Vaillant Issues

[vince101]

I'm pulling my hair out on some issues with my newly installed Vaillant system. The installer has been responsive but I think the issues are beyond them so seek the input of specialists on this forum.

Details:

• Ecotech 428
• Open Vent condensing boiler
• Fully pumped system (2 motorised valves)
• DAB VA55-130: 3 speed pump on setting 2
• Power flushed prior to installation
• D0 setting = 30

Issue 1
It generally works fine (except see 4) when both the hot water and heaters are selected. However on Hot Water only it starts up for about 30 secs and then turns off for over a minute. Hence it takes about 45 mins to get the hot water up to a reasonable temperature.

Details: D41 quickly fires up from 55 deg C to ~ 76 deg C taking ~ 30 secs, the flame cuts out and only fires up again when it cools down to 55 deg C. The temp difference between D41 and D40 is about 13 deg C. I've tried different pump speeds to no avail.

Is this intermittent firing normal? I can't see it being a good thing?

Issue 2
After the system shuts down (on either hot water or heating) the pump overrun kicks in with hot water going into the expansion tank in the loft for about 4 mins. It gets quite frothy and I'm guessing aerating the water can't be good for corrosion?

There is an automatic bypass fitted about 3 metres away from the boiler. Even opening this to minimum DP does not prevent the overrun into the expansion tank on shutdown so I can't really understand what it does? I wonder if issue 3 is preventing the pressure build up and so stopping the valve doing its job properly?

Issue 3
I note that the location of the open vent/ cold water feed straddles the hot water cylinder. Would have thought it should be on the pump suction per instruction manual. What's the consequences of having this set up?


Issue 4
I’ve just started getting the dreaded S53 error message in the mornings when on auto timer which prevents it running up. For some strange reason it then works fine about 30 mins later when I activate remotely.

Comments appreciated

 

[Tibbot]

Assuming everything is clean, as you state, then it may be piped incorrectly. This shouldn't be beyond any installer other than those that think bashing combis in makes them a heating engineer.

 

[Garfeild]

How many radiators have you got?

 

[Agile]

Immediately set the power in d0 to 18 kW and then calculate the total radiator power plus 2 kW for hot water.

As usual your boiler has been grossly over sized and you are reaping the consequences. What size, type and age is the property? Who choose that boiler and what was the previous model that it replaced?

The pipework is incorrect and pumping over is going to cause pinholing in your rads in days or months!

Was anything power flushed or chemically treated?

Did he fill in the Benchmark certificate?

I am always very sorry to hear of these cases of totally inadequate installers doing work like this so badly.

Tony

 

[vince101]

Appreciate comments so far. More info as follows:

It replaced a Potterton Netaheat 16-22 so increase in size didn't seem too great. I have 14 radiators and size chosen was similar for 3 quotes I got.

I had system powerflushed beforehand. Took a day for them to do all radiators.

Wish I'd never replaced the old system....at least it worked!

System layout drawing is on my profile. (didn't know how to attach)

Vince

 

[Agile]

It replaced a Potterton Netaheat 16-22 so increase in size didn't seem too great. I have 14 radiators and size chosen was similar for 3 quotes I got.

Vince

You have not given the size of the property.

14 rads are probably between 14-21 kw depending on their sizes.

If your old boiler was set at mid range of 19 kW then your new boiler is 47% more powerful. To me thatas a serious oversize! Thats totally unnecessary and reduces operating efficiency. An 18 kW boiler would probably have been quite sufficient.

Since your old boiler was installed about 17 years ago, most properties have had improved loft insulation ( typically 300mm ) double glazing and draught proofing and the heat required is now usually considerable less than before.

Just because THREE local installers dont know how to calculate heat losses and all oversize the boiler that does not mean that its correct !

I am very sorry that you have been the victim of incompetent people.

Tony

 

[Tibbot]

Your diagram shows incorrect piping which can be cured by moving the pump, moving the feed & vent or converting to a sealed or semi-sealed system.

 

[Agile]

The layout is so badly designed that I find it difficult to understand how anyone working as an installer can do it so badly.

Perhaps a good legal claim for about £1600 to replace all the pin holed rads might get them to see some sense?

Where is DeltaT to comment on just how bad it is?

Is this installer a short course plumber who was previously doing a different job?

Tony

 

[Whitespirit66]

Yes, as said, right lash-up.

Too late to cancel the cheque?

 

[Garfeild]

Jeez,total abortion,have you paid yet? if not DONT.

 

[spudkey]

Why have they fitted an ABV, the F&E does the job !!

 

[Dan Robinson]

Oh dear....

That is all.

Except, perhaps stick the pump on the return.

 

[Dan Robinson]

Why have they fitted an ABV, the F&E does the job !!

but it shouldn't

 

[vince101]

Many thanks to all. Terrific advice and I wish I'd posted earlier!. I have derated the boiler as suggested and that seems to have solved the S23 issue. (issue no.4).

Rerouting the feed/vent of the expansion tank will no doubt solve issues 2,3.

Only remaining issue is no.1 which is the intemittent firing when on hot water only duty. It's still happening. Is the 30 secs on/ 90 secs off sequence correct?

Cheers

Vince

 

[Agile]

No of course its not correct but short cycling is one of the problems you face when a boiler is seriously oversized!

Calculate the whole house heat loss, add 2 kW, and then set d0 to that value. Probably close to 18 kW !

There may be some things we can do to improve it slightly. Do you have a gate valve on the HW heating coil ?

Tony Glazier