Earlier this year we were invited to provide a costed design solution for a new boiler plant at St Johns Church, Tunbridge Wells.
A large, Grade II listed building, probably the largest church in the area, it comprises an enormous high ceiling worship space, with the addition of vestry and offices.
The church building management team knew pretty much what they wanted to achieve, helped by their professional engineering roles in the electrical power industry.
We found a cascaded set of three commercial 50Kw cast iron Ideal atmospheric boilers. The Church technical team had previously fitted a BMS (Building Management System) that allowed them to set heating temperatures and this also did a basic weather compensation function.
There was an ability to use one of the boilers to heat the administration areas separate from the large church when required, but this had been piped in a way that meant it was going to have many more ‘run hours’ than the other members of the cascade.
The boilers were starting to show their age, and a couple had begun to show signs of ‘back end corrosion’ where the continual cold warm ups had created condensation based corrosion issues over the years.
Ideally the new boiler plant would be able to run in weather compensation mode via their BMS, which was used to minimise energy wastage, while allowing the heating schedule to be planned remotely, and also to facilitate zoned heating of the office accommodation.
Our proposal, working with their team, was to separate the office and main church boiler plant, as these are used in very different ways.
We suggested using our favourite light commercial solution, the Viessmann 200W, which is a heavyweight stainless steel wall hung boiler – and use a cascade rig to link three of these together on a single flue header. Fortunately the existing chimney was just large enough to fit a new stainless lining system inside.
The new boilers would be linked to a Viessmann 300K control unit, that would sequence, rotate and load share the boilers. Our customers at St Johns would use their BMS to send a ‘flow temperature’ requirement to the Viessmann cascade, and this would make its own decisions on how many boilers to use, and at what power output. In essence, this gives a variable power output of between 10-150Kw.
In practice this will mean that for a heating request, three units will fire up and as the building temperature rises, the number of boilers used will reduce.
We competitively tendered for this work, and were awarded the contract.
Our proposal included a Mikrofill automatic filling device, and a dosing pot. The dosing pot allows the church staff to monitor the radiator water quality and add chemical dosing easily when required.
The management team were concerned about dirt in the system, we recommended the use of a SpiroTrap commercial magnetic separator. Unfortunately, having decided to exercise their option for this around 4 weeks before start date, we found there was a 2.5 month lead time for these items, none were available in the UK. In the end, a new old stock DN65 unit was found on eBay, which worked out very well as it was indeed unused, and in as new condition.
Moving on to the offices, some new pipework and radiators were needed here. We fitted a Worcester Greenstar 4000 combination boiler, spaced on a Unistrut frame to avoid a damp wall, to carry out the office heating functions. This has been augmented with Honeywell Evohome zoning, so that there are six separately addressable areas.
Both the main church BMS, and Evohome, can be scheduled from the internet or on site at their respective control panels.
Our scaffold contractor got us to the top of the church chimney, where unfortunately we found significant structural deterioration at the top, which not unusual, and is undetectable from the ground. The church brought in their stonemason and an excellent repair was made.
A large bore liner was installed by us, having been designed by our flue supplier, linking to the Viessmann flue header in the boiler room. An access panel has been put in place to inspect the transition from flexible to rigid flue at the very base of the chimney.
The boilers were supplied by us with a full Viessmann 10 year warranty (yes, on a commercial boiler plant) and we also arranged Viessmann commissioning, which went without a hitch, the commissioning engineer being very complimentary on our work.
The Worcester Greenstar 4000 was also supplied with a 10 year warranty; it also has the Greenstar intelligent filling option fitted.
The St Johns Team were very supportive, and of course, they had an unusually good technical appreciation of what they wanted, so working with them, the installation came out on time, and on budget!
This is our third Viessmann commercial ‘up a chimney’ job in 2021.
