Combi with hot water tank - no HW

[jtheobald]

Hi,

I wonder if somebody can help me please.

I have a HW systems fed by a Worcester Combi boiler. One side of the house takes the hot water direct from the boiler, the other uses the tank from the previous gravity fed system.

Whilst the water direct from the boiler is hot, the tank doesn't have any hot water and from what I can gather is not sending a signal to the boiler to activate. Running the hot water does not fire the boiler.

I have removed the timer and connected the 1 (live) and 3 (HW) together but that made no difference. I also changed the water tank thermostat - again it doesn't appear to have made any difference.

Is there likely to be motorised valve and if so where would it be - e.g. on the pipes or in the boiler? Is there anything else it's likely to be?

I appreciate any pointers, advice please. I hope this provides enough info.

 

[CountryFan]

Yes, there should be a motorised valve and it will be on the pipework, this then receives a switch live from the programmer and cylinder thermostat and then sends a switch live to the boiler.

 

[Madrab]

What model of WB is it?

There probably will be a 2 port valve out on the flow to the cylinder. Where that is is anyone's guess though it would make sense to have it close to the cylinder. Either that or cabling/power may have dictated where it was situated.

 

[ericmark]

Motorised valves have micro switches, which do fail, idea is valve opens before it fires the boiler, but in the main they stick on rather than off.

As to what valve is fitted, is anyone's guess, I have motorised valves on my C Plan system, and with electronic TRV heads they are not really required, but were fitted before the electronic TRV heads.

However I looked at heating water with oil boiler, and also with an immersion heater, and although when I looked oil fifth of the price to electric, by time it had heated to boiler and pipework, it used over five times as much energy, so actually cheaper to use an immersion heater.

As to combi-boiler v immersion hard to say, as can't run both, once combi fitted it is hard to return to a storage tank system. But a little thought, it must cool again after firing up, we can feel heat coming out of the flue after it has fired up, so running a bowl of water, it may work out the same, but just enough to wash hands, it is an expensive way to get hot water.

 

[jtheobald]

What model of WB is it?

There probably will be a 2 port valve out on the flow to the cylinder. Where that is is anyone's guess though it would make sense to have it close to the cylinder. Either that or cabling/power may have dictated where it was situated.

Its a Greestar CDi Classic

 

[jtheobald]

This forum never ceases to amaze me, thanks so much guys..

I've added some pictures, if that's ok.

 

[Madrab]

You have an S plan using a combi. you have 2x2 port valves - 1 will connect to the central heating, the other to the hot water cylinder.


Does the system have a programmer/timeclock? Has that been checked and is it switching the HW on? If so then chances are the microswitch to the one connected to the hot water is no longer sending a switched live to the boiler to turn it on, if everything else is working. That needs checked and possibly replaced. Unless you are familiar with the system, how it's wired and comfortable working with 240V then it'll be time to get someone in.

 

[jtheobald]

Thank you, great dvice. I replaced the top ones motor about three months ago as it had failed and I wasn't getting any CH. Therefore, I assume the bottom one is HW amd maybe at fault.

In answer to your question, I removed the timer and connected the Live to HW (terminal 3) on the backplate but that made no difference.

I agree, I think I will need to call somebody kn tomorrow.

Thanks again.

 

[jtheobald]

Hi, also a quick question. If the microswitch has gone, putting the valve into manual won't make any difference?

It sounds as though I will need a whole new motorised valve unit as the microswitch is part of the unit. Over to the pros.

And finally if I completely replace the valve (v4043) do I need to drain the system?

 

[jtheobald]

Quick update, I havs replaced the motorised valve motor but no difference. I thought I'd eliminate something else!

When putting the valve into manual I get resistance. I thought when it was open there wouldn't be any resistance.. the timer is set to on..

 

[Madrab]

OK - you need to check that :-

a) when the hot water is on at the programmer that the valve to the HW cylinder is getting 240v @ the brown wire and 240v @ the grey wire,
b) if so and the motor moves and opens the valve when powered on, once fully open then make sure there is 240V @ the orange wire.

If that is all ok then it needs checking at the boiler

Using the manual lever is really only for draining and won't usually activate the microswitch to turn the boiler on but you can 'force' the HW to be warmed by locking open the HW 2 port's manual lever and running the CH, until the issue is found, obviously quite wasteful and I guess the heating isn't needed right now.

 

[jtheobald]

Thank you so much for your advice Madrab.

 

[gas112]

Thank you, great dvice. I replaced the top ones motor about three months ago as it had failed and I wasn't getting any CH. Therefore, I assume the bottom one is HW amd maybe at fault.

In answer to your question, I removed the timer and connected the Live to HW (terminal 3) on the backplate but that made no difference.

I agree, I think I will need to call somebody kn tomorrow.

Thanks again.

pretty certain the top one is HW you can see the pipe going to cylinder