Re: [EnergyPlus_Support] Re: ASHRAE 90.1-2007 App G G3.1.3.2 boiler sizing

Sean,

After thinking about it, I think you're right, and the HVACTemplate from E+ is misleading.

One primary, constant-speed, branch pump per chiller on the ChW Loop (supply side)
One Secondary pump (VSD or constant speed depending if > 300 ton or not) on the demand side
On the condenser loop, one constant-speed branch pump for each chiller (on the demand side then)

References:

Code reference:

ASHRAE 90.1-2007 - Section 6.5.4.2 - Pump Isolation
When a chilled-water plant includes more than one chiller, provisions shall be made so that
the flow in the chiller plant can be automatically reduced, correspondingly, when a chiller is shut down.

ASHRAE 90.1-2010 User's Manual, section HVAC Systems | Prescriptive Path 6.5 (page '6-101' or 232/470)

Appendix G specific:

ASHRAE 90.1-2007, Appendix G, section G3.1.3.11:
Each chiller shall be modeled with separate condenser water and chilled-water pumps interlocked to operate with the associated chiller.

ASHRAE 90.1-2010, Appendix G, G3.1.3.11 Heat Rejection (Systems 7 and 8).
Each chiller shall be modeled with separate condenser water and chilled water pumps interlocked to operate with the associated chiller.

Best,

Julien

--
Julien Marrec, EBCP, BPI MFBA
Energy&Sustainability Engineer
T: +33 6 95 14 42 13

LinkedIn (en) : www.linkedin.com/in/julienmarrec
LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr

2016-02-22 12:12 GMT+01:00 seanking.1970@xxxxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx>:

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Hi Julien,

Thank you very much for your useful inputs.

However, when checking LEED table 1.4 form, it looks the case is different for boilers and chillers, there should be one HW pump even if two boilers are required (the hot water loop must be primary only), while one pump for each chiller shall be required together with one pump each at condenser side (CW pump). And for Chilled Water Loop they do require primary-secondary setting so the primary subloop should use constant pump(s).

Is above observation right?

Thanks a lot.

Sean

---In EnergyPlus_Support@xxxxxxxxxxxxxxx, <julien.marrec@...> wrote :

G3.1.3.5 is pretty clear on that

G3.1.3.5 Hot-Water Pumps (Systems 1, 5, and 7).
The baseline building design hot-water pump power shall
be 19 W/gpm. The pumping system shall be modeled as
primary-only with continuous variable flow. Hot-water
systems serving 120,000 ft2 or more shall be modeled
with variable-speed drives, and systems serving less than
120,000 ft2 shall be modeled as riding the pump curve.

So, just one pump (put it just after the supply side inlet or just before the supply side outlet), either constant or variable.

By the way for chillers, when they say (G3.1.3.10) that if you have 300 tons or more you need a primary secondary pumping system... That doesn't mean you should put one pump per chiller, and then one pump on the supply side. What it means is that you should have a constant speed pump on the supply side (typically right after the supply inlet node) and one variable speed pump on the demand side, typically right after the demand side supply inlet node. If you use the HVACTemplate:ChillerWaterLoop and select ConstantPrimaryVariableSecondaryas pumping configuration, that's what you get...See attached

--
Julien Marrec, EBCP, BPI MFBA
Energy&Sustainability Engineer
T: +33 6 95 14 42 13

LinkedIn (en) : www.linkedin.com/in/julienmarrec
LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr

2016-02-18 12:09 GMT+01:00 seanking.1970@... [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx>:
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Also another question arisen from the same section: if 2 boilers are required, do we need to model two pumps (branch pumps) with one serves each boiler or just need one pump to serve both boilers please?

Thank you very much.

Sean