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Plants
Overview
This chapter covers plants used to produce thermal energy for cooling or heating. Haystack standardizes the following types of plants:
chilled-water-plant
: produces chilled water for coolinghot-water-plant
: produces hot water for heatingsteam-plant
: produces steam water
Typically, these plants supply AHUs and VAVs for HVAC applications. But they can also be used for industrial processes.
We typically use the term central plant to describe a plant that supplies a building or group of buildings. When the plant supplies a municipality, we use the term district plant. However, the Haystack modeling techniques described here are identical.
Haystack models an entire plant as a single blackbox equip
entity. Equipment within the plant, including heat exchangers, pumps, boilers, and chillers, are modeled as children of the plant via the equipRef
tag.
Chilled Water Plants
Chilled water plants are modeled as a single black box using the chilled-water-plant
conjunct along with the equip
tag. These plants are composed of the following types of sub-equipment:
This diagram shows the salient equipment and fluid flows:
Hot Water Plants
Hot water plants are modeled using the hot-water-plant
conjunct along with the equip
tag. These plants are composed of the following types of sub-equipment:
Steam Plants
Steam plants are modeled using the steam-plant
conjunct along with the equip
tag. These plants are composed of the following types of sub-equipment:
Loops
Plants typically maintain a separation between the working fluid within the plant versus the fluid that supplies thermal energy to the building. We term the pipework within the central plant the primaryLoop
and the pipework from the plant to the building the secondaryLoop
. These two loops are connected through heat exchangers
. In the case of a third loop connected to the second loop through a second set of heat exchangers we use the term tertiaryLoop
.
For example, here is how we would model a heat exchanger with a temperature sensor on the primary entering pipe and on the secondary leaving pipe:
id: @hx dis: "Heat Exchanger" chilled water heatExchanger equip equipRef: @plant siteRef: @site id: @primary-temp dis: "Primary Entering Temp Sensor" chilled water primaryLoop entering temp sensor point unit: "°C" kind: "Number" equipRef: @hx siteRef: @site id: @secondary-temp dis: "Secondary Leaving Temp Sensor" chilled water secondaryLoop leaving temp sensor point unit: "°C" kind: "Number" equipRef: @hx siteRef: @site