Problems with Vallaint 428 after CP12 check

[scoobydo123]

All,

Had gas check done on Friday, the guy but it in SFH mode to check the emissions. I have remote monitoring for gas use with live info. Since yesterday I can see it has been firing up at 17kw for 8mins then 4 mins off! The only time I have seen it behave normally is when there has been call for heat by the roomstat (which I can control remotely). During call for heat it correctly modulates down.

Note it has HW set to constant (unvented cylinder with 18kw coil).

See attached graphs showing gas used

During the cp12 the stat on the unvented was not altered so see no reason why all of a sudden the hw is not being satisifed on the first burn.

Boiler has the modified PCB that corrects the microfiring that many suffered from when using advance controls.

 

[scoobydo123]

Here is a graph that I have managed to get back as a historical one (area in grey) from a few days ago. You can see how it fires up at a lower gas rate and has nice long burns whilst stat is calling for heat. And none of the non stop firing like it is doing now, watching it remotely now and is still doing this short burns at 18kw

 

[AGAS]

testing emissions on SFH isn't doing it properly

 

[scoobydo123]

Why would he do that then? I am sitting here watching the damn thing fire with no call for heat by the room stat so must be the cylinder. Going to have to go round there to see what is going on but wondered if anyone has experienced anything like this before. This boiler had been a pain for a few years but around 4 years ago I got the modified PCB and it has been fine. I wonder if putting it in SFH mode has upset the min-max fan rating parameter (previous CP12's never been put in SFH mode). Either that or tenant has cracked the cylinder stat up really high just prior to CP12 and the flow temp is below the cylinder stat.

 

[AGAS]

it isn't caused by putting it in SFH mode , when testing it needs to put in high rate max P1 check the tenant first or other alterations

 

[scoobydo123]

Yes I always called P1 full Bifta mode Still not understanding why all of a sudden the gas use is jumping to 17kw whereby before it was 12kw. Hope he didnt change d.0 what a nuisance. I would have thought that it would have gone into anti cycle mode if not modulating down when flow and return are up to temp yet load not satisfied this dont appear to be the case as it is cycling like crazy and really annoying me now

So on reading SFH mode has been used because he didnt understand how to use the controls and also hasnt tested the boilers emissions according to full output :-0

More cycling than an olympic velodrome

 

[scoobydo123]

Could it be stuck in an endless SFH mode. Am I correct that the boiler when in SFH mode fires regardless of external controls. When put in this mode it is opening the valves (sPlan) so it will just be heating the whole system until it decides to stop and then start up again if the logic has somehow gone cranky. Failing that maybe my smart meter has gone not so smart and giving me false readings. Going to go round there in the morning

 

[gazdaz36]

Why are you blaming the engineer? SFH will clear after the boiler has run at the kw rating set on D0 after 10 mins. Personally IMO I think you have an oversized boiler with undersized pipe work and poor circulation so boiler short cycles

 

[scoobydo123]

Yes the boiler is oversized but it never done this before. Look at the 3rd graph above, ignore the blue look at the grey that is how it normally works. Never had all this microfiring (well at least not in the past 4years) since I got the development PCB. I keep a close eye on it remotely (as I pay the tenants gas bill) and it started after the CP12. Already established I think that the engineer was questionable putting it in SFH mode rather than P1. Dont think it was the tenant messing with the tank as it is a Megaflo 145L the ones where the tank stat is under the electrical cover. Will update once I have been round there.

 

[scoobydo123]

Just for completeness here is all last night also you can see when CH was called for by the room stat

 

[gazdaz36]

My guess from looking at things is that your air gap in your megaflo cylinder needs recharging. If your constantly losing hot water at a small rate through the tundish that is replaced by cold,the boiler will keep firing for small periods to bring your cylinder back up to temp.

 

[scoobydo123]

Already thought of that and asked the tenant last night to check that

 

[scoobydo123]

Here it is nearing the set point of 19.5 this morning

 

[gazdaz36]

Jesus talk about over complicate things it’s so clear you have a problem with your hot water creating short demands for heat from your boiler. Therefore you have to be losing hot water from your cylinder either through leaking PRV into tundish, dripping hot tap or leak on the dhw pipe work.

 

[scoobydo123]

Ok so there has been no call for heat after over 2hrs (so tank stat finally satisfied only when CH was calling this morning between 7:30 and 9:30 which was one long burn). Just come back from there and can confirm the following. Stat on Megaflo set to 50c (so hadnt been altered). Flow temp had been cranked up to 75 from 69 so have altered the max flow on the dial via d.71 so no one can tinker with that. One of the tenants came out and said they had just had a shower this was at around 10:00 so had not drawn off enough to cause tank stat to call . Tundish was dry, no air in primaries. What I did find is that the 2port was not moving freely on the spring return for the DHW actually felt jammed half open. Gave it a good old jiggle and it then seemed to be running better (prob fail again i guess?). It is not a honeywell it is some scottish gas item can the heads be changed on these? So guess it was not fully opening so boiler was short cycling didnt help that the flow was set higher than I normally run it at as the anti-cycling timer is not very long when @ 75.