Select between fixed rate (on-off), three position
(high-low-off), and modulating controls. Combustion
controls will be fixed-rate, on-off for gross
outputs up to 200 kW (700,000 Btuh); high-low-off or
fixed-rate on-of, depending on anticipated load
profile, for gross output from 200 to 600 kW
(700,000 to 2,000,000 Btuh); high-low-off or
modulating, depending on anticipated load profile,
for gross output from 600 to 12000 kW (2,000,000 to
4,000,000 Btuh); modulating for gross outputs above
1200 kW (4,000,000 Btuh). Modular boilers will be
fixed-rate on-off for each module. Delete
inappropriate paragraphs.
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a.
[Gas] [Combination gas-oil fired] boiler units shall be provided
with [fixed rate (on-off)] [three position (high-low-off)]
[modulating] combustion controls with gas pilot or spark ignition.
Modulating controls shall be provided with a means for manually
controlling the firing rate.
b.
Oil fired boiler units shall be provided with [on-off]
[high-low-off] [modulating] combustion controls with [direct
electric spark ignition system] [spark ignited [No. 2 oil]
[natural gas] [liquified petroleum gas] pilot]. Modulating
controls shall be provided with a means for manually controlling
the firing rate.
c.
Modulating control function shall be accomplished using
positioning type controls. Air flow ratio and fuel control valve
shall be controlled by relative positions of operative levers on a
jackshaft responding to a [water temperature controller] [steam
pressure controller]. Positioning type combustion control
equipment shall include draft controls with synchronized fuel feed
and combustion air supply controls, while and shall maintain the
proper air/fuel ratio. The desired furnace draft shall be
maintained within 0.25 mm 0.01 inch of water column.
d.
[Fixed rate on-off] [High-low-off] controls for boilers with
capacities up to 600 kW 2,000,000 Btuh shall use a [water
temperature controller in a temperature well in direct contact
with the water] [steam pressure controller in direct contact with
the steam].
2.3.7
Combustion Safety Controls and Equipment
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NOTE: Provide feed water regulator with low-water
cutoff on close coupled boilers (i.e. short supply
and return lines with low pick-up losses) under 1200
kW (4,000,000 Btuh) gross output with no process
loads. Provide pump controller with low-water
cutoff for all other boilers. Low-water cutoff will
require a manual reset unless a supplementary
low-water cutoff is provided. A supplementary
low-water cutoff is required for boilers utilizing a
pumped condensate return system. State and local
codes may also require supplementary low-water
cutoffs. When a supplementary low-water cutoff is
SECTION 15569A
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