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Twickenham United Reformed Church

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This page isn't meant for the world at large, just for those with an interesting in church heating systems. I don't claim to be an expert or want to suggest that the way we have tackled the challenge of providing a warm building on Sundays is the only one, but our experience may help someone else. For the rest of you who are very happy to leave these things to someone else, before you leave you might enjoy this piece from our September 2001 newsletter:

There are those whose contribution to our church life is very obvious and others, who we value no less highly, who stay out of the limelight, quietly getting on with their allotted tasks. Potterton - no one ever found out his first name - was one of the latter. For 25 years he devoted himself to bringing a sense of warmth to our fellowship. Show him people arriving cold and wet and he'd put heart and soul into sending them home with a warm feeling. It has to be said that he weighed 31 stone, had a hearty appetite, and insisted on hiding under the gallery stairs on the grounds that he'd been put there when he first came in, but the few of us who knew him well valued what he did.
But sadly he was beginning to show his age: several times last winter he fell asleep, leaving others to apologise for him, and when one evening he unleashed a torrent of bad smells we knew his days with us were numbered. So a few weeks ago Norman Kearon and Tony Bryer had the unenviable task of escorting him off the premises. He didn't want to move but with the aid of a ramp he was eventually did. His place has been taken by slim 6-stone twins from Kent with, we are assured, appetites to match. They look forward to giving you a warm welcome in the years to come no matter what you weigh!
Confused? The 31-stone Potterton and the twins from Kent are our old and new church boilers. We hope to be warmer in the winter and cut our gas usage by a third.

The challenge

This list doesn't claim to be complete, and some of the items may not apply to you (it's written by a member of a small SW London church housed in an 1866 building), but here are some of the problems facing those who us who are responsible for church heating:

  • Heating-unfriendly buildings: solid walls, no insulation (and often no possibility of adding it), draughty stained glass windows, and a high ceiling up to which all the heat seems to disappear. The building may also limit where heating apparatus can be fitted, particularly if there are pews built into walls, fine panelling or the building is listed.
  • Smaller congregations: each person generates 100-150W of heating depending on how active they are. That's something like 25kW from 200 people, but only 5kW from 40. This can work the other way as when a lot of people come into a building the heating required may reduce significantly.
  • Higher expectations: 50 and more years ago people probably walked to church, wearing, in the winter, heavy coats. Now most come from centrally heated homes in warm cars and expect a similar level of comfort in our churches.
  • Starting from cold: if we were heating our buildings to the required temperature every day of the week the fabric would warm up, and maintaining the temperature would be much easier. Instead we may start off early on Sunday morning with a mass of cold air surrounded by near freezing walls and roof. Our heating systems don't just have to able to maintain a certain temperature, they have to be able to raise the temperature significantly over a relatively short period
  • Time critical performance required: people want the building to be at a comfortable temperature at 10.30 (or whatever). not 11.00 or 11.30. But if you reach that temperature long before you need to, you're wasting a lot of energy. And if you decide that you've got the time clock settings wrong you have to wait another week to find out whether your new settings are correct (by which time the weather will have changed)
  • Vulnerability to system failure: if the heating malfunctions you probably find out on Sunday morning when it's too late to do anything.

Where we've come from

Our heating system has evolved over the years:

  1. Originally (from 1866) we had a coal fired boiler in a boiler pit feeding a network of large iron pipes run along the edges of the dropped aisles.
  2. This was replaced by a time clock controlled gas boiler in 1964, which cut out most of the work but the system was still very unresponsive: the pipework would only be properly hot about two hours after starting the boiler.
  3. In 1976 the church floor was replaced by a level concrete floor and the fixed half pews next to the side walls removed. As part of this work the iron heating pipes were removed and we put fan convectors in to replace them - like many of the major projects at our church, this was DIY. During the period that the system was drained down the seals on the old boiler dried out and when the system was refilled the boiler leaked like a sieve. At short notice we installed a new CF105 (35kW) boiler, the largest that could be used without replacing the existing flue. This gave a system that started producing heat after about 20 minutes.
  4. We subsequently added a couple of extra fan convectors as the boiler was not being used to capacity.
  5. This system worked reasonably well in the winter, but in the spring and autumn the regulation of temperature was unsatisfactory, as we had not been able to mount a thermostat in a representative position.
  6. After the old 7x24 time clock failed we replaced it with a wireless programmable thermostat mounted on a gallery post. The first model we installed was unreliable, but we replaced it with a Honeywell CM67RF which has proved to be an excellent choice.
  7. Now that we could reliably stop the building from overheating on mild spring and autumn days we were able to add a large Dunham Bush fan convector (10kW output) at the front of the church. This gave a better balance of heat output and ensured that the boiler would be running at full output in the winter.
  8. After 25 years the old boiler began to be less than reliable. The original plan was to install one Keston 130 boiler, but as the cost of two Keston Celsius boilers was about the same we decided that they would be a better option. We did all the work ourselves with the exception of commissioning the boilers which was done by our local CORGI engineer.
  9. In the light of the first winter's experience we have revised the layout of thermostats controlling the boilers - initially we had some problems with one boiler running when two were needed and vice versa. We've also changed the wiring within the Myson fan convectors. The local thermostat on each heater (previously not used) now bridges the fan speed rheostat so that whilst the building is heating up from cold the heater runs at full speed (thus dissipating more heat) and when it begins to approach the desired temperature it drops back to low speed (to reduce the noise to an acceptable level)

Key parts of the system

Boilers: 2 x Keston Celsius

We chose the Keston boilers for several reasons:

  1. A uk.d-i-y newsgroup contributor recommended Keston boilers, and when I looked at them at InterBuild 2000 I was quite impressed
  2. These boilers use 50mm muPVC waste pipe for the air inlet and flue pipes. Our building is tight on the boundaries and the preferred boiler location made the installation of standard balanced flue (even with extensions) impracticable. By agreement with the local authority the two flue outlets discharge over the pavement at a height of about 3.5m and are routed up under the gallery stairs and over a doorway.
  3. We could buy two of these boilers for the same price as 1xKeston 130. Of course this necessitated quite a lot more (voluntary) work and some additional pipework, but provides a much greater heat output when required (2x25kW v. 40kW). They also provide better controllability in the spring and autumn: the 130 is not modulating and there was a slight concern that with a low capacity system, such a large boiler cutting in and out might be unsatisfactory; the Celsius boilers will modulate from 25kW down to 7kW depending on load, giving us an output range of 7-50kW.
  4. The indicator lights on the boilers can be wired back to a remote location, in our case the control panel at the back of the church. I can see whether a boiler is running or whether there is a problem without going into the boiler room
  5. The Keston web site http://www.keston.co.uk contained lots of hard technical information (personally I hate gimmicky graphics) including a downloadable set of installation instructions: we were able to go through these in detail before ordering the boilers to ensure that there would be no nasty surprises. Keston's technical support were most helpful in confirming the piping arrangement for two boilers.

After one heating season I am very happy with the choice we made. There have been some minor problems with one of the boilers, fixed under warranty, and we had to revise the boiler control stat arrangement, but from now on I anticipate no problems.

Control: Honeywell CM67RF

This programmable stat comes in various flavours: the '7' indicates that it is a 7-day model and the RF that the sensor communicates with the receiver by a radio link (i.e. no cable required). Ours in mounted at head height on a gallery support post, which seems to give a temperature much the same as experienced by the congregation.

The CM67 allows 6 independent time and temperature settings for each day of the week so (for example) you can provide some low level heating during the week for cleaning and flower arranging. Unless it is reprogrammed any override of the temperature self cancels at the next time point, so it is easy to provide a little more or less heating when a particular occasion demands (for example if we are not having an evening service, after the morning service I press the 'Party' button and set eight hours at 8C (the minimum we maintain when the building is not being used). At the end of the eight hours this self cancels)


This is our approach, shaped by what we have inherited and our willingness to get stuck in and DIY. We have spent money on quality equipment, but have not spent money on more sophisticated controls (e.g. boiler sequencer) that would not be cost effective.

Last updated 11 July 2002.