Fan Coil Unit Expand Objects Template

Overview

This template generates a central DOAS air handling unit that provides a constant volume of conditioned outside air to all zones. It also generates an object in each zone that can provide heating and cooling, supplied by central chilled water and heating hot water plant.


Application

This system is used for five system options within Sefaira:

  • Fan Coil Units (4-pipe)
  • Active Chilled Beams
  • Passive Chilled Beams
  • Ventilation and Heating Only
  • Radiant Floor

For each option the central AHU is virtually identical, with the exception of some defaults.

Changes were made to defaults and equipment at the zone level to achieve equivalents to the above systems.


Air Handling Unit (AHU) – Return Air

The table below describes the key properties of the AHU for this system where there is return air:

AHU Feature

Default

Extent of user-control

Airflow Rate

Based on ventilation rate by zone

Can change zone ventilation rate or set a fixed constant primary air flow rate

Supply Air dry bulb Temperature

Constant with defaults as follows: 

13 C or 55.4 F (Fan Coil)

11C or 51.8F (Active beams)

14C or 57.2F (Passive beams)

Can change constant value

Supply Air Temperature Reset Controls

None

No control

Supply Air Dew Point Controls

Constant with defaults as follows:

Min: -5 C or 23 F

Max: 13 C or 55.4 F (Fan Coil)

Max: 11 C or 51.8 F (Active Beam)

Max: 10 C or 50 F (Passive Beam)

None

Supply Air Humidification Controls

Via Min Supply Air Dew Point Control

None

Peak Fan Power

3.5 W/(L/s) or

1.65 W/cfm

Can control peak load

Fan Curve

Standard ASHRAE. Click to see fan curve. Note airflow is not variable

No control

Outside air configuration

100% outside air

No control

Return Air Rate

100% of air assumed to be returned for heat recovery

No control

Heat Recovery Efficiency

Sensible and Latent effectiveness available. Default is 50% sensible and 0% Latent.

User can change sensible and latent effectiveness

Cooling Coil

Chilled Water coil post heat recovery

No

Heating Coil

Hot water coil post chilled water coil

Can change to electric coil or direct gas

Frost Coil

Electric coil pre-heat recovery

Can change to hot water

Frost Coil Setpoint

Setpoint for coil – default is 2C

Can Change default


Zone Fan Coil Units

Fan Coil Units are the basic system applied to the following options: 

  • Fan Coil Units (4-pipe)
  • Active Chilled Beams
  • Passive Chilled Beams
  • Ventilation and Heating Only 

In other words – for all of the above systems it is assumed that heat transfer by the zone heating and cooling unit is purely convective. For the above systems the only variables that are changed are defaults.

The table below describes the key properties of the zone level Fan Coil Units for this system: 

Fan Coil Unit Feature

Default

Extent of user-control

Heating Coil Type

Hot water

No control

Cooling Coil Type

Chilled Water

No control

Fan Coil Motor Type

Constant Volume (On/Off) except for Chilled Beam Systems that has none

No control

Peak Fan Power

0.64 W/(L/s) or 0.3 W/cfm

Can control peak load

Fan Curve

Constant Volume Fan 

No control

Supply Air Temperature - Heating

Variable for Fan Coils and Heating Only.

Constant for all zones (35C / 95F)

User can change constant

Supply Air Temperature - Cooling

Variable for Fan Coils and Heating Only.

Constant for all zones (13C/55.4F)

User can change constant

Demand Control Ventilation

None

None

Dehumidification Load

All systems will dehumidify to achieve the cooling setpoint at 60% Relative Humidity in the zone

None


Radiant Floor

 A radiant floor element replaces the fan coil units for the radiant panel option

The table below describes the key properties of the zone level Fan Coil Units for this system: 

Fan Coil Unit Feature

Default

Extent of user-control

Heating Coil Type

Hot water

Can change to electric coil

Cooling Coil Type

Chilled Water

No control

Temperature Control Method

Operative Temperature. Note this means that the setpoints in internal conditions become operative temperature setpoints

User can change to dry bulb or radiant temperature.

Surfaces conditioned

Floor only

No Control


Central Plant

The base case option is assumed to have a central plant that provides heating hot water to the AHU and Fan Coil Units and a chilled water system that provides chilled water to the central AHU.  The only exception is the heating plus ventilation system which does not include a cooling plant.

Central Plant Feature

Default

Extent of user-control

Heating Hot Water Source

Natural Gas

Can change to electric boiler

Boiler Peak Efficiency

Assumed to be 0.9

Value can be changed

Boiler Performance Curve

Click to see curve

No Control

Supply and Return Temperatures – hot water

80/70 C or 176/158 F

User can control

System losses

Constant efficiency of 15%

User can control loss rate only.

Peak Pumping Energy

1.32 W/(L/s) or 21 W/gpm

No control

Pump Efficiency Controls

Variable Speed Drives

No control

Efficiency Curve for Variable Pumping

Click to see curve

No control

Pumping Configuration

Primary Only

No control

Chilled Water Source

Water-cooled Chiller

Can change to air-cooled

Chiller Peak Load Efficiency

5

Value can be changed

Chiller Performance Curve

Water-cooled chiller here

Air-cooled chiller here

No Control

Supply and Return Temperatures – chilled  water

7/12 C or 44.6/53.6 F

User can control

System losses

Constant efficiency of 10%

User can control loss rate only.

Peak Pumping Energy

1.32 W/(L/s) or 21 W/gpm

No control

Pump Efficiency Controls

Variable Speed Drives

No control

Efficiency Curve for Variable Pumping

Click to see curve

No control

Pumping Configuration

Primary Only 

No control

Separate chilled water loop for fan coils

None

None

Waterside Economiser

None

None

     

Condenser Water Source

Cooling Tower

No extra options

Cooling Tower Efficiency

245.7 W/(L/s) or 15.5 W/gpm

Value can be changed

Supply and Return Temperatures – condenser water

29/35 C or 84.2/95 F

User can control

System losses

Constant efficiency at 5%

User can control loss rate only.


Post Expansion notes about Fan Coil Units

There are a large number of objects that are modified post-expansion which can result in inconsistencies between some outputs in the standard E+ reports and the Sefaira outputs.

  1. Impact of Ventilation Air on space load
  2. Heat Recovery in the central air handling unit
  3. Insertion of radiant heating in lieu of fan coil units
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