Open vented system, No HW, CH works fine, BAXI 80HE boiler shows Dry Fire after every restart

[fandyman]

Thanks @DP I certainly think there is something acting up in the boiler (PCB/terminals etc as per page 45). Another interesting thing is before going to DRY FIRE the boiler was going to IGNITION LOCKOUT failure about 2 months ago. That was not stopping it from working for HW and CH but I had to go and press reset button on the boiler every now and then.

Is there any way I can do the checks on page 45 myself if it goes to DRY FIRE again?

 

[Madrab]

Rab, no reflection on what you posted. I sometimes read a reply in the post way down after it has been posted and write something that may or may not be relevant. Your advice is always to the point and worth its weight in gold
Furthermore, I am sure you have had this fault too, last dry fire among host of other issues was in a new build near Braehead Shopping Ctre

No bother at all @DP - thick skinned with this place after all this time as I am sure you are so no bother m8 . Yeah - like you, have had these types of problems every now and again, funnily enough last one I had like that was like you, a new build over @ Parkhead, turned out to the diverter had jammed.

As you say tho - if the system is only calling for HW then the 3 port shouldn't come into it at all as the valve should be @ rest in HW mode (B) and it's the cylinder stat that switches the live from the programmer through to the boiler. The only thought there was if the 3 port was getting jammed or the motor locked in another position, that could upset the whole thing but even then there should still be flow through the valve given it's will always have an open port regardless, so there should be a dry fire, so we're back to your excellent impeded flow point as being the issue and understanding why that's happening. Or not now, as suggested by the OP. I hate it when the cause isn't found tho as I'm sure you appreciate, to me that's a problem just waiting to rear its head again sometime down the line.

My approach though is anyone that installs a Y plan these days should be shot and given it's so easy to do, then upgrade this system to at least an S plan or similar and take that twitchy MID valve out of the process once and for all.

 

[Johntheo5]

Thanks @DP I certainly think there is something acting up in the boiler (PCB/terminals etc as per page 45). Another interesting thing is before going to DRY FIRE the boiler was going to IGNITION LOCKOUT failure about 2 months ago. That was not stopping it from working for HW and CH but I had to go and press reset button on the boiler every now and then.

Is there any way I can do the checks on page 45 myself if it goes to DRY FIRE again?

You said in post #1 that the circ pump sounds as if its pumping well at 36W. It probably is but depending on the pump type and mode & settiung its on, it might actually be pumping very little which will flag a Dry Fire code.
Was it still reading 36W on HW only with the dry Fire up?
If you post a close up snapshot of the pump to show its model and setting the exact pumping rate can be got from the pump curves.
It looks like a Grundfos Alpha2 and you should see its max output on the pump head or casing, it will probably be 45W or 35W

 

[DP]

Another interesting thing is before going to DRY FIRE the boiler was going to IGNITION LOCKOUT failure about 2 months ago

That will be due to several issues. One is combustion seals and other is condensate trap. Bottom part of the heat exchanger needs to be dropped and possibly seals replaced. This is not a task you will be able to carry out
Get him to check combustion gases and air inlet ratio since flue seals fail at times.
Suggest you get a heating engineer and get him to check above as well as the electrodes. Not just any heating guy but one who repairs boilers. Anyone can fit a boiler. Repairing is another case
Get him to listen to pump running. He should be able to distinguish if the pump is running.
If it is, get him to check the flow switch is making.

Having said all above, not being on site, I would be checking each item one by one. Equally, I could be way off the mark

 

[fandyman]

Thank you @DP and everyone else for your help. I appreciate your every comment as I am learning how the system is put together. I will definitely get a heating engineer for an investigation next week. Many thanks again!

 

[fandyman]

You said in post #1 that the circ pump sounds as if its pumping well at 36W. It probably is but depending on the pump type and mode & settiung its on, it might actually be pumping very little which will flag a Dry Fire code.
Was it still reading 36W on HW only with the dry Fire up?
If you post a close up snapshot of the pump to show its model and setting the exact pumping rate can be got from the pump curves.
It looks like a Grundfos Alpha2 and you should see its max output on the pump head or casing, it will probably be 45W or 35W

Hi @Johntheo5 I think the boiler and the pump have died now.

I have started observing DRY FIRE alert again this afternoon and then went upstairs after maybe 30 minutes from noticing and noticed no lights on the pump at all. I went to the boiler and the lights do not come on at all. It looked like the 3 port diverter valve was still ok (showing voltage) albeit very hot and the pipework also hot from the time the boiler was still functioning earlier today I suppose.

I went to the RCD fuse board and flipped the boiler off and on few times and it is still no lights on....

I need to leave for the evening so I will flip the fuse off for time being but I am afraid now few components (boiler, pump and maybe valve too if I am unlucky) just died on me.

Any advise? Contacting heating engineer too now.

 

[gazfen]

I’d say your pump is knackered if there is 240v going there. If not your cold feed is blocked

 

[Johntheo5]

Hi @Johntheo5 I think the boiler and the pump have died now.

I have started observing DRY FIRE alert again this afternoon and then went upstairs after maybe 30 minutes from noticing and noticed no lights on the pump at all. I went to the boiler and the lights do not come on at all. It looked like the 3 port diverter valve was still ok (showing voltage) albeit very hot and the pipework also hot from the time the boiler was still functioning earlier today I suppose.

I went to the RCD fuse board and flipped the boiler off and on few times and it is still no lights on....

I need to leave for the evening so I will flip the fuse off for time being but I am afraid now few components (boiler, pump and maybe valve too if I am unlucky) just died on me.

Any advise? Contacting heating engineer too now.

Afraid can't offer any advise as to why everything has died.

Re the pump, we still don't know whether its a 35W or 45W because this is vital in determining the flowrate when it is/was running at 38W, if its a 35W pump then its circulating at a very healthy rate of ~ 15 to 20LPM but if its a 45W pump then the flowrate, (running on fullspeed III) at 38W is only ~ 3 to 5LPM which can definitely cause problems. It's output will definitely be written somewhere on it.

 

[fandyman]

Afraid can't offer any advise as to why everything has died.

Re the pump, we still don't know whether its a 35W or 45W because this is vital in determining the flowrate when it is/was running at 38W, if its a 35W pump then its circulating at a very healthy rate of ~ 15 to 20LPM but if its a 45W pump then the flowrate, (running on fullspeed III) at 38W is only ~ 3 to 5LPM which can definitely cause problems. It's output will definitely be written somewhere on it.

Hi @Johntheo5 As strange as it may sound after my return tonight I tried to switch on the boiler one more time to make sure it is dead by flipping the fuse and the boiler started as normal. I then turned HW only on the programmer and went to the loft to check the pump and it was showing 45W.

I've got HW and CH back as normal again now. One other thing I noticed is that both A and B pipes were equally hot even though only HW was on the programmer as being tested at the time.

Any ideas what could it mean and what to do next?

 

[Johntheo5]

Hi @Johntheo5 As strange as it may sound after my return tonight I tried to switch on the boiler one more time to make sure it is dead by flipping the fuse and the boiler started as normal. I then turned HW only on the programmer and went to the loft to check the pump and it was showing 45W.

I've got HW and CH back as normal again now. One other thing I noticed is that both A and B pipes were equally hot even though only HW was on the programmer as being tested at the time.

Any ideas what could it mean and what to do next?

It means that at 45W you are circulating between 10.8LPM at a 6M head and say 25.0LPM at a 4M head, (the exact flowrate can't be derived, apart from the minimum, once the pump is running at full power), the other interesting point is that the pump is running at 36W in photo which means it was only circulating 2.0LPM, you also said it was running at 38W which gives a flowrate of 5.0LPM, ( flowrate at 33W will be 0.0LPM), don't know if this means there is a intermittent pump problem or not but letting that aside for the moment, in the photo below, there is a pipe that goes vertically upwards after port B (HW) in the mid position valve, can you find out where this is going or coming from?., if its a (the) vent or the cold feed then its in the wrong position and will affect the whole system IMO, the normal set up is, from the boiler flow you have the Vent, then (no more than 150mm from the vent) the Cold feed and then the Pump, (then the mid position valve).
EDIT: That vertical pipe has the manual air vent on top and may be causing problems, I will explain it later today.

 

[Johntheo5]

Can you see if the vertical pipe is higher than the water level in the F&E (feed and expansion) cistern, if any portion of the pipe is above the water level then it can cause problems as it will try and drain down to the F&E cistern water level each time the pump stops and possibly air in that upper portion of pipe.
Can you also follow the pump inlet (bottom) pipe back and see where the vent and cold feed enter it, there should be two pipes, probably a smaller diameter one (cold feed) nearest to the pump and the larger one (Vent) not more than 150mm further on, it might also be done like in my 52 year old system below.
Anytime you feel like it, run on HW only which may need upping the cylinder stat a little, as soon as you have done this, check the pump power, if its still only 35W (ish), open the manual bleed on the vertical pipe to expel any air, then close it and again note the pump power.
To see if the MPV is staying on HW only (port B) pull on the manual lever, there should be a immediate fairly stiff resistance, then release it, the valve shoud then return to HW only on its spring return.
Also, lokk into the F&E cistern to see if there is any sign (there shouldn't) of water pumpiny over through the vent pipe.

 

[Madrab]

@fandyman - You are dancing about on the head of a pin here - If the system was working fine before all of this started then it was fundamentally OK. Your issue are now down to something having changed/failed/intermittent

If something has since caused an issue then there is only so much that can be suggested over the internet to direct you to follow these fault finding procedures.

The latest failure where everything went down is just another symptom of a system that isn't happy for one reason or another. Ultimately you need a recommended pro in that is experienced with an open vent Y plan system running on a boiler that could be around 20yrs old to get to the bottom of this for you.

 

[fandyman]

Can you see if the vertical pipe is higher than the water level in the F&E (feed and expansion) cistern, if any portion of the pipe is above the water level then it can cause problems as it will try and drain down to the F&E cistern water level each time the pump stops and possibly air in that upper portion of pipe.
Can you also follow the pump inlet (bottom) pipe back and see where the vent and cold feed enter it, there should be two pipes, probably a smaller diameter one (cold feed) nearest to the pump and the larger one (Vent) not more than 150mm further on, it might also be done like in my 52 year old system below.
Anytime you feel like it, run on HW only which may need upping the cylinder stat a little, as soon as you have done this, check the pump power, if its still only 35W (ish), open the manual bleed on the vertical pipe to expel any air, then close it and again note the pump power.
To see if the MPV is staying on HW only (port B) pull on the manual lever, there should be a immediate fairly stiff resistance, then release it, the valve shoud then return to HW only on its spring return.
Also, lokk into the F&E cistern to see if there is any sign (there shouldn't) of water pumpiny over through the vent pipe.

@Johntheo5 I have attached some photos of the piping where it follows the pump inlet (bottom) pipe back. Hope it is more visible what goes where.

I've checked the vertical pipe (the manual air vent) and it is not higher than the water level in F&E cistern but not much lower either. Hope that is also visible from the photos.

I tried carrying out the test you mentioned later in your last post but as soon as I switch the programmer to HW only the power to the boiler and loft shuts off. Currently it works only when both HW and CH are selected.

@Madrab In terms of looking for a good heating engineer how do you go about finding a good one? The last two I found on the CORGI gas safe website came over charged me (did not explain a thing) and left. When they arrived the system was working correctly but they said they fixed it telling me some checks they did but the system failed few days later the same way. Upon calling them back they said I would have to replace a boiler but they did not give me any explanation. Finally they offered they could replace the whole system...

 

[Madrab]

@fandyman - That's a hard one I'm afraid - places like this forum can sometimes be your best friend - if you pop in your postcode/rough location someone may be able to help or offer a recommendation.

Please don't get me wrong, I'm not suggesting for a sec that you aren't capable of getting to the bottom of this and getting it corrected, especially given it's OV but there are a few areas that need specialist expertise that you may not have. There are certainly areas within the boiler that you should steer clear of, unless you have the experience, as things can be made worse when applying a limited amount of understanding or when taking advice.

You mention that it still has the HW only issue where power is curt when the programmer is in that mode - that has to be the programmer or the cylinder stat - that needs testing of that circuit to see where the power is stopping - either the programmer isn't supply so it's new programmer or the stat isn't switching it so its a new stat.

BTW looks like you already have a combined feed and vent. Also can't seem to see the Cold water cistern (CWSC) that feeds the HW cylinder?

 

[gazfen]

Open vent on cylinder, check for any air in there. Could be valve or worse still flow switch on boiler.