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Hydronic System With An Electric Mini-Boiler


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Hi All,

Had an interesting new home inspection yesterday. The home is heated mostly with in-wall forced-air hydronic heaters and in-floor hydronic radiant heat that uses an electric mini-boiler for heat. It's the first time I've seen this system.

The client had remarked to me that her heat and hot water was supplied by an "on-demand" type water heater, so I'd expected to find a tankless type water heater under the house in the crawl. Instead, I found a conventional electric tank-type 50-gallon water heater next to an electric 9Kw mini-boiler that heats the water that's circulated to the wall heaters and the floor heat. I took the shroud off the boiler to get a look at its inner workings. It looks like it's essentially a small coil tank about 4 inches in diameter and about 18-inches long with a total of 3 heating elements (1 on top and 2 on the bottom) heating the water very quickly as soon as there's a demand ordered from one of the heating circuits.

The system heats up fast - a lot faster than a hydronic system run off of a conventional water heater tank heats up; I'm just wondering whether the cost will be prohibitive - maybe not in the Seattle area with our comparatively mild winters.

The system is made by Electro-Industries Inc. in Monticello, MN.



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How many circuits did it take to power that thing? At my day job we recently were looking at an electric on demand domestic water heater for an apartment conversion for the owner's son (we like to call him the CE Uh-O). To supply adequate hot water the unit needed three 60 amp 220 circuits, one for each element. Even with the subsidized small muni electric this thing would have cost a fortune to run.


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Would you happen to have a photo of the in-wall forced-air hydronic heater?

I'm visualizing a rather large unit heater style cabinet vertically buried between two studs.

Did it have a fan?

"Two level hi-limit protection-160° pipe protection"

Now that's protection![:-bigeyes

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