Powerflush question

[Harry Bloomfield]

Is the water circulating forcefully through all the pipes? When oxide particles reach the filter it should trap them. Eventually there will be less and less to trap.

I would suggest not, the kettling suggests inadequate flow through the boiler and the filter.

 

[Madrab]

Well there is a 22mm backbone, about 19 metres of it, then there are 4 branches off near the end of that, I put it in writing on the diagram on the previous page.

A 22mm backbone would be 22mm all the way from one end of the system to the other with 15mm branches off to each rad. That system has a ~19m backbone of 22mm but over 36m of 15mm, the differentials in flow at a set pump speed will be significant (edit) and that added to the fact that 15mm has less than half the heat carrying capacity at a given flow rate. Anyway, we digress, that doesn't solve the immediate issue.

The reason that the system design is so important here though is that it can have a direct impact on how it should be cleaned, you may find though to get the system back properly you may have to spend. Is the system sealed and has a filling loop so can be mains flushed?

I am in a situation where the Hex seems damaged

How bad was the system to start with, sounds like it might have been oily black?

We need to understand what the system started as, the HEX may not be stuffed, restricted - maybe but that may be able to be sorted out if you are still getting some flow through the boiler. Vaillant's are very sensitive to flow, hence all the errors it's throwing up. I think you need to bin this guy, he's obviously tried to clean the system and has made a horses a$$ job of it several times, he's had a chance to sort it and hasn't managed it, to me that means he doesn't really know what he doing. If he's not been paid and the system's still stuffed after the work then I'd give him a nominal fee for his time and tell him to do one. Then you need to find an experienced bod who will take the system design into account and do the job properly. In the mean time I'd get a couple of bottles of normal cleaner (X400/MC3/F3) into the system and get that running around it.

 

[Mike13]

It is a sealed combi, Ecotec Pro 30, he did use a 2 bar pump.
It has been working ok for 4 years, keeping the house warm on even the coldest of days, so if designed from scratch it would be done differently. but seeing as it was working, then it is sort of adequate,
Currently I have upped the 5 min timer to 15 mins, and set the pump to 100% all the time, a bit more in electricity and humming noise, but it will try and reduce the kettling and allow the system to carry the debris better.
He is visiting again during today, I am still unsure about letting him have another go, he is personable, but unsure he understands hydraulics properly. My previous roles experience tops out at 2,000 bar systems!

 

[Johntheo5]

A Combi.
Does it produce DHW.

 

[Mike13]

Yes, hot water has not been affected. yet.

 

[Johntheo5]

Thats a good sign IMO re state of the boiler HEX and the DHW PHEX. next time you run it on DHW look at d.40&d.41., depending on where the sensors are installed, may give a good indication of the state of the HEX.

Does your system have a external ABV, if so maybe increase that setting a bit if its set to say 2.5M (index), increase it to 3.5/4.0.
there is also a internal by pass which is adjustable from 1.7M to 3.5M, factory set, 2.5M, you could check this and maybe increase it to max, 3.5m, (may need a GRI) might force a little more water through the system.
You also said you "have upped the 5 min timer to 15 mins", is this the overrun timer d.001 or the anticycle timer d.002, the overrun timer is a fixed time, what ever you set to, but the anticycle timer uses a look up table based on the set time + the target temperature.

 

[Mike13]

It was D.001 that I increased, I figured more time actually circulating the cleaner and letting things cool down was safer. I suspect that if I do a factory reset I will get many more F.24's per day

 

[Mike13]

Does your system have a external ABV, if so maybe increase that setting a bit if its set to say 2.5M (index), increase it to 3.5/4.0.

On a recommendation from the previous thread about this boiler, that has already been done. It is on the side of the diverter valve.

 

[Johntheo5]

On a recommendation from the previous thread about this boiler, that has already been done. It is on the side of the diverter valve.

I remember the thread now., the above implies that its the internal bypass setting has been increased, does you system have a external ABV as well?.
You are getting S.07, pump overrun, this normally only happens if the boiler is programmed to stop it, or you stop it, some fault conditions may also probably flag it, otherwise, if say the flow temperature exceeds the target temp by +5C or the flow/return dT exceeds ~ 30C then it shuts the burner down and runs the anticycle time but you should get S.08 in this case. The default anticycle time is 20 mins but the actual time is based on the table, below, if you find the boiler has difficulty in getting away after a recycle then you may need to increase this time, to give say the equivalent pump overun time of 15 minute which you have set.
In the previous thread you were getting flo/returns of 59C/36C, dT 23C, which is OK, the power wash now seems to have dis improved matters

 

[Mike13]

No external one, it i just the boiler.
I sometimes see s.08

 

[Johntheo5]

Forgot to ask the boiler flow target temperature.

If d.002, anticycle time, is set to its default of 20C then the actual anticycle times at boiler flow target temps of 50/55/60/65c are 9.5/8.0/6.0/4.5 minutes, if you require the burner to stay off for 15 minutes after every (anticycle ) trip then for boiler flow target temps of 50/55/60/65C set the anticycle time to 30/40/50/60 minutes.

 

[Mike13]

Forgot to ask the boiler flow target temperature.

Currently 51C, as it was overshooting so badly before I set it lower to give more headroom before it kettles. I have set 35 instead of 20 mins for the d setting

 

[Johntheo5]

Is the boiler getting away so at that setting(s)?, what have you set d.000, heating part load to?.

 

[Mike13]

Is the boiler getting away so at that setting(s)?, what have you set d.000, heating part load to?.

12Kw for now, that seems no different to 6Kw

 

[Johntheo5]

These boilers fire up at ~ 65% of rated output (heating part load has no effect on this) in your case 19.5kw and maintain this for up to 1 minute (or used to be 1 minute at any rate). You don't want (1) the dT to rise above 30C and (2) don't want to exceed target temp+5C, you have given a very long overrun & anticycle period to get the system temperature as low as possible on refiring, you won't get it lower than say 23C so if you want to restrict the dT to say 25C you require a minimum flowrate of 11.2LPM, if you achieve this then the flow temp will rise to 48C within ~ 20secs or less, you then don't want it to exceed say 51/52C in the next ~ 40 secs, the boiler controls are then released to modulate, if the flow temperature is still below the target temperature then the boiler will fire flat out and can exceed the target temp by +5C and go back into cycling mode, this where limiting the output with d.000 can help prevent this.