Hi again @Crìstian,

So... responding to your points in quick succession:

1. The radiator with no TRV is generally called the "bypass" or "Over-run" because it needs to remain open when the boiler switches off and the pump runs for a seconds more to remove the very hot water from the boiler heat-exchanger.

This bypass radiator should be in the same room as your wall-thermostat.

b. Many C/H systems do not require a bypass radiator. If its preferred position did not coincide with the best position for the wall thermostat, then it was common practice to install a "bypass loop" within the pipework somewhere. You should have one or the other, but not both.

c. Most modern pumps do not require a bypass because they operate in modulating mode. They have a sensor which checks the flow in their output, varying as TRVs open/close. This uses a feedback loop to change the pump speed accordingly.


2. Condensing Mode: You only use "more gas" if you heat the C/H water so high that it retains most of its heat in the return rather than releasing it through the radiators.

Having the temperature set too low merely means that the boiler will simply fire up too often in an attempt to keep the house warm. (The hysteresis cycle is too great). This will induce extra wear & tear on the boiler, reducing its service life.

I still think 60°C seems low. If ambient temperature was steady for a few hours (an overcast, rainy day perhaps) you could time how many occasions the boiler fires up over an hour when set at 60°C and 70°C. But your experiment is obviously ruined if other factors kick in such as an external door being opened.

As you suggest - it's a matter of hitting a happy medium.

I once tried to hit a happy medium... but she kept ducking. That's clairvoyants for you! :P


3. A quick online check suggests that your CH/ feed is at extreme left, and the return is extreme right.

The second pipe from the left is the safety-valve relief pipe and should be empty. It's not shown at all in the above diagram.


4. I don't think you'd get adequate contact with a copper pipe using a cooking thermometer. You could try wrapping it parallel to the pipe with strips of aluminium-foil - basically encasing it within a thermally-stable environment, controlled only by the return water temperature. But its response time may just be too sluggish.

I have a thermometer probe as an accessory to my digital multimeter. This is small and responds very fast.

Hope that helps.

How's the counting going on the boiler firing @Crìstian?

Here's a photo of the multimeter type I use showing the temperature probe in the centre.

The last time I bought one of these, in 2016, I got it direct from China for about £14. But they're actually not much more than that now on Amazon.

If you tape the small sensor to your boiler return pipe, you'll get a reasonably accurate readout of the water temperature being returned from the radiator circuit. Once this reaches around 55-60ºC, the boiler will have dropped out of condensing mode. In cold weather you can sometimes get a visual indication of this by watching the white vapour leaving the flue outside.

Hi @Crìstian and hi to any visitors to this boiler page. 

 

I wanted to share two recent guides our Content team have written:

 

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If you’re thinking about it and wanted some advice from forum members who already have a heat pump, just create a topic to ask your question and we’ll make sure you get an answer!