Specification Sheet

Rinnai Corporation • 103 International Drive • Peachtree City, GA 30269 • Toll-Free: 1-800-621-9419 • Fax: [phone] • www.rinnai.us
3/2011 1 MSB-SP
MSB Kits for Connecting Multiple Water Heaters
The MSB kits can electronically connect up to 25 water
heaters.
For proper operation, it is not recommended that different
models be connected together. Combining different
models may result in lower performance.
Models
For use with Rinnai Tankless Water Heaters* (except for
models V53e, V53i, and R63LSe which must use
pressure activation valves, PVA).
System Operation
When multiple water heaters are operating, they will
attempt to supply equal amounts of hot water.
The order in which each water heater operates is
occasionally rotated to ensure equal usage among the
entire system.
On initial water flow demand, 1 to 3 units are in standby
which means that their servos valves are open until flow
demand is determined. Only the necessary number of
water heaters will begin to fire to meet demand. Water
heaters not firing will close their valves.
The number of units that are in standby can be
determined by a dip switch setting of the master MSB
board. It is recommended that the dip switch settings on
MSB boards other than the master MSB board be set for
1 unit in standby.
The number of units in standby will affect the activation
flow rate. With 3 units in standby, the activation flow rate
is 3 times the rate for a single water heater. If the
activation flow rate for a single water heater is 0.4 gal/min
then for a system with 3 waters heaters in standby, the
activation flow rate will be 1.2 gal/min.
Temperature
The temperature setting for all of the connected water
heaters is controlled by the temperature controller
connected to the water heater with the master MSB
Board. Temperature controllers connected to the other
units will provide maintenance codes for their respective
units.
If water heaters do not use a temperature controller, the
temperature will be that temperature setting of the water
heater with the master MSB board (120ºF or 140ºF).
On applicable models (VA, VB), a single MCC-91 can be
connected to the master MSB Board to provide
temperatures greater than 140ºF for all the water heaters
in the MSB system.
M MSB-M control board
A Connector cable A (part of MSB-M kit; replace
with MSB-C3 cables for V Series)
C1 MSB-C1 cable for connecting water heaters
within a banked system (up to 5), (use MSB-C3
cables for V Series)
C2 MSB-C2 cable for connecting MSB-M control
boards (up to 5)
In the diagram above, 25 water heaters are
electronically connected. Each bank of 5 is controlled
by an MSB-M control board. These boards are
connected to each other with MSB-C2 cables. One
MSB-M is the controlling or master MSB-M for the
entire system.
M
A
C2
C1
Water Heater
PC board