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Example 2:
Return ESP before Filter 0.10 in.w.c.
Filter Static Pressure Drop 2000 cfm 0.10 in.w.c.
Supply ESP after Coil 0.20 in.w.c.
Coil Static Pressure Drop Wet 0.20 in.w.c.
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Total ESP 0.60 in.w.c.
Both Examples 1 and 2 are correct. Example 1 ESP readings were taken as laid out in static pressure reading location diagrams (Figure 6 - 8).
Example 2 readings are taken as described. The coil and filter static pressure drops were taken from the manufacturer’s product data sheets with
the assumption that 2000 cfm is being delivered.
APPENDIX E
QUICK REFEREMCE INFORMATION
FLAME SENSOR MICROAMPERAGE
Microamp Range: 0.5 to 6.0 microamps
Typical Reading: 4 to 6 microamps
HOT SURFACE IGNITOR READING
Ohm reading of HSI new cold: 40 to 90 ohms (resistance will go up with HSI life and exceed the new HSI resistance over time).
GAS VALVE OHM READINGS
M to C: 98 ohms (solenoid coil)
Hi to C: 1.5 ohms (bridge rectifier, use diode test function setting on meter)
POWER CHOKE (INDUCTOR)
Run unit in cooling mode, measure motor amp draw before power choke. Then rerun unit in cooling mode, but this time measure amp draw
without power choke in line. The amp draw should be higher without power choke. Some ammeters will register a lower amp draw (look for
a change in amperage).
APPENDIX F
FURNACE STAGING ALGORITHM
On initial thermostat call for heat after power-up, furnace staging algorithm will provide 16 minutes of low heat provided setup switch SW1-2
is off. If call for heat still exists after operating for 16 minutes in low heat, furnace switches to high heat until the thermostat is satisfied.
During subsequent calls for heat:
•
Low heat run time is calculated based on previous heating cycle.
•
High heat run time is not calculated. High heat is energized in 1 of 3 ways and runs until the thermostat is satisfied:
1. After low heat has run for 16 minutes and call for heat is still present.
2. When the furnace staging algorithm (using previous cycle information) determines high heat is necessary for the entire thermostat cycle.
3. After the calculated low heat on time has elapsed and the call for heat is still present.
•
The following flow chart shows how the furnace staging algorithm calculates low heat on times. To predict low heat operation, the times
in Low Heat (LH) and High Heat (HH) on the previous cycle must be known. The furnace staging algorithm uses these values to determine
how much low heat operation will occur on the next call for heat.
•
Four examples are shown below to illustrate what the furnace will do on a cold start, coming out of night setback, coming on in low heat,
and coming on in high heat.
Pressure Switch Make/Break Points
UNIT SIZE (BTUH)
HIGH-HEAT PRESSURE SWITCH
LOW-HEAT PRESSURE SWITCH
Make Point
Break Point
Make Point
Break Point
40,000
1.81 in. wc max
1.63 in. wc +/- 0.05
0.75 in. wc max
0.60 in. wc +/- 0.05
60,000
1.81 in. wc max
1.63 in. wc +/- 0.05
0.95 in. wc max
0.80 in. wc +/- 0.05
80,000
100,000
120,000
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