The distribution system multiplier (DSM, unitless) is an adjustment for alternative water heating distribution systems within the dwelling unit. A value of 1.00 for “standard” distribution systems, defined as a non-recirculating system with the following mandatory requirements:
The full length of distribution piping is insulated in accordance with Section 150.0(j)2.
For all four system types, values for alternative distribution systems are given in Table B-1. Improved DSM values are available for cases where voluntary HERS inspections are completed, as per the eligibility criteria shown in Reference Residential Appendix RA 4.4. Detailed descriptions of all of the distribution system measures are found in Residential Appendix RA 4.4.
Table B-1. Distribution System Multipliers within a Dwelling Unit with One or More Water Heaters
|
Distribution System Types |
Assigned Distribution System Multiplier |
System Type 1 and 2 |
System Type 3 and 4 |
|
No HERS Inspection Required | |||
|
Trunk and Branch -Standard (STD) |
1.0 |
Yes |
Yes |
|
Central Parallel Piping (PP) |
1.10 |
Yes |
|
|
Point of Use (POU) |
0.30 |
Yes |
|
|
Recirculation: Non-Demand Control Options (R-ND) |
9.80* |
Yes |
|
|
Recirculation with Manual Demand Control (R-DRmc) |
1.75* |
Yes |
|
|
Recirculation with Motion Sensor Demand Control (R-DRsc) |
2.60* |
Yes |
|
|
Optional Cases: HERS Inspection Required | |||
|
Pipe Insulation (PIC-H) |
0..85 |
Yes |
Yes |
|
Central Parallel Piping with 5’ maximum length (PP-H) |
1.00 |
Yes |
|
|
Compact Design (CHWDS-H) |
0.7 |
Yes |
|
|
Recirculation with Manual Demand Control (R-DRmc-H) |
1.60 |
Yes |
|
|
Recirculation with Motion Sensor Demand Control (RDRsc-H)rculation with Motion Sensor Demand Control (RDRsc-H) |
2.40 .40 |
Yes |
|
|
*Recirculation DSMs reflect impact of reduced hot water consumption associated with recirculation systems. | |||