20 for a hamburger when you can buy the same thing at the same counter for $5. You'll need a separate thermostat for the coal boiler, if you go on winter vacation just turn down the coal boiler to "keep fire" mode and shut off the valves so it won't give up any heat to the oil boiler and then have the oil boiler keep the house warm, and when you get back the coal will still be lit. The oil boiler can be turned off when you don't use it.