SCHEDULED MAINTENANCE
45
5. Use this formula to verify the Cubic Feet per Hour (CFH) input determined in step 4 is correct:
(3600 x Gas Meter Dial Size) / Time (seconds) = Cubic Feet per Hour (CFH)
3600 is used as there are 60 seconds in
a minute and 60 minutes in an hour.
6. Check with your local utility for actual BTU content (caloric value) of natural gas in the area (the average is 1025
BTU’s).
7. Use this formula to calculate the BTU/HR input (See BTU/HR Calculation Example):
increase pressure and input, and upward (counterclockwise) to decrease pressure and input. A properly operating unit
must have the BTU per hour input and CFM of air, within the limits shown to prevent short cycling of the equipment.
As the external static pressure goes up, the temperature rise will also increase. Consult the proper tables for tempera-
ture rise limitation.
The unit being tested takes 40 seconds for the 1 cubic foot dial to make one complete revolution. Using the chart, this
translates to 90 cubic feet per hour. Based upon the assumption that one cubic foot of natural gas has 1,025 BTU’s (Check
with your local utility for actual BTU content), the
90,000 BTU/HR
92,250 BTU/HR
This example is within the 5% tolerance input and does not need adjustment.
Set Point on Max Make Pressure Low Fi re Low Fi re High Fire High Fire Low / Hi gh
Pres s ure Fa ll Press ure On Swi tch Set Poi nt on Max Make Set Poi nt on Max Make Pres s ure Swi tch
(PF) W.C. Ri se W.C. Part # Pres sure Fall Pres sure On Pres s ure Fa ll Press ure On Assembly
(PF) W.C. Ri s e W.C. (PF) W.C. Ri s e W.C. Pa rt #
*MEC960303ANAA - 0.08 ± .04 - 0.16 0130F00647
- 0.15 ± .05 - 0.30 - 0.40 ± .05 - 0.55 0130F00643
*MEC960403ANAA - 0.08 ± .04 - 0.16 0130F00647
- 0.10 ± .05 - 0.25 - 0.20 ± .05 - 0.35 0130F00645
*MEC960603ANAA - 0.10 ± .05 - 0.25 0130F00646
- 0.10 ± .05 - 0.25 - 0.25 ± .07 - 0.40 0130F00645
*MEC960302BNAB - 0.08 ± .04 - 0.16 0130F00486
- 0.67 ± .05 - 0.82 - 1.15 ± .07 - 1.36 0130F00472
*MEC960402BNAA / AB - 0.08 ± .04 - 0.16 0130F00486
- 0.72 ± .05 - 0.87 - 0.97 ± .05 - 1.12 0130F00471
- 0.10 ± .05 - 0.25 0130F00481 - 0.92 ± .05 - 1.07 - 1.47 ± .07 - 1.68 0130F00473
- 0.10 ± .05 - 0.25 0130F00481 - 0.72 ± .05 - 0.87 - 1.47 ± .07 - 1.68 0130F00474
- 0.10 ± .05 - 0.25 0130F00481 - 0.67 ± .05 - 0.82 - 1.15 ± .07 - 1.36 0130F00472
- 0.10
± .05 - 0.25 0130F00481 - 0.50 ± .05 - 0.67 - 1.15 ± .07 - 1.36 0130F00446
- 0.10 ± .05 - 0.25 0130F00429 - 0.92 ± .05 -1.07 - 1.47 ± .07 - 1.68 0130F00435
- 0.10 ± .05 - 0.25 0130F00429 - 0.92 ± .05 -1.07 - 1.47 ± .07 - 1.68 0130F00435
- 0.10 ± .05 - 0.25 0130F00429 - 0.70 ± .05 - 0.87 - 1.47 ± .07 - 1.68 0130F00436
- 0.10 ± .05 - 0.25 0130F00429 - 067 ± .05 - 0.82 - 1.15 ± .07 - 1.36 0130F00434
A / GMEC96 Pressure Switch Trip Points And Usage Chart
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