Wasting money? Time to take control

Boiler control  is one of the fastest and simplest ways organisations can cut energy costs and reduce their carbon footprint. This is especially important since heating and hot water comprise more than a third of a typical organisation's overall energy consumption. 

 

Most boilers lack native intelligence, but older boilers are particularly unintelligent – commonly adding 30%+ to energy bills because of poor control. A common cause of wasted energy and inefficiency in older boilers is the unnecessary re-heating of water. The boiler fires up when there is still sufficient heat within the system, re-heating water that is already heated. Excess heat is wasted up the boiler flue. This is commonly called dry-cycling.

 

The boiler setting is fixed and usually set to cater for the coldest external temperatures and maximum boiler load. By implementing a controls strategy, a boiler doesn't need a clock to tell it when to run – it is demand-driven.

 

It is a basic principle of thermodynamics that if the return temperature is low, the boiler heat exchanger will operate more efficiently. Good boiler control will monitor flow and return and vary the threshold settings and firing cycle, in order to regulate the heating demand. The return temperature is used to determine when to reduce the boiler setting and when to extend the firing cycle, without affecting comfort levels. This means the module controlling the boiler plant works out when the boiler should fire to satisfy the load. In this way, the boiler plant will only run when it needs to do so.

 

Optimised control will prevent the boiler from firing up until the return temperature has dropped to a pre-calculated temperature. When there is capacity in the heating system, these temperatures can be reduced. Savings can also be made by taking into account elements such as weather compensation and optimum stop/start.

 

In installations where there is a continual heating demand, boiler flow temperatures can be reduced at times of the day when demand is lower.

 

It is the level of control strategy applied to boilers which adds the intelligence. On modern boilers, intelligence may be added internally as part of the boiler electronics, or remotely as part of an Energy Management System (EMS), or both. However, internal boiler intelligence, even on many modern boilers, is limited. Without remote thermostatic related occupancy control, dry cycling will occur within the limit of the boiler settings.

 

This level of control strategy is rarely applied, and we see many instances, particularly on smaller energy intensive sites, where businesses are reluctant to invest in bringing boilers under direct switching control.

 

It is in this type of scenario that boiler optimisation may prove to be an affordable proposition. The self-learning intelligence of these units will reduce the act of boiler dry cycling. The ultimate control, of course, is the installation of a direct switching EMS, giving total control and management of energy consumption.

 

While installation of modern boilers in conjunction with an EMS may be the ultimate, the cost can be prohibitive. However, good control of older boilers via an EMS and/or a boiler optimiser will provide a fuel saving that could then contribute to investment in new boilers. The control system should be compatible with both old and new boilers.

 

Modern energy management systems should be capable of both monitoring and reporting, enabling the client to maintain performance, target further possible savings and access data from a PC for compliance and reporting purposes.

 

The efficiency of boilers and controls is reliant on: Who installs the system, who commissions it, and how the system is maintained and managed. These criteria can make the difference between a large reduction in fuel consumption, a mediocre reduction, or none at all.

 

In general, the trigger for installation of new boilers is the failure, or possible failure, of existing systems. Some projects are undertaken following an energy audit, but all too often the recommended actions are ignored.  This is short-sighted since savings from properly optimised boilers are impressive – often there is payback in 12 to 24 months. 

 

ENER-G can finance such projects under energy performance contracts, whereby payment is taken from the savings over an agreed contract period: The client can make a healthy profit without any capital outlay.