This was a repair I did on a Vaillant System boiler which was an ecoTEC Plus 637, for a customer in Sheffield S10 this week. The issue being that they had no hot water and no central heating.
Vaillant used to manufacture a control unit that could be used to control the hot water and central heating etc, which would be wired in instead of a conventional wiring centre. The thermostat being used on this system being the VRC 430F. The control centre communicates with the boiler via a BUS and is also connected to a sensor on the cylinder.
The actual thermostats in my opinion are way too complicated for the average person to understand and a time consuming pain for an installer to setup. Plus the control centre is very expensive and now obsolete, so if you have a system like these with a faulty thermostat/control unit then you have to replace it with something else. On top of that the average “plumber” or whatever is unlikely to understand how to the control centre/thermostat works hence making repairs more difficult.
The control centre itself also has limitations because you can only have two zone valves plus the cylinder valve wired into it. As such, having a third zone is not possible with this control centre and the only way to add an extra zone is to replace the control centre with something else such as a conventional wiring centre.
Now a system with this Vaillant control centre works a bit like a combination boiler in that you can only have hot water or heating working at any given time. When the cylinder needs to be heated the central heating valve closes, the hot water valve opens and the cylinder is heated until the control centre is satisfied its up to the desired temperature.
Blocked Vaillant filter inside manifold
The reason that the central heating or hot water wasn’t working on this system is because the hot water zone valve had failed in the closed position. As such, when the control unit was trying to heat the cylinder the heat wasn’t getting through and the control unit was never getting to a point where it was satisfied because the tank wasn’t warming up. As a consequence the heating wouldn’t come on until the cylinder had heated up.
When the heating had been working only the two upper floors had been getting warm. The previous guy who had a look said the Vaillant control unit/thermostat was faulty and was the cause of these problems which wasn’t the case(they do fail though sometimes).
So my diagnosis was that they needed a new pump, pressure sensor, hot water zone valve motor(which turned out to be a loose wire in the valve strangely enough). The central heating valve did need a new synchro motor because that was failing. The expansion vessels in the boiler and cylinder were completely flat and needed to be recharged. Also there is a little plastic filter in the boiler on the flow pipe which tends to get blocked and this needed to be replaced.
So in one visit I was able to determine the cause of all the issues and replace all the components necessary, get the hot water and heating working back as they should be and service the boiler and cylinder(properly).
Vaillant VRC 430F control centre
Areas where I can repair your Vaillant ecotec plus system boiler
I am located in Elsecar, Barnsley, South Yorkshire. I cover a large part of South Yorkshire including most of Sheffield, Rotherham and Barnsley. I also cover a small part of Doncaster.
Sheffield:
I cover most of Sheffield including central Sheffield, Chapeltown, Ecclesfield, Grenoside, High Green, Oughtibridge, Thurgoland, Wortley, Aston, Aughton, Swallownest, Todwick, Hillsborough and Stannington.
Rotherham:
I cover the whole area of Rotherham including central Rotherham, Brinsworth, Catcliffe, Canklow, Masbrough, Treeton, Whiston, Greasbrough, Kimberworth, Thorpe Hesley, Rawmarsh, Wentworth, Bolton-on-Dearne, Goldthorpe, Thurnscoe, Wath-on-Dearne, Mexborough, Swinton, Kilnhurst, Hooton Roberts, Ravenfield, Thrybergh, Bramley, Hellaby, Maltby, Thurcroft, Wickersley and Braithwell.
Barnsley:
I cover most of Barnsley including central Barnsley, Birdwell, Stairfoot, Worsborough, Kendray, Ardsley, Athersley, Monk Bretton, Lundwood, Royston, Brierley, Cudworth, Cortonwood, Great Houghton, Shafton, South Hiendley, Brampton, Darfield, Wombwell, Hemingfield, Elsecar, Hoyland, Jump, Barugh Green, Cawthorne, Darton, Dodworth, Gawber, Mapplewell, Pogmoor, Staincross, Wilthorpe, Worsbrough, Thurnscoe and Tankersley.
Doncaster:
I cover a small part of Doncaster including central Adwick, Conisborough, Edlington, Warmsworth and Mexborough.