Just Replaced CH/HW Timer Switch - Seems Odd??

10 Mar 2008
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United Kingdom

My boiler mechanical timer switch was broken so I replaced it with a new digital model.

I have replaced the original "Landis & Staefa RWB2E" with a "Siemens RB29" - The backplate was a like for like replacement - I did not do any rewiring it just 'fit'. (i used the original RWB2E plate)

The boiler is a "Glow Worm 45-60B"

Both the CH & HW neons light as expected

When the HW is switched on, the boiler "kicks" into life and I can visual see huge flames in the pilot light window (sorry for the non-technical terminology)

When the CH is switched on, the boiler "pump" comes on but I do not see a mass of flames or hear the same noise as I do when the HW is switched on.

I can feel the water pumping through the radiators - but they are not getting hot.

If i turn both HW & CH on then the radiators warm up - I am assuming this is because the pump is on and the HW switch is allowing gas into the boiler.

Can anybody comment as to what i may be doing wrong.

*** Note that when i fitted the new unit I only turned the boiler built in thermostat to "off" and turned the electricity off.

The room thermostat if adjusted seems to switch the boiler pump on/off
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Take the clock back of and alter the little switches on the back to gravity

read the instructions it will mention 10 and 16 yours is set for 16 when it needs setting at ten
More questions

Does this boiler support seperate switching of CH/HW ?

Can anyone suggest any electrical test I can do - i have a multimeter and know how to use it - but I do not know in what area I need to be looking for the fault.

I am making the assumption that the boiler functioned fine prior to me fitting the new timer ...

** One of the reasons I changed the switch is that the HW & CH were always permanently "ON" maybe the issue was an existing one **

I have rang GlowWorm to ask for the specs of the boiler (45-60B) but it will take "weeks" to get me the literature so if anyone has worked on one of these before it will be much appreciated

its not a case of boiler taking seperate switching , its the system that allows that .
Does your boiler have 2 or 4 pipes coming from it
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The boiler has 4 pipes on it

The new Siemens Rb29 does not have a 10/16 switch it has dip switches only to say 7 day prog/week prog etc..

The old (now i find non original timer RWB2E Landis Staefa) had the switch set to 10 as you directed.

Someone has replaced the original unit with the RWB2E and now i am replacing this faulty one

Boiler is ~15 years old...


Thankyou for all your help...Your posts sorted me out

On the back of the new Siemens model was a dip switch - as you correctly summarised it was set to "16" - Setting it to "10" as per the original spec solved my issue...

Much appreciated..

PS.. Now when CH is on and the main boiler ignites should i expect to see both CH & HW lights on

Once again thanks
You have what is known as gravity hot water pumped Ch system.
Yep both lights should be on this is how your system works
i fitted the same siemens RWB29 in place of a mechanical timer, i had the same issue, it was set to fully pumped. on the back of the RWB29 there are dip switches, i cant remember which one it is but you need to change it. you cannot get independent central heating control with a gravity hot water system, the boiler fires when the hot water comes on, and for heating the timer just turns on the pump to circulate hot water. on fully pumped mode the boiler has no way of firing up, only the pump will come on. After changing the dip switch you need to press the reset button on the front of the RWB29
Sorry to repost, your last post didnt show up at the time i wrote mine so i didnt know you were sorted

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