Pump VSD gets hotel into hot water
The importance of a hotel’s hot water system cannot be underestimated. For the guests, it’s right up there with comfort, cleanliness, security and Internet access. For one UK hotel, installing ABB VSDs improved the hot water pumping and returned a 53% energy saving.
The 200-room Daresbury Park Hotel & Spa came under the Britannia Hotel Group in 2015. From the outset it was clear the existing pumping system needed an overhaul. The system supplies hot water to the entire hotel including guest rooms, public areas and the spa.
“From day one we experienced many problems. They ranged from intermittent changes in water pressure to banging in the pipes. Sometimes it resulted in a complete hot water pumping breakdown,” explains Britannia’s head of maintenance Lol Bennett. “We needed to make the entire system more reliable, reduce wear on the pumps and save energy.”
To achieve this, the hotel turned to water pressurisation specialist PressBoost to provide a solution. They install and maintain pump systems in all Britannia Hotels locations.
Weakness of standby-duty-standby
Examination of the hot water pumping system revealed three large pumps operating in a duty-standby-standby configuration. The pump capacity was enough to meet the hot water needs of the hotel and its guests. Moreover, the lead pump was suffering from excessive wear, causing it, on occasion, to break down. ”Duty-standby-standby is a bad arrangement. It means most of the time, pump number one was doing all the work. Pumps two and three were idle,” explains Antony Chesters, the specialists senior engineer.
Markedly, they also discovered the variable-speed drive fitted to the lead pump was not working. This meant that the pump ran at full speed regardless of demand, putting further strain on the motor. It also meant the VSD was not delivering the energy savings it could provide.
The next step was to install a 7.5 kW ABB drive each of the three pumps. The drives adjust the speed of the pumps depending on the level of demand. As demand for hot water falls, it reduces energy to the pump motor. Consequently, this enabled the hotel to cut the energy it uses to supply hot water by 53 percent.
They also reconfigured the system to duty-assist-standby, further reducing wear on the lead pump. “Should demand exceed pump one’s capacity, the second pump switches on to assist the lead pump. Moreover, regardless of demand, the pumps switch over every 24 hours to spread demand and reduce wear on the lead pump.”
Hot water pumping
The VSDs keep water pressure constant at 3.5 bar, which also helps to reduce wear on other parts of the hot water system. “Before installing VSDs, water pressure fluctuated between 3 and 6 bar, causing water hammer in the pipes. It put stress on the pipework, bearings and seals, contributing to the unreliability the hotel was experiencing. It also annoyed the guests.”
Controlling the ABB drives was a control panel using a PLC. In the unlikely event the PLC fails, a fail-safe programme switches the pump system to single pump, fixed speed operation. This ensures there is no loss of supply. As a result, the specialist is applying the same solution to the hotel’s cold-water system.
Since the system was installed the hotel and its guests have finally enjoyed an uninterrupted supply of hot water.
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