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batteries were crammed into the compartment and it took a team wearing full PPE because of the hazardous materials two days to pry them out. The lead time to acquire replacement batteries meant further downtime and costs.

Standard maintenance procedures The standard HTM 06-01 Electrical Services Supply and Distribution: Part B – Operational management relating to Uninterruptible Power Supplies, inverters and batteries lays down specific guidance for maintenance of UPS systems. The maintenance team is normally

responsible for the non-intrusive visual inspection of UPSs, inverters and batteries, which should be considered as a frequent maintenance task to be carried out at least once a month. The non-intrusive visual inspection should include a visual check that no alarms have been activated and that rooms are apparently at design condition. Where the UPS, inverter or battery

includes self-monitoring or data-logging facilities, visual inspection should include a printout of these facilities. In this way, a condition-based maintenance system can be initiated for full-service maintenance checks. The cleaning of ventilation grilles on the

UPS should be carried out at the same time – because blocked ventilation grills again lead to higher temperatures. In addition, the room’s general environmental conditions should be noted and most particularly its temperature; as a general rule maintenance crews should follow their instincts – so if a room appears to be warm or even hot then you may have a problem and it should be investigated. For the medical sector Bender UK

advocates six monthly service checks on UPS installations In line with the recommendations of HTM 06-01 Part B. Some suppliers claim that annual checks are sufficient but six months is the most prudent maintenance period to safeguard systems and avoid unscheduled downtime. For example, a battery which is not

connected to a power system for charging – perhaps due to a fuse blowing or some other minor system failure – will retain its charge for up to six months and therefore is still available for service. But beyond six months it will almost certainly not be available when required. Therefore Bender UK recommends non-

intrusive functional tests of UPS installations, inverters and batteries to be carried out every six months by dedicated service personnel. These functional tests for UPSs, inverters

and batteries should include a physical test of any connected automatic or visual alarms. Functional UPS tests should verify that the inverter input would change from the rectifier output to battery output within 0.5 seconds. Similarly, the static switch should operate within 0.5 seconds following any fault condition of the inverter unit. In the same way the full service of UPSs,

inverters and batteries should be considered as an occasional frequent maintenance task every six months to improve the likelihood of a successful outcome when the batteries are called upon. Industry guidelines suggest that UPS

systems above 80 kVA may have self- diagnostic test facilities for battery condition, and that these can be used to safeguard the system. But in practice these self-diagnostic test facilities are very rarely specified or installed, and battery testing therefore falls to the UPS service engineer. Full-service tests should demonstrate that

the batteries can hold their fully charged state while the UPS is on bypass. Secondly, the batteries and UPS should be tested online (with the mains disconnected). The battery discharge voltage and current should be monitored over a 10-minute period. Following this, the battery voltage and current-recharge conditions must be observed, and any adverse conditions should be corrected. The test should also verify the condition

of the rectifier and inverter components, including the static switch and all bypass switches, and inverter input and output waveforms should be checked and verified. All cable and component connections should be tightened as required.

Service/test/record documentation A simple single-line diagram of the UPS/inverter arrangement indicating how the units are connected into the electrical infrastructure should be maintained as part of the operational and maintenance manual and site logbook. The site logbook should contain full

details of the UPS, inverter and battery units including:

• Battery autonomy. • UPS rating (kVA).

‘Temperature is overwhelmingly the single biggest factor in UPS battery failures.’

• Rectifier type (six or 12 pulse).

• Single supply or dual supply. • Date of installation. • Manufacturer. • Service contract details.

Automatic changeover solutions The increased use of parallel power sources operating as back up or redundancy solutions provides further resilience for medical power infrastructure. Many healthcare installations are

instituting high integrity changeover systems to bring in power from another board or source. The ATICS unit from Bender is the only

changeover solution purpose-designed for medical applications with patient safety at the very core of its conception and development. Central to the ATICS design is the incorporation of permanent self- testing across all critical components bringing increased peace of mind over other products that are susceptible to failure without prior warning. ATICS has the unique distinction of

achieving independent (TUV) accreditation to the Safety Integrity Level (SIL) Level 2 standard and compliance with BS7671 2008 (2001) It removes the single-point-of-failure

threat to power resilience inherent in the traditional single supply cable, by enabling supply from two different sources. The primary supply maintains normal operation but in the event of failure ATICs transfers over to the secondary supply within 0.5 seconds to comply with HTM06-01. Other third party changeover devices are

developed primarily for non-medical, industrial applications where the intrinsic level of device safety and reliability is set against the continuity of an industrial process, not the support of human life. n

• Mode of operation (single/double conversion, on/offline).

Providing insights into the vast field of healthcare engineering and facility management


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