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Andrew Peak

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HELP!,,,, E125 error code
Been trying to get to the bottom of problem with potterton titanium 40.
keep getting e125 which is circulation fault ( primary circuit). Fault is intermittent.
Thought about system flush but seem am reluctant as
all rads are red hot. Return pipe also hot.
Fault generally becomes noticeable when hot water is drawn off and then just runs cold.
May also happen when just on heating mode but not sure if this is triggered by water being drawn off while the heating is on, that locks up
again giving E125. can usually get it to reset ok but usually goes again same day.
sometimes can go a week or more without problem


have done the following with no success:

Back In December drained system down. (water was a bit black but no sludge) , ran system cleaner for few hours.
then drained off. Flushed. fit inhibitor and refilled. Next day got e125 but was then ok for about 8 weeks. Rads still all getting hot enough

Renewed C H temp sensor and safety thermostat.
Pump appeared to be a bit ‘sticky’ so fitted new one
Removed and cleaned 3 way valve and fitted new diverted valve ( didn’t really need cleaning)
Removed and checked flow pipe from burner to 3 way diverted valve. Was clean.
Removed and flushed plate heat exchange ( was clean anyway! Great flow on DHW side and primary circuit when using hose pipe on it)
As fault appears intermittent also ran it with a new pcb. Still got same e125 code so refitted original.

Back to square one!,



any pointers will be appreciated.
 

johnnyt74

Messages
24
Hi Andrew
I've got exactly the same fault as you and I wondered if you'd managed to get anywhere with this?

Many thanks for any help matey :)
 

John.g

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2,953
circ problem may be detected by primary flow/return temp sensors so if still flagging alarm after renewing circ pump perhaps one of these sensors, if return sensor fitted.
 
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johnnyt74

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Thanks for the replies @John.g and @Undertrained

My particularly problem is slightly different than the OP. I have a Baxi Platinum combi boiler. Working fine until I had wet UFH fitted.
If I just turn on UFH then it runs fine. If I turn on the radiators as well then I get E125 circ fault.
If I turn off the UFH then radiators work fine. So it's just a problem with both of them on.

Sounded very similar to the original post that I found during a bit of Googling so wondered if his answer would help lead me to sorting my problem. :)
 

Undertrained

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Thanks for the replies @John.g and @Undertrained

My particularly problem is slightly different than the OP. I have a Baxi Platinum combi boiler. Working fine until I had wet UFH fitted.
If I just turn on UFH then it runs fine. If I turn on the radiators as well then I get E125 circ fault.
If I turn off the UFH then radiators work fine. So it's just a problem with both of them on.

Sounded very similar to the original post that I found during a bit of Googling so wondered if his answer would help lead me to sorting my problem. :)
I suppose this is why threads shouldn’t be hijacked 😉 It’ll still be a circulation issue, perhaps the pump isn’t capable of the 2 circuits together?
 

johnnyt74

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24
I suppose this is why threads shouldn’t be hijacked 😉 It’ll still be a circulation issue, perhaps the pump isn’t capable of the 2 circuits together?
Yep, was conscious I was hijacking the thread with my last post :(

Was originally just wanting to learn from whatever solution the OP ended up with. But, didn't account for other experts pitching in to help :)

As for the pump, there is a separate pump on the UFH manifold and then the boiler pump itself so (although a good suggestion) I'm not sure that would be it? (although worth noting that you could probably write what I know about plumbing on the back of a stamp!) :)
 

johnnyt74

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Some boilers detect the slight rise in pressure when the circ pump starts so possibly a blocked/partially blocked pressure sensor or tubing..
Thanks John G. The boiler was going quite high with pressure previously but the plumber fitted another expansion vessel above the manifold. I'll put on the heating though and see what pressure the boiler jumps to when it tries to run both the UFH and the heating. Thanks for the potential diagnosis :)
 

John.g

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2,953
Is the boiler pump inside the boiler (system boiler). Did the problem start after the installation of the extra expansion vessel? is it positioned on the flow manifold or the return manifold?.
 

johnnyt74

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24
Is the boiler pump inside the boiler (system boiler). Did the problem start after the installation of the extra expansion vessel? is it positioned on the flow manifold or the return manifold?.

The boiler is a Baxi Platinum boiler and has a pump inside it. There's another pump on the manifold of the UFH. The problem started after the UFH was fitted but before the expansion vessel was fitted.

Sequence of events was...
Boiler running fine with just rads.
UFH installed and turned on
Boiler dropped out with E125 (which the manual lists as "Circulation Fault (Primary Circuit)"
I powered off the UFH Wiring Centre (it's fed from a switched fused spur) - rads all ran fine
Plumber came back out and said a valve was shut on the manifold which he opened - he was concerned about the pressure the boiler was reaching though (around 2.5 bar) so also fitted an expansion vessel above the UFH manifold
UFH ran fine for several days (until last night when I put the heating back on as it was a bit chilly).
With heating on got the E125 fault again.

As for whether the expansion vessel is fitted on the flow / return I'm not 100% sure. I've just got to nip out for an hour but I'll take some photos when I get back and post them up here to show you the set up. Thanks for all your help. Very much appreciated :)
 

johnnyt74

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24
Here are some photos of the installation as promised.....
 

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John.g

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HELP!,,,, E125 error code
Been trying to get to the bottom of problem with potterton titanium 40.
keep getting e125 which is circulation fault ( primary circuit). Fault is intermittent.
Thought about system flush but seem am reluctant as
all rads are red hot. Return pipe also hot.
Fault generally becomes noticeable when hot water is drawn off and then just runs cold.
May also happen when just on heating mode but not sure if this is triggered by water being drawn off while the heating is on, that locks up
again giving E125. can usually get it to reset ok but usually goes again same day.
sometimes can go a week or more without problem


have done the following with no success:

Back In December drained system down. (water was a bit black but no sludge) , ran system cleaner for few hours.
then drained off. Flushed. fit inhibitor and refilled. Next day got e125 but was then ok for about 8 weeks. Rads still all getting hot enough

Renewed C H temp sensor and safety thermostat.
Pump appeared to be a bit ‘sticky’ so fitted new one
Removed and cleaned 3 way valve and fitted new diverted valve ( didn’t really need cleaning)
Removed and checked flow pipe from burner to 3 way diverted valve. Was clean.
Removed and flushed plate heat exchange ( was clean anyway! Great flow on DHW side and primary circuit when using hose pipe on it)
As fault appears intermittent also ran it with a new pcb. Still got same e125 code so refitted original.

Back to square one!,



any pointers will be appreciated.
Found this somewhere but can't download your manual.......

E125 is displayed in either of two situations:-
i) If within 15 seconds of the burner lighting the boiler
temperature has not changed by 1°.
ii) If within 10 minutes of the burner lighting the boiler
temperature twice exceeds the selected temperature by 30°.
In these instances poor primary circulation is indicated.

So seems to be solely based on temperature, presume it means in (i) that if the temp doesn't increase by 1C in 15 secs that it flags the alarm, it would be quite possible to get a slug of cold water for > 15 secs after burner start up with no increase in temperature.
ii) might seem a bit unlikely as the burner should shut down when the temperature = target temperature+5C, except that its stll monitoring it during pump overrun.

At least its something to concentrate on as it seems to be purely boiler flow temperature monitored?.

Maybe try and monitor the time after ignition and see how long it takes to trip.
 
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johnnyt74

Messages
24
At least its something to concentrate on as it seems to be purely boiler flow temperature monitored?.

Maybe try and monitor the time after ignition and see how long it takes to trip.
Yep, I'm planning on giving that a go later. I've got a couple of guys working here at the moment through in the extension (where the UFH is) so don't want to cook them! It's quite a warm day today and they're plasterboarding which is hard going so will wait until they finish later and then try and put both the UFH and rads on and monitor the boiler pressure / temperature and the time to trip.

I've attached the manual for the boiler.

Thanks for all your help :)
 

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ShaunCorbs

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:D there’s no external auto bypass also the install looks like the builder has done it

So when the ufh shuts and the rads are just calling eg just opening the pump is dead heading against two port valves so no circulation for a few seconds hence e125
 

ShaunCorbs

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There is a ABV set to ~ 1.2M in photo 7 post #12, what does this do?.

That’s the minimum flow rate to stop the boiler cycling too much and throwing errors up as the ufh doesn’t need much flow hence why it’s set to 1 eg open all the time

Also looks after the upstairs port valve I’m guessing the 2 hep feeds going through the wall central of the boiler is the ufh feed
 

johnnyt74

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24
:D there’s no external auto bypass also the install looks like the builder has done it

So when the ufh shuts and the rads are just calling eg just opening the pump is dead heading against two port valves so no circulation for a few seconds hence e125

Which part looks like the builder has done it? In the boiler cupboard? Or the UFH?
If it's the UFH it's just been lashed in at the moment for testing. It'll all need cleaning up and re-wiring etc to make it neat. The plumber only has one guy who can do the electrics so he'll come back and sort it at some point.

That’s the minimum flow rate to stop the boiler cycling too much and throwing errors up as the ufh doesn’t need much flow hence why it’s set to 1 eg open all the time

Also looks after the upstairs port valve I’m guessing the 2 hep feeds going through the wall central of the boiler is the ufh feed
You're right, the two white plastic pipes going through the wall are the ones he ran in for the UFH.

So, I need to ask the plumber to install an external auto bypass? I thought that's what that black thing at the top right of the UFH manifold did? The plumber said that "automatically bleeds the system"? Is that not correct? (the bit I've circled in the attached photo)

Thanks for all the help. I really appreciate you taking the time to have a look at this. :)
 

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ShaunCorbs

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All the pipework under the boiler

Do you know what’s the tee above the port valve in the cupboard eg the grey hep pipe where this goes ?
 

johnnyt74

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24
All the pipework under the boiler

Do you know what’s the tee above the port valve in the cupboard eg the grey hep pipe where this goes ?
Yep, I must admit, I did think the boiler cupboard pipework looked like it was done by someone missing their mecanno set...

The grey pipe feeds a radiator that was an extra when the previous guy converted the garage to a room. The boiler is in the "what was" garage. And the grey pipes feed this radiator.

Thanks :)
 

johnnyt74

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Does this have a trv ?
Yep, it has a TRV to the bottom left of the manifold, it's hidden away a bit. I've circled it in this photo.

Why? Is that significant?

Thanks :)
 

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John.g

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I assume that is a TMV to give the required much lower UFH temperatures required.
If one of the actual boiler trips is the deltaT between the flow & return then most trip at a deltaT of 30C so perhaps this is what is tripping the boiler but this would/should only happen if no ABV is fitted, you have which we assume is working OK, you can see the effect of by pass vs no pass in the attachments if my calcs are correct.
I think the first thing to establish is what actually are the conditions that flag this low flow circ trip, there is no explanation in your manual and mine might be completely wrong.

I am just assuming UFH requirements but the relative flows and temps should still be correct.

I see the UFH TMV is on the left of the manifold but havn't a clue what you mean by a TRV on the manifold (circled).

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ShaunCorbs

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Yep, it has a TRV to the bottom left of the manifold, it's hidden away a bit. I've circled it in this photo.

Why? Is that significant?

Thanks :)

No sorry on the rad that the grey hep supplies can you remove it to test something eg the trv head
 

johnnyt74

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24
I assume that is a TMV to give the required much lower UFH temperatures required.
If one of the actual boiler trips is the deltaT between the flow & return then most trip at a deltaT of 30C so perhaps this is what is tripping the boiler but this would/should only happen if no ABV is fitted, you have which we assume is working OK, you can see the effect of by pass vs no pass in the attachments if my calcs are correct.
I think the first thing to establish is what actually are the conditions that flag this low flow circ trip, there is no explanation in your manual and mine might be completely wrong.

I am just assuming UFH requirements but the relative flows and temps should still be correct.

I see the UFH TMV is on the left of the manifold but havn't a clue what you mean by a TRV on the manifold (circled).

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Wow John!! Thanks for doing those calculations and drawing that out. I'm embarrassed to say that I'm struggling to interpret the findings of them. Am I correct in thinking the "DeltaT" is the difference in temperature between the flow and return? And, if I have an automatic bypass fitted then I need to maintain a difference of 15 deg between the flow and return or the boiler will trip? However, if I don't have an automatic bypass fitted (which I don't now as far as I'm aware) then I can have a difference of 30 degrees between the flow and return?

So, if I'm correct above, I'm better to not have a bypass? Is that correct?

Thank you again for your hard work on this. I'll answer other questions/support in another reply on here. :)
 

johnnyt74

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No sorry on the rad that the grey hep supplies can you remove it to test something eg the trv head

Apologies, all. It seems that (what I thought) was a TRV on the UFH manifold is, in fact, a "TMV" (Thermostatic Mixing Valve). as oppose to a Thermostatic Radiator Valve (I got a clue when I Googled TRV and saw that the "R" stands for Radiator :) )

@ShaunCorbs yes, there's a TRV on the radiator that has the grey pipe going to it and I can remove and test anything you would like? Just let me know what you'd like me to do and I'll try it. Thanks :)
 

John.g

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2,953
Wow John!! Thanks for doing those calculations and drawing that out. I'm embarrassed to say that I'm struggling to interpret the findings of them. Am I correct in thinking the "DeltaT" is the difference in temperature between the flow and return? And, if I have an automatic bypass fitted then I need to maintain a difference of 15 deg between the flow and return or the boiler will trip? However, if I don't have an automatic bypass fitted (which I don't now as far as I'm aware) then I can have a difference of 30 degrees between the flow and return?

So, if I'm correct above, I'm better to not have a bypass? Is that correct?

Thank you again for your hard work on this. I'll answer other questions/support in another reply on here. :)
Yes, the deltaT is the difference between the flow/return and ideally should be kept ~ 15/20C but with UFH only on because of the ratio of boiler flow to UFH flow then you can have a huge boiler deltaT depending on the boiler flow temp and the UFH (mixed) flow temperatures which means that you can have a very high undesirable boiler deltaT which on some boilers will initiate a trip if it exceeds 30C or so, I only used the attachments to show how the deltaT can change with/without by pass.

You have a bypass which is set very low IMO, phot 7 post#12, see posts #15&16 as well.

I find it a bit strange that the systems work fine when running separately but not with both on together.

Can you say how long it takes the boiler to trip if you have, say, the Rads on and you then call in the UFH, does it trip immediately or is there a time delay or whatever.
If its not a immediate trip can you monitor the boiler flow temperature immediately before and after calling in the second system to see if it changes dramatically.
 

johnnyt74

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Yes, the deltaT is the difference between the flow/return and ideally should be kept ~ 15/20C but with UFH only on because of the ratio of boiler flow to UFH flow then you can have a huge boiler deltaT depending on the boiler flow temp and the UFH (mixed) flow temperatures which means that you can have a very high undesirable boiler deltaT which on some boilers will initiate a rip if it exceeds 30C or so, I only used the attachments to show how the deltaT can change with/without by pass.

You have a bypass which is set very low IMO, phot 7 post#12, see posts #15&16 as well.

I find it a bit strange that the systems work fine when running separately but not with both on together.

Can you say how long it takes the boiler to trip if you have, say, the Rads on and you then call in the UFH, does it trip immediately or is there a time delay or whatever.

Thanks John for the clarification.

I tried this last night. I set up my phone to video the boiler temperature and the boiler pressure and then put the radiators and the UFH on. Unfortunately it didn't trip!! However, it was only a quick test as my wife was working nights so I didn't have long before we needed to eat and let her get ready for work.

I'm planning on trying it again tonight to see what happens.

I've also got the plumber coming back tomorrow as the heated floor is very 'patchy'. I'm wondering if it could possibly be a combination of air locks etc causing issues? However, he has promised to get to the bottom of it tomorrow.

I'll fire everything up properly tonight and see if it trips again. It certainly isn't tripping within a minute or two. If I had to guess I would say that it stays working for at least 20 minutes.

Obviouisly, I'll keep posting back with any developments this end - especially if the plumber gets to the bottom of it. :)
 

ShaunCorbs

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Apologies, all. It seems that (what I thought) was a TRV on the UFH manifold is, in fact, a "TMV" (Thermostatic Mixing Valve). as oppose to a Thermostatic Radiator Valve (I got a clue when I Googled TRV and saw that the "R" stands for Radiator :) )

@ShaunCorbs yes, there's a TRV on the radiator that has the grey pipe going to it and I can remove and test anything you would like? Just let me know what you'd like me to do and I'll try it. Thanks :)

Remove the trv the rad will act like a bypass and the 125 shouldn’t appear
 

John.g

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2,953
Shaun, isn't the existing ABV acting (if in fact its opening at 1.2 M) as a huge by pass all the time with UFH on?.
 
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johnnyt74

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Remove the trv the rad will act like a bypass and the 125 shouldn’t appear

Shaun, isn't the existing ABV acting (if in fact its opening at 1.2 M) as a huge by pass all the time?.

Shaun, really clever solution! Thanks.

I've spoken to the plumber and he has assured me that I already have auto bypass valve fitted and I'm hoping to keep that TRV on that radiator as I spend a lot of time in that room (converted garage) as it has my computer in there and an exercise bike (I'll melt if I can't turn that radiator down!! :) )

What is the "M" referring to in 1.2M? Is that metres cubed relating to the flow? Could the setting on the ABV be the issue?

Thanks :)
 

John.g

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2,953
M = Meters, the ABV indexed setting is 0.1 to 0.5Bar which is 1 to 5 meters and as the pump head is always given in Meters (M) I just convert the ABV scale.
Regarding the garage rad, when you have the two systems on (and which subsequently trip) surely you have a number of other rads on? so one (garage) rad with a TRV should have little or no effect IMO.
That setting of 1.2M seems very low.
 

johnnyt74

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24
M = Meters, the ABV indexed setting is 0.1 to 0.5Bar which is 1 to 5 meters and as the pump head is always given in Meters (M) I just convert the ABV scale.
Regarding the garage rad, when you have the two systems on (and which subsequently trip) surely you have a number of other rads on? so one (garage) rad with a TRV should have little or no effect IMO.

Thanks for the explanation. Yes, I have rads on through-out the house - albeit at different levels on the TRV's.

Thanks :)
 

John.g

Messages
2,953
Something strange alright as ironically, the more the rad TRVs throttle in the more the set up tends to the UFH side (no trip). Is the ABV very hot on both sides of the pipework.
I think monitoring the boiler flow temperature later on will tell a lot, hopefully.

Also if the rad system is on alone then you can get huge deltaTs with no by pass and TRVs, my oil fired boiler regularly has a delta T of > 35C as I have no by pass fitted so again strange why your system doesn't trip on the rad system only.
 
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johnnyt74

Messages
24
Something strange alright as ironically, the more the rad TRVs throttle in the more the set up tends to the UFH side (no trip). Is the ABV very hot on both sides of the pipework.
I think monitoring the boiler flow temperature later on will tell a lot, hopefully.

Also if the rad system is on alone then you can get huge deltaTs with no by pass and TRVs, my oil fired boiler regularly has a delta T of > 35C as I have no by pass fitted so again strange why your system doesn't trip on the rad system only.
The full fault description of E125 is:
Circulation Fault (Primary Circuit)

Displayed in either of two situations:
- If within 15 seconds of the burner lighting the boiler temperature has not changed by 1°.
-If within 10 minutes of the burner lighting the boiler temperature twice exceeds the selected temperature by 30°. In these instances poor primary circulation is indicated.

So, are you saying that the DeltaT is the measurement for that second fault reason (If within 10 minutes of the burner lighting the boiler temperature twice exceeds the selected temperature by 30°. In these instances poor primary circulation is indicated.) ?
 

ShaunCorbs

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Can we just try removing the trv head for a day or two when you want either on will prove if there’s no flow eg no auto bypass on the primary’s
 

John.g

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2,953
The full fault description of E125 is:
Circulation Fault (Primary Circuit)

Displayed in either of two situations:
- If within 15 seconds of the burner lighting the boiler temperature has not changed by 1°.
-If within 10 minutes of the burner lighting the boiler temperature twice exceeds the selected temperature by 30°. In these instances poor primary circulation is indicated.

So, are you saying that the DeltaT is the measurement for that second fault reason (If within 10 minutes of the burner lighting the boiler temperature twice exceeds the selected temperature by 30°. In these instances poor primary circulation is indicated.) ?
If it's the deltaT that its monitoring then yes, definitely a indication of poor circulation, but the actual wording doesn't say that, its says:
"the boiler temperature twice exceeds the selected temperature by 30°. In these instances poor primary circulation is indicated" which I interpret to mean that the boiler temperature must exceed the target or set point flow temperature by 30C, so if you have the boiler target (setpoint) temp set to 65C then the boiler flow temperature must exceed 95C before flagging this alarm/trip and perhaps this what is happening.
 

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