Dump Zone hook up.

Any suggestions out there of what I need and how to hook up a dump zone on my coal boiler that is linked up with my oil boiler. Any help will be appreciated.

Get an aquastat that makes contact on temperature rise (e.g. Honeywell L4006B, L6006A, or L6006C), and mount it on the coal boiler. If you have an unused boiler tapping that can accept an aquastat well, that is ideal...if not, get a strap-on aquastat and mount it on the supply pipe leaving the boiler. Connect the aquastat to the zone relay of your choice.

Thanks for the help!!

You don't need a dump zone at all when you have a properly sized expansion tank. In a closed pressurized hydronic system when the water temperature goes up the pressure goes up. Water expands when it is heated. Provide a sufficiently large expansion tank and that expanding water will have a place to go. You design it so your highest design temperature still has a pressure below the safety valve. A typical design margin is 5 psi. I've had operational mistakes that have caused my boiler temperature to reach 250 deg F and not pop the safety release. When the boiler cools the displaced water in the expansion tank, pushed by the air side pressure, returns to the boiler. When sizing the expansion tank remember only the water in the coal boiler will reach the abnormally high temperature. The rest of the system water temperature is much lower. Knowing this permits a smaller expansion that if you assume all the the water in your system will be a the abnormally high temperature. I repeat again, for a closed system with a properly sized expansion tank there is no need for a dump zone. The only exception are systems that use PEX tubing where the abnormally hot water could cause PEX tubing failure. And even with PEX, analysis might show the temperature at the PEX might be within the specs.

Check out how Tarm does it, I believe their install manuals are online. I hooked my neighbors up, because it has been known to happen that sometimes a feed door or ash door is left open for a little longer than was safe, and the dump zone helps absorb the excessive heat, providing the operator reacts to the unsafe condition before all hell breaks loose.

The largest zone is the best for the dump zone, something that the output is close to the boilers. I use 2 dump zones, set 5-10 degrees apart. If one fails, the other takes over and I can switch aquastat settings to change zones from summer to winter, excess goes to my garage in the summer. I like the idea of the dump zone, and it doesn't overwelm the house, pay me now or pay me later. Like was said, if the expansion tank is large enough it's not needed. But my opinion, the warmer the boiler is, the more btu's lost, put them where you want them.

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2 dump zones?/ That sounds keen!
How do you have them tapped in?

GoodProphets wrote:/\/\/\

2 dump zones?/ That sounds keen!
How do you have them tapped in?

1 strap on and 1 immersion well in an unused steam port. I have a 6 zone switching relay for 4 zones, the one is just hooked to my thermostat wire to start the pump, the other is on it's own relay. When I bought the switching relay, I was thinking of doing radiant floor heat, but the nails in the hardwood changed my idea (for now) so I had the capacity for the extra dump zone. Ebay was helpful for the aquastats.

AA130FIREMAN wrote:The largest zone is the best for the dump zone, something that the output is close to the boilers. I use 2 dump zones, set 5-10 degrees apart. If one fails, the other takes over and I can switch aquastat settings to change zones from summer to winter, excess goes to my garage in the summer. I like the idea of the dump zone, and it doesn't overwelm the house, pay me now or pay me later. Like was said, if the expansion tank is large enough it's not needed. But my opinion, the warmer the boiler is, the more btu's lost, put them where you want them.

I assume the basic purpose for a dump zone is for a over run temperature condition. Ideally a fail safe design. How well does your design work when there's no electricity? Lets say you just had a large heat demand, the combustion blower has the coal burning hot and now you have a power failure. What happens? Does your PRV release? Do you loose boiler water? How much? Lets assume you do and the power now comes back on. Does the impeller of your pumps have water to pump? Can the automatic fill valve replenish the lost water? Do so without manual venting? What happens if the coal is still blazing hot when the power returns. Does it make steam because the trickle of flow from the automatic fill valve isn't fast enough to fill the boiler? The only fail safe design I can come up with is one that has sufficient expansion tank volume to fully absorb the boiler water during run away temperatures. I don't see how you can depend on any pump.

I agree getting the heat out of the house in the summer is a good idea, but your design still needs to be fail safe.

Yanche wrote:The only fail safe design I can come up with is one that has sufficient expansion tank volume to fully absorb the boiler water during run away temperatures. I don't see how you can depend on any pump.

I agree getting the heat out of the house in the summer is a good idea, but your design still needs to be fail safe.

What happens if the bladder in the expansion tank leaks out the precharged air ? As one told me, the only 2 shure things in life are death and taxes. Is their anything that is 100% fail safe ? Some sort of radiator or water storage tank higher than the boiler with a zone valve held closed with electric, power off,valve opens and flo begins. I do like belt and suspenders but I'm not going to get that carried away I do have a generator, but not an automatic transfer switch, then again I could run out of diesel