Vaillant Ecotec boiler

[Doctor5]

Three years ago I had a Vaillant Ecotec Condensing Boiler installed in place of my old Potterton (which worked fine). From the outset I had a problem with the overheat warning (Code S 53 on the diagnosis system). Three different Vaillant engineers said that the boiler was OK and the problem was that insufficient water was circulating in the system. The installer,of course, agreed despite the fact that the system worked with the previous boiler. I called on another plumber who also agreed and said that it was due to the system being a single pipe one.
So I paid to have the house re-piped as a dual system. This seemed to alleviate the problem although I had to have the hot water and heating on together and the house never heated above 70 deg even with everything set high. I now find that the colder the weather outside, the more cut-outs I get.
Another plumber tells me that he has heard of this problem and that it could be due to the boiler being too large at 28kW and that I should reduce the setting. I calculate that my 10 radiators need about 15Kw plus say 3Kw for hot water. Anyway, I tried to turn the setting down but it won't go below 24 Kw.
The sytem is a vented one and the pump is a Grundfos UPS 15-60, running on 3.
Some of my radiators are single panel and I am willing to have them changed for double panel with fins to increase the load if that would help (I could use some extra heat anyway) and/or is there a bigger pump which would circulate the water more quickly?
If anyone can advise I would be grateful.

 

[bobw1956]

Press the i and + buttons simultanously
takes you to D0 part load setting
to reduce this setting press the minus button to 18
to save this setting press the i button for 5 seconds or untill the new setting stops flashing

Sounds like your boiler has a blockage,the first place to check is the rubber hose

 

[kevindgas]

use d.0 to adjust the settings

allow 1.5 kw per rad and 2kw for a cylinder if you have a system rather than a combi

press i and + together to get d.0
press i
adjust the number to the kw you need
press and hold i for 5 seconds until display no longer flashes.

 

[gas4you]

Do you have a 400 series boiler? If so the S53 is annoyingly too common on these.

S53 is not an overheat warning, it is just the boiler waitng for the correct temperatures to be read by the ntc's. More often than not caused by poor circulation.

If you have a 400 series the pump should always be set on max speed.

 

[Doctor5]

Thanks to the instructions on how to set the heating to part load I have suceeded in re-setting the load to 18kW. The boiler is running at the moment but it is usually better after it has been 'on' for two or three hours, so I'll reserve judgement until after start-up tomorrow.
For 'gas4you': it is a 428 and the pump is on maximum speed, which is why I enquired about a bigger pump--if the circulation is poor despite the re-piping that was done, would a bigger pump force the water around more quickly? Any idea why the problem seems less when central heating and hot water are both selected? This seems counter intuitive!!

Thank you all for your interest and help

David

 

[gas4you]

When both heating and hot water are on there is the possiblity of greater flow through the boiler.

Other than that it could be the heating circuit is too restrictive on its own.

 

[Agile]

David, you seem to have had a nupty installer who has fitted a boiler which is nearly twice as powerful as you needed.

15 kW + 2 kW ( for water ) = 17 kW so an 18 kW is what you needed!

Resetting maximum power output to 18 kW will probably cure most of the problems but it will still be over cycling as the minimum power output is far too high for your needs.

You seem to have had a complete nupty installer who not only fits a boiler to a one pipe system but seriously oversized it.

Tony