Hot Water Heating and JUCA

However, since they work so very well at this task, customers sometimes realize that the JUCA is capable of creating and supplying even more heat than they are using. Sometimes they use this extra capability to send heat to a basement, a workshop or a garage that otherwise wouldn't be heated. But then sometimes people ask about getting some benefit from their JUCA in heating water.

There are three primary applications for which they are thinking.

• Hydronic Hot Water House Heating. This use, of supplying enough hot water to entirely heat a home, is NOT realistic with a JUCA. There MAY be possibilities of a PARTIAL Hydronic system, if the JUCA is allowed to heat most of the house with its warm air, and the Hydronic heating is only needed in one or two distant rooms.
• Heating water to supplement a Solar Heating System. This is often a realistic usage of heat that a JUCA could put into a water medium.
• Domestic Hot Water. This is the most realistic usage of heat that a JUCA can put into water.

Over the years, we have been aware of many different approaches that people (and competing products) have used to accomplish this goal.

• There used to be a company from California that made a thin, heavy steel box, with pipe fittings, that was meant to be put into the firebox of a woodstove. We always thought this was a bad idea. It certainly could produce hot water, and was probably one of the most effective ways of doing it, since the water filled box was just inches from the fire's flames. But, such contraptions OFTEN got too hot, allowing the water inside to get above 212°F. Since the water wanted to boil, it would build up HUGE pressures, and would depend on a Temperature-Pressure Relief Valve to keep it from exploding. If that valve failed, then the device or the attached piping could burst, spraying scalding water all over. Please DON'T consider such devices!
• For many years, we experimented with inserting coils of copper tubing INSIDE the heat exchange tubes of a JUCA (up above the fire). The tubing was protected from the corrosive atmosphere of the firebox. It was located in a very hot area above the fire. And, best of all, the warm AIR passing through that heat exchanger tube (and through the middle of the coil) would TEMPER the water. IF the water ever got to 200°F, for example, the 140°F AIR would actually cool it down and would keep it from boiling. And, we found, if we put a partial restriction in that heat exchange tube, we could cause the AIR passing through that tube to be regularly at 120°F, 140°F or 160°F, thereby sort of pre-setting the average water temperature it would produce.
• Finally, a customer recently suggested this approach. Before pouring the castable firebrick in the floor of the JUCA, he was going to lay a flat copper tubing coil (the way it's usually sold these days in 50 foot lengths) on the bottom. By burying it under the castable firebrick, making sure that it is beneath more than an inch thick of that material, he expected to make sure the water never boiled. And yet, the castable is quite near the fire and is able to absorb quite a bit or radiant heat from it. The castable firebrick should act to temper the water temperature, and generally keep it from boiling.

IF YOU EXPERIMENT WITH ANY OF THIS, YOU MUST INCLUDE A CIRCULATING PUMP AND PRESSURE-RELIEF VALVE IN THE WATER LOOP because you definitely DON'T want the water to boil and burst the pipe or otherwise explode!

All of these ideas depend on the small hydronic circulating pump to keep removing the heated water from the box or tubing in the firebox. In general, the idea is to just raise the temperature of the water a couple degrees each time it passes through the coil, gradually raising the temperature of the hot water tank's contents. After many passes through the coil, all of the water in the circuit (tank, pipes and coils) will be near the desired temperature.

Obviously, this brings up an important consideration. IF you have a power outage (and you will), the pump will stop circulating, and it becomes rather likely that the small amount of water in the coil will build up very high pressures. THIS is why the Temperature- Pressure Relief Valve must be in the circuit, and it should be relatively near the heating coil. Superheated steam would be ejected from the valve at that time. This subject is VERY IMPORTANT to consider because it WILL HAPPEN. And you DEFINITELY don't want anyone to get hurt or anything to get damaged as a result.

Don't try any of this unless a professional plumber gives guidance and / or does the installation.