Gravity Flow Overheat Loop in EKO Boiler setup

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markpee

New Member
Hearth Supporter
Aug 12, 2008
151
Huson Valley New York
In getting prepared for our install of an EKO 40, I notice in the new manual that they are calling for a "gravity flow overheat loop" in the event of a power failure. Is this something new? We're trying to plan, and notice this tank above the boiler. Anyone else do this or plan on it?
 
markpee said:
In getting prepared for our install of an EKO 40, I notice in the new manual that they are calling for a "gravity flow overheat loop" in the event of a power failure. Is this something new? We're trying to plan, and notice this tank above the boiler. Anyone else do this or plan on it?

The theory behind it is this: you are running a fire, full-boil and your pumps are circulating the hot water around the house...the power goes out, circulation stops. Your boiler will overheat very quickly...a gravity loop is one that will flow when the power is out, so you have a "normally closed" zone valve that uses power to stay closed...when the power goes out, it automatically opens and allows flow....and because hot water rises, water flows out of your boiler UP to a section of baseboard/radiator, dissipates at least some of the heat to the atmosphere, and then back down to the boiler until the power comes back on, or else the fire goes out.

Besides the cost of the automag zone valve, its not a very expensive proposition to set one up, so cheap insurance to do so. I'll be setting up one for my tarm soon - just need to get some help with how much baseboard is enough.
 
Mr. Ed,
The way its was explained to me is:
The over-heat loop is sized to handle 10% of the maximum capacity of
the
boiler. So for an SP40 we recommend about 25' of baseboard.

Example:

SP40 140,000 btu max output
10% is 14,000 btu
At 600 btu capacity per foot of baseboard = approximately 23 feet.
Now you have the Solo60. Just substitute the figures.
160,000 max. btu, 10%=16,000btu
At 600 btu capacity per foot of baseboard=approximately 27 feet.
 
Is all baseboard rated at 600BTU per foot? I have various used ones at my house that I want to use for this purpose...
 
Tarm dealer advised me to use 500 btu/ft/hr to size the overheat loop. I went a little bigger based on the lengths of baseboard I had. Most important is to test the loop to make sure it functions as intended.
 
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