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The Johnson and Starley WarmCair range of warm air gas boilers...

My guess is there are still perhaps about half a million Johnson and Starley warm air boilers out there in regular use, that were made more than 20 years ago. Users often comment to me about much they like their warm air heating but would like a new, modern, more efficient warm air boiler installed then ask me about the options. Until now I've only been able to suggest the imported Lennox G61MPVT which alyhough a high efficiency condensing boiler, is larger than many J&S units so not a simple swap. Nor does it have any water heating functionality.

Now there is the Johnson and Starley WarmCair range of boilers. High efficiency condensing warm air boilers, available with or without a built-in hot water function, designed specifically for owners of older, standard efficiency Johnson and Starley warm air boilers wanting to upgrade.

I'm beginning to encounter WarmCair boilers installed in people's houses now - call-outs for annual servicing and for breakdown repairs - so I've been getting a good look at them. They are a modern incarnation of the old warm air boilers popular from the 1960s, using modern technology. The boilers with hot water are completely different inside from those without. The heat only boilers heat the air directly in an annular condensing heat exchanger, and those with hot water function heat an annular water-filled heat exchanger the same as inside an ordinary wet central heating boiler. The hot water output from the gas-to-water heat exchanger is passed to a water-to-air heat exchanger in the base of the unit to generate the hot air. This version of the WarmCair boiler is consequently capable of heating a conventional hot water cylinder (or a mains pressure MEGAflo) and also some radiators if necessary. This is especially useful in a house about to be extended as warm air ductwork can rarely be effectively extended, and radiators can be fitted in the new parts instead and powered from the warm air boiler.

One of the problems installers encounter when installing a high efficiency condensing boiler is disposal of the waste condensate. A condensing boiler generates slightly acidic waste water all the time it is running in 'high efficiency' mode - one or two drips a second, so any condensing boiler needs a drain connection. An older 'normal efficiency' Johnson and Starley boiler would have no drain connection in the airing cupboard so the WarmCair deals with this problem by incorporating a pump and long thin tube which the installer runs up into the loft, and connects into the top of the soil stack, so the boiler can pump away the waste condensate into the household drain.

Servicing a WarmCair is very similar to servicing a modern water-filled condensing boiler. Clean the main burner and the pre-mix fan, clean the condensate trap, check the gas consumption rate and the constituents of the flue gas, and in addition remove and clean the air circulation fan and filters.

Regarding common breakdowns I've only seen one failure so far, the Honeywell ignition control board 'piggybacked' onto the gas control valve. A new board fixed it.




Page first published 18th January 2017
Last updated 18th January 2017


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