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Large Versus Small Hot Water and AC Systems

Hotels Use Large System but are they Efficient?

Traditionally hotels have tended to use large centralised systems to supply air conditioning, water and hot water to their rooms. For many of us the frustrations of these systems are well known but are they efficients. Here we look at the new trend for hotels to use small independent systems for each room and the advantages of going small.

Hotels tend to use large systems

Many hotels use large centralised systems for air conditioning, water supply and water heating. We must assume that the reason is for greater efficiency and therefore lower cost but is this really the case?

These large systems must keep running regardless of how many or how few people are in the building. They may be fine for a factory with large open spaces or in an office building where rooms are nearly always occupied through the day but in a hotel where occupancy fluctuates there are great advantages in only cooling and providing hot water to the spaces that are occupied.

These large centralised systems present a major challenge in terms of control at the local (individual room) level.

Large air conditioning systems distribute air by sending cold air down long networks of ducting. Delivering the right amount of air at the right temperature can be very difficult particularly when you consider that some rooms are close to the air conditioner while others are 25 million miles away.

Similarly problems occur with hot water systems. Corridors can be very long and, once again, some rooms may be fairly close to the water heater while other rooms may be a long way away and it may take several minutes for the hot water to get to bathrooms in the nether regions. To solve this problem large hotels often use recirculating hot water systems. A circulation pipe carries the hot water from a large centralised heater around the rooms and back to the heater. A pump keeps the hot water continuously circulating so that there is always hot water in the pipe as it passes close to each bathroom and (theoretically) if you turn a hot tap on you will always get instant hot water.

All very well in theory but we all know that theory and practice are often two totally different things. This arrangement has several problems. The first is that the hotel is continuously heating water even if it is not being used or, at times of low occupancy only a small amount is being used, this is expensive. Secondly the reality is that one heater is supplying hot water in varying amounts to many bathrooms, some near and some far away through a single pipe. Inevitably the people in the furthest bathrooms are likely to be the last in the queue for hot water and the pressure in the pipe is going to vary as people all along the way turn their showers on and off. This is why there are fluctuations both in the pressure and temperature of the water you receive in your bathroom.

Multiple small systems are easier to maintain and provide individual control

A far better approach that is becoming more popular these days is to have small independent systems for each room. You will note that many hotels these days are starting to install individual air conditioning units for each room.

This approach can also be applied to plumbing services with small individual pressure pumps and water heaters to supply the bathrooms. A large bore pipe delivers cold low pressure water to the rooms. At each bathroom a small individual pump draws water from the supply pipe and feeds it to the bathroom thereby providing stable water pressure that is independent of the rest of the system. Each bathroom also has its own water heater thereby guaranteeing hot water regardless of what is happening in the rest of the hotel. Water is only heated when the room is occupied and only pressurised when it is being used.

In addition if the hotel has independent air conditioners and water heaters for the rooms a further step can be taken and that is to provide an air conditioner water heater with an electric booster element on a timer for each bathroom. These units are only a little more expensive to buy than a standard electric water heater and provide free hot water. Hot water bills in a hotel can be a very expensive item in the budget.

Advantages of small systems in hotels

The use of small independent systems can provide a number of advantages:

  • They use standard mass produced air conditioners, water heaters and pumps and so are not expensive to install.

  • If a unit fails only one room is put our of action.

  • Customers have far greater control over the room temperature and the pressure and temperature of the water in the bathroom.

  • You don’t need a highly trained engineer to continuously manage a complex system.

  • Operating costs reduce proportionally when occupancy rates are low.

  • You save the cost of continually maintaining pressure and heat in the system whether people are using it or not.

These principles may also apply to small villa developments and ordinary houses particularly if they have more than one floor or there are long distances between buildings. If some profit minded individual wishes to sell you a more expensive pump and provides you with something large enough to irrigate the Sahara Desert you are left with the problem of trying to tame the beast. A design that breaks down your systems into small independently managed services may well provide you with a more effective system.

Copyright © Phil WilsonDecember 2012
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