Warmcair CDW by Johnson and Starley - combined warm air/hot water boilers:

 

C10DW, C16DW, C20DW

 

The Warmcair CDW condensing warm air boilers are completely different from the more common Warmcair CD and CU condensing warm air boilers, in that the DW versions produce heated water as well as warm air. The heated water output is intended to heat a hot water cylinder but can also heat radiators, so is a good option for use when extending a house or bungalow with an existing warm air heating system. (Warm air heating is not easily extended so an extension usually needs to be heated with radiators, even when warm air is being retained in the original part of the house.)

 

Inside a DW series Warmcair, there is a conventional modern water-filled condensing gas boiler inside the top half, and a water-to-air heat exchanger, fan etc in the base producing warm air. (A complete Aquair appliance in fact.) The warm air is blown into the ductwork system in the house to send warm air to the vents in each room. The heated water output can be used to heat a hot water cylinder in the conventional way, and if required for an extension, to heat any number of radiators. 

 

I’ve not seen that many CDW series boilers but those that I have, like the CD series, seem to suffer from condensate leaks which corrode the lower half of the appliance making it look quite shocking. The bad appearance doesn’t matter particularly, unless the leaks are corroding right through any metalwork. Here is a good example: 

 

 

Common faults and fixes:

 

I’m not sure I can say any are exactly common and I haven’t seen that many of these CDW series yet, but the faults I have seen so far are as follows: 

 

 

Diverter valve failure:

 

The boiler itself appears to light and run normally, often for short periods only but the warm air vents will not work. Hot water continues to be available. This happens when the electric diverter valve head fails. This is a common fault on lots of brands of combi boilers too. Quick and easy to fit a new diverter motor head, available directly from Johnson and Starley.

 

 

Condensate leaks:

 

All the post-2015 Johnson and Starley gas-fired warm air heaters seem to suffer from condensate leaks. A shame as the leaking water is corrosive and can damage a variety of parts (often electrical) if the leak is making them wet. Condensate leaks can be from a variety of places in the boiler, or can also originate inside a badly installed flue system. EDIT to add: This problem is developing into a more specific leak on the DW series heat exchanger. I’ve now seen two DW boilers where the main heat exchanger itself is leaking condensate and on one, products of combustion (POCs) were leaking too. POCs leaking is dangerous and means the boiler must not be used. The solution is to fit a new heat exchanger.

 

 

User display panel showing fault code “E01”

 

E01 is the dreaded “flame failure” or “ignition lockout” message most modern boilers will display when they won’t light. No help at all to us gas technicians as we already know it won’t light - it’s why we’ve been called! What the electronics never tell us is WHY it won’t light, and the manual usually gives a huge long list of possibilities with no advice on which on the list is probable and which is possible but highly unlikely. Anyway, rant over now. Normal service is resumed. This E01 error message can be particularly difficult to deal with if the boiler re-sets and runs perfectly when we arrive, only to stop again showing the same message an hour or a day later. Sometimes it can be the control board failing, which is often not on the list of possibilities in the manual! 

 

 

 

 

In the meantime if yours needs servicing or repairing I’d be delighted to help if you are within driving distance of me in West Berkshire. My number is 07866 766364. Texting me often works better as I don’t pick up the phone when driving, or working on someone’s boiler, or sleeping, or cooking, eating, or… the list goes on…. :) 

 

Mike

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A Johnson and Starley C16DW. These DW Series boilers are HUGE, standing approx 5ft tall.