Boiler central heating dial

Jeepers_Creepers

chrisw said:

Bear in mind that a radiator at 80 degrees will be extremely hot to touch and could cause burns if in skin contact for more than a few seconds.

Absolutely. Very dangerous especially for young kids and the elderly. The rads themselves will almost certainly be slightly cooler than the boiler-delivered water temp, but still - that's burn hot should you not manage to remove the skin contact in an ouch-instant. 

quattros

Jeepers_Creepers said:

quattros said:

Jeepers_Creepers said:

Doesn't it has a series of lights on the front panel to indicate temp? Seems it's adjustable between around 35oC and 85oC.

Anyhoo, set it at a temp that makes your system work well - heat up your home adequately fast - but no higher. In warmer months when it's likely only to come on during the coolest parts of an evening, turn it down lower. It's very scientific :-)

Hi yes infact it does have a series of LEDs but I don’t think they light up when turning the dial on their own only when system is running up to temp , So i will have to try and set it when the heating is on , What sort of Temperature should the CH be set at ideally ?

As low as possible that still works :-)

1) When do you turn up your heating in the mornings?

2) And from what overnight temp to what 'morning' temp?

3) And how long does it take to get to that comfy morning temp?

1) When do you turn up your heating in the mornings?   Well i have set the Heating to come on from the room stat from 4.30 am as i get up at 5am for work sometimes .

2) And from what overnight temp to what 'morning' temp? I have recently turned up the low temp to 19.5 degrees and then to turn off after reaching 21.5 degrees , The Room stat is in the living room. I have set the it so at 10.30pm the heating does not come on till 4.30am in the morning.

3) And how long does it take to get to that comfy morning temp? I Would say roughly about 30 mins ish 

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Jeepers_Creepers

quattros said:

1) When do you turn up your heating in the mornings?   Well i have set the Heating to come on from the room stat from 4.30 am as i get up at 5am for work sometimes .

2) And from what overnight temp to what 'morning' temp? I have recently turned up the low temp to 19.5 degrees and then to turn off after reaching 21.5 degrees , The Room stat is in the living room. I have set the it so at 10.30pm the heating does not come on till 4.30am in the morning.

3) And how long does it take to get to that comfy morning temp? I Would say roughly about 30 mins ish 

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So you give your heating roughly half an hour to do its business? And it manages fine? Cool.

What's the 'low' temp - your overnight temp? 19.5oC? Blimey, that's balmy :-)

I would have been looking at an overnight set temp of 14 to 16 oC (that's why Gawd gave you a duvet) and going up to 20 or 21oC for the morning. Based on that, if your system gets from 16oC (in reality most houses will be warmer than this as they retain heat quite well overnight) to 20-21oC in a half hour, that's pretty good.

So, at what setting is your dial for this performance? 3/4-up?

And are you happy with the rad temps - not too 'ouch'?

It won't make a huge amount of difference, but if you can tweak the temp control down without losing your current performance, then do so - it'll probably save you a teeny bit as your boiler will be slightly more efficient. But if you find that you no longer get the cosy 21oC temp by 5am, you've probably turned it down too far...

There's no point chillin'. But don't have it higher than is needed either :-)

Ectophile

Any condensing boiler is best not run at the maximum temperature, as it becomes less efficient.

A condensing boiler pre-heats the water going into it by passing the flue gases over an extra heat exchanger.  The steam mixed in with the exhaust condenses out onto the heat exchanger, warming the incoming water.  the condensed water drips away through the condensate pipe.

But that only works if the heat exchanger is below about 55C.  If you crank the heat up to max, then even after passing through your radiators, the returning water will still be over 55C, and the condensing feature of your boiler won't work.  You'll get a big plume of steam coming out of the flue, and that's wasted heat.

It will depend on your heating system, but an output temperature of around 65C is probably about right, and also won't leave you with scalding hot radiators.

Jeepers_Creepers

Ectophile said:

Any condensing boiler is best not run at the maximum temperature, as it becomes less efficient.

A condensing boiler pre-heats the water going into it by passing the flue gases over an extra heat exchanger.  The steam mixed in with the exhaust condenses out onto the heat exchanger, warming the incoming water.  the condensed water drips away through the condensate pipe.

But that only works if the heat exchanger is below about 55C.  If you crank the heat up to max, then even after passing through your radiators, the returning water will still be over 55C, and the condensing feature of your boiler won't work.  You'll get a big plume of steam coming out of the flue, and that's wasted heat.

It will depend on your heating system, but an output temperature of around 65C is probably about right, and also won't leave you with scalding hot radiators.

You've succinctly summed up what was my understanding of this too - until a plumber on another forum added slightly to what's going on with HE boilers.

The first is that the boiler will still 'condense' to some degree even if the return temp is higher even than 60oC. Obviously not as effectively, but it's all about 'saturation' levels or summat. The flue gas contains a LOT of 'steam' which is created in the combustion process. Steam is invisible. The flue gases are pretty saturated with this water content given that it's at a pretty high temp, so it'll condense out even on warm surfaces like the return exchanger. Not as much as it would on cooler surfaces, obviously, but still some.

Place your hand on the return pipe after your system has been running for an hour and is fully up to temp - good chance you won't be able to keep your hand on it, which suggest it'll be at around 60-odd degrees. BUT, your boiler will still be producing slugs of condensate.

The other issue is the visible 'plume' that comes from your flue. That's a specific feature of condensing boilers, and what you are seeing there is not 'steam' - which is invisible - but water vapour which is a sign of the flue gas being at a lower temp and the steam having been condensed out to visible water vapour - and that's due to a correctly working return exchanger which has extracted useful heat from the flue gas, cooling it and thereby producing the plume.

If you can recall pre-HE boilers of old, you wouldn't see 'plumes' coming from their flues as the exiting gas was too hot; hold your hand over the flue terminals of these and you'd receive some nasty scalds if you didn't remove it pdq. Have you tried testing the temp of exhaust from an HE boiler? 'Warm' at most - no risk at all of 'ouches'. They really do work well.

A downside of HE boilers due to this preferred lower working temp is that normal-sized radiators will struggle more to provide enough warmth. If you were starting a system from scratch, you'd fit oversized rads in order for them to provide the same output at a lower water temp.

When we bought our current house, the owners had a 30+ year old Mexico floor boiler in the kitchen, with an enamelled flue pipe coming off it. That boiler was set to - almost literally - boil; it kettled away and the rads were piping. A brief touch of the flue pipe would have your skin removed. The GlowWorm condensing boiler I replaced it with - running in the high-70s oC - takes a lot longer to get the house up to temp on the original rads, but I just need to factor in an earlier starting time to compensate.

When you look at modern boiler flues and realise they are largely made of plastic, you real;ise just how far the improvements have been made.

quattros

Jeepers_Creepers said:

quattros said:

1) When do you turn up your heating in the mornings?   Well i have set the Heating to come on from the room stat from 4.30 am as i get up at 5am for work sometimes .

2) And from what overnight temp to what 'morning' temp? I have recently turned up the low temp to 19.5 degrees and then to turn off after reaching 21.5 degrees , The Room stat is in the living room. I have set the it so at 10.30pm the heating does not come on till 4.30am in the morning.

3) And how long does it take to get to that comfy morning temp? I Would say roughly about 30 mins ish 

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So you give your heating roughly half an hour to do its business? And it manages fine? Cool.

What's the 'low' temp - your overnight temp? 19.5oC? Blimey, that's balmy :-)

I would have been looking at an overnight set temp of 14 to 16 oC (that's why Gawd gave you a duvet) and going up to 20 or 21oC for the morning. Based on that, if your system gets from 16oC (in reality most houses will be warmer than this as they retain heat quite well overnight) to 20-21oC in a half hour, that's pretty good.

So, at what setting is your dial for this performance? 3/4-up?

And are you happy with the rad temps - not too 'ouch'?

It won't make a huge amount of difference, but if you can tweak the temp control down without losing your current performance, then do so - it'll probably save you a teeny bit as your boiler will be slightly more efficient. But if you find that you no longer get the cosy 21oC temp by 5am, you've probably turned it down too far...

There's no point chillin'. But don't have it higher than is needed either :-)

I think I got the question wrong it takes say about 1hr to reach a comfortable temperature. Not 30 mins
that’s with boiler temp control set say at about 65 degrees mark 3/4 way turned

radiators feel ok to touch briefly.

we used to have the heating on during the night years ago until we got a room stat , then set it so comes on at set periods , Is it advisable to have the heating trickling on and of during the night when in bed?

My boilers just a Combi one and not condensing type so probably not the most efficient.

Jeepers_Creepers

'Combi' and 'condensing' are two different things. I think your boiler is a 'condensing combi'.

'Condensing' means it's 'high efficiency', and all the boilers from the past - ooh - 15 years are like this. Does your flue make a 'plume'? Do you have a white plastic 22mm pipe going out through your wall and in to a drain?

'Combi' means you don't have a water tank - it heats your DHW instantly as you need it.

A 65oC delivery temp is a bit low, I reckon, especially for Winter. If it takes an hour to get your house to the required temp, that would reinforce this. I have mine set to around the mid-70s for these months, but do turn it down to more like 65oC when it gets warmer outside.

You want to be comfortable, but not waste energy. You don't want your house temp to plummet during the night, but neither do you want it 'warm' - that's the job of your bodies and duvets. I personally think that 14 to 16oC would suit most folk during the night - that's what my Prog Stat turns it down to. Even tho' I have an oldish (1930's) house, I think it's rare for my heating to come on during the night (it just doesn't fall that far), but it's good to know that it will keep the chill off even if it's super-frosty outside. It also allows for a quick & predictable heat-up in the morning. You certainly don't want the house 'warm' during the night - anything like 18oC upwards is simply a waste - unless you have a specific reason like a new-born babe or an elderly person.

I think, based on what you've said, I would turn the CH output up to the mid-70s. I think it sounds a little under-powered at the moment. Set your Prog Stat for whatever you want during the night, but I'd not have it completely 'off' and not higher than 16oc - but that's your call. You don't really want it above or below 'mild'!

Then a nice warm blast in the morn - 20 or 21oC - dropping down to, say, 18oC during the day if no-one is in, and then back up to 20 or 21oC in preparation for the first folk coming home. (Mine comes on at 20oC at around 4pm - people are still pretty mobile and active, preparing food etc at that time - and then it jumps slightly to 21oC at 6pm when folk are becoming lazy and settling in for the eve...)

Having it at 18oC during the day when no-one is in might seem unnecessary, but you'll find the heating will rarely need to come on since the house will be warmer due to solar gain and just the higher outside temps. 18oC just gives it a minimum level of consistency, so that it can climb up reliably to 20o and above when needed.

So, I'd tweak up your flow to 75oC for the cold months, and then back down to 65oC when the ambient outside temp is getting consistently above 10oC again :-)

ic

A feature that hasn't become commonplace so far, but I believe is recognised in the regulations is weather optimisation.  I had this on the last house - basically there was a temperature sensor mounted on the north facing side of the building.  The boiler controller used the outside temperature to decide the flow temp of the radiators and effectively adjusted the dial you describe second by second in reaction to the outside.  The colder the weather, the hotter the flow.  This worked well as it meant on a mild day, there wasn't a cycle of the radiators producing waves of heat as they ran at full blast, then off, then full blast, then off.  Instead they'd run constantly on a lower temperature, and maximised the chance of condensing mode (as is described by earlier posters).  Likewise in depths of winter they'd run very hot to keep us toasty.

To answer the question - the temp should be towards the max end when outdoor temperatures are sub zero, but much much lower when we're in spring.  Modern boilers are modulating - they vary the amount of gas used, and the pump speed in reaction to how much heat is expelled by the rads, and how much comes back to the boiler.  The boiler may simply circulate the water until it cools before firing up again, so unless your boiler is old, you're probably trying to beat the boiler at what it does very well.

quattros

Jeepers_Creepers said:

'Combi' and 'condensing' are two different things. I think your boiler is a 'condensing combi'.

'Condensing' means it's 'high efficiency', and all the boilers from the past - ooh - 15 years are like this. Does your flue make a 'plume'? Do you have a white plastic 22mm pipe going out through your wall and in to a drain?

'Combi' means you don't have a water tank - it heats your DHW instantly as you need it.

A 65oC delivery temp is a bit low, I reckon, especially for Winter. If it takes an hour to get your house to the required temp, that would reinforce this. I have mine set to around the mid-70s for these months, but do turn it down to more like 65oC when it gets warmer outside.

You want to be comfortable, but not waste energy. You don't want your house temp to plummet during the night, but neither do you want it 'warm' - that's the job of your bodies and duvets. I personally think that 14 to 16oC would suit most folk during the night - that's what my Prog Stat turns it down to. Even tho' I have an oldish (1930's) house, I think it's rare for my heating to come on during the night (it just doesn't fall that far), but it's good to know that it will keep the chill off even if it's super-frosty outside. It also allows for a quick & predictable heat-up in the morning. You certainly don't want the house 'warm' during the night - anything like 18oC upwards is simply a waste - unless you have a specific reason like a new-born babe or an elderly person.

I think, based on what you've said, I would turn the CH output up to the mid-70s. I think it sounds a little under-powered at the moment. Set your Prog Stat for whatever you want during the night, but I'd not have it completely 'off' and not higher than 16oc - but that's your call. You don't really want it above or below 'mild'!

Then a nice warm blast in the morn - 20 or 21oC - dropping down to, say, 18oC during the day if no-one is in, and then back up to 20 or 21oC in preparation for the first folk coming home. (Mine comes on at 20oC at around 4pm - people are still pretty mobile and active, preparing food etc at that time - and then it jumps slightly to 21oC at 6pm when folk are becoming lazy and settling in for the eve...)

Having it at 18oC during the day when no-one is in might seem unnecessary, but you'll find the heating will rarely need to come on since the house will be warmer due to solar gain and just the higher outside temps. 18oC just gives it a minimum level of consistency, so that it can climb up reliably to 20o and above when needed.

So, I'd tweak up your flow to 75oC for the cold months, and then back down to 65oC when the ambient outside temp is getting consistently above 10oC again :-)

Thanks for Your Reply , I will try and Up the Temperature on the Boiler a little , It’s Hard on my Boiler as there are only LED indications of Temperature  only when boilers running . I may Use my Temperature gun on the pipes out the boiler to get a quick reading.
I checked my boiler And its only a Combi one and not condensing type this version on Baxi did do a 105 condensing but had HE Letters for Condensing type.

Jeepers_Creepers

Not condensing? Wow - how old is it?!

In that case there's even less to gain by keeping the temp low. Priority one is to be comfy :-)