Combi boiler heat curve

Alkers

Had our Viesmann combi boiler serviced last week, and the plumber said he reset the heat curve as it should save money.

I had a look there and the heat curve is adjustable in increments of 5 between 0 and 35. The plumber set it to 20.

The next day my home office failed to get up to temperature (we have smart TRVs in all rooms) and the heating system recorded nearly 12 hours of boiler run time

I set the heat curve back to 35 and all is well, office heats up in an hour and I'm getting 2 or 3 hrs run time per day even with the cold snap.

Should I try to reduce the heat curve or just leave it at 35? Is it more efficient to have the boiler ticking away all day rather than heating at full whack to get temps up asap?

1950s house retrofitted to A3.

10-10-20

I think that's one of those "that depends" answers, but others will have stronger opinions.

I take the view that if you need the heat during the day (ie there is somebody in the house) then it should be left running at the minimum set-back to maintain the temps. Otherwise Id be one for just turning on the heat for a blast or as-needed in the evening.

Does the boiler have weather compensation fitted and is the office external to the main body of the house? I think I would have increased the curve by one and then checked the office after a few hours, then increment it again if needed. Try set it to 25 or so once this very cold spell ends on Saturday or so?

Alkers

Thanks for that, there is weather compensation on the boiler yes, fitted on the north facing front of the house.

The home office is internal in the house, an old bedroom but is only heated three days per week (2 days in work's office and not used weekends). On my work office days, there is no one home and heating only comes on in the evening after a short blast in the am dependent on temperatures.

With the heat curve at 20, the office couldn't be brought up to 19.5c which I have it set to for work. There are only two increments between 35 and 20 (25 and 30) so I'm surprised the setting change had such strong an impact.

10-10-20

Maybe the office is getting too cold on the days where its not used meaning that the heat supply isn't sufficient as the house is being satisfied long before the office comes up to temp? Maybe ot needs to be less isolated between times. Just a thought.

dbas

Can you measure flow temperature on the pipework?

I'm interested to see what difference those options make. Plumber set at 20, and you changed to 35. Wonder what the flow temperatures were at both settings

Does your system record heat output from the boiler.

stiophan

Would it not be best to contact your service engineer and note the change in temp. Why not set it to 25 and see what happens? Should be able to monitor the gas use for a few days (bar any dramatic cold snap) and see what works.

Alkers

Yeah have been putting off tinkering while it has been so cold but will have another look now next few days and update the thread!

John.G

Can you post these WC curves, these are normally in single digits like the one for a Vaillant boiler, below.