C16D WARMCAIR boiler by Johnson and Starley reviewed:

The WARMCAIR from Johnson and Starley is a modern high efficiency iteration of the warm air boilers which became popular in the 1960s and 1970s before radiator central heating gained ascendency. People with warm air heating are generally very pleased with it and reluctant to switch to radiators, warm air systems heat the house so quickly and (obviously) don’t need wall space to be given up for radiators. 

The C16D is a downdraft unit which means the hot air outlet is though the base of the boiler, designed for houses with the warm air ducting installed under the ground floor.  

Although the C16D is designed to replace several of Johnson and Starley’s old open flue design warm air boilers, it is not a straightforward installation as the C16D is a room sealed appliance, which means the whole flue all the way to outside must be replaced at the same time as the boiler. Being a fan-powered flue it can be routed either horizontally to outside through the wall, or vertically up and through the roof. Roof termination is not straightforward as you can imagine, as it involves the installer climbing on the roof for which scaffolding may well be required. 

The WARMCAIR is a condensing boiler, which means it uses significantly less gas than older warm air heaters and consequently issues less carbon dioxide into the atmosphere. Other harmful flue gases are also reduced. A drawback of condensing gas appliances is they produce waste water as a by-product of the condensing process and this needs to be disposed of via a drain connection. The C16D has a pump fitted to send this condensate via a long thin polythene tube to a suitable drain or soil pipe up to ten metres away. Condensate pumps can be a source of trouble although I have yet to see one fail on a C16D. Time will tell. 

The C16D is a modulating warm air boiler which communicates digitally with any room thermostat/time controller which uses the industry standard “OpenTherm” protocol, including the Google “Nest” thermostat which can be controlled remotely from a mobile Smart Phone. (Connecting the C16D to an old format, conventional non-OpenTherm controller will damage the appliance, Johnson and Starley warn.) OpenTherm controllers continually adjust the boiler heat output up or down to match the heat demand of a house, instead of switching the boiler fully ON or completely OFF in the manner of old format controls. 

The WARMCAIR range of heaters seems to have some teething problems. Firstly I have seen more than one with rusting due to condensate leaks. One I saw yesterday was leaking from the flue collector gasket and needs repairing urgently as condensate water is pooling in the base of the boiler when it is running. 

Secondly as with most warm air appliances, it can be difficult finding anyone willing to repair them as few technicians have the necessary warm air qualification necessary to work on them. 

Thirdly the owner of the C16D I saw yesterday finds the air circulation fan intrusively noisy throughout the house and I am currently seeking a solution to this. It’s hard to imagine what can be done though as the air circulation fan in the C16D is considerably than the slow-spinning and quiet fan that would have been in the 40-year-old warm air boiler this particular C16D replaced. Being much smaller in physical size, the C16D air circulation fan needs to run faster and consequently makes more air movement noise.

Mike

11/3/21