Temperature of a radiator?

[ericmark]

Is a radiator a part which need not be touched for normal operation, or a a part intended be touched for normal operation? Is the maximum temperature 70°C or 80°C?

OK this does not apply to radiators in a box using the chimney effect or fan assisted, since electrical controlled the electrical regulations do limit temperature, but is there any other regulation that limits temperature? With underfloor heating depending on surface it is around 27°C but where does it actually say that is the limit.

Tried to google it seems -18 to 70°C is the range, but can't find where it states that is the range permitted only seems to be a recommendation.

 

[securespark]

Are these radiators for use in a vulnerable persons setting?

 

[ericmark]

Are these radiators for use in a vulnerable persons setting?

No I was considering what temperature was best for boiler but was not sure what the limit is.

 

[EFLImpudence]

Can you set a boiler above its limit?

 

[ericmark]

There is a large dial on my boiler which sets the temperature of circulating water, there are also stages on the water pump to set flow rate, and there are lock shield valves to set individually radiators flow rate and thermostatic radiator valves to set the room temperature, plus a wall thermostat to turn pump and boiler off.

I am trying to get my head around how each control affects the performance of the system, so at the moment the water temperature is set low, this reduces the speed the rooms heat, and is likely why the boiler starts to cycle after just 20 minutes, it also means DHW is not too hot, not tried turning it up, house heats fast enough, but I have no idea what turning it up, or down would do, clearly it would take some time to find out, as likely the thermostat would need to learn how long it takes to heat the hall and also may need to adjust the lock shield valve and difference between TRV and wall thermostat.

I would guess if the weather was really cold then it may need the extra temperature and if weather warms up, a lower temperature could improve the hysteresis. But as it stands it's guess work.

The heating works well, but that does not mean it can't be improved, but no point reinventing the wheel, so trying to gleam information then consider a series of tests to see if there is room for improvement.

 

[JohnW2]

No I was considering what temperature was best for boiler but was not sure what the limit is.

I'm not really sure what you mean by 'best for the boiler' but I would have thought that, from the POV of heating, the 'best' would probably be as close to 100° that one dared go without a risk of boiling. Indeed, hypothetically speaking, it would probably be 'best' ('for heating') to use a liquid with a higher boiling point than water and run the system at a temperature considerably above 100°!

I would imagine that any recommendations/regulations will relate only to the 'touchability' issue - but, having said that, even 70° is really too high, since around 60° is usually regarded as the highest temperature which one can sensibly/safely touch.

Kind Regards, John

 

[ericmark]

I think 60°C is the lower limit for legionnaires, so must be some loses, so can't see it being set that low, not sure of temperature of cooker hob, the pan heats it so would depend on how good the contact is pan to hob, but likely around 90°C, not metal but ceramic so limit "A part which need not be touched for normal operation Non-metallic 90°C" so that would pass, and if one tripped and tried to safe ones self by pressing on the hob, it would hurt, but would not cause any great injury, clearly only the new induction same would not be true for old halogen types.

So if a radiator is painted is it still metallic, or is the paint non metallic?

 

[JohnW2]

I think 60°C is the lower limit for legionnaires, so must be some loses, so can't see it being set that low ....

There's nothing magic about legionnaire's disease. With a few troublesome exceptions, 60° is high enough to kill almost all bacteria. That consideration is obviously only relevant if the CH system is being used to heat DHW. In very hard water areas (like mine) DHW temps much above 70° are bad news!

.. not sure of temperature of cooker hob, the pan heats it so would depend on how good the contact is pan to hob, but likely around 90°C ...

That obviously depends upon the type of hob. The primary hotplate of my Aga is well over 200°. With any form of conventional hob, one obviously needs a temp of at least 100° to boil water.

... "A part which need not be touched for normal operation Non-metallic 90°C" so that would pass, ... So if a radiator is painted is it still metallic, or is the paint non metallic?

I think this is at risk of getting silly. Common sense is surely the name of the day?

Kind Regards, John

 

[Mottie]

it would probably be 'best' ('for heating') to use a liquid with a higher boiling point than water and run the system at a temperature considerably above 100°!

Or just pressurise the system to raise the boiling point. A sealed system will do.

 

[333rocky333]

I was once told you work it out by the temperature of the water returning to the boiler, I seem to recall 55 degrees

 

[JohnW2]

I was once told you work it out by the temperature of the water returning to the boiler, I seem to recall 55 degrees

That's an important consideration, but it depends upon the size/extent of the radiators and the flow rate. The temp of the water leaving the boiler and going to the radiators could be 98°, yet the return temp only 55°.

Kind Regards, John

 

[flameport]

A simplified summary:

Old non-condensing boilers - set to maximum, which is generally a flow of 70 - 80C. Any lower and your house just takes longer to heat up.

Newer condensing boilers - set so that the return temperature is 55 or below so that it does actually consense, otherwise its less efficient at higher non-condensing return temperatures. Generally better with oversized radiators or UFH.

Added complication - settings may need to be different when heating a hot water cylinder. Some boiler controls can deal with that. Others not.

 

[JohnW2]

Newer condensing boilers - set so that the return temperature is 55 or below so that it does actually consense, otherwise its less efficient at higher non-condensing return temperatures. Generally better with oversized radiators or UFH.

Is not a major problem there that, when moving from non-condensing to condensing boilers, most people do not at the same time address the (almost inevitable) 'inadequacy' of their existing radiators ('addressing' by installing more/larger radiators and/or fan-assisting them) - with the result that achieving a ≤55° return temp means that the radiators do not provide adequate heating?

Kind Regards, John

 

[ericmark]

Is not a major problem there that, when moving from non-condensing to condensing boilers, most people do not at the same time address the (almost inevitable) 'inadequacy' of their existing radiators ('addressing' by installing more/larger radiators and/or fan-assisting them) - with the result that achieving a ≤55° return temp means that the radiators do not provide adequate heating?

Kind Regards, John

I have a fan assisted radiator at old house, and yes very good, however not sure how a condensing boiler will work with them? With a standard radiator we have a TRV controlling room temperature which restricts water flow and force more through radiators not yet restricted, and will once all are restricted so far cause the by-pass valve to lift with the net result as a system the return water will get warmer and the boiler will respond to that by reducing its output.

However the fan assisted radiator does not restrict water flow, the return water temperature will increase as the fan turns off, or with modern versions down a speed, but the unrestricted water will turn the boiler down prematurely, unless every radiator in the system is fan assisted, you may get away with one in the kitchen built into the plinth, but I question if mixing the two types of radiator would work? With standard radiators we have a by-pass valve, with fan assisted there is no need for a by-pass valve.

I have looked at a few modern systems and scratched my head wondering how it works, I still can't get my head around zone valves, OK from a programmer so dormitory area independent to living area, however with a modulating boiler it needs to be controlled either by return water or a modulating thermostat the latter is not able to work in tandem with other thermostats, so it would need three zones one dormitory, one living and one control where there is no zone valve just the thermostat, but there only seems to be two zones, you can't control the zone valve with a thermostat, so if swapping one zone to other there would need to be some change over relay which also swaps which thermostat is active, but not found this change over relay in any property I looked at. OK with oil fired where the boiler does not modulate, but can't see how it works with a modulating boiler?

 

[JohnW2]

.... I still can't get my head around zone valves, OK from a programmer so dormitory area independent to living area, however with a modulating boiler it needs to be controlled either by return water or a modulating thermostat the latter is not able to work in tandem with other thermostats, so it would need three zones one dormitory, one living and one control where there is no zone valve just the thermostat, but there only seems to be two zones, you can't control the zone valve with a thermostat, so if swapping one zone to other there would need to be some change over relay which also swaps which thermostat is active, but not found this change over relay in any property I looked at. OK with oil fired where the boiler does not modulate, but can't see how it works with a modulating boiler?

I can't see any problem if one uses zone valves just as zone valves - i.e. to allowing the switching on/off of heating to various physical zones, either manually or by a programmer. In such cases, operating the zone valve is just the same as adding or removing bits of the heating system, and the other controlling processes can be left to do what they normally do.

However, it sounds as if you're talking about using zone valves as part of temperature control as well as for 'switching'. How possible that would be with a new-fangled boiler is, as you say, not so straightforward - and, as you also imply, is likely to involve relays (or equivalent).

With old-fashioned systems like mine, it's easy enough to combine the two functions with zone valves. I have 5 zones in my house, controlled by motorised valves, but some of those valves are controlled not only by the 'remote switching' but also by a local thermostat.

Kind Regards, John