I am doing an ASHRAE 90.1-2007 PRM analysis. We have a DOAS CV laboratory design.

Our proposed service hot water (DHW) is an indirect twin coil calorifier being served by the main gas boiler LTHW loop and a second DHW loop served by a CHP unit. The only dedicated DHW pump is a single 1.1kw DHW pump between the CHP and the calorifier, as the other pumps serve DHW and Space heating.

For service Hot water systems our baseline building comes under Table G3.1 section 11 Service Hot water systems option (b) ‘Where a new service hot water system has been specified, the system shall be sized according to the provisions of section 7.4.1 and equipment shall match the minimum efficiency requirements in section 7.4.2'.

And option (e) ‘Where a combined system has been specified to meet both space heating and service water heating loads, the baseline building system shall use separate systems meeting the minimum efficiency requirements applicable to each system individually’.

I can’t see where it mentions how to model the DHW pumps in the baseline building. Therefore I have used Section G3.1.3.5 Hot Water Pumps – The baseline building hot water pumps shall be 301kW/1000l/s…

Therefore my Baseline service hot water pumps are modelled as 301kW/1000l/s.

However when filling out the section 1.4 tables for submission the Service Hot water section states:

• Service hot water pumps should be modelled identically between the Proposed and Baseline case.

Is this correct?

If so, in the baseline building do I model only the proposed 1.1kW CHP pump as the other proposed DHW related pumps are also linked to space heating LTHW?