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WARNING
The gas valve manifold pressures are factory set and should rarely need to be adjusted.
Failure to adjust the gas valve in strict accordance with these instructions could result in
unreliable operation, property damage, personal injury or death due to carbon monoxide
poisoning. When making adjustments, pay particular attention to the following precautions:
Be certain that the inlet pressure are within the limits shown before attempting to make •
manifold pressure adjustments.
Be sure that the boiler is not modulating when making the high fi re adjustment•
Be sure to remove the inner cover before reading or adjusting the manifold pressure.•
Loosen the screw in the gas inlet tap on the gas valve and connect a manometer (see Figure 12.6). b)
Make sure the boiler is at high fi re. To do this:c)
On heat only boilers, make sure that the heating system knob is rotated fully clockwise and that •
the supply temperature is less than 150F during the entire conduct of this test.
For combi units, rotate the DHW knob fully clockwise and open enough hot water fi xtures to keep •
the exiting hot water temperature under 110F during the entire conduct of this test.
Check the inlet pressure with all the MWC, and all other gas appliances turned on and off. The inlet d)
pressure at the boiler must be within the following limits regardless of what combination of appliances
is fi ring:
Inlet Press. (inches w.c.) Natural Gas LP Gas
Minimum 5.6 10.4
Maximum 10.5 13.0
If the inlet pressure falls outside of these limits, fi nd and correct the cause of the problem before
proceeding further.
Connect a manometer to the manifold (outlet) pressure tap on the gas valve (Figure 12.6).e)
Read the high fi re manifold pressure. It should be set at:f)
Natural Gas LP Gas
Manifold Press. (inches w.c.) 4.8 +/-0.25” w.c. 10.3 +/- 0.50” w.c.
If an adjustment is necessary, pry the clear plastic cap off of the regulator. Turn the outer brass nut g)
clockwise to increase the manifold pressure or counter-clockwise to reduce the pressure.
Check the low fi re manifold pressure. To do this, turn off the boiler and remove one of the modulation h)
leads (Figure 12.6). Turn the boiler back on. Read the low fi re manifold pressure. It should be set at:
Model Number Fuel L.F, Manifold Pressure (in w.c.)
MWC116ENL (Heat Only) Natural 2.2 +/- 0.10
MWC116ELL (Heat Only) LP 4.8 +/- 0.10
MWC116ENT (Combi) Natural 1.0 +/-0.10
MWC116ELT (Combi) LP 2.0 +/-0.10
If an adjustment is necessary, turn the inner black hex shaft clockwise to increase the manifold i)
pressure or counter-clockwise to reduce the pressure (Figure 12.7).
Turn off the boiler, reconnect the modulation lead removed in Step (h) and restart the boiler.j)
Recheck the manifold pressure at high fi rek)
Recheck the inlet pressurel)
Replace the inner cover.m)