There are some key issues to consider when planning a replacement install that will ensure longevity and reliability.
Ageing boilers can cost more in repair and running costs than a replacement, burning money without giving out any discernible heat. Replacement with new boilers can achieve a quick payback with good planning.
For example, it sounds simple, but people rarely consider building use. During the consultation stages it’s worth the end-user considering utilising or creating a different space for any new boilers, which would minimise downtime from the old system being shut down.
It’s also important to remember multi-use buildings can be heated by one system but may need a control system intelligent enough to manage the different areas at the same time.
Another consideration for public sector buildings, particularly schools and healthcare establishments, is the appetite to install a heating system which has backup.
A cascade set up can therefore offer the best of both worlds. So, for example, rather than two 300kW units making a total output of 600kW, six 100kW boilers arranged in a cascade will provide the same output and – in this scenario – an even greater modulation rate of 30:1.
Regardless of what they have been used for in the past, the main risk with old buildings is the sludge and dirt that will have accumulated in the system over the years and risks depositing in the new boiler. Blocked waterways resulting from this system debris can result in a premature failure of the boiler. Ideal Commercial’s technical teams’ experience shows that this is often the root cause.
Costs on some projects can escalate and levels of protection, such as plate heat exchangers and magnetic filters, can sometimes be taken out of a proposal. However, when looking at the life-cycle costs of boilers, this is potentially a risky move. System protection is key to extending the lifespan of a boiler and by communicating the long-term savings to an end-user you add value to your services.
Open vented or sealed?
It is crucial to think of the whole system when installing new condensing boilers. Older heating systems will most likely be open vented with a feed and expansion tank which means pollutants are able to enter the system water. Installing brand-new boilers onto an old system that is clogged with debris and dirt will immediately reduce its effectiveness. If dirty water is transferred into the new boilers it will negatively impact their ability to run efficiently and, potentially lead to breakdowns and even failure.
Prior to the installation of the new boilers, we encourage installers to consider treating the water within the existing system. This helps to ensure the boiler’s longevity and can protect its internal parts from corrosion and the build-up of scale over time.
If introducing a new boiler installation to an existing system, another consideration is ‘system separation’ via a plate heat exchanger. A plate heat exchanger works by transferring heat from the primary circuit to the second via heat transfer and without the system’s potentially dirty water coming into direct contact with the circuit. This also maintainsa constant water velocity despite changes in the secondary circuits. This eliminates the need for a low-loss header as the system’s pumps won’t have influence over the boiler shunt pumps.
However, a heat exchanger will only function at its peak efficiency when the water velocity passing through it is maintained within prescribed parameters. Therefore, accurate sizing of the plate heat exchanger is required before installation.
By taking a lifecycle costing approach to installing new boilers in an old building, a business can realise multiple financial benefits over the lifetime of the boilers. And while it’s easy to win business on price, reputation lasts much longer. There are some key things to remember when approaching a boiler retrofit: system preparation and ongoing water treatment; adding levels of protection such as low loss headers, plate heat exchangers and filters; and understanding the needs of the building occupants. If all of these are considered and clearly communicated to the end-customer, it’s a win-win for all involved.
Chris Caton is Product Manager at Ideal Commercial Boilers.
This article first appeared in MBS magazine, March 2018.