No hot water on Combi Worcester Bosch 24i

Hi all,

Is there any chance someone could confirm what they think is wrong with my combi boiler. I believe I know, but I'm not an expert for sure ....

Its a Worcester Bosch 24i

Symptoms:

1. Boiler does not light if central heating is off and hot tap is turned on.

2. Central Heating works fine, boiler ignites if thermostat calls for heat

3. Only way to get "some" hot water is to force central heating on (using theromstat) and wait for boiler to turn on then run tap. Its not hot hot kinda warmish but enough at the moment for a shower.


I believe the flow switch has probably stopped working, which is why i'm guessing the boiler doesnt turn on and why I only get warm water if the CH is on. I believe ? that the boiler is meant to stop heating the CH when it detects water flow, and as thats not happening it can't heat both the water and the CH enough ... but thats just a guess

I've also turned the boiler off disconnected the two wires from the flow switch and put my multimeter on them to check for resistance. Even with the hot water taps on my multimeter stays at 1, i.e. there is no circuit.


Is there any chance someone could confirm my suspicions before I call my plumber in ? I would very much appreciate it !

thanks in advance

Cheers

Andy

Yes it should go short circuit when there's flow. If you DIY it might be worth trying to clean it, but reed switches get magnetised and need replacement. Part about £40

The first thing to establish is the flow rate. Has this decreased recentley over time. If yes then the flow rate will not be enough to push the paddle in the flow switch. If the flow is ok (more than a dribble and a little slower the cold tap) then it can only be a faulty flow switch.

This is all relevant as per your diagnosis.

Thanks

Well the flow rate to the hot tap in the bathroom has decreased significantly but I think thats been happening over a while and I havent yet investigated if theres a blockage somewhere restricting that tap.

The hot tap in the kitched downstairs (the boiler is upstairs) has a good flow rate, well reasonable anyway definetly more than a dribble. Think I measured it filling 1 litre in around 15 seconds. But it hasnt reduced significantly since i've has this problem its about the same.

Cheers

Andy

Hi,

Just phoned to get a replacement flow switch, and I'm told that they no longer make the type of flow switch I have (plastic housing with the swtich coming off at 90 degrees also plastic, a padel thing does into the pipe) and I have to replace the whole housing with a new brass reed one.

I was farly happy to just replace the swtich held in by a clip. I'm unconvinced about replacing the entire housing myself. Is this a farily easy job ? does it involve cutting pipes or is the new housing the same size.

Just wondering if anyone has done the same thing I guess I will pick it up and if I dont fancy it get a plumber in ....

Cheers

Andy

Hi sounds like you have had the same problem as me, ive the same combi

taking off the water diverter valve, is a bit fiddly but if i can do it any one can. i cleaned it out replaced all o rings and fiber washers and fitted new diaphram (£18). still no joy. so im now looking at header tanks

Good luck
Kath

After two days with no hot water in a household with 5 kids I'm looking at jerry rigging a tank system this evening

saintsman said:

After two days with no hot water in a household with 5 kids I'm looking at jerry rigging a tank system this evening

Click to expand...

Keep your eye on this thread and it might come to live again

Half pint said:

...taking off the water diverter valve, is a bit fiddly but if i can do it any one can...

Click to expand...

I seriously doubt that you are capable of replacing a diverter on a 24i.

fasea said:

...The hot tap in the kitched downstairs (the boiler is upstairs) has a good flow rate, well reasonable anyway definetly more than a dribble. Think I measured it filling 1 litre in around 15 seconds.

Click to expand...

That would be 4 litres per minute, chances are your inlet filter is blocked, or another kind of restriction has occurred. On a new boiler, 4 l/min should be ample to get it going, but might not be enough in your situation.