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eQUEST_4-Pipe FCU system with ASHP(heating) and chiller(cooling)

asked 2016-09-25 23:01:18 -0500

Allison Pan 611 gravatar image

updated 2016-10-18 14:27:06 -0500

Dear all,

I am modelling a hotel with system through eQUEST as below,

•System: 4 -pipe FCU with seperate OA induction (dummy zone has been built to model the OA induction unit) •Heating source: air source heat pump •Cooling source: water cooled chiller

I encountered two problems:

1.As the ASHP can only be constructed in water side by selecting a chiller type as heat pump and attached to a 2-pipe circulation loop. I found that ASHP is supporting both heating and cooling for the building though the cooling source has been selected as chilled water loop at air-side. This does not comply with the design intention and do no good for energy conservation since the chiller has higher COP than the ASHP.

2.Another problem is that the 2-pipe circulation loop lead to some overheating unmet hours during winter when there is both heating and cooling load, even the system itself is a 4-pipe one.

I tried to set the heating and cooling schedule for the heat pump loop but somehow it gives me a 99.99% unmet when I turn off the cooling for heat pump loop. Only certain load is charged from the chilled water loop though the chiller capacity is autosizing at present...

I m totally stuck here, and wondering if anyone got any experience like this? any tips or advice is much appreciated, thanks in advance!

Allison

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answered 2016-09-26 13:43:41 -0500

Anna gravatar image

How did you define your heating and cooling schedules? Have you tried to use Load Management Type: Scheduled and Equipment Control? Maybe you can create Equipment Control for cooling and specify the chiller as the Seq 1.

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Hi, Thanks for your advice! I did try as you metioned,,see below.

1) I define the heating and cooling schedule based on the heating and cooling load in the hourly report. so basically when there is a heating load, the heating schedule (on/off/temp) will be defined as 'on' and cooling schedule as 'off'.

Allison Pan 611 gravatar image Allison Pan 611  ( 2016-09-26 20:10:28 -0500 )edit

2) I tried the equipment control with chillers defined as priority and heat pumps as the least. While since the chillers and heat pump is not in the same circulation loop, and based on the software help session that only equipment in the same loop can be driven by the control sequence. The result did not change before and after I set the equipment control, it seems that the equipment control does not help.

Allison Pan 611 gravatar image Allison Pan 611  ( 2016-09-26 20:10:51 -0500 )edit

Have you considered using System type: Single Zone CI instead of Fan Coil? I’m not sure how well it will represent your actual system, but it would allow you to specify HP at zone level for heating and chilled water coils for cooling.

Anna gravatar image Anna  ( 2016-09-27 07:52:02 -0500 )edit

Dear Anna,

Yes I have checked the heat pump at zone level. The problem is that the zone level HP is air-to-air HP while mine are central air-to water HPs. Not sure how big difference it will cause, one first thing is that I cannot then define the hot water supply and return temperature with zone HP.

Allison Pan 611 gravatar image Allison Pan 611  ( 2016-09-27 20:05:58 -0500 )edit

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Asked: 2016-09-25 23:01:18 -0500

Seen: 626 times

Last updated: Sep 26 '16