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2-1/2 in. NPT
Model
No.
N
P
2503
55
135
3003
40
85
3503
30
45
4003
25
35
•
Natural Gas – 1,000 BTU/ft
WC pressure drop
•
Propane Gas – 2,500 BTU/ft
WC pressure drop
Table H: Maximum Equivalent Pipe Length
Manifold Gas Pressure
Model
(High Fire Values)
No.
Natural Gas
2503
-4.8
3003
-6.7
3503
-6.8
4003
-4.7
NOTE: Manifold pressures should be ±0.2 in. WC.
Table I: 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.
•
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 heaters are wired for a 240 VAC, single-
phase power supply. Consult the wiring diagram
shipped with the heater. Before starting the heater,
check to ensure proper voltage to the heater and
3 in. NPT
4 in. NPT
N
P
N
160
400
600
120
250
500
80
200
400
600
65
160
300
400
3
, 0.60 specific gravity at 0.5 in.
3
, 1.53 specific gravity at 0.6 in.
Propane Gas
-6.4
-8.8
-9.5
-7.4
acceptable.
Under
pump.
Pumps must use a separate power supply and run the
P
power through a field-supplied contactor. Use appro-
priately-sized wire as defined by NEC, CSA and/or
--
local codes. All primary wiring should be 125% of min-
imum 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.
All high voltage wiring connections to the MVB heater
are made inside the rear wiring box as shown in
Fig. 18. There are three factory supplied pump inter-
lock relays in the rear wiring box to provide an enable
signal via dry contact (5A max) for the Boiler Pump,
System Pump and Indirect DHW Pump as required for
the system depending on the mode selected within the
VERSA IC control system.
Fig. 19: Wiring Electrical Connections
Field-Connected Controllers
no
It is strongly recommended that all individually-pow-
ered control modules and the heater should be
NOTE: Field-supplied isolation relays should be
installed when field-connected controllers are
mounted more than 50 equivalent feet (18 AWG)
from heater. See wiring diagrams.
NOTE: Minimum 18 AWG, 105°C, stranded wire
must be used for all low voltage (less than 30 volts)
external connections to the unit. Solid conductors
should not be used because they can cause
excessive tension on contact points. Install conduit
as appropriate. All high voltage wires must be the
same size (105°C, stranded wire) as the ones on the
unit or larger.
20
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