HW but no CH ??????

[Softus]

So if it’s a boiler fault then what’s the next stage? Replace?

Give me strength

The next stage is the same as it always has been - start the boiler fault-finding process.

 

[conundrums]

Just a bit of input, in the late 60', Honeywell promoted a number of types of heating control systems called plans. Y Plan, W Plan S Plan etc utilising 3 way valves or 2 way valves Honeywell will supply schematics, wiring diagrams, etc if contacted.
Suggest you stay with problem, there is always a solution. My suggestion is to check all connections on the programmer for tightness. Found problem in this area on three recent occasions after 3 way valves & 2 way Zone valves have been changed by others.
If this fails suspect gas valve, check supply to gas valve if present and no gas then either valve or coil is at fault. Intermittent operation of the gas valve can occur and the valve can give up after short spells and work again after cooling down for a while. What make of gas valve is on your boiler.

 

[Softus]

Just a bit of input, in the late 60', Honeywell promoted a number of types of heating control systems called plans. Y Plan, W Plan S Plan etc utilising 3 way valves or 2 way valves Honeywell will supply schematics, wiring diagrams, etc if contacted.
Suggest you stay with problem, there is always a solution. My suggestion is to check all connections on the programmer for tightness. Found problem in this area on three recent occasions after 3 way valves & 2 way Zone valves have been changed by others.

This is all very well, but have you read the previous posts by dfranklin72? He says that the MZVs are actuating, and that SL is present and correct at the boiler as a result. Clearly the programmer is working, or are you suggesting a high impedence connection with a resultant voltage drop on the SL?

If this fails suspect gas valve, check supply to gas valve if present and no gas then either valve or coil is at fault. Intermittent operation of the gas valve can occur and the valve can give up after short spells and work again after cooling down for a while. What make of gas valve is on your boiler.

Ye gods. Is there no end to the ways in which people will propose implausible ways to go about finding a boiler fault? There's only so many times the same thing can be said, so I'm out of this one.

 

[conundrums]

Precisely, what does your fault finding guide suggest. You sound as if you know what you are talking about what is your guestimation of the fault. It is a long time since christmas only trying to help.

 

[Softus]

Precisely, what does your fault finding guide suggest. You sound as if you know what you are talking about what is your guestimation of the fault. It is a long time since christmas only trying to help.

Fair point, and I was unnecessarily brusque towards you, for which I apologise.

To answer your question about a guestimation, I prefer to keep my hunches to myself, because the alternative is that everyone posts their own different hunch, and the poster doesn't know which way to turn. Hence I always follow a process, even when I'm physically at the appliance and confirming my own hunch. However, please note the following post:

See http://www.partsarena.com/baxi/.

And just because it has a new PCB doesn't mean that the PCB isn't faulty. For one thing, if the pump is faulty then it's capable of damaging the PCB. but the heating engineer you've used should know all of this...

Regarding the fault-finding, I've given (see above) him the link to the manufacturer's web site. I'm hugely reluctant to spoon-feed someone who shows an ability to investigate the problem but declines to answer straightforward questions. However, what's obvious to me may not be obvious to everyone else, so...

There might be more than one system fault.
There might be more than one boiler fault.
The parts that have already been replaced might themselves have been faulty, and might have become faulty since.

So, the big question is: does the electrical supply to the boiler become live when you expect it to?
If it does, and the boiler does not operate, then it is a boiler fault.
If not, then there is another fault.

Reading between the lines, dfranklin72 appears not to regard the problem as urgently as you think, because he only posted his "Christmas Eve" problem on Jan 17th.

 

[dfranklin72]

So Meldrews_mate. Thanks for the advice. i went throough your step by step guide and the answer to the first 4 questions, everything was as you said. All working. So this leads me to a boiler fault which is where my question comes from earlier. What on the boiler can prevent the switched live going to the gas valve. I know the switched live goes to the PCB and also to the REPLACEMENT PCB. Is there something I am missing here?

I spoke to a few HEATING TECHNICIANS today. They all seem very interested to change the boiler. Apparentley this is the only way to rectify the issue.

 

[Soggy_weetabix]

Look, this a complicated one, and a fault Ive come across and not really understood how I fixed it. Ill hold my hands up to that!

With electrical checks I found a broken neutral and this was through the PCB. NOT POSSIBLE!

New PCB and fault remained. Put old PCB back and hey presto.

Had that fault 2 times on profiles, and to behonest I'd love some input from any other angineers who have experienced it.

David

 

[Softus]

So this leads me to a boiler fault which is where my question comes from earlier.

We're getting there!

What on the boiler can prevent the switched live going to the gas valve. I know the switched live goes to the PCB and also to the REPLACEMENT PCB. Is there something I am missing here?

Yes - you're missing the manufacturer's fault-finding chart and text. Have you downloaded them yet?

You're also asking the wrong question, or the right question wrongly. Nothing "prevents" the SL "going to" the GV - the GV is controlled from the PCB, and under the right conditions it will provide the supply to the GV. The right conditions are:

1. There is a demand for heat (switched live).
2. The safety devices on the boiler do not indicate a problem.
3. The upper limit temperature for the water in the heat exchanger has not already been reached
4. The PCB is not faulty.
5. The wires to the GV are connected and are not damaged.

I spoke to a few HEATING TECHNICIANS today. They all seem very interested to change the boiler.

In that case you've spoken only to greedy technicians, not respectable heating engineers.

Apparentley this is the only way to rectify the issue.

Apparently they are talking nonsense - why else does the manufacturer provide spare parts and sell them to a distribution network of merchants and retailers?

 

[dfranklin72]

Assuming that the PCB is ok and that I have all the necessary power and start-up sequence working you stated that it must be a fault in the boiler. Sorry forgot to say I looked at the fault finding diagram about 2 weeks ago which is why I agreed to purchase the new PCB.

So in conclusion there can only be a safety device that is stopping my boiler from firing up?

I thought this was the case last week so went though the procedures in the instructions to reset the boiler as in the case of a overheat cut off. I made no difference.

Yesterday the CH went off around 16:00 but came back at 11:00?
Another V cold evening!

My wife and child have had enough so thanks all for you help but new boiler looks like its the only way at t the moment.

Or I could replace most of the parts on this 20 year old one at the same cost? Bearing in mind its already cost me £300.