Reliability of fault codes potterton

[ShaunCorbs]

Does this have a trv ?

 

[johnnyt74]

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

 

[John.g]

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).

 

[ShaunCorbs]

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

 

[John.g]

Isn't the item circled on top of the manifold a thermostatic air vent?.

 

[ShaunCorbs]

Isn't the item circled on top of the manifold a thermostatic air vent?.

Just an automatic air vent yes

 

[johnnyt74]

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).

View attachment 63686

View attachment 63687

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]

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]

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]

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.