Central Heating problem and unexpected cause/fix

TadleyBaggie

Background: 4 bedroom detached property, Glowworm Energy 25r system boiler with a MiGo thermostat.

I noticed late last week that the temperature in the house was sitting at around 18 degrees (as indicated on the thermostat ) and although the required temperature was set to 19 degrees, the boiler wasn't running normally. The indication on the boiler that heat was being requested (flashing radiator symbol) but the temperature of the boiler was at best 40 degrees. Hot water however hasn't been a problem however, i.e. nobody complaining of cold showers.So this seemed to indicate the boiler was basically working. Ran the hot tap for a while and when requesting hot water the boiler fired up normally.

I also have a Netatmo weather station with two indoor sensors, by going back I could see that the last morning that the system ran normally was the 18th October. At 7AM the thermostat setting is automatically changes from the overnight setting (16 degrees) to the daytime setting (19 degrees). This should result in the CH firing up most cold mornings for a period to achieve this, visible in the temperature graphs. So something seemed to have happened on the 18/19th October.

I called my boiler cover provider and an heating engineer was dispatched. He checked the obvious things, such as was the pump running (yes) and were the zone valves operating normally (again yes). He was a bit baffled at this point and so called Valiant tech support, they ran through a few boiler checks which were OK. They then asked how the MiGo thermostat was configured. Asked me to check the "heat curve" value. It was set to 1.2, was asked to change it to 2.3. Within 30 seconds the boiler fired up, temperature rose to 65 degrees as it used to. System now working normally and radiators starting to get properly hot.

So what had happened on the 18th? The answer was I switched to a new iPhone and the MiGo app was was reinstalled and the previously MiGo app settings were set to defaults. It seems the default value for the heating curve is 1.2 which is probably fine for a small house, but not mine. Heating engineer had never come across anything like this before. Seems every day is a school day!

Ebe_Scrooge

A great example of why sometimes the old-fashioned technology is better - a simple thermostat where you twiddle a dial to set the temperature you want.  I can't fathom the need for "smart-everything"   :-)

tacpot12

Thank you for posting this. It could turn out to be very useful for others.