Timer Problem

JOHNPT

Hi
I have a problem with a siemens 2 channel timer. Basically when you press the hot water button on the timer the light on timer lights up and the gas boiler kicks in and starts. It heats the water. However when you press central heating button although the light on timer comes on the boiler does not start. Now i have checked the stat in living room and it seems to be working fine. The sysytem is wired ok i think as it used to work fine.
What could the problem be or what can i test to find the problem

Would really appreciate any help

mazthespark

could you swap the wires on timer so c/h function controls the h/w would test then to see if its the timer or a problem with the wiring etc

JOHNPT

Thanks for reply I tried that but still dosent work. Would it be zone valve or how can i test this. Am I right in presuming that the thermostat that is located on hot water cylinder is nothing to do with the central heating zone?

mazthespark

i would assume the same. is there a switch on side of any of your room stats? its like some thing is stopping the signal gettin to your boiler. is there motorised valves in your system to govern what part of system is heated? some times an auxillary contact in these is used to switch on your boiler and your fault may lie there.

crosstownk

You'll need to locate the zone valve for the CH. This valve could be anywhere but the hot press is a good place to start. Most zone valves have a manual override lever that let you open the valve manually. This may temporarily solve your problem. There is a chance that the switch contact in the zone vale is faulty in which case you will need a new one. Some valves can have the electrics replaced without the need to remove the valve itself and drain down the system.

JOHNPT

Stat is working fine i checked it for continuity. Yes i think there is a valve but not sure how to test if working. Can u explain how to test motorised valve working? Should there be constant live at them and a switch live when siemens timer is switched on?
Ant help appreciated

mazthespark

im afraid they all differ in wiring terms but the way i usually do them is when the time clock switches on it opens the valve and then depending on the state of the thermostat (if room needs heat or not.) it starts up the boiler using the auxillary contact in the motorised valve. if possible to access the valve you may be able to switch it over to manual mode and operate your stat to see if it will start the boiler or turn the heating on at the timer and if u listen to valve u may be able to hear it open or close.

JOHNPT

Thanks so would i be right in saying there is usual a permanent live at the valve. And when the timer switches on it operates a switch live at the valve?

mazthespark

not really the opening and closing of the valve would be controlled by the timer. then the aux contact in valve would now be closed but only if stat is calling for heat will the aux contact be live pulling in the boiler. well thats the way its usually done anyway but every one is different. is there a manual setting on the valve? swap it over to that and see if u can get boiler to fire when timer is on

JOHNPT

Thanks not sure if manual selection. How do i change it over manually?
Thanks for your help

mazthespark

should be a switch or lever some where on the motorised valve itseld some times marked auto on one position and man on the other. if u find it and has no markings move it to other side any way wont do any harm, it haeting runs then u prob need a new valve.

davelerave

as already said check stat and zone valve .if it's stuck or faulty boiler may not fire

JOHNPT

Thanks Davelerave. I have just found out that the central heating will come on but only when the hot water channel is selected will it heat hot water and heating. However when the central heating in selected on its own although the light comes on on timer the boiler does not kick in. Does that eliminate the valve being faulty or does it sound more like a timer problem.

Thanks

mazthespark

sounds like a timer problem. if its only letting heating on when hot water is on also. could be a prgoramming issue within the timer? do u have a manual. could be an easy fix or mite be a faulty timer. some timers have special functions that only allow one channel to come on if the other is off/on depending on how its set up.

JOHNPT

Where would i get a siemens timer RWB9 in Dublin. Thanks for your help

MiniGolf

JOHNPT wrote: »

Where would i get a siemens timer RWB9 in Dublin. Thanks for your help

The RWB9 has been superceded by the RWB29...... heatmerchants stock them!

davelerave

mazthespark wrote: »

sounds like a timer problem. if its only letting heating on when hot water is on also. could be a prgoramming issue within the timer? do u have a manual. could be an easy fix or mite be a faulty timer. some timers have special functions that only allow one channel to come on if the other is off/on depending on how its set up.

http://www.knh.org.uk/knh/publications/pdf/centralheating/rwb9dailywendday.pdf
i'm not that familiar but looks like it might be setup this way (gravity h/w, pumped rads)
there was a similar question here http://www.boards.ie/vbulletin/showthread.php?t=2055685564

Dotsie~tmp

Sounds pretty simple. The boiler is only switched from the HW side of the clock (as normal). When you call CH, the CH valve/stats are powered but the boiler is not fired thus giving no HW for the rads.

This is becuase you also need to call HW at the same time (this is usually done with a feed return from the CH valve to activate the boiler but is often left out due to the extra work). What need to do is have HW and CH activated together when you need rads. There is no such thing as CH being on without the HW being on anyway, that's where the hot water comes from too feed the rads.

Setup a timer prog for CH that has duplicate time for CH and HW zones. If you only need HW leave the CH prog out or use HW zone manual boost function. Set your stats and forget about it.

P.S. there is a wiring solution to give you CH puling in properly with 1 button but it costs and if the sparks/plumber is long gone its not necessary.

davelerave

For most systems i see DHW is independent of RADS or UFH except maybe for the 'gravity HW /pumped rads setup.

"The boiler is only switched from the HW side of the clock (as normal)"
what system is this?

JOHNPT

Thanks for replies Dave. How do i know if the system is gravity or fully pumped. the boiler is downstairs in kitchen and the hot water tank is upstairs

davelerave

afaik the rads would be pumped and the cylinder coil heats by gravity circulation (when the boiler is on).a plumber will advise you better.
When you select HW the pump or pumps would prob be off is my best guess!