Adjusting | Impulse Multiplier
Figure 1. Typical Installation
gas or oil
to burner
Example: Q 1 = 30,000 scfh combustion air at high fire Q 2 = 6000 scfh combustion air at low fire (5:1 turndown) ΔP 1 = 6"wc combustion air differential pressure at high fire: Adjust 7266A bleed for up to 27"w.c. to ratio regulator (4.5 × 6"w.c.). ΔP 2 = combustion air differential pressure at low fire 5. Set impulse pressure for required low fire value by adjusting the spring on the bottom of the 7266A: CW to increase, CCW to decrease. (See example below).
R690-1407 Regulator (for compressed air only)
air/gas or air/oil ratio regulator
8645A-01 air filter/seperator
adjustable bleed
vent
low air pressure switch
differential orifi ce
to recuperator if used
combustion air supply
air control valve
10 pipe diameters
per orifice mfg's specs
Using the square root law, determine ΔP 2 as follows:
ADJUSTING THE 7266A Initial
or (
P 2 = P 1
Q 2 Q 1
2
Q 2 Q 1
P 1 P 2
(compressed air and combustion air only -- gas off)
FINAL 1. Light burners and adjust limiting orifice valves (1807 or1813) and ratio regulators (7218 or 7052) as in a conventional system. Adjust spring for 1.1"w.c. impulse (for 4.5 × multiplication). 6"w.c. P = 0.24"w.c. low fire combustion air: 6000 30 000 2 (
1. Set compressed air regulator (R690-1407) oultet pressure (for 7266A supply air pressure) between a maximum of 55"w.c. and a minimum of 7"w.c. above desired high fire impulse pressure.
2. Set combustion air control valve at high fire (for maximum static or differential combustion air pressure).
3. Set impulse pressure for required high fire value (up to 4.5 × combustion air static or differential) by adjusting Bleed Adjust- ing Screw: CW to decrease, CCW to increase.
2. Recheck all settings at low and high fire; readjust as necessary.
4. Set combustion air control valve at low fire. A turndown rate of 5:1 is within the capability of the 7266A.
Figure 2. 7266A Impulse Multiplier (dimensions)
2 ½
2 ½
¾ fpt outlet
¾ fpt inlet
1 7⁄8
3 5⁄8
4 7 /
16
bleed orifi ce
Bleed Adjusting Screw
10 ¾
¼ fpt vent for 7266
¼ fpt, downstream air press. connection
3 15⁄16
10 ½ dia.
¼ fpt, upstream air press. connection
low fire adjusting spring
Bulletin 7266A Page 3
weight: 26 lb
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