Which thing uses about 30watts, the fan or the pump?

23 Jan 2011
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United Kingdom

I have a WB Greenstar 8000, 35kw. Under warranty, serviced yearly. Installed 2 years ago.

I noticed via our smart electric meter than something somewhere was consuming about 30 watts constantly. After much searching I noticed than something in the boiler is running all the time. It consumes about 30 watts. This will be happening when the boiler has not been on for hours and will not stop unless you turn it off at the switch.

I am going to call WB but I wanted to be able to give good information. Does anyone know if 30 watts approx would be the fan or the pump?

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It says the pump uses 108Watts running and 1Watt in standby, it doesn't mention the fan, although this only runs when the boiler is consuming gas. In what way is the boiler running? Try turning it off and see what is being used then?
30 watts sounds about right for the fan. We have a Vaillant 35kW c ombi and when running consumes approx 150W. Fan should only run when the boiler is on and then after for a while when it's gone off to cool the heat exchangers etc.
Thanks guys, it is definitely the fan then, as when everything is fired up is uses about 140 watts, so that would be about 110 for the pump and 30 for the fan.

One thing that worries me is that this issue is not necessarily reproducible on demand. It is happening 75% of the time, but not 100%.

In order to help an engineer I wonder if I should say video the boiler for an hour, where you can hear the fan running but see that no demand for HW or CH occurs, the flame never lights, and then with the smart meter in view, turn it off at the wall to see the 30watt power drop and the noise from the fan stop.

I am only thinking this, is I had a microwave on the blink and the engineer initially was not planning on doing anything as the issue would not present itself there and then, but once I showed the video he fitted a new pcb and the problem never came back.

30watts may not seem a lot, but sometimes it is 24/7 and that cost can mount up.
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I would get the guy out who installed it to check it out especially if it's under warranty. You could phone WB direct but there are plently of WB approved heating engineers about.
The water pump will be the much larger load, between fan and pump, though 30w seem excessive for just the fan on it's own.

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