Noritz SCU-401-12M, Installation Manual, Page: 3 / 39

3. Introduction (see list of points below)
This manual is intended to provide instruction for the installation, operation, and features of the SCU-401 system
controller. It is divided into 4 main sections:
1. Installation of the SCU-401 system controller
2. Initial programming of the remote controller
3. Additional features of the remote controller and the SCU-401 system controller
4. Plumbing diagrams and general information about water and gas piping
Read this manual carefully and follow the instructions as written.
If you have any questions, contact Noritz America at 866-766-7489 or visit http://support.
noritz.com/.
Introduction to the “SCU-401” System Controller
Overview
Basic Operation
The SCU-401 system controller is used to combine 7 to 12 / 13 to 24 Noritz heaters into a single “multi-unit system.”
The system controller stages units on and off based on hot water demand and rotates their operation to ensure even
usage. It also has two additional modes which optimize the system for operation with a recirculation line or storage
tank.(Note: for systems of 1 to 6 units use the SC-401-6M system controller)
Unit Staging
Staging allows the multi-unit system to track hot water demand from the minimum flow rate of a single unit up to the
maximum output of several units. When the primary firing heater reaches ~50% of its maximum output, the system
controller activates the next unit in the system. When both these units reach ~50% of their maximum output, a third
unit is activated and so on. The SCU-401 may also be configured to activate two heaters during primary firing to allow
for rapid initial hot water demand.
Unit Rotation
The SCU-401 system controller rotates operation of the primary firing heater every 8 hours of combustion time.
This helps to ensure even usage of all units.
Water heater
Instant hot
water is
available.
<Recirc>
Hot water is circulated
in the piping.
The system controller
operates these pumps.
Pump
Pump
<Tank recirc>
The system controller
operates these pumps.
Pump
Pump
Hot water
storage
tank
Instant hot
water is
available.
Water heater
Pump
Hot water is circulated
to the tank.
* These diagrams are for illustration purposes only.
System Selection
The SCU-401 allows the user to select two additional system types: “Recirc” and “Tank recirc.” These settings optimize
performance with recirculation and storage tank systems, and allow the system controller to operate one or two pumps.
GROUP 1 GROUP 2 GROUP 4
UNIT1 UNIT2 UNIT3 UNIT4 UNIT5 UNIT6 UNIT7 UNIT8 UNIT9 UNIT10 UNIT11 UNIT12 UNIT19 UNIT20 UNIT21 UNIT22 UNIT23 UNIT24
1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th 19th 20th 21st 22nd 23rd 24th
Rotation
6th 1st 2nd 3rd 4th 5th 12th 7th 8th 9th 10th 11th 24th 19th 20th 21st 22nd 23rd
Rotation
2nd 3rd 4th 5th 6th 1st 8th 9th 10th 11th 12th 7th 20th 21st 22nd 23rd 24th 19th
Rotation
19th 20th 21st 22nd 23rd 24th 1st 2nd 3rd 4th 5th 6th 13th 14th 15th 16th 17th 18th
Rotation
24th 19th 20th 21st 22nd 23rd 6th 1st 2nd 3rd 4th 5th 18th 13th 14th 15th 16th 17th
Rotation
14th 15th 16th 17th 18th 13th 20th 21st 22nd 23rd 24th 19th 8th 9th 10th 11th 12th 7th
Rotation
7th 8th 9th 10th 11th 12th 13th 14th 15th 16th 17th 18th 1st 2nd 3rd 4th 5th 6th
Rotation
12th 7th 8th 9th 10th 11th 18th 13th 14th 15th 16th 17th 6th 1st 2nd 3rd 4th 5th
Rotation
20th 21st 22nd 23rd 24th 19th 14th 15th 16th 17th 18th 13th 2nd 3rd 4th 5th 6th 1st
For
SCU-401-12M
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