General Information
900414-00 12/2015
Innovative Hearth Products
MHD 35/40 Series Direct-Vent Gas Fireplaces
9
BTU Input
Table 1 - Input Rate (BTU/HR), Gas Valves
Models
Natural Gas
Propane Gas
High Rate
Low Rate
High Rate
Low Rate
35” Models
16,000
11,000
15,000
11,000
40” Models
20,000
14,000
19,000
14,000
Table 2 - Thermal Efficiency (%)
Model
Millivolt
Electronic
AFUE *
P4 **
AFUE *
P4 **
35” Models
66
61
66
63
40” Models
66
61
66
63
* AFUE is a measurement of the US Department of Energy, ** P4 (EnerGuide) is a measurement of the Canadian Office of Energy Efficiency.
Efficiencies are based on Normal input operation.
Gas Pressure
Table 3 - Inlet Gas Supply Pressure
Fuel
Minimum
Maximum
Natural Gas
5” WC / (1.25 kPa)
10.5” WC / (2.61 kPa)
Propane
11.0” WC / (2.74 kPa)
13.0” WC / (3.23 kPa)
Table 4 - Manifold Gas Supply Pressure
Fuel
Pressure
Natural Gas
3.5” WC / (0.87 kPa)
Propane
10.0” WC / (2.49 kPa)
Test gauge connections are provided on the front of the millivolt gas control valve (identified IN for the inlet and OUT for
the manifold side). The control valves have a 3/8” (10 mm) NPT thread inlet and outlet side of the valve (
Figure 1
).
Figure 1 - Millivolt Gas Valve
Propane tanks are at pressures that will cause damage to valve components. Verify that the tanks have step down
regulators to reduce the pressure to safe levels.
The appliance and its appliance main gas valve must be disconnected from the gas supply piping system during
any pressure testing of that system at test pressures
in excess of
1/2 psi (3.5 kPa).
The appliance must be isolated from the gas supply piping system by closing its equipment shutoff valve during
any pressure testing of the gas supply piping system at test pressures
equal to or less than
1/2 psi (3.5 kPa).
