Combi Boiler where are the sensors

[Agile]

You seem to be missing the point here.

If there is air in the pipework after the boiler then any pressure fluctuations at the supply side of the boiler will cause a water flow through the boiler. An increasing pressure will cause the air to be compressed.

Any flow detection device will respond, whatever the type, as it is a real flow occurring!

 

[Terrywookfit]

These may be from the wrong manual. The manual is a public domain document

THESE INSTRUCTIONS APPLY TO UK MODELS ONLY
THESE INSTRUCTIONS ARE TO BE LEFT WITH THE APPLIANCE



Which suggests the flow switch operates on pressure or pressure fluctuations due to very small amoumts of flow as the air trapped in hot side pipe work is compressed by the water hammer of the cold tap shutting off.

If the flow switch is a pressure ( differential ) operated device and the mains pressure is as high as quoted then possibly the switch is unable to detect the comparatively small change in pressure due to the tap close to the boiler. ( small percentage change ) Pressure reduction valve on the incoming mains may be needed.

The OP asked where the flow switch is located.

View attachment 110414

Wrong again. OP has said the boiler is a Greenstar 18/25!!

 

[Terrywookfit]

Not a problem if your water supply is not metered but if the customers is on a metered water supply then the cost of wasted water has to be included in the overall cost ( savings ? ) of a combi installation.

The Boiler / Heatslave tank is pre heated and stored.
A draw off for hot water only wastes the same as a conventional system would. ie the volume of the pipework!

 

[AGAS]

bernardgreen that shovel is getting worn out

 

[steph57]

Hello folks,
Thank youy all for your comments on this issue, i did start by admitting to being an ignoramus on this matter and now know a little more, namely:

1. There are no sensors in or on any of the pipework in the system, all the sensing is done within the boiler mechanism itself.

2. We had previously been mislead about combi-boilers having been repeatedly told that there is no hot water tank with a combi-boiler when in fact there is a hot water tank, albeit a small one, built into the boiler itself.

The second point is important because it seems to be the way we have worked round our problem. It seems that when the boiler is turned on for hot water it should burst into action to heat up this small hot water tank irrespective of any flow in the system. However, we had the hot water control on our boiler down at around 1.5/2 and for some reason (tired thermostat?) this did not result in the boiler firing up to heat this hot water tank and the boiler waited to detect a flow before firing up. We have now found that by turning the thermostat up to 3.5 (Max setting 6 so should be safe enough) it will now fire up and heat this hot water tank irrespective of any flow in the system. This hot water tank gives us all the hot water we need for our compact utility sink. It also means that we are having to run less water through our other taps before we get a hot water flow. We suspect that some aspects of the system may be (like us) a bit old and tired and we will get our plumber to look at them when we next have a service but it looks OK for now.

So our apologies, in essence and from a position of ignorance, we seem to have started a whole technical discussion which we have eventually solved by turning up the hot water thermostat! oh well you live and learn, thank you all for your comments.

P.S. Running less water is helpful as water is very expensive in the South West, the combined sewage and water charge on our metered supply is £5.35 per cubic metre, which over the last 12 months resulted in a total water bill of £559, whereas Moorland fuels have just delivered 800 litres of heating oil for £337 and this will last us 9 - 12 months depending on the weather. So for us saving water is a higher priority than saving fuel.

 

[AGAS]

FFS ... 3 pages and you didnt have the stat turned up

 

[Dan Robinson]

LOLs