Posted By: djhwireless Friedland bell

My dream is to find a wireless door bell with a vintage looking bell push.....oh lockdown has gone on a very long time!

So, been doing lots of temperature readings at the thermal store. For context, the Boiler is on a timer that came on at 14:30, and downstairs CH doesn't come on till 16:00 (upstairs comes on at 18:00), but only started taking readings at 15:10...when i remembered to do it!

See attached a pdf version of what I found. I thrilling read no doubt!

Posted By: Peter_in_HungaryLooking at the boiler temps. it looks like the boiler is not producing the heat. During the 15:10 - 15:59 time was the boiler running full chat tor this time or was it cycling or modulating down? This will tell your if the boiler was/is set somehow to 62deg. or just not capable of producing its design temp.

With no heat load and in 50mins with the in/out temps remaining the same at 62deg it looks to me as if the boiler is set to about 62deg (or 65deg ?). Once the heating starts the boiler temp.drops in line with the return temp. - no surprise there but perhaps a note that I would expect the boiler to be able to raise the temp. by more than 10deg.
However with the boiler holding 62deg.flow temp its not surprising the CH fails.

Unfortunately I didn’t have time to check what the boiler was doing, but I admit that would have been useful. The TS is on the 2nd floor and the boiler in the basement, so swapping between the two is a trek! However, will take readings tomorrow on flow and return at the boiler and make note of how it’s behaving.

Should have said that these readings were done with the control stat on the TS set to maximum.

Posted By: djhBetween 15:20 and 15:59 what was the boiler doing? It looks like it was off but the pump was still running circulating water from the TS through the boiler and back.

Once the CH turns on you've got a steady 10°C difference across the boiler, and no difference at all across the radiators, and the CH flow temp is about the same as the boiler return.

I'm really not sure what it all means. The TS confuses things in my mind. I think your pump rates are definitely high enough now and maybe would be worth turning them down a bit. But quite what the CH flow matching the boiler return means, I have no idea. And it seems clear there is something limiting your boiler's flow temperature that we don't understand yet. Another stat, or a fault maybe?

I think the boiler is going dormant (I.e. burner not running) and the pump just running when the CH is not on.

I’ll be frequenting the cellar to check the flow and return temps on the boiler tomorrow, and check when the boiler is actually firing. Sneaking suspicion it’s a fault on the boiler, along the lines it thinks it’s up to temp and powering down but keeping the pump running because the control on the TS demanding it. Perhaps a faulty internal stat on the boiler (that doesn’t get tested in a service) or something wrong in the settings on the board.

Posted By: Peter_in_HungaryWhen did this problem become apparent - and did anything happen to the system immediately prior to this?

It’s been going on a while, hence our massive solid fuel usage to try to get, and keep, the TS to a decent temp.

I am surprised this didn’t come up in the service.

Plumber (@ListysDad) hopefully coming next week, so will investigate further then.

Those temp results show what would be expected of a boiler set to control output to roughly 62oC. Not withstanding that 10oC delta T isn't amazing, but we don't know what the CH pump speed and modulation is set at (until you check the parameters), so assume it's fine for the moment.

The boiler is being called by the TS, but will only fire up once it draws water from the TS that takes the boilers internal temp sensor down below the set point. Remember, the set point isn't one number, otherwise it would constantly cycle. It may off@62 and on@52, for example.

Before assuming the boiler is faulty, have you been through the set-up parameters to CHECK not CHANGE anything. This boiler has quite a lot of functionality, not a bog standard unit. The factory set values are all shown, so you just need to visually confirm the settings are as per the manual. The key one to watch out for is the "Heat Only" parameter. Otherwise, the boiler could be looking for DHW temp limits etc.

You can also do a basic boiler test, by forcing a run at max power. This is a standard test option in the installation manual 10.9.1. It's for testing flue gases, but you just want to see can your boiler accelerate to full speed, and how does it perform, checking the boiler flow & return temps. (CH temps aren't important at this point. That's a later test involving the configuration at the TS and pump speeds. Confirm the boiler output first).

Bottom line - your boiler may be working fine, doing it's job, but its control is telling it that it's job is to make water only at 62oC. I'd still like you to do a hand drawing of the system (don't bother with fancy electronic drawings), especially around the TS, to see pipe connections and stat relative heights. That's the next step after understanding your boiler and getting it to make water hotter than 62oC, but will enable you to control the status of the TS, and how the DHW/CH are served.

That's good. Puts any queries about settings to bed, and also gets you a bit more knowledge/confidence with the boiler.

Deleted.

Posted By: GreenPaddyThat's good. Put's any queries about settings to bed, and also gets you a bit more knowledge/confidence with the boiler.

My recurring nightmare is I change some setting I can’t undo and we all end up huddling round the fire until spring!

Posted By: Peter_in_HungaryBenm85 - you said there was another thermostat (DHW?) set to 65deg. Has this been jacked up as high as it will go - and what is the top temp. available on it?

65c is what the DHW is set to on the boiler, should it be running as a combi. Think it’s a red herring that, as it’s definitely in Heating Only mode now I went through the settings.

I was taking readings at different times today, as work was much busier and didn’t have the time to keep popping up to the TS. I did register a reading of 73c in the boiler flow at the TS for about 30 seconds, before the boiler must have knocked off and it went back down to 60c odd (with no CH on). Control stat was set to max. Still same issues after CH came on this evening, boiler can’t get the TS back up to temp to keep the CH at anywhere near 60 or 65c.

Have a look at the electrical terminal rail in the boiler that I mentioned previously. Its the only way you know whats connected to the boiler. Post up a photo if you can