Greenheck Fan 470656 manual Start-Up 21 Electronic Modulation, High Fire Adjustment

Start-Up - 2:1 Electronic Modulation

1. Send Unit to High Fire

Turn the temperature	Temperature
selector to its maximum
	Selector
setting to send the unit
to high fire.

2.Check the High Fire Manifold Pressure

With the unit at high fire, use a manometer to measure the burner manifold pressure at the manifold pressure test port. See the Gas Train Layout in the Reference section for the manifold pressure test port location.

The recommended high fire manifold pressure is 3-1/2 in. wg for natural gas and 10 in. wg for LP gas.

Note

The low fire manifold pressure should always be rechecked after adjusting the high fire.

Note

Once the high and low fire manifold pressures are properly set, reset the discharge air temperature to the desired setting.

If needed, use the high fire adjustment screw on the shut-off gas valve to adjust the high fire manifold pressure. Counterclockwise rotation will decrease the gas pressure and clockwise rotation will increase the gas pressure.

High Fire

Adjustment

3. Send Unit to Low Fire

Remove and isolate one wire from the modulating gas valve terminal to send the unit to low fire.

4. Check the Low Fire Manifold Pressure

With the unit at low fire, use a manometer to measure the burner manifold pressure at the manifold pressure test port. See the Gas Train Layout in the Reference section for the manifold pressure test port location.

The recommended low		2:1 Manifold Pressure
fire manifold pressure is		(in. wg)
7/8 in. wg for		Natural Gas	LP
natural gas and	Low Fire	7/8	2-1/2
2‑1/2 in. wg
	High Fire	3-1/2	10
for LP gas.

If needed, use the low fire adjustment screw on the

modulating gas valve to adjust the low fire manifold
pressure. Counterclockwise	Terminal
rotation will decrease the
gas pressure and clockwise
rotation will increase the gas
pressure.

Once the low fire is set, reattach the disconnected wire to the modulating valve

and reset the temperature Low Fire

selector.

®

Adjustment

Model IG / IGX Make-Up Air 29