Another combi boiler hot water question

[Max Demian]

Diverter valve.

DHW thermostat.

[John Rumm]

Not sure about that - all it can do is fail to divert (either at all, or completely), that would leave the rads still partly in circuit. That will increase the heating load rather than reduce it.

Possibly - although I would expect it to shut off faster and also produce water not actually hot enough in the first place if it were over reading. Could be worth disconnecting it from the PCB, and measuring its resistance though.

[AnthonyL]

New one put in 2017 though a lot of problem initially with cutting out due to a microswitch lever setting. I've not checked whether the nearby radiator gets warm when the CH is off.

I've taken some smartphone video of the panel whilst doing some tests. However I wasn't smart enough to use a smaller resolution that the max I can readily upload to video.com and I'm sure no-one really want 2Gb of LEDs going on/off.

I'll post again once done.

Meanwhile I note that when I run the hot water into a basin it looks creamy which then settles and I'm assuming it is just very small air bubbles.

The Severn Trent website describes the water in the area as "Moderately hard". It gives a full list of chemical etc found in the water, but not Calcium (I thought that's what I'd be looking for.

There's no major issue with kettle furring. Not too happy about Arsenic, Benzine and e-coli but I doubt that boiler minds.

[The Natural Philosopher]

I am sure handbrake could edit that down a bit.

[John Rumm]

As TNP suggested, Handbrake could squish that into something far smaller if you want.

Yup, not uncommon...

They may give a figure for overall hardness in degrees Clarke?

[AnthonyL]

My Handbrake installation (requiring also an install of Framework) failed but I've also had a flakey connection for a day or so. Anyway copy/pasting a FFMPEG command into my Linux terminal worked without needing any addition software and has seriously reduced the file sizes.

There are three videos, sorry a bit like watching paint dry, with narrative included to say what I'm doing:

I've left the temperature setting at minimum and my wife has just had a shower, needed the Mira turned right up to max which we've never had before and it was just hot enough for her and no cut outs. So that, plus possibly what is to be seen in the videos, indicates that something is overheating.

Noted

Analysis Typical Value Hardness Level Moderately Hard Hardness Clark 13.53

That was for the year to last September.

[Thomas Prufer]

Maybe the heat exchanger between hot water and combi water is furred up. Low flow, combi can't dump heat to the DHW fast enough. And local hot spots in the heat exchanger cause more scale to precipitate, starting a vicious circle.

It's possible to descale them by pumping a suitable acid through the combi, heat exchanger in situ...

Rothenberger, for instance, make units with an acid tank, reversible pump, hoses, and bells and whistles. Nothing you can't jury-rig with a "drill pump"...

Thomas Prufer

[Andrew Gabriel]

I've done one. I took it out and did it in a washing up bowl. It used a lot of descaler (Furnox DS-3). There was also a lot of rust debris caught in the primary side, which came out during the descaling.

[Jim K..]

+1 Sounds extremely likely. Turn hw temp setting down, try experiment again?

Perhaps watching wife showering unless they are both boilers? :-)