Heating control temperature settings

5500

Hi Guys

I have 3 zone gas central heating installed. When the RGI last serviced the boiler, he set the temp at 60 on the boiler itself, and said this was the most economical setting and to leave as is.

With the zones he advised not to overlap times, eg none are all on at the same time, again saying it was the most economical way. Stats are set at 20 downstairs and 18 upstairs.

No issues untill a friend was asking me about bills ect recently and was saying the boiler should be at a higher temp eg 70+ to be most efficient, and that it's probably costing more in the long run as its taking longer to get to temp, and that it costs the same amount to run upstairs/downstairs together and no need to split times unless yiu don't want upstairs warm ect

Is said friend talking cr@p and the way the rgi set it the way it should be?

Domicio

"he advised not to overlap times" -- I was having a discussion with my wife about it earlier today as we also have a 3 zone system.

I think it does make sense to don't overlap but it is just a guess.

Regarding the boiler temp, mine is the Ideal Logic Max System Boiler and it runs around 68c, as advised by the supplier as the most efficient temp.

5500

His argument was that the water is circulating in the system, so say turning on upstairs at the same time was no different. My assumption was that it's more water to heat/boiler has to work harder and use more gas so not as economical.

The boiler is a worcester bosch greenstar, I noticed there's an actual "eco" Mark on the temp dial, which is at 60 degrees and where its set, incidentally was chatting to a friend about same this evening with a glow worm boiler and they said theirs is set at 75, so I'm wondering is it boiler specific or house/system specific

KildareP

https://www.boards.ie/discussion/2058219493/heating-control-temperature-settings

Running your boiler at higher temperature is not more efficient - especially if it's a condensing boiler. Condensing boilers operate at their most efficient when the water coming back from the rads is 54C or lower (lower the better). Any higher and the condensing effect is significantly reduced. Running a condensing boiler at a flow temperature of 70C or higher, unless it's a severely undersized boiler, means the temperature going back to the boiler is very likely above 54C and so it's only going to spend the first few minutes condensing and won't be as efficient as a result.

Older boilers, on the other hand, need the return temperature to be above 60C so that they don't condense on their heat exchanger which will eat away at the heat exchanger. That's why older boilers would have had flow temperatures of 70C or 80C. A lot of people seem to confuse condensing boilers not getting the rads as hot as not being as efficient but it's consuming less oil or gas as it's extracting most of the heat that an older, non-condensing boiler (or a condensing boiler with too high a return temp) just blows out the flue.

In terms of rads on, rads off, if you close the doors upstairs and then only run downstairs rads then yes you will use less fuel. Heat out is always less than heat in (from burning fuel). More rads means more heat needed means more fuel needed since the whole point of a rad is to "lose" the heat from the water into the room. The more rads you have losing heat, the more heat your boiler has to replace into the water.

Of course, in practise, if you only run downstairs rads then heat will naturally move upstairs, meaning downstairs will take longer to come up to temperature and the downstairs stat will be calling for heat more often to maintain temp. But it certainly won't consume the same amount of fuel as having both on when you don't need upstairs heated.

A lot of heating is horses for courses - my own system is set to a flow temp of 50C (well insulated house with big rads) and we have the heating "on" for 2 hours in the morning and 4 hours in the evening. We use about a tank (1200L) of oil a year and the house is a relatively steady 20C within an hour of the the heating being turned on. The rads are warm - you could keep your hand on them comfortably. The boiler spends all of the operating time in condensing mode. It's also a good test to prove an A2W heat pump would work for us down the line to retrofit in place of our oil boiler without having to change or add rads. Only issue as such is we need to whack the immersion on for 2 hours once a week for legionella prevention.

Whereas the neighbour, same boiler, same house, has theirs up at the max flow temp (75C). They go through as many as 3 fills a year (3000L!) but they have the rads practically hopping off the wall as they like the house to be t-shirt temperature year round.