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Hi,
I have an issue of the radiators.

When the boiler starts to work, all house radiators start to get hot, but after about 30-40 mins, there are upstairs 3 or 4 radiators are getting cool down (maybe because the house temperature reaches the set temperature?), but others are still warm/hot (not as hot as when it started) why is that? Why those 3 or 4 radiators will get cool down (boiler is still operating)?

BTW, when installed a gas hob, are we supposed to get the Building Regulation Compliance Gas Safety Certificate? Or no certificate for gas hob installation?

Thanks for any advice!
 
Do the upstairs radiators have thermostatic valves and if so what are the set to?
 
Do the upstairs radiators have thermostatic valves and if so what are the set to?
Thank you for your reply!
All radiators have thermostatic valves. Upstairs have 9 radiators in total, but only 3 will cool down after getting hot initially.
They were all set to 5, recently I set all upstairs and downstairs to 3, since then I think 3 of them will cool down after getting hot & boiler starts.
So it looks like it is relevant to setting from 5 to 3, but other 6 not cool down.
That's why I am not sure why this is.
 
The upstairs radiators are doing there job on a lower thermostatic valve setting. The valve shuts down as the room heats. You could have the heating on full blast but if the room is warm enough for the valve it will stay closed down and the radiator will be cold.

Just had a new boiler or thermostatic valves?
 
The upstairs radiators are doing there job on a lower thermostatic valve setting. The valve shuts down as the room heats. You could have the heating on full blast but if the room is warm enough for the valve it will stay closed down and the radiator will be cold.

Just had a new boiler or thermostatic valves?
Thank you for your reply again!
I am not very clear of your meaning.
Both upstairs and downstair radiators are set to level 3, but all downstairs and upstairs 6 of them remain warm but only 3 of upstairs will cool down after getting hot firstly.
I am not sure why only 3 upstairs radiators (2 rooms +1 bathroom towel rail) will cool down.

The boiler is new and valves all are new.
 
Thank you for your reply again!
I am not very clear of your meaning.
Both upstairs and downstair radiators are set to level 3, but all downstairs and upstairs 6 of them remain warm but only 3 of upstairs will cool down after getting hot firstly.
I am not sure why only 3 upstairs radiators (2 rooms +1 bathroom towel rail) will cool down.

The boiler is new and valves all are new.
What you describe sounds entirely reasonable to me. Given that heat tends to rise, and all your thermostatic valves are at the same setting, as the house warms up you might expect at least some of the upper rooms to reach their set temperature sooner (at which point the valves throttle the flow and the rads go cold). Meanwhile the ground floor is still warming (cos some of its heat has percolated upwards in the fabric of the house) so the downstairs radiators are still warm to the touch.
If you really believe there is a problem, get at least two thermometers, and check the temperature in the various rooms is actually what you want to achieve.
 
What you describe sounds entirely reasonable to me. Given that heat tends to rise, and all your thermostatic valves are at the same setting, as the house warms up you might expect at least some of the upper rooms to reach their set temperature sooner (at which point the valves throttle the flow and the rads go cold). Meanwhile the ground floor is still warming (cos some of its heat has percolated upwards in the fabric of the house) so the downstairs radiators are still warm to the touch.
If you really believe there is a problem, get at least two thermometers, and check the temperature in the various rooms is actually what you want to achieve.
Thank you for explaining it!
Precisely speaking, out of 9 radiators upstairs, only 1 valve of towel rail is set level five (as the valve lost and cannot be re-set to 3 now) the rest all be set at 3. Downstairs 1 radiator in hallway is set 2, the rest downstairs are set as level 3.
But I don't think this will make difference?

I understand your point. Those 3 radiators that later cool down after getting hot first, 1 is in main bedroom next to cylinder/pump room, 1 is in main bathroom, 1 is in 2nd bedroom. But the nearest radiator to the cylinder/pump room is upstairs hallway radiator which always get hot first. So should this upstairs hallway radiator get cold first? But it keeps hot & not cool down.

I just don't understand why those 3 radiators get cooling down but not other radiators? As you said, some of the upper rooms to reach their set temperature sooner?

Oh, the other thing is, when less a week ago, all radiators valves were all set at level 5, only recently we changed the valves to level3, but as said, we found 3 radiators cool down later after getting hot first.
 
Thank you for explaining it!
Precisely speaking, out of 9 radiators upstairs, only 1 valve of towel rail is set level five (as the valve lost and cannot be re-set to 3 now) the rest all be set at 3. Downstairs 1 radiator in hallway is set 2, the rest downstairs are set as level 3.
But I don't think this will make difference?

I understand your point. Those 3 radiators that later cool down after getting hot first, 1 is in main bedroom next to cylinder/pump room, 1 is in main bathroom, 1 is in 2nd bedroom. But the nearest radiator to the cylinder/pump room is upstairs hallway radiator which always get hot first. So should this upstairs hallway radiator get cold first? But it keeps hot & not cool down.

I just don't understand why those 3 radiators get cooling down but not other radiators? As you said, some of the upper rooms to reach their set temperature sooner?

Oh, the other thing is, when less a week ago, all radiators valves were all set at level 5, only recently we changed the valves to level3, but as said, we found 3 radiators cool down later after getting hot first.
Just to day I'm not a professional plumber - this is just my take on your postings 😀

You must appreciate that the behaviour of each valve will depend on its precise environment - the style of radiator, the distance of the sensor from the rad, the wall and other pipes, probably the colour of the decor, whether there is a window above or near etc. etc. The thermostatic valves are not perfect, and may behave slightly differently.

All they are trying to do is moderate the room temperature as best they can to what you require.

If you are saying the cooling down radiators are actually causing a problem because the rooms are cold, you may just need to adjust the setting to compensate for the particular thermal requirements of that room.
The number on the valve is not a precise equivalent to a particular temperature - it's a guide, and depends on the requirements of the room, as I tried to explain above.

I feel you are concentrating on the touch temperature of the radiators, and not explaining if you have a problem with rooms not being at the right temperature (which to a degree is about setting the valve to a number that produces the right result!)

If you want the radiators to all feel hot, just wind all the valves up to maximum and see what they feel like - that's a better way of checking the water is circulating OK!
 
Just to day I'm not a professional plumber - this is just my take on your postings 😀

You must appreciate that the behaviour of each valve will depend on its precise environment - the style of radiator, the distance of the sensor from the rad, the wall and other pipes, probably the colour of the decor, whether there is a window above or near etc. etc. The thermostatic valves are not perfect, and may behave slightly differently.

All they are trying to do is moderate the room temperature as best they can to what you require.

If you are saying the cooling down radiators are actually causing a problem because the rooms are cold, you may just need to adjust the setting to compensate for the particular thermal requirements of that room.
The number on the valve is not a precise equivalent to a particular temperature - it's a guide, and depends on the requirements of the room, as I tried to explain above.

I feel you are concentrating on the touch temperature of the radiators, and not explaining if you have a problem with rooms not being at the right temperature (which to a degree is about setting the valve to a number that produces the right result!)

If you want the radiators to all feel hot, just wind all the valves up to maximum and see what they feel like - that's a better way of checking the water is circulating OK!
Thank you for your input!
I understand your theory which makes sense!

Before this week, I set the valves all to the max which was 5, and all the radiators did NOT cool down when boiler was operating.

Only this week on, I set most of the radiators to level 3, then I found upstairs 3 of them will cool down after getting hot once boiler starts.

As this week is not cold, so I do not feel cold entering those three rooms after cooling down.
Maybe when the weather is cold I would feel different if they cool down?

These 3 room radiators do get hot once boiler starts to operate, but unlike others that will keep hot/warm, these three rooms will cool down after 1 hour-ish of boiler operation.

So strange....
 
Thank you for your input!
I understand your theory which makes sense!

Before this week, I set the valves all to the max which was 5, and all the radiators did NOT cool down when boiler was operating.

Only this week on, I set most of the radiators to level 3, then I found upstairs 3 of them will cool down after getting hot once boiler starts.

As this week is not cold, so I do not feel cold entering those three rooms after cooling down.
Maybe when the weather is cold I would feel different if they cool down?

These 3 room radiators do get hot once boiler starts to operate, but unlike others that will keep hot/warm, these three rooms will cool down after 1 hour-ish of boiler operation.

So strange....

Nothing strange about it at all. Everything is working as it should. If you find the rooms cold turn up the valves.
 
Nothing strange about it at all. Everything is working as it should. If you find the rooms cold turn up the valves.
Thank you! I will take it as normal then!
Just out of curiosity, you are a plumper, have you seen things like this before that all other room radiators keep warm/hot but just some rooms radiators cool down after getting hot itinially?
 
As Simon above.
I'm sorry my comments were not clear enough.
There is absolutely nothing strange about what you describe. The trv's are doing what they should.
It's physics/thermodynamics.
Don't worry - it's all working!
Thank you!
Yes, it works in terms once boiler starts & radiators get hot.
As this is first time I notice this kind of thing, therefore raised this question.

Basically, all other radiators keep warm as long as boiler in operation, but only those 3 will cool down.
 
Remove the trv head sorted they will stay hot aslong as the boiler is on
 
Remove the trv head sorted they will stay hot aslong as the boiler is on
Thank you!

Did you mean remove the head of TRV like attached photos, just take that part off & no need to bother the setting is level 5 or 3?
 

Attachments

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    WechatIMG37.png
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Correct remove that eg unscrew the silver collar and it and the head will pop off
 
It’s easier to remove when on setting 5 but not a must
 

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