It says 6 to 10.5" w.c.
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It says 4.5 to 10.5" w.c.
It's basically the same thing.
The meter will put out either low pressure (about 7.0" to 13.8538" w.c (0.5 psi)) or high pressure (about 2 psi).
If the meter puts out 2 psi, then you use a regulator near the appliance to drop the pressure to about 7.5" w.c.
The meter is not going to put out 4" w.c.
Normal output is about 1/4 psi to 1/2 psi.
0.25 psi is 6.9269" w.c.
If the pressure is lower than 7", then it is too low and it should be increased.
As long as the line is sized correctly, the pressure will be fine.
You will have a static pressure and a dynamic pressure.
Static is when the heater is off and dynamic is when the heater is running.
The dynamic should not be more than about 0.5" w.c lower than the static.
The dynamic should not be lower than the minimum.
Don't worry about the manifold pressure.
As long as the supply inlet dynamic pressure is above the minimum, the manifold should be fine.
Can you show your meter data plate?
What is your current pressure?
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