At 01:37 PM 1/25/2009, you wrote:

I am in the process of building a log home in Kentucky and I would like to have a masonry heater to heat, provide hot water and to use for my radiant floor heating.  My question is, can your masonry heaters provide me with all three of my needs?

Hi:

Because masonry heaters burn in batch mode, there is a limit on the amount of wood they can burn per day. This puts a limit on the maximum heat output. Traditionally in Europe, they were only used as room heaters. Nobody ever tried to heat a whole house with one.

The ones we build here in North America tend to be larger. The typical North American heater has about twice the firebox capacity of the average Austrian heater, for example.

Our heater is designed to burn a maximum of 100 lbs of wood per day (2 fires at 50 lbs each). This gives you an output of 20,000 BTU/hr, or 6 kW. Typical usage is with a single 60 lb fire per day, which gives you 12,000 BTU/hr, or 3.5 kW.

The heating load of your house depends on your location (heating degree-days), the size of the house, and to what level of energy efficiency it is built. A house built to conventional construction standards could easily have twice the heating load of a modern low energy house of equal size. A conventional house here in Ottawa, for example could have 4 times the heating load of an equally sized low energy house in Kentucky. By the same token, a log house in Kentucky could have the same heating load as a low energy house in Ottawa, which has twice the heating degree-days.

If you add a hot water coil to the heater, it will move some of that heat into a hot water tank, but it will not increase the overall heat output.

It is possible to put a relatively small coil directly into the hottest part of the firebox, which is suitable for providing domestic hot water. Too large a coil in the firebox will cool the fire, and result in poor combustion.

It is possible to place multiple coils downstream of the fire, in the upper chamber. We have a few clients experimenting with this for hydronic heating. However I consider it an experimental application at this time. It does theoretically give you the ability to fire the heater harder, ie., burn more than 100 lbs of wood per day. However, as a manufacturer we are not prepared to warrant firing the heater with more than 100 lbs per day.