Stationary UPS Sizing Calculations – Part Seven ~ Electrical Knowhow

in Article “Stationary UPS Sizing Calculations – Part Six”, we explained the following:

1- Battery Room Design Criteria

2- Ventilation Design Criteria

3- Battery Room Ventilation Calculations:

NFPA method,
British (metric) units method.

4- Requirement of Air Conditioner for UPS

Today, we will explain the Requirements for UPS Installation and Testing.

Requirements for UPS Installation

There are (4) major Requirements for UPS Installation:

Location,
Ventilation,
Floor loading capacity,
Floor Space Requirements.

1- Location

Preferably the UPS has to be installed close to the loads. If the distance between the load and the UPS is higher, we must consider the voltage drop based on the distance of the cable and suitable action like oversizing the cable needs to be considered.

2- Ventilation

Most of the UPSs are designed for a maximum operating temperature of 40°C. The losses of the UPS is dissipated as heat and the UPS room should have the ventilation arrangement to remove the heat to maintain the ambient temperature below 40°C.The ventilation can be in the form of cross ventilation of hot & cold air (using air exchangers-inlet & exhaust fans with suitable filters) or with air conditioner.

It is also possible to install a duct either on the top side or the rear side of the UPS to suck out the heat produced by the UPS.

In order to provide for adequate ventilation, the UPS should be installed in a room, which has at least 1000mm of clearance on the top side or the rear side of the UPS based on the ventilation type. This area of UPS should be cleared of any obstruction, which would impede air flow. Since cooling air enters through a grill at the bottom front/front of the equipment, this area must also be kept clear of any obstructions.

The UPS room should be relatively free of dust and dirt and other airborne contaminates as heavy layers of dust will reduce the cooling efficiency of the electronic components.

It is important that the room low temperature control be adjusted to maintain the room temperature above the dew point in order to prevent condensation of moisture on the UPS. Also in areas of high humidity, UPS designed to operate under such conditions must be chosen or an adequate dehumidifier or precision air conditioner must be deployed to maintain humidity.

However, we explained the Battery Room Ventilation Calculations in article “Stationary UPS Sizing Calculations – Part Six”

3- Floor loading capacity

Care should be taken to assure that the floor loading capacity is sufficient to support the

UPS and batteries. Floor loading of UPS will vary based on the capacity and the type of the UPS. If there is a raised floor, the weight of the entire UPS system may require a concrete base to be installed upon.

4- Floor Space Requirements

It is important that adequate floor space has to be provided for the UPS. Check the dimensional information on the appropriate data sheets from the manufacturers for the floor space requirements.

Front Clearance:

A clear area in front of the unit of at least 1meter should be maintained for service personnel.

Rear Clearance:

The UPS equipment can be mounted with the back against a wall if rear access is not specifically required; however, if side and rear access can be maintained, it may be helpful should service become necessary.

However, the requirement of rear clearance will be based on the construction of UPS. If the UPS is of modular construction then a rear clearance is mandatory.

4.1- Floor space requirements in design stage

In case of design which means that there is no data sheets from the manufacturers for the floor space requirements, the following floor space requirements can be followed:

Minimum clearance required will be as per table-1 and fig-1.

Clearance Required	Front Suction, Top Throw	Front Suction, Rear Throw
Front Clearance	1000mm	1000mm
Rear Clearance	200mm	1000mm
Side Clearance	200mm	400mm
Top Clearance	1000mm	400mm

Table-1

Where:

Front Suction, Top Throw: removing air from a space from front and throw it to top side (Top Air Flow)

Front Suction, Rear Throw: removing air from a space from front and throw it to Rear side (Rear Air Flow)

Fig.1 Typical Requirement Of Clearance

4.2- Floor space requirements from manufacturers’ data sheets

Each manufacturer provide data sheets for his UPS products, from which we can assign the Floor space requirements for each UPS product. Most of the manufactures divide their UPS products into two types of arrangement:

UPS with built-in batteries
UPS with separated battery cabinets

And of course, the floor space requirements will differ for each arrangement as shown in the below examples:

Example#1: Schneider UPS Model Galaxy VS

Note#1: This UPS can come with internal batteries or with external batteries.

Note#2: dimension of UPS can differ between the one with internal batteries and the one with external batteries.

But the dimensions will not differ for the ones with internal batteries even if the number of internal battery strings changes as shown in below table-2.

Table-2

Note#3: the UPS with external batteries, the battery cabinets differ in dimensions based on its type as follows:

Modular battery cabinets
Classic battery cabinets
Galaxy Lithium-ion battery cabinets

Also, the dimensions will not differ for the same model even if the UPS rating changes as shown in below table-3

Table-3

Now, the clearance and space flor requirements for a Schneider UPS Model Galaxy VS will be as shown in Fig.2