Are all combi-boilers like this or is mine just rubbish? - HotUKDeals
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Are all combi-boilers like this or is mine just rubbish?

Benjimoron Avatar
7y, 10m agoPosted 7 years, 10 months ago
If you have a steady flow of water then it's fine, ie shower is ok once it's been running for a minute. But if you have to turn the tap on or off or change the flow rate then the water temerature flutuates like crazy.

Example: I just had a shave and the water was fine during the shave but when I used it to wash my face afterwards it pretty much burnt my hands. Surely there should be something to stop scaulding hot water coming out? I have the temp on the boiler pretty low, much lower and the normal water temerature is too cold, ie a bath doesn't come out hot like it should.

Any help appreciated.

Thanks!
Benjimoron Avatar
7y, 10m agoPosted 7 years, 10 months ago
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1 Like #1
The heat of the water is high if you run the tap slowly(half open), if you put the tap on "Full blast", the water will be lukewarm.

If it's not that, it sounds like you have a problem.
#2
thesaint
The heat of the water is high if you run the tap slowly(half open), if you put the tap on "Full blast", the water will be lukewarm.

If it's not that, it sounds like you have a problem.


Thanks saint. I would've thought that the water temp should be pretty much the same however much you have the tap on?

If left running at constant speed the temp is fine, like running a bath.

If turning on and off, ie washing hands/face/having a shave/doing the washing up etc then it'll sometimes be really cold and sometimes be scaulding hot. I have two young kids and I don't want them washing their hands and the water coming out boiling hot!!
1 Like #3
Just to let you know. I have a 4 bedroom detached house and an oilfired combi boiler (something like 90.000BTU). Somebody can be in the shower, somebody else flushing the toilet and a person doing the washing up and although it might alter the flow a little bit, the temperature stays the same. I have swivel taps and thermostatic controlled taps (shower and bath). Hope this helps.
1 Like #4
Most combi are like this i'm afraid but as the saint says if you open the tap a little cold water will run through the boiler slower so giving the boiler time to warm it up if you open the tap full then the water flow will be going through the boiler before it can warm up properly as a combi does not store hot water it just heats it up on demand I'm not a plumber but that the way i see it
#5
Benjimoron
Thanks saint. I would've thought that the water temp should be pretty much the same however much you have the tap on?

If left running at constant speed the temp is fine, like running a bath.

If turning on and off, ie washing hands/face/having a shave/doing the washing up etc then it'll sometimes be really cold and sometimes be scaulding hot. I have two young kids and I don't want them washing their hands and the water coming out boiling hot!!


No, the water is heated "On demand".

So, if the water is rushing out the tap, it doesn't have time to heat fully. If the flow rate is slow(When the tap is half open), then the water has more time to be heated.

My boiler allows you to adjust the temperature manually, so the hottest, isn't that hot.
I have mine on full, as my son is aware of how it works.

Just teach your kids to put the plug in the sink, add some cold water, then add the hot water until it's the correct temperature.
1 Like #6
The boiler heats the water instantly as it runs through it therefore if you only have a small amount of water running through at a time (tap half open) the boiler has more time to heat that smaller amount of water upto a higher temperature. When you have the tap fully open a lot of water is passing through the boiler so it does not have time to heat all the water to a really hot temperature therefore you have only lukewarm water
1 Like #7
Learn something every day..............
I'm astonished these things don't have a temperature regulator ?? How many kids are getting burned like this I wonder ??
#8
I can understand that if you're putting a large amount of water through it's going to take a few seconds to catch up and you'll get cold water for a while. But surely there's a safety issue when just running the tap a little bit, ie rinsing plates under the tap puts out some of the hottest water I've ever felt!

My eldest is only 3 so only just reaches the tap let alone put a plug in and get the temp just right.
#9
hottoshop
Learn something every day..............
I'm astonished these things don't have a temperature regulator ?? How many kids are getting burned like this I wonder ??


Thanks Tony. Tbh I've put up with it for a few years now but now my kids are getting old enough to use the tap on their own I worry that they'll burn themselves.
#10
I should say though that once the tap has been running for a while the temp is the same whether the tap is full or half open. ie it obviously detects the amount of water going through and heats accordingly, although gets confused/lags behind when the tap is being turned on/off/very low every so often.
#11
hottoshop
Learn something every day..............
I'm astonished these things don't have a temperature regulator ?? How many kids are getting burned like this I wonder ??


This is how my boiler regulates the temperature, I am no expert on boilers, but would think that most modern boilers have something similar.

http://i254.photobucket.com/albums/hh89/thesaint01/pics%20for%20forum/DSC00217.jpg

If I were to turn it right down, the temperature of the water through the tap would drop accordingly.
So no burnt hands. If parents don't read their instruction manual, then it's not the fault of anyone else but them.

Benjimoron
I can understand that if you're putting a large amount of water through it's going to take a few seconds to catch up and you'll get cold water for a while. But surely there's a safety issue when just running the tap a little bit, ie rinsing plates under the tap puts out some of the hottest water I've ever felt!

My eldest is only 3 so only just reaches the tap let alone put a plug in and get the temp just right.


Rinsing dishes is the only quibble with a combi bolier.
If your 3 year old can't use the plug, then you will be better off not allowing him wash his hands unsupervised.
#12
I am slightly puzzled that the 'hot tap' issue only gets assigned to the combi boiler. As far as I am concerned this only happends if you have just ran the tap on hot for a while and there is still hot water in the pipes. This would happen whatever the boiler is that you use. It depends on where your boiler is in the house, or where your hot water tank is as to how quickly the water will go hot.
Swivel taps will help a little to prevent water that is too hot coming out but I think it is up to the adults to make sure that they do not switch off a tap before they have put a back to cold. I.e. if you have seperate taps hot water will always come out of the hot tap if it has just been run.
I have lived with combi boilers all my life and have never scolded myself as a child where it was not due to myself. In the bathroom I have only had temperature controlled taps for the last 20 years and these are certainly 100% safer than any other tap!
#13
I hate my combi boiler, I've had nothing but black mould since having it fitted :(
#14
Is this a new bolier? I was told by a plumber that when anything is put in to do with running water it has to be to a new saftey law that for instance if you are in the shower and someone runs the tap in the sink then the cold does not turn off in the shower. I am probably not explaining it very well. Does anyone else know what I am on about?
#15
thesaint
This is how my boiler regulates the temperature, I am no expert on boilers, but would think that most modern boilers have something similar.

http://i254.photobucket.com/albums/hh89/thesaint01/pics%20for%20forum/DSC00217.jpg

If I were to turn it right down, the temperature of the water through the tap would drop accordingly.
So no burnt hands. If parents don't read their instruction manual, then it's not the fault of anyone else but them.



Rinsing dishes is the only quibble with a combi bolier.
If your 3 year old can't use the plug, then you will be better off not allowing him wash his hands unsupervised.



Alright mate, calm down!

I have my water temp turned to 3 o clock which is alot cooler than yours at 7-8 o clock.


So you reckon this is a standard thing for scaulding hot water to come out? No way to fix it other than to put a tank back in?
#16
debbielon
Is this a new bolier? I was told by a plumber that when anything is put in to do with running water it has to be to a new saftey law that for instance if you are in the shower and someone runs the tap in the sink then the cold does not turn off in the shower. I am probably not explaining it very well. Does anyone else know what I am on about?


I think you're right and I think it's a law for rented properties or something?

Anyway, I've not notice that happen really, the pressure drops but haven't noticed any major shift in temp. What I'm on about is when you turn a tap on/off/full/half etc, then you can get scaulding hot water.

Boiler is 5 years old, has done it since day one.
#17
pegsw
I am slightly puzzled that the 'hot tap' issue only gets assigned to the combi boiler. As far as I am concerned this only happends if you have just ran the tap on hot for a while and there is still hot water in the pipes. This would happen whatever the boiler is that you use. It depends on where your boiler is in the house, or where your hot water tank is as to how quickly the water will go hot.
Swivel taps will help a little to prevent water that is too hot coming out but I think it is up to the adults to make sure that they do not switch off a tap before they have put a back to cold. I.e. if you have seperate taps hot water will always come out of the hot tap if it has just been run.
I have lived with combi boilers all my life and have never scolded myself as a child where it was not due to myself. In the bathroom I have only had temperature controlled taps for the last 20 years and these are certainly 100% safer than any other tap!


Sorry, I don't really understand. I've never had this issue in any other house other than this one with this combi boiler.

As I understand it it's because the heating of the water lags behind the water actually going through. So if you turn the tap on then it will be cold for a few seconds first before the boiler has had time to heat the water. If you then turn the tap down to half flow then the water will presumably still be heated as if there was twice as much water flowing for a few seconds. This results in some very hot water coming out for a few seconds.

Because of the boiling hot water coming out I usually have to turn the tap off to stop boiling water spraying everywhere, which then makes the problem worse when I turn the tap back on again!
#18
Benjimoron
Alright mate, calm down!


I am perfectly calm. I thought I was helping you to understand your system, and went to the trouble of taking a picture and uploaded it to others that may not understand.

Good luck.
#19
thesaint
I am perfectly calm. I thought I was helping you to understand your system, and went to the trouble of taking a picture and uploaded it to others that may not understand.

Good luck.


"If parents don't read their instruction manual, then it's not the fault of anyone else but them."

I understand how it works thanks and it's not my fault as a parent if whoever designed this system designed it so that scaulding hot water can come out.
#20
I've never had one of these boilers so have no experience whatsoever but could it have something to do with water pressure Benji ??
#21
hottoshop
I've never had one of these boilers so have no experience whatsoever but could it have something to do with water pressure Benji ??


How do you mean? The water pressure remains the same from the supply. If another tap is turned on then it causes drop of pressure but no effect on temp.

The only time the temp is an issue is when you don't leave a tap at a constant speed for more than a minute or so. The only time I'd do that is running a bath.
#22
Benji have you looked up the specs of your boiler. A quick google tells me there is usually a flow switch or flow sensor ??
What make/model is the boiler ?

Ignore the water pressure thing if it doesn't apply, like I write I have no experience of combi boilers.
#23
Benjimoron
"

I understand how it works thanks and it's not my fault as a parent if whoever designed this system designed it so that scaulding hot water can come out.


Previous:

Benjimoron
Thanks saint. I would've thought that the water temp should be pretty much the same however much you have the tap on?

#24
I've got an awful PUMA boiler. Its quite honestly the worst thing I have ever come across. It locks out every five minutes after I've ran a load of water. Gets on my t*ts.
#25
http://ezinearticles.com/?Scalding-Water-From-the-Tap?-Thermostatic-Mixing-Valve-Can-Help&id=1563581

Maybe I can get temperature controlled mixer taps installed? Anyone have them?
#26
thesaint
Previous:


The temp should be the same, you shouldn't expect scalding hot water when running the tap slowly and only luke warm water when running it fast.
#27
Benji have a look here and see if it's any use to you:

http://www.diyfaq.org.uk/plumbing/combi.html
#28
Mine starts off cold for about 10 seconds then it starts heating up and then its red hot,steam comes off it and i can't keep my hands under the hot tap when its running.
#29
mhh1981
I've got an awful PUMA boiler. Its quite honestly the worst thing I have ever come across. It locks out every five minutes after I've ran a load of water. Gets on my t*ts.


Assuming you're female this post is useless without pics ??
#30
hottoshop
Assuming you're female this post is useless without pics ??



How is it useless,i know what they mean, my old boiler used to do that.
#31
deb8z
How is it useless,i know what they mean, my old boiler used to do that.


Sorry deb8z, my attempt at bringing a little light humour into the thread. Read the last sentence of mhh's post again :)

Taxi for hotto..................
#32
Oh you were being rude,i'm such an angel i never thought of that:whistling:
#33
Sounds like there could be a problem with the flow meter. As Saint says, all combi's give out water at a temperature proportional to the flow, but also all should turn off the boiler if the flow is below a certain amount. If the flow is just a trickle, the boiler shouldn't turn on...

Mixer taps are a good idea though :)
#34
mhh1981
I've got an awful PUMA boiler. Its quite honestly the worst thing I have ever come across. It locks out every five minutes after I've ran a load of water. Gets on my t*ts.


hottoshop
Assuming you're female this post is useless without pics ??


I laughed!! :)
#35
hottoshop
Assuming you're female this post is useless without pics ??


no, not female.....nor am I sexist like some.....:-)
#36
jah128
Sounds like there could be a problem with the flow meter. As Saint says, all combi's give out water at a temperature proportional to the flow, but also all should turn off the boiler if the flow is below a certain amount. If the flow is just a trickle, the boiler shouldn't turn on...

Mixer taps are a good idea though :)


Yeah it turns off if the flow is slow, but that doesn't stop boiling water coming out quite often.

You mean mixers that control the temp? Are they any good?
#37
deb8z
Mine starts off cold for about 10 seconds then it starts heating up and then its red hot,steam comes off it and i can't keep my hands under the hot tap when its running.


Same here, maybe your temp is too high, mine is set very low and boiling hot water only comes out when you don't have the tap as a consistent speed, ie running a bath.
#38
Not taps that control the temp, just taps that mix cold+hot water at the same time. But to be honest it shouldn't really let water out thats hot enough to scald anyway (when the temp. control is set so low), it might be worth having it serviced...
banned#39
mhh1981
no, not female.....nor am I sexist like some.....:-)


im not sexist, post away :thumbsup:
#40
My taps take an age to have hot water coming out. For this reason I have taught my children to just use the cold tap when they are only washing their hands, eg. after they've been to the toilet. It saves the boiler getting fired up, hands being washed in water that is still cold, then the boiler not settling down for a few minutes afterwards.
Once the water does heat up though, it does get extremely hot. If the water flow is increased or decreased during use then it does affect the water temp. I thought this was the case for all combi boilers.

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