No hot water

[80Sprint]

Timer seems to kick in ok and works the heating. Heating off now and hot water light comes on with the timer. No hot water.
Motorised valves seem to be working and no difference on manual.
Power ok to stat on tank. Conventional boiler system.

Any ideas why the boiler starts with the heating but not with hot water. Could it be a clock fault but only replaced last year.

[Galileo]

Mate had a similar problem, valve replaced, temperature sensor replaced, still no hot water but the radiators worked fine. He had a short piece of pipe that dropped down to the bolier and somehow it had got so furred up that water from the boiler could not get through, had to be cut out and replaced. I'm assuming the boiler actually fires when hot water is selected, for a minute at least?

[xvivalve]

Sticky diverter valve? Usually fails in autumn preventing the heating from working, but could happen the other way I suppose...

[new to this]

if you turn the cylinder stat, up and down can you hear the motorised valve moving,what valve is it 2 port of 3 port

Dave

[80Sprint]

I have a 2 port downstairs near the pump which I assume is the heating. I have another upstairs next to the tank which I assume feeds that. With just the heating light on the boiler does not fire and no hot water. If I turn the heating on it starts the boiler and the water pipes heat up to the tank. If the motor valve was not working near the tank I assume the heating should make no difference. Thermostat in the tank must be ok if it heats up this way.

[RodR]

If I've read it all correctly my guess would be the limit switch on the hot water valve failed or the wiring to it faulty. The switched live to the boiler to tell it to fire is fed via a switch in the valve that is only made when the valve is fully open.

A check with a meter will confirm if there's is power to and from the switch.

[TrustNo1]

Another vote for faulty divertor valve. google (other equally god search engines may be avalible) your boiler make and model it might be a cheap easy fix (you are only playing with the water system not the gas side so any plumber can do the job)

[Slowmo]

Mike,

As you have a conventional boiler, you do not have a diverter valve.

When your cylinder calls for heat, it operates the adjacent two-port motorised valve. As RodR says the valve has a microswitch inside which makes contact when the valve opens fully. This microswitch then calls for the boiler to fire up.

If you have hot water and heating demands on at the same time does the boiler water flow through the hot water motorised valve and around the cylinder coil as well as the heating? If so, this suggests the valve is opening but the microswitch does not signal the boiler to switch on.

Failure of the valve motor is quite common, as is failure of the microswitch. You can replace either of these components if you are good with small electrical repairs. If not, you can usually replace just the actuator head without having to drain the water side of the valve. Very occasionally the actual valve operating spindle gets very stiff and seizes, but it's much more likely to be the actuator head.

Hope this helps, Peter

[xvivalve]

Ha! That shows up the Architect, when using the term 'conventional' with boilers, I think combination, because plumbers fit them everywhere these days (the cynic in me says so they can weigh in the redundant cylinders they remove!) and they've seemingly become the convention!

[Slowmo]

Agee - combi boilers have become the convention now. Modern combis are very competent, and also release lots of lovely scrap copper pipes and cylinders

Peter

[Carledo]

I still have an old fashioned back boiler. But it's a Baxi Bermuda, one of the last ever made, a 2001 model. My gas service engineer says its the best thing I could possibly have and not to even THINK about replacing it with a new fangled combi type! To be fair to it, it's been utterly reliable with only a service every 2 or 3 years and it's now 17 years old, way over the normal lifespan of most combis!

Steve

[GTS290N]

Our Ferroli combi boiler is 17 years old, had a couple of parts replaced over the years, serviced every year. It works.

[80Sprint]

Just to close this one off for anyone who has a similar issue in the future. It was the valve next to the hot water cylinder. It was stuck, and even on manual it did nothing.
I changed the whole unit and all was well.

Thanks to all those who offered advice.