Low temp boiler protection

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Nov 29, 2010
172
Central WI
What product would be best for low temp boiler protection. I have a corn boiler/ pellet boiler, that will be hooked directly to 1500 gallons of unpressurized water storage. All loads are taken off of the storage, not directly from the boiler. I have nothing plumbed as of yet, so I can make anything work. Thanks in advance for any help.....
 
Off the top of my head you could implement different scenarios depending on your preference.

First would be the scenario recommended or required by the boiler manufacturer, usually a three way thermostatic loading unit like the Akaso LK 810. Tying the boiler directly to storage, you are probably looking for something like that.

One of the alternate scenarios, especially if you were going directly from the boiler to the load, is a reset controller with boiler return protection. The reset controller runs a variable speed pump that ramps up to the reset setpoint, but only as fast as the boiler return water temp sensor allows. That would probably be a two pump method, a pumped bypass straight supply to return with a variable speed setpoint pump like a bumblebee (set to maintain ~150 F), then an outdoor reset controlled pump with the boiler return protection sensor.

Those are the two choices I would be looking at. Neither are the cheap way. Preferring one or the other would probably depend on the system arrangement after the boiler, load type, how far to the loads.

Maxing boiler output straight into storage with no use for a reset control, that's probably a job for a thermostatic loading unit.
 
I like the loading unit myself, nice all in one solution to handle near-boiler circ plus low temp protection. Not cheap, but doesnt take lots of tinkering to get working either.
 
Is your corn boiler something like a Central Boiler Maxim? If so, keep in mind the elevation of storage as related to the open boiler. Also, you are going to have an issue with expansion, as you will have 50 or 100 gallons of water to put somewhere when hot.
 
No, my boiler is about the size of a 80 gallon water heater, I think it contains only 20 gallons of water in the jacket. My tank water level will be around 2' higher than the boiler water height.
 
The problem still exists. How will you keep the water from storage which is 2' higher than your boiler from coming back and flooding out the fill opening ( assuming it's an open system ). And when that 1500 gallons of water goes from 70* to 170* it becomes 1575 gallons or so - can it be accommodated in the system ( it may be as simple as leaving the storage tank slightly low when cold ).
 
There is no fill opening on this boiler, the boiler is meant to be used in a closed system, but I am using it in an open system.
 
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