Whichever way you intend to hook up the ducting, make sure to have a heating contractor do the work. He will know all the safe procedures necessary to keep you and your family safe. Also, make sure that you take into account that the first 10 feet of hot air ducting MUST be insulated from any wood.
Reasonable air flow and heat delivery requires certain planning that must be done for your particular application. Each house is unique and so is its ducting system. That's another reason for having a local heating contractor do this work. Even if we would try to give guidance over the phone, it would ONLY be general, and might not apply because of unique aspects of YOUR house.
Elbows and angle fittings in both directions are standard available items for the size ducting that JUCAs feed.
The warm air outlet on a JUCA is either 8"x16" or 8"x12" to directly be able to join modern main heating trunk lines. IF YOUR DUCTS ARE NOT ALL METAL THEN IT MAY NOT BE SAFE TO USE THEM FOR ANY SOLID FUEL HEATER. Consult your local building inspector. We strongly recommend that only a knowledgeable person plan and install the duct connection. We are sure that you join us in wanting a very, very safe installation in your house. We know we're repeating ourselves here. Get it?
FEEDING INTO WARM AIR DUCTS:This allows the JUCA and the other furnace to be totally independent of each other but generally requires one of our optional blowers (to duplicate the air circulation capability of the other furnace blower. Join the existing system at or near its thickest section (probably near the other furnace). A check-flow damper may need to be installed (See Check-Flow Damper) to eliminate back flow through either furnace whenever the other one is operating. Of course, it must not stop warm air that is trying to leave either furnace (for example, if BOTH try to operate at the same time), and only keep air from going backward into either.
This connection method involves considering installing air filters and a humidifier in the JUCA air path, because its air does NOT go through those features of the other furnace. JUCAs are compatible with ALL standard air filters and humidifiers.
Another way sometimes usedSometimes people try to feed the JUCAs warm air into the warm air ducts with our standard blower and then operate their other furnace blower to pick it up from there and spread it through the house ducts. This will only work if the joining point is very carefully designed so that it has the effect of a venturi section (like a carburetor works in a car). Otherwise, what happens is that the bigger furnace blower tends to try to push air backward through that new connecting duct, back into the JUCA and the JUCAs air will tend to get very hot since it has no place to go. If you choose to try this, and find that the outer shell of the JUCA is too warm to continuously touch, you probably have this problem.
This "alternate" type of connection is a little more complicated than it first seems even though it is a way recommended by some of our competitors (we think, incorrectly). The ONLY appropriate ways to do this involve EITHER getting the JUCA blower that is about the same size and capacity as the blower in the other furnace (so it can't be over-powered) OR to design the connecting point to have a "venturi effect" as mentioned above. If this is done correctly, the air flow of the other (big) blower, is capable of causing a "sucking" action to actually help pull the JUCA's warm air out into its path.
If you do use this method, you should check the JUCA's hood temperature when operating. If it is hotter than allowing you to hold your hand against it, then probably the air is not being able to leave the stove properly and some change in the connection area is necessary.
FEEDING INTO A COLD AIR RETURN:The two furnace blowers work in "series" in this installation. The JUCA heats the air then sends it to the other furnace where it is mixed with some unheated air then pushed through without its burners being on. You use the other furnace blower to do the bulk of the work of circulating throughout the house, but the JUCA blower is still necessary to get the heated air to the other furnace blower. It is very important to make sure that the JUCAs heated air cannot overheat anything. Study every place that hot air could wind up, even backwards in the ducting system.
When the JUCA is operating, the air in the cold air return duct is drawn into the JUCA, heated up there, and then put back into that same cold air return duct (after the BAFFLE shown). Then the JUCA-warmed air proceeds to and through the other furnace's blower, on its way to the house ducts. ONLY the blower of the conventional furnace operates (NOT the burner, so no fuel is used). That (large) blower does most of the work of distributing the JUCA-warmed air throughout the house.
This configuration still requires at least the standard blower to operate on the JUCA. The other furnace's blower is not designed to "suck" the air through the JUCA, as that would cause something bad called "cavitation."
When the JUCA is NOT operating, the conventional furnace pulls MOST of its air by its original path, past the BAFFLE, and pulls the remainder through the JUCA heat exchanger path. The conventional furnace operates normally.
It would also be possible to make the BAFFLE motorized. Then, the cold air return duct would remain totally unobstructed for the normal operation of the conventional furnace, and the BAFFLE would swing out and divert most of the air through the JUCA air path when the JUCA blower turns on. The motor of that damper would just be wired in parallel with the JUCA blower, so it would turn on and close at the correct times.
This general arrangement's air path ALWAYS passes through the conventional furnace's air filter system and humidifier.
A SEPARATE DUCT SYSTEMOf course, it would be possible to install a duct system JUST for the JUCA. If the house currently didn't have warm air ducts, this may be the way to go. There could be some other extenuating circumstances that suggest going this way. The heating contractor will have the best vantage point on just which way to go.
Sometimes, in houses that currently don't have ducts, people operate the JUCA for one winter, to see how much of the house can be heated to the comfort level desired, without ducting. If the results are satisfactory, then nothing else would ever need to be done. But, if it was found that a single distant bedroom or bathroom was not warm enough, it would be possible to run one small duct the following year, to get some extra heat to that area. JUCAs are amazingly flexible in such ways!
AN UN-DUCTED DUCT SYSTEM!Finally, there may be yet another approach to consider. IF the house has a good conventional furnace system, AND if that system has a large COLD AIR RETURN INTAKE near the JUCA, then consider the following. Use the JUCA to JUST send its warm air into the area around it (without feeding into the house heating or duct system.) Then, use the "SUMMER FAN" switch on the sub-base of the wall thermostat of the conventional furnace to turn JUST THE BLOWER on. (Not the burner.) The warm air that the JUCA is creating in the room that it is in, will then be drawn into the Cold Air Return and therefore be distributed to all the rooms of the house. Without ACTUALLY being connected into the house duct system!
It would even be possible to automate this kind of installation with a Relay as described below.
RelayIn some of the installations described above, the blower of the conventional furnace is used to help distribute the heat throughout the house. It could be left ON (controlled manually) with its "SUMMER FAN" switch (on the sub-base of the wall thermostat for that furnace) or it could be hooked up to turn on normally and/or with the JUCA. A simple, inexpensive RELAY could be bought locally. It should be a 110-volt COIL, relay, with SPST contacts, as mentioned below.
The following describes a "NON-invasive" method of connection that does NOT involve doing anything inside the other furnace. The SPST relay would be used. The coil of this relay would be wired in parallel with the JUCA's blower motor, so the relay would be actuated whenever the JUCA blower was on.
The SPST switch contacts would be wired in parallel with the 24-volt circuit SUMMER FAN switch in the sub-base of the conventional furnace's wall thermostat. The effect would be so that the SUMMER FAN circuit would be automatically closed, just as if you manually moved that switch on the sub-base. This method does NOT invade the other furnace, so it does not affect any warranties or anything!
Other NotesThe bypass duct and the opening past the BAFFLE (in the Cold Air Duct Feed method) can be VERY important to allow the other furnace to operate properly when the JUCA wasn't being used. This is especially important if the JUCA blower is smaller than the blower on the other furnace. The filters, humidifier, etc of the other furnace work for both in this installation. The initial cost might be less (a smaller JUCA blower could be used) but electricity for two blowers will eventually make up for that.
MAKE ABSOLUTELY SURE THAT ALL OF THE FIRST 10 FEET OF WARM AIR DUCTING FROM THE JUCA IS INSULATED FROM ANY WOOD OR OTHER COMBUSTIBLES, EVEN IF IT MEANS MODIFYING EXISTING DUCTWORK.
If the JUCA is installed in an unheated space, then a cold air return MUST be provided for the JUCA. There are a LOT of good reasons for this. Trust us!
If ducts pass through an unheated basement or crawlspace, they should be insulated with Fiberglas insulation, to minimize heat loss in those ducts, just like with any other furnace.
It is extremely important to measure the "Static Pressure Levels" and air flow rates. Otherwise, any or all of several problems could occur.
allowable/pressure load ranges.
The JUCA Home Page is at: juca