MACH
®
Gas Fired Boiler
56
APPENDIX 2 – MACH
®
BOILER ALTITUDE DERATE SCHEDULE
For installations over 2000 ft elevations, a de-rate schedule is applied. The boiler input rating must be
reduced by 4% per 1000 ft above sea level, as illustrated using the following graph.
4% Derate Schedule
0
5
10
15
20
25
30
35
40
45
2000
3000
4000
5000
6000
7000
8000
9000
10000
11000
Altitude (ft)
T
o
tal
D
er
at
e (
%
)
De-rate procedure is as follows:
With the boiler at high fire, adjust the gas valves (as described in section 3.10.4) to get 5% O
2
in the flue
gas. If this cannot be achieved, perform the following steps:
•
If the O
2
% is too high, then the inlet gas pressure should be adjusted to the minimum pressure
allowed, typically 5” w.c. The gas valve should be adjusted to obtain approximately 5% O
2
. If the
O
2
% is still too high, the fan speed may be lowered. This procedure should only be performed by
factory trained personnel.
•
If the O
2
% is too low, the gas valve settings should be reduced.
This procedure is also described in Bulletin 06-08.