When selecting a new commercial heating boiler or commercial plant room there are more factors to consider than in domestic properties, simply replacing the heat source may be suitable but will the new boiler deliver the same temperature and allow the same flow to the system?  All too often we come across a new commercial installation that has been clearly delivered by a domestic level installer, this may appear fine to start with but the issues will not take long to appear. If you are located in the Farnborough, Aldershot, Farnham or Camberley areas this is something we will well aware of when completing your installation.

Too little 

Many older boilers are cast iron construction, they were non-modulating so ran at one burner output and they often had a maximum operating temperature slightly higher than any modern boiler prefers to run at.  For example, an Ideal commercial boiler like a Concord could run happily between 80-90°c as long as there is sufficient flow rate provided to the system or buffer.   

A modern condensing boiler will attempt to keep the maximum flow temperature below around 75°c so that the return is within condensing range or dew point.  Some commercial boilers can be set up to run at high temperature but this will reduce the overall efficiency, the system radiators will likely be designed with a high flow temperature in mind and these may be difficult to change without large expense so will your property be adequately heated at <75°c and could a weather compensation system be installed to further reduce the running costs?   

Any new boiler will need to be selected carefully and the output calculated to avoid a wasteful new installation that does no perform.  We were asked to quote for a church with a single pipe system recently, this requires a low delta-t and high flow temperature with a (relatively) low heat input and that is not an efficient way to run a modern boiler.  We recommended a plate heat exchanger or low loss header and specified a boiler that could run at higher temperatures when necessary but was linked to a room influence to prevent overshoot. 

Too much 

As in domestic we very often see massively oversized and complicated boilers and plant rooms, we recently conducted a survey in which the remit from the consultant was for 2x 180kw boilers installed on a cascade with full BMS and expensive flue header.  We performed a basic on-site heat loss calculation and found that even at -3°c outside temperature the heat loss would not exceed 40kw, the consultant specified boilers only had a minimum output of around 60kw each so would always output too much energy on even the coldest days of the year.  This will lead to cycling which is both inefficient and will reduce the life-span of the boilers. 

In this case we recommended 2x 32kw Viessmann 200-W boilers on a bespoke cascade system, not only are these the most efficient boilers on the market but as they are the domestic models they have cheaper components, cheaper flues and come with a 10 year warranty.  They will provide enough heat on the coldest days and modulate down to keep a perfect internal temperature all year round. 

Just right  

Over specified plant rooms are considerably more expensive both to run and to install but often there is one good reason to increase the number of boilers and that is simply a backup system.  When installing a new system it is advisable to install a cascade in which 50-100% more than the maximum required output can be provided, this is usually done with either a proprietary control platform like the Viessmann 300k or a 3rd party BMS like Trend.  The cascade can then be set up to have a lead and lag swap to reduce run times of each unit which increases longevity and reduces failure rates as well as the capability of one or more units taking the strain when one is faulty. 

Care must be taken when increasing the maximum output that the minimum output can be met, it is no good having 360kw of maximum output and 120kw of minimum if it constantly cycles.  This will be expensive and constantly have problems like the emitters being too hot or the pumps running all the time to escape the heat. 

A good new commercial system will be capable of providing the most amount of heat required, overcoming one or more failures to avoid commercial boiler repairs with no down-time and crucially minimise waste energy. 

A great new commercial heating system will do all of the above but last for a generation.