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Discuss Central heating pump and boiler in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Have you a wiring diagram SJB for this type of diverter valve.
The frost stat did cross my mind also but the big mystery is why the circ pump doesn't run with the random boiler run.

This is what’s called a W plan mate, not the Y plan. It gives HW priority, meaning once CH is satisfied it will spring return to HW port. Of course if the boiler is getting a feed from somewhere other than intended then through gravity circulation the cylinder will continue to heat until boiler water and cylinder temperature reach thermal equilibrium but you know that already.
It is a Honeywell wiring diagram but this is the principle behind the diverter.
3EB878CD-D883-4B70-9439-0F2B855A7658.png
 
Guys , thank you so much for advices.

What shall I do first to strat with ? Change the boiler as plumber said or try to fix the current problem and how?
 
Guys , thank you so much for advices.

What shall I do first to strat with ? Change the boiler as plumber said or try to fix the current problem and how?


The boiler has to run through a signal from somewhere. Im not convinced you need a new boiler but it does require someone to test the wiring.
 
Is it possible that wiring faults develops after a while?. Previously it was fine.

Also why is plumber suggest to change the boiler bxoz of increased emmissions.wht is the risk. Is it dangerous etc?
 
To answer your first question. Yes electrical faults can occur at any time, they can also coincide coincidentally with other work undertaken. Having said that boilers don't just magically ignite it takes a series of commands starting with a demand electrically.
Question 2. I imagine the plumber who attended just checked the ratios. He is right that high CO readings are potentially dangerous, carbon monoxide is a silent, odorless and tasteless killer, it only takes a small ppm number to be affected, however a good engineer can keep a boiler running safely, which ALWAYS comes first and operating properly thereafter, providing parts are still available. I cant say too much about gas as I'm not qualified but I am an oil man and know that not only is carbon monoxide a by product of burning hydrocarbons, it can also be controlled if someone knows what they're doing and again parts are available. I suspect and I could be wrong he was just pushing for a new install and to be fair your boiler is getting on a bit.
 
This is what’s called a W plan mate, not the Y plan. It gives HW priority, meaning once CH is satisfied it will spring return to HW port. Of course if the boiler is getting a feed from somewhere other than intended then through gravity circulation the cylinder will continue to heat until boiler water and cylinder temperature reach thermal equilibrium but you know that already.
It is a Honeywell wiring diagram but this is the principle behind the diverter.View attachment 45876

The W plan diverter valve wiring is quite easy to understand but SJB or someone might comment on the wiring if pump overrun is fitted.
referring to the boiler terminal box, assuming L is taken from terminal 7 and assuming a call for CH or HW then L will be live and the boiler PCB should then energise PL ,pump Live, and keep it running continuously until terminal 7 is de energised. L should also enable the boiler to run continuously also unless its minimum output exceeds the heat demand, at which point it will cycle on/off, again until terminal 7 is de energised.
When terminal 7 is de energised (no call for CH or HW) and if the pump overrun is initiated via terminal 10 then SL should tell the PCB to energise PL only and run it for the overrun time. If what I have written is basically correct then can some one see how this could have been (mis) wired to run the boiler on pump overrun but not the pump? or could it be a PCB fault?.
Possibly by wiring the pump directly from terminal 7 and not connected to PL on the boiler and terminal box?. and connecting terminal 10 (as well as terminal 7) to L on the boiler terminal box.?.
 
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I assume you're referring to the image above John. The SL (switch live) you see will be demand from system and starts the boiler sequence. The pump live will most likely be switched from the permanent live into boiler block and continue energising pump for a set time after the burner has shut down.
Of course without seeing something in person we can only ever guess whats happening and where.
Personally I think the op should employ the help of another engineer and have it thoroughly checked over.
 
From discussions, I undertand that I have a W style system where hot water is prioritised. Knowing from the discussions about how the triport valve works. . I did the following:
1. Used all hot water so that water in taps becomes cold
2. Heated the water for 30mis and sitched off
3. Turned central heating for 5 mins and switched off. I assumed that the valve position now would be in its last used place ie; CH and way towards hot water cyclinder would be closed.
4. This evening I checked the water temprature felt normaly hot in the taps and it has not been overheating.
5. I touched all the pipes in the airing cupboard and noted that pipe diverted to central heating was HOT (It shouldn't be as CH has been off since morning. Although no rads are hot). The hot water pipe that goes to the cylinder after the valve was cold. It appears that boiler has been still firing up now. The water has been going toward the pipe that feeds radiators. Pump has been alwatys off.

Does this rule out fault of valve? and supports what is being said that wiring/ electric connections are at fault?
 
W plans do not hold the last port off call like a Y plan does. It is a diverter valve which should spring return to HW port once CH demand has ended.
 
I know you stated that the you have always only had CH or HW which would point to a W system but it is just possible that you actually have a Y plan (however unlikely) with a mid position valve which either has been wrongly wired or is faulty. To rule out any confusion can you just read the valve details and post back please.
 
You could have a sticking valve yes but that wouldn't justify the boiler coming on, that would require a signal from elsewhere.
As above confirm the type of valve you have but I think its time you had an engineer out to check it all over with a multimeter
 
It is a mid position valve and can you get the details off another motorised valve?? to the right of it in the second picture please. Forget that the grey unit is the pump, apoligies.
 
That is a mid position valve, meaning you can have heating and hot water on at the same time or independently, unless of course its been wired as a diverter.
This does need a multimeter now. Someone needs to check what feeds you have where.
 
Okay , I call another plumber tommorow and highlight that electrical connection needs to be checked. Hope they don't rush to change valves to start with...
 
Okay , I call another plumber tommorow and highlight that electrical connection needs to be checked. Hope they don't rush to change valves to start with...

Thats your best bet mate. As I said above boilers don't just ignite on their own, something somewhere is telling it to. This could be a number of things all the way back to the boiler.
 
From an earlier post you indicated that sludge in the system had been dislodged by Sentinel X400. Do you have a magnetic filter on the system return? If so is it removing magnetite?

Before you replace the boiler, run it independently by opening the heating valve, bridging the thermostat input and running the system on the boiler stat. If ok, then address the control system issues.

The best approach is a simple logical process to find the gremlin. Initially, eliminate the boiler as the culprit. From your postings, I doubt it is the boiler, but sludge in the system does not help with the diagnosis. Eliminate this as an issue first
 
There is no magnetic filter. May be drain and refill it...
I see what the new plumber suggests. I will share the outcome in any case...
 
I managed to get hold of two plumbers. Entire three port valve and programmer is charged. None of the plumber checked wiring plan completely. They were more interested in changing above parts.
Since three port valve is changed water and central heating now work together.

The main problem remains that boiler keeps randomly switching on for a minute to two and water becomes v hot. I have called another plumber who can only make next Monday..

Apart from wrong wiring, what are the other reasons for this. Any other suggestions?
 
In view of what you told them about random boiler firing then i presume (if they were capable of changing the programmer and valve) that they would have checked the wiring at the boiler and pump to see if separately wired or if the boiler PCB is switching the pump or whatever, maybe its something as simple as the pump being wired correctly and the boiler having a permanent supply to its switched live.
 
In view of what you told them about random boiler firing then i presume (if they were capable of changing the programmer and valve) that they would have checked the wiring at the boiler and pump to see if separately wired or if the boiler PCB is switching the pump or whatever.
[/QUOT
In view of what you told them about random boiler firing then i presume (if they were capable of changing the programmer and valve) that they would have checked the wiring at the boiler and pump to see if separately wired or if the boiler PCB is switching the pump or whatever.
I was told that it doesn't have a PCB. It is with pilot light. Pump only gets on, when switched by programmer....
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Pump can be switched on by programmer, even when the boiler power is switched off from plug on the wall
 
That implies that you have two incoming electrical supplies to the one system and the boiler is getting a feed from elsewhere. If this genuinely the case then you need someone with a good understanding of electricity to put right for you.
 
IF that is the case then it wouldn't be unheard of.
I learnt the hard way once when isolated what was thought to be the only incoming live to a system, I then touched what should have been dead only to get a shock.
I would have someone with suitable electrical qualifications to check it out and rectify.
 
A glowworm 50BF is a fairly basic boiler. It does not have a permanent live. As long as the mechanical pilot light is lit, when a live is applied to the boiler, it will fire and run until it reaches operating temperature. Thereafter it will shut off, turning on once the temperature falls below the set point level.

If the boiler is “randomly” firing that can only be because the boiler is receiving a live (+240v) feed and is below the set temperature.

If the boiler has been wired with a permanent 240v supply it will operate 24/7 switching off when it reaches set temperature and on again as the temperature falls below the set point.

In that configuration any external controls may operate the pump and open / close valves, but will not call the boiler for heat - the boiler is operating independently feeding the heating system when the pump runs.

You should not be replacing parts on a whim.

Any credible heating engineer should be able to diagnose and resolve the issue. A heating engineer that has not checked out the control wiring is not credible.

It is also important to know what the system is. Is it gravity hot water and pumped heating or pumped hot water and heating. If it is the latter has it recently been converted from gravity hot water? - That can cause a host of issues if not done properly.

At the end of the day, the boiler will only fire when it is in receipt of a live feed -so your Engineer needs to find out where it is coming from.
 
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I was told that it doesn't have a PCB. It is with pilot light. Pump only gets on, when switched by programmer..
[automerge]1604153209[/automerge]
Pump can be switched on by programmer, even when the boiler power is switched off from plug on the wall

"Pump can be switched on by programmer, even when the boiler power is switched off from plug on the wall"
Are you saying that the boiler is just "plugged" into a wall socket?.
 
Thanks, this does clarify a lot about how the boiler and system works

We always had to run the programmer either mannualy or on timer, for hot water and CH. The pump use to come in both scenarios. No modifictions has been made to connections
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"Pump can be switched on by programmer, even when the boiler power is switched off from plug on the wall"
Are you saying that the boiler is just "plugged" into a wall socket?.
Yes , it is. Here is the picture
"Pump can be switched on by programmer, even when the boiler power is switched off from plug on the wall"
Are you saying that the boiler is just "plugged" into a wall socket?.
Yes it is. Here is the pic of boiler
IMG_20201031_155905.jpg
 
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If the above is correct the system is dangerous and needs to be rectified ASAP. I strongly suggest employing a decent electrician and heating engineer.
 
Hello all, the problem is sorted. There was an extra live red wire in the wiring box in the airing cupboard that was keeping the boiler on. The electrician checked and disconnected the wire. Wrong wiring was the case for around last 20 years. The boiler appear to have survvied this for so many years!!
Thank you for all the discussions here that enabled to point in the right direction....
 

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