Maximising boiler life

[colin_]

Hi

I have 3 zones across 3 floors for central heating (top two in parallel).

These come on by 2 thermostat controls with settings for 24/7 operation. During the night (10pm-4am as I start work early) the minimum temperature is set to 17 degrees. I have done this in the belief that it is better for the boiler to heat up from 17-20 degrees rather than from a lower temperature, and hence not be on for so long a continuous period, but this may not be correct and it may be better to let the temperature drop (as the boiler will come on more during the night when colder as it heats it up and then a bigger temp diffferntial so cool squicker in winter).

I have a new Worcestor boiler fitted and I am looking for advice on what the best choice would be.

1. What is best practice, have 24/7 with set temperatures or let it go colder?
2. Which would be best to preserve boiler life?
3. Which would be best to lower gas bills?
4. If off over night I preseume there needs to be a minimum temperature especially when the outside temerpature is is less than say 10 degrees, so what would be a good setting ?

I am also having an Evohome fitted so I can control the different room temerpatures better, does this affect the above queries in any way?

Thank you.
Colin

 

[Timmy D]

This will be an interesting thread.

In my opinion low and slow is best. The longer you keep the boiler on, the better. You want to reduce cycling.

Nothing you do will really make a huge difference to gas consumption. The property requires X amount of heat energy to maintain a certain temp. Weather that energy is used in one lump or over a period of time, you still need X amount of energy.

The biggest contribution to gas consumption will be insulation.

 

[Ric2013]

Agree. It will be an interesting thread.

In terms of gas consumption, the colder the house, the less heat it will lose to outside and therefore the less gas used. In theory, therefore, it makes sense to let the house go cold overnight as once the house cools down it will use less heat. This works especially if the house is draughty as any heated air in the building is soon lost to outside.

In practice, however, this does not always work (but sometimes it does). You may find the occupants are satisfied with a lower room temperature if the walls are kept warm (the surface temperature of the surfaces surrounding us often has greater effect on our perception of heat than the temperature of the air), so keeping a lowish temperature overnight rather than actually turning the heating completely off may mean you feel warmer in the morning at a lower temperature than you would had you let the walls chill to stone cold.

If you have solid brick walls, a steady low heat will help keep the wall fabric dry. If they are dry, they will insulate better, and, being kept warm will prevent condensation from forming.

Having said all this, sometimes the best way is to read your gas meter (all the digits, even the ones after the decimal point) and compare a few similar days at one regime with a few days at another. If you do this, make sure to try to keep your hot water usage similar.

 

[colin_]

Many thanks for the reply.

It is an old house and will lose a lot of heat through the walls and so it may make sense to keep it set lower.

I will probably set to a lower temperature of 15 degrees rather than 17 and suck it and see.

Main concern would be that the boiler will obviously be on continually for quite a while longer to heat up from the extra 2 degree drop but, as long as this does not adversly affect the boiler, as in th eother case it comes on more often but for less time during the night.

Thanks
Colin

 

[gmartine]

Two things will prolong the lifespan of your boiler....minimal cycling (turning on and off) and system cleanliness.

For cleanliness plate seperation is best but it's too late now you've had the boiler installed, keep a sharp eye on your filtration system (regular maintenance) and it's PH. Weather compensation is often best to prevent excessive cycling, boiler stress and excessive gas consumption because it reacts to the change in outside temperature before your interior thermostats ever can.

Evohome doesn't include weather comp so at least connect it to your boiler via Open Therm (if it can) so it can modulate.

 

[colin_]

Two things will prolong the lifespan of your boiler....minimal cycling (turning on and off) and system cleanliness.

For cleanliness plate seperation is best but it's too late now you've had the boiler installed, keep a sharp eye on your filtration system (regular maintenance) and it's PH. Weather compensation is often best to prevent excessive cycling, boiler stress and excessive gas consumption because it reacts to the change in outside temperature before your interior thermostats ever can.

Evohome doesn't include weather comp so at least connect it to your boiler via Open Therm (if it can) so it can modulate.

It will have to be maintained regularly so I get the 12 years manufacturers warranty. I will ask the people who are installing the Evohome to look into the weather compensation. Thanks, Colin

 

[Ric2013]

Realistically, (question for the gas installers on here), how vulnerable are modern Worcestor boilers to cycling anyway?

The old cast-iron heat exchanger boilers often lasted 30-50 years and were cycled constantly because they did not modulate and because I'm not sure running heating overnight was ever common back when programmable thermostats did not exist. But then there was precious little else could go wrong, certainly nothing that would put the boiler beyond economic repair.

With a properly maintained modern boiler, are the heat exchangers so fragile that a bit of cycling will wear out the heat exchanger before the various mechanical and electronic components are either unavailable to purchase or just so near their end of life that they start to make the boiler too unreliable and expensive to maintain?

 

[gmartine]

Short cycling can cause thermal stress as well increase component wear and tear, neither of which is good for the long term viability of the boiler's components or it's hex although I'd say that a system's cleanliness has more effect on the life expectancy of the hex than excessive cycling.

However as the modulation range of most boilers isn't usually adequate coupled with availability of bolt on control systems that can throttle individual emitters at the touch of a button, app or stat they can be made and do short cycle more than you think especially on poorly designed systems.

 

[Ric2013]

Thanks for that gmartine. Agree most boiler modulation systems aren't always as good as we'd like. I'd need a boiler to be able to modulate effectively down to below 1.4kW (my ground floor UFH heating load) to avoid cycling altogether. That's if I left it switched on - the fact that I turn it off at night means the radiators at least kick in with the UFH in the mornings which at least increases the load a little and reduces condensation on a boiler not designed to condense.

What's worse for a modern boiler though, I wonder - a large number of short cycles when the burner kicks in and out as the demand falls below the boiler's minimum modulation or a startup from cold when the system temperature has dropped after being switched off?

To put it into context, on a sunny winter day, I'd guess my own house runs the boiler at around a 50% duty cycle in the mornings for an hour or two until the sun takes over, and then for perhaps 15 minutes an hour every hour after the sun goes down, but at full output for those 15 minutes. At 21.00 or 22.00, the heating goes off. Heating a vented cylinder from cold seems to take the boiler output for 30 minutes, and then the boiler runs increasingly short cycles for another 30 minutes until the thermostat is satisfied. In this sort of environment (a bad system), how long would you give a modern condensing boiler, assuming the water quality was maintained?

 

[SJB060685]

Unfortunately nothing is made like it used to be. My dad used to have customers with 30-40 year old oil boilers. Now, even with proper water management and burner maintenance most boilers won't reach 20 years.

 

[EvilDrPorkChop]

Unfortunately nothing is made like it used to be. My dad used to have customers with 30-40 year old oil boilers. Now, even with proper water management and burner maintenance most boilers won't reach 20 years.

Think you'd be lucky if you get 15.

Got to remember though a combi does a lot of work, lots of moving parts etc, where as 30 years ago they were just heat only boilers.