Are your panels ready for the summer?
posted by: Christian Westwood, Rittal
It’s recently been suggested in the press that this summer could be the hottest in Britain for 40 years.
(Click here to view article in digi-issue)
If the forecasters have got it right and we’re in for a scorcher, then it’s worth being prepared, not least to ensure that critical control and automation equipment is protected against the heat. High temperatures are a common cause of sensitive electrical and electronic components tripping or even failing.
A tripped device can disrupt production, costing the company tens or even hundreds of thousands of pounds per hour. The cost of catastrophic equipment failure is even higher as it means an extended period of downtime whilst replacement products are sourced and fitted. Temperatures inside the panel can get so high that there is even a point at which fire becomes a very real risk.
To put the amount of heat produced by electrical devices into context, consider inverter drives. More and more are being used in electrical equipment because they are very effective at reducing the amount of energy used – which means lower production costs. Assuming an efficiency of 97 per cent, a 250 kW drive can produce up to 7.5 kW of heat, much of which is retained inside the enclosure in which it’s installed. The heat dissipated by the equipment in an enclosure may not be known, but it can be estimated by either considering each component individually or by measuring the temperature inside and outside the panel and calculating the heat transfer through the walls.
The good news is that there are ways to mitigate and indeed eliminate the risk of heat damage to automation equipment.
Cooling requirements for panels can be calculated using software that is readily available. Most versions also show the temperature that will be reached inside the panel should no climate control equipment be fitted. These figures can reach heights that are absolutely staggering.
As to the solution, there are plenty of options. They range from fan-and-filter units and air-to-air heat exchangers (both of which use cool ambient air to lower the internal temperature) to cooling units and air/water heat exchangers. The latter are each able to keep the temperature inside the panel below that of its surroundings.
The decision, ultimately depends on the amount of heat produced inside the panel and the environment in which it’s installed. Each choice, in other words, will be specific to the particular application.
The main consideration is whether the panel is located in a cold or hot environment and if that environment is clean or dirty. It would be nice, actually, if the answers were as black and white as these questions suggest! They typically fall somewhere in between. Conditions may also change over the course of the working day, week, month or year, so the final selection of an appropriate cooling solution may not be entirely straightforward.
If the enclosures are located in a cool and clean environment, then fan-and-filter units may be sufficient. A single device can provide over 4 kW of cooling in ideal conditions. What’s more, recent technological advances around fan-and-filter units, such as diagonal fan technology and electronically commutated motors, as well as long available control devices, all serve to maximise performance, reduce energy consumption and extend service intervals.
If the air is dirty, low ambient temperatures can still be utilised by using energy efficient air-to-air heat exchangers for cooling the equipment. Air from inside the panel is recirculated through a circuit that is separate to the one through which air from outside it is passed and hence there is less opportunity for dirt, dust and debris to ingress the enclosure.
For applications where the temperature inside the enclosure needs to be lower than that outside it, a cooling unit solution may be the best option. These units can operate effectively in ambient temperatures up to 60 degrees Celsius but they can also provide free cooling when the external air is cooler than that required internally. They do this through the innovative use of heat pipe technology. And by switching to “hybrid mode” (where the heat pipe operates alongside a refrigerant circuit containing speed-controlled components) they maximise energy efficiency even when passive cooling cannot satisfy the entire demand.
Air-to-water heat exchangers may be another alternative for cooling units in warmer conditions. The water here is delivered to a remote location in which the heat from the equipment - up to 10 kW from one unit - can be dissipated more effectively. It also means the waste heat doesn’t end up adding to the heat already inside the factory.
Air-to-water heat exchangers have a centralised chiller, which is responsible for delivering chilled water to multiple air-to-water heat exchangers or process cooling applications. If the chiller can also be placed outside the factory, it will operate more efficiently in cooler conditions. What’s more, free cooling is possible when the ambient air temperature falls more than 2 degrees Celsius below the temperature of the cooled water.
Planning climate control
The first step in evaluating cooling requirements is likely to be running a thermal survey.
This can be helpful regardless of whether or not there is currently any form of enclosure climate control installed. It can also help with understanding how well any existing system is working within the current environment, whether a different service and maintenance regime could improve its efficiency and if a different technology would improve performance, reduce energy consumption or benefit the applications from both perspectives.
Begin by asking some simple questions:
• Is equipment tripping or failing due to high temperatures?
• Is this having an impact on production, slowing or stopping it completely?
• Do your enclosures feel hot to the touch?
• At the height of summer, are enclosure doors regularly left open and are large fans blowing into the panels to cool the devices inside them?
• Does inadequate chilling of process fluids result in production down-time?
• Would the existing cooling solution benefit from a health check?
If the answered was yes to any of these questions then a survey could be needed.
Now is the time to find out how to best protect the crucial equipment that controls processes and act before the heat of the summer pushes operating temperatures beyond its limit.
Not to have climate control units installed means that a business is running a serious risk that the systems responsible for managing its manufacturing processes will fail. And any consideration of the cost of the climate control system needs to be weighed up against the potentially far higher losses associated with replacement drives, reduced productivity or even worse scenarios.
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