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chiller IPLV in IES-VE

asked 2018-09-03 05:20:48 -0500

updated 2018-09-04 08:50:34 -0500

In IES-VE I’m modeling a baseline model for ASHRAE 90.1-2007. The chiller efficiency has to respect Table 6.8.1C for screw chillers. Suppose that the autosized cooling power for every chiller is 600 kW (2 chillers). The efficiency should be 4.90 COP and 5.60 IPLV. How can I be sure that the IPLV is respected? Can I see the IPLV value in ApacheHVAC or in some output report? Best Regards

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answered 2018-09-04 01:15:35 -0500

updated 2018-09-04 01:21:48 -0500

I don't know of any output reports where you can see IPLV. You can calculate it based on the chiller curve you have used and the design condition COP.

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Just use the coefficients and the basic bi-quadratic formula to to create a table for the EIRfPLR&dT values you need to do the calculation, where X is part load ratio at 100%, 75%, 50%, 25%, and y is chiller lift (ECWT - Design LCHWT). For ECWT, use the values outlined in AHRI Std 550, depending on your condenser type:

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The values you calculate are just correction factors. To get the COP from these correction factors, use the equation:

COP = PLR / EIR Correction factor

Here is an example table, this has more data than you need for just the IPLV calculation, though:

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Then use the standard IPLV equation, also outlined in AHRI Std 550.

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answered 2018-09-04 10:06:57 -0500

crduggin's avatar

It sounds like you are really looking to confirm that you are meeting the IPLV requirement in addition to the full load kW/ton. IPLV has more to do with the shape of the chiller curve since it deals with the efficiency of the chiller as it unloads. You could get the IPLV via several different combinations of part load chiller efficiencies since it is a weighted average. As far as I know there isn't a way to plug in an IPLV and get a chiller curve. The only way I can think of is to find a chiller that has that IPLV and full load kW/ton. Then use it's curve. When modeling the baseline, I typically just use one of the default curves based on chiller type and input the full load kW/ton, which just offsets the curve so the full load efficiency matches.

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answered 2018-09-07 15:40:44 -0500

Brett M's avatar

There is a really good conversation about this topic I recommend here:

Several approaches are outlined in the conversation linked above each with their own merits.

Unfortunately the full load kW/ton and IPLV requirements do not correspond to a realistic piece of equipment on the market but is rather intended to be a set of maximum limits inclusive of multiple manufacturers. I suspect this is intentional as it would not necessarily be a fair for the ASHRAE 90.1 committee to designate a particular manufacturer's equipment as the "code minimum" and of course various competing manufacturers provide input to the committee and the standard.

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Asked: 2018-09-03 05:20:48 -0500

Seen: 1,167 times

Last updated: Sep 04 '18