JUCA Performance Chart

Customers are always impressed with how well their JUCAs produce heat. They sometimes ask us how to estimate how much their JUCA is really producing. Just use a normal thermometer to measure the warm air Outlet Temperature near the warm air outlet and then use the following chart to learn just how much heat the JUCA is actually sending out into the house.

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.Cool Return Air From House (65F)
In living area or using cold air return
Cold Return Air From Basement (25F)
WITHOUT a cold air return
Outlt
Temp
Std
465cfm
Mid
1240cfm
Large
1460cfm
3/4 HP
2550cfm
Std
465cfm
Mid
1240cfm
Large
1460cfm
3/4 HP
2550cfm
70F 3 KBtu 5 KBtu 8 KBtu 14 KBtu 23 KBtu 45 KBtu 72 KBtu 126 KBtu
80F 8 KBtu 15 KBtu 24 KBtu 42 KBtu 28 KBtu 55 KBtu 88 KBtu 154 KBtu
90F 13 KBtu 25 KBtu 40 KBtu 70 KBtu 33 KBtu 65 KBtu 104 KBtu 182 KBtu
100F 18 KBtu 35 KBtu 56 KBtu 98 KBtu 38 KBtu 75 KBtu 120 KBtu Not Recc
110F 23 KBtu 45 KBtu 72 KBtu 126 KBtu 43 KBtu 86 KBtu 137 KBtu Not Recc
120F 28 KBtu 55 KBtu 88 KBtu 154 KBtu 48 KBtu 96 KBtu 153 KBtu Not Recc
130F 33 KBtu 65 KBtu 104 KBtu 182 KBtu 53 KBtu 106 KBtu 169 KBtu Not Recc
140F 38 KBtu 75 KBtu 120 KBtu Not Recc 58 KBtu 116 KBtu 185 KBtu Not Recc
150F 43 KBtu 86 KBtu 137 KBtu Not Recc 64 KBtu 126 KBtu Not Recc Not Recc
160F 48 KBtu 96 KBtu 153 KBtu Not Recc 69 KBtu 136 KBtu Not Recc Not Recc
170F 53 KBtu 106 KBtu 169 KBtu Not Recc 74 KBtu 146 KBtu Not Recc Not Recc
180F 59 KBtu 116 KBtu 185 KBtu Not Recc 79 KBtu 156 KBtu Not Recc Not Recc
190F 64 KBtu 126 KBtu Not Recc Not Recc 84 KBtu 166 KBtu Not Recc Not Recc
200F 69 KBtu 136 KBtu Not Recc Not Recc 90 KBtu 176 KBtu Not Recc Not Recc

. Example: a JUCA with a Large Blower is putting out warm air at an average temperature of 120°F. How much heat is it producing for the house?

In the table above, go down to the 120°F line. Then go across to the LARGE column(s). As long as the JUCA was drawing its blower air from the house (if it's in the living area) or from a cold air return, then it must be producing 88,000 Btu/hr for the house. If, instead, it had been installed in a basement or garage with the blower drawing cold air from that space, it would have to work MUCH harder to create the 120°F air, having to create about 153,000 Btu/hr. Think about this. In both cases, you would get the same effective heat in the house. But in the second case, the JUCA would have to work nearly twice as hard and burn nearly TWICE AS MUCH wood to accomplish the same heat! Much more intense fires would need to be used as well. In addition, the humidity in the house would also be messed up, because air that was upstairs that was already humidifed would have to be pushed out of the house through cracks to make room for the new warm but un-humidified air you were sending up there. This is why ALL central furnaces use cold air returns!

The physical explanation of this is that, in the second setup, you would necessarily be pushing previously heated warmed and humidified house air OUT through cracks to make room for the new air you're heating and bringing in. (The first method RE-CIRCULATED the warmed house air over and over, just adding a little more heat and humidity each time through the JUCA / furnace.)


There is another thing that can be learned fron this chart. It makes clear the value in using an optional blower when heating large areas. In our example above, (a rather large house in a cold climate), we needed about 88,000 Btu/hr to supply all the heat for the whole house. By using the LARGE blower, we had the air come out at about 120°F, a nice, safe, comfortable temperature. If, instead, we had just used the standard blower, (to create the SAME 88,000 Btu/hr for the house), you can see that the JUCA would have to be putting its air out at over 200°F (actually about 240°F), a VERY hot air temperature, which could even have safety implications. Again, the same amount of heat would be supplied to the house. But the very hot air from the smaller blower has some other consequences as well. The very hot air would immediately try to rise to the ceiling (remember High School Chemistry, where heat rises?) and it would move at relatively slow velocities. That means that it wouldn't be able to get as far out into the room before rising to the ceiling, so if you were sitting across the room, less heat would likely get to you to keep you cozy. In contrast, the larger blower's more moderate air temperature would allow the air to stay down where WE are longer, and the bigger air flow would distribute the heat more evenly over a large area, and even through ducts to the rest of the house.

Also note that the huge 3/4 HP blower would supply all that heat as air that would be under 100°F, resembling the air that Heat Pumps give out.


If you feel that your JUCA is not producing enough heat for the house, then there are three obvious things to check.
The JUCA Home Page is at: juca