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1 in. NPT
Model
No.
N
503
15
753
5
1103
1253
1503
1753
2003
Natural Gas – 1,000 BTU/ft
3
, 0.60 specific gravity at 0.5 in. WC pressure drop
3
Propane Gas – 2,500 BTU/ft
The gas valve pressure regulator on the heater is
nominally preset as noted in Table J.
During normal operation, carbon dioxide should be 8.5
to 9.0% at full fire for natural gas and between 9.5 and
10.0% for propane gas. Carbon monoxide should be
‹100ppm.
Manifold Gas Pressure
Model
No.
Natural Gas
503
-0.1
753
-0.4
1003
-0.8
1253
-1.6
1503
-2.4
1753
-0.4
2003
-1.0
NOTE: Manifold pressures should be ±0.2 in. WC.
Table J: Manifold Gas Pressure Settings
CAUTION: For proper operation, no more than a
30% drop in gas supply pressure from no-load to full-
load
conditions
is
circumstances should the pressure be outside the
listed operational range.
Electrical Power Connections
Installations must follow these codes:
•
National Electrical Code and any other national,
state, provincial or local codes or regulations hav-
ing jurisdiction.
1-1/4 in. NPT
P
N
P
35
65
150
15
65
100
35
55
15
25
10
15
, 1.53 specific gravity at 0.6 in. WC pressure drop
Table I: Maximum Equivalent Pipe Length
(High Fire Values)
Propane Gas
-0.1
-0.1
-0.2
-0.2
-0.6
-0.1
-0.5
acceptable.
Under
1-1/2 in. NPT
N
P
130
360
75
180
35
90
25
60
15
25
•
Safety wiring must be NEC Class 1.
•
Heater must be electrically grounded as required
by the NEC.
•
In Canada, CSA C22. 1 C.E.C. Part 1.
The MVB 503-1503 heaters are wired for 120 VAC, 12
amps while the MVB 1753 & 2003 heaters are wired
for 120 VAC, 18 amps. Consult the wiring diagram
shipped with the heater. Before starting the heater,
check to ensure proper voltage to the heater and
pump.
Boiler mounted pumps (up to
supply directly from the boiler power supply (connec-
tions in rear wiring box). Install a circuit breaker sized
sufficiently for both the heater and the pump. Pumps
larger than
⁄
hp must use a separate power supply
3
4
and run the power through the optional pump contac-
tor which is located in the rear wiring box. Use
appropriately-sized wire as defined by NEC, CSA
and/or local codes. All primary wiring should be 125%
of minimum rating.
If any of the original wire as supplied with the heater
must be replaced, it must be replaced with 105°C wire
or its equivalent.
no
All high voltage wiring connections to the MVB heater
are made inside the rear wiring box as shown in Fig.
18. Pump power should be taken from terminals 2
(Com), 3 (GND) and 6 (Hot) –
Power to the MVB heater should be connected to ter-
minals 1, 2, and 3 as noted in Fig. 18. All low voltage
wiring, including sensors, interlocks, enable/disable,
and various options are wired into terminals 1–20 on
the front wiring panel as noted in Fig. 18.
20
2 in. NPT
2-1/2 in. NPT
N
P
N
250
125
300
300
85
225
200
60
150
150
45
110
115
35
90
85
⁄
hp) get their power
3
4
⁄
hp and smaller ONLY.
3
4
P
300
275
230
210
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