Overheat Solution

I am trying to come up with a way to deal with a possible overheating boiler. Since I have to cut into the piping around the boiler I am going to try and solve this too.
The heated water travels from the boiler to the house 100' underground through 1&1/4" PEX.
I want to put a tee into the return line before it gets to the Laddomat. The return line is 1&1/4" and the new line coming off would be 3/4". On this line there would be a circulator (hooked up to a relay, battery and an inverter to power it during an outage) that would go into the boiler through a previously unused tapping.
I have attached a piss-poor diagram of my idea. The yellow box is what I would like to add to the current setup.
My plan was to use a Grundfos UPS15-58FC circulator to move the water. I want to move enough cool water into the boiler, by bypassing the Laddomat, as soon as the power cuts off.
Will this work for my situation?

jebatty said:

I think the water flow in your diagram will short circuit and not achieve the result you want. How fast does your EKO fire die down after the power is cut? For my Tarm the fire dies down very rapidly once the draft fan is off.

A good solution would be to have your laddomat/boiler circ on the inverter and a zone in the house that would open in a power outage Then that zone would be the heat sink to prevent the EKO from overheating. A heat sink zone plus fire die down should prevent any overheat problem.

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The fire will continue to burn long enough to bring the boiler temp up to 195* within 10 minutes (the high setting is 180*). The dump zone in the house will be set to circulate in the event of a power failure. I was trying to avoid putting the Laddomat on the inverter because it is 240V. I was not 100% confident that there wouldn't be a problem somewhere between the relay, battery, inverter, converter, and pump. I was trying to get something more simplified.

Bob

Clarkbug said:

Do you currently have a dump zone or overheat loop on your boiler as it stands today? What about piping up something like this inside your boiler shed with some fin tube or a salvaged radiator? That dumps heat at the source, and in case of an extended outage, heats up your boiler space to give you a little freeze protection.

I like jebatty's idea about running a zone of your house on the inverter. If you could swing it, would keep your house toasty while the power was out also...

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I had considered this when I first was designing the system. I was faced with lack of space in the boiler room -- both square footage and headroom. The ceilings are only 7 feet tall and I was concerned that the height would not be sufficient to create a differential that would facilitate the gravity flow. I was also concerned that since the finned tubing would be placed at a height of 6&1/2 feet, there would not be sufficient convection because of the limited air flow and space. The boiler room is usually 100 to 120*.
Something else I had considered was getting an old cast iron radiator and putting that on top of the boiler room. Since this would be exposed to the outside, I would have to fill it with an antifreeze solution. In the event of a power failure, the valve would open and the hot water from the boiler would be able to rise into the radiator and the cold antifreeze solution would then come down into the boiler. That would bring up another possible problem. If it worked as designed, and the boiler water displaced the antifreeze solution, then I would have a problem with the water freezing when power was restored (if I was not there to take care of it).
Is this a viable alternative or should I stick with jebatty and wire up the Laddomat and dump zone?

Bob

BoilerMan said:

The only bad thing about Jim's idea (which I like) is boiler pump failure. Say you have a rip-roaring fire going in boiler....180+ boiler temps, everything is working well. House is warming up, storage is charging, elves are dancing........

Then the boiler circulator cooks, no water flow through boiler, boiler goes into idle, but natural draft easily takes 180+ to 230F and ketteling starts. Pressures get to 30psi relief valve pops, superheated steam in boiler room, possible pex failure, the list goes on from the collected experience here.

A gravity dump zone is the best way to avoid this. The UPS and the boiler, circulator, and controls is a plus, but for ultimate failure or one critical component is gravity flow. Super-heated water is a scary thing to be respected. 1800:1 expansion ratio.

TS

Click to expand...

I don't understand exactly what you mean. Are you saying that the circulator fails because the boiler overheats or just because the circulator fails on its own?

Bob

ewdudley said:

Read a report "Preliminary Lessons Learned from the Fukushima Daiichi Accident ..." that agrees gravity flow is the way to go.

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ewdudly,

I wanted to thank you for your previous help with the problem I had with the Aquasmart, TEKMAR, and actuator problem. Ron Mannino figured it out for me last week. I tried to send you a PM but it wouldn't let me.

Bob

BoilerMan said:

Just pump failing from old age, ,Murphy showing up.

TS

Click to expand...

OK. Then I have a different question because I missed something. How would the gravity system work in this case? Is there an aquastat that would cut power to the zone valve to cause it to open up?

Bob

ewdudley said:

Can the Laddomat pump be replaced with a 120 VAC version?

If not possible, it should work to put another pump in series with the Laddomat between the Laddomat and the boiler. This would also give redundancy if Laddomat pump failed or fell behind and overheat kicked the second pump on. The backup pump could also be placed in-line on the boiler supply side between the boiler and the bypass tee.

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The Laddomat had to be 240V according to the guy that sold it to me.
I can not fit a pump between the Laddomat and the boiler.
I can definitely fit a pump on the supply side between the boiler and the tee. I like that idea a lot. It will mean less pipe work for me.
If a pump fails, will it still allow circulation to occur if there is another pump in line with it?

Bob

ewdudley said:

If you have a situation where the top of storage is a few feet above the top of the boiler, the Laddomat is designed to allow gravity flow for power fail overheat protection (assuming it is equipped with the internal low-resistance check valve, I believe there is such a thing a Laddomat that has the check valve deleted or disabled):

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They include instructions on how to disable the check valve if you need to.


Blocking the check valve

If you, for some reason, want to completely shut off the self circulation function, the check valve must be blocked.

Use the blocking clip, placed at the bottom of the EPP insulation to block the check valve. The clip is fastened around to check valve axis according to picture 5.

To reach the axis, the spring needs to be removed.


Picture 4


Picture 5
Blocking clip