Overheat Advice

The safest approach to this is to assume the the overheat loop is always at system pressure, therefore it should meet the same overall system specs.

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I agree. And this does NOT include 50 gallon steel drums on the list of possibilities.

DaveBP said:

The safest approach to this is to assume the the overheat loop is always at system pressure, therefore it should meet the same overall system specs.

Click to expand...

I agree. And this does NOT include 50 gallon steel drums on the list of possibilities.

Click to expand...

Go down to a plumbing shop and see if they have some old fin tube. Don't need the outside metal, just the fin tube. Mount high as possible above boiler( supply/return), install automag, done. I wouldn't think you'd need pressure relief, as system should already have it. Same with expansion tank. Put a little more fin tube in that is needed, if it makes you feel better. Takes up a lot less room than steel drums. Tarm was happy with this set up, as they had it in their layout. I'm not second guessing them. I just drive a truck.

BUT I do agree w/Goose to on the electricity use, but this works

This has been interesting ready but I choose a different tact for a power failure. My system is powered through a power inverter which has a built in Battery Charger and a Transfer Switch. If the power goes out a 12 volt deep cycle battery runs the system for 6+ hrs. I do have a Acuastat to handle a boiler overheat.

I agree with the UPS approach, though presumably you would want to have some sort of a system to deal with what happens if the UPS fails null, or even fails to deliver the expected run-time...

It certainly makes sense to me to have a UPS backed system, but I would probably want it wired so that if the UPS went into backup mode, it would send a shutdown sequence to the boiler, followed by limiting the power to only drive those components needed to cool the boiler as it is shutting down - with a "recover" setup if the power comes back on in the meantime...

(If using a NoFo style computer controller, this would be relatively easy to do - connect the UPS "power state" signal to the controler as an input - and put a program in the controller to deal with it... I would probably include a delay of 5 minutes or so to allow for short interruptions, and / or to make sure the power is hopefully up and stable before firing back up...)

Gooserider

timberr said:

This has been interesting ready but I choose a different tact for a power failure. My system is powered through a power inverter which has a built in Battery Charger and a Transfer Switch. If the power goes out a 12 volt deep cycle battery runs the system for 6+ hrs. I do have a Acuastat to handle a boiler overheat.

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Power backup is good, however it doesn't cover it all. What if you have a pump failure or a jammed danfose? I tried to consider all possibilities for failure. I have most of them covered but I still have a couple of situations to resolve. When I get some form of computer control set up that should help. However, the computer like the automag will use a small bit of power, but I'm totally OK with that.

I'm new to the forum and in the planning stages of my wood boiler install, a Jensen 24B in an shed outside. My idea for a simple non-powered dump zone was to put a Watts temperature and pressure relief valve in at the top of my boiler in a tee were the supply line heads to the house and hook the discharge to finned tubing looped back to the return. It seams to me this would give a non-powered 210 deg safety that would automatically close when the temp came back down. Just wanted to run this idea past the forum.

I'm still looking around but it looks like lots of good info.

jamierah

jamierah said:

I'm new to the forum and in the planning stages of my wood boiler install, a Jensen 24B in an shed outside. My idea for a simple non-powered dump zone was to put a Watts temperature and pressure relief valve in at the top of my boiler in a tee were the supply line heads to the house and hook the discharge to finned tubing looped back to the return. It seams to me this would give a non-powered 210 deg safety that would automatically close when the temp came back down. Just wanted to run this idea past the forum.

I'm still looking around but it looks like lots of good info.

jamierah

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Jeremiah:
Welcome to the Boiler Room At first glance your idea seems like it would work bu I don't think it would because of equal high pressure conditions of both side of the T&P;valve..... Maybe one of the hydronic experts will chime in on this one

Bob

Take some time to think through overheat and what needs to happen, and it ends up pretty simple on a gravity or pumped system. You want the overheat loop to activate on both an actual overheat and on a power failure to prevent an overheat from occurring.

Per Tarm install directions, I installed an open on rise aquastat which I set at 210F which cuts power to the Automag, thus causing the Automag to open and activating the overheat loop when temp reaches 210F. On a power failure to the boiler circuit, power to the Automag also is cut, causing it to open and activating the overheat loop. My system is pressurized, so at 15 psi the boiling point of water is about 257F, and there is no "boiling" that would occur on an overheat.

If the overheat loop needs a circ and cannot operate on gravity, then a UPS, generator or other arrangement needs to be made to power the circ on an overheat and over-ride any thermostat which otherwise would shut the circ down when a setpoint is reached.

If possible, a gravity system would be preferred as it would provide overheat protection in the event of failure of the overheat loop circ. My power failure overheat loop is 32' of finned copper on the ceiling of the boiler room. As I have 1000 gal of storage, overheat in my system is just about impossible absent a power failure, as storage would continue to charge and draw off excess boiler heat.

IMO the cost of the watts consumed by an Automag (which I haven't measured) are far outweighed by the safety and boiler protection provided.

Addendum: whatever overheat method you choose, it would be very advisable to cause an overheat actually to occur to test whether the system performs as intended.