Combi boiler- How water not that hot anymore

[adammid]

Does anyone know why over the last couple of weeks, i have had to turn the stat on the shower to max in order to get adequate hot water. Prior to that I could have the stat at the half way point. The boiler has been changed a few months ago.

I was wondering if maybe the pipes are sludged up as its a hard water area, or maybe the boiler is not big enough. All the radiators are on but then its a combi and then when the hot water tap is tunred on, the water takes priority, so I wouldn't expect that to be a problem.

Any thoughts?

 

[telectrix]

tank stat. set too low???

 

[cobrauk]

Its A Combi No Tank.

My bet is that the cold water feeding the boiler is that much colder, electric showers are the same this time of the year, you just need to slow the speed of the water a bit by not having the shower not running at full pressure to help combi, well that's what I do.

 

[Geordie Spark]

It's a Combi Tel .............. doesn't have a tank.

The most likely cause is the cold weather we're experiencing just now cos it's winter !!

The water coming into your house is a hell of a lot colder now than it was during the summer - or even a few weeks ago -because it's being transported to you through a pipe buried in the frozen ground. This means that the boiler has to work a bit harder to raise the temperature of the water.

The answer is to turn up the temperature control for domestic hot water on the boiler during the winter months and back down again in the summer. (the control knob for this usually has a picture of a tap beside it)

If we're talking about an older boiler - say over 3 years old - then the cause can be a knackered diverter valve which means the boiler is trying to heat radiators and domestic at the same time (instead of either or) which it will struggle to do and that's why it has a diverter valve fitted in the first place !

Having said all that, if you're able to get an acceptable shower simply by turning up the thermostat on the shower itself, what's wrong with that?

 

[telectrix]

It's a Combi Tel .............. doesn't have a tank.

The most likely cause is the cold weather we're experiencing just now cos it's winter !!

The water coming into your house is a hell of a lot colder now than it was during the summer - or even a few weeks ago -because it's being transported to you through a pipe buried in the frozen ground. This means that the boiler has to work a bit harder to raise the temperature of the water.

The answer is to turn up the temperature control for domestic hot water on the boiler during the winter months and back down again in the summer. (the control knob for this usually has a picture of a tap beside it)

If we're talking about an older boiler - say over 3 years old - then the cause can be a knackered diverter valve which means the boiler is trying to heat radiators and domestic at the same time (instead of either or) which it will struggle to do and that's why it has a diverter valve fitted in the first place !

Having said all that, if you're able to get an acceptable shower simply by turning up the thermostat on the shower itself, what's wrong with that?

i told you i knew f. all about heating systems. :hanged:

 

[Geordie Spark]

i told you i knew f. all about heating systems. :hanged:

Aye .. maybe you'd better stick to replacing main switches on consumer units. :winkiss:

But to be fair, it is possible to have a tank heated by a combi and this is probably a good thing to do if you have a large house and / or solar panels. In this scenario you'd probably use the "instant" hot water from the combi to supply the kitchen taps & the tank for baths etc.

 

[adammid]

Thanks guys. The boiler was actually replaced a few months ago as the old one had a dodgy diverter valve. When the hot tap was turned on, the radiators came on too. My girlfriend, who lived in the house before me, thought that was normal and had been doing it for a year or so. When I moved in and realised that wasn't right we got the plumber to come and he replaced the boiler.

Back to the current issue with colder hot water. I have turned the hot water stat on the boiler to max which is 60c but doesn't make much difference. it makes sense though, when you say the water entering the property is colder and therefore the boiler has to work harder to heat it up, but I would have thought that 60c is 60c and if thats what my stat says then that is how hot the water should be that comes out of the tap.

Yes i understand that the boiler has to work harder, but it should still be the same temp that comes out of the tap. It just means the boiler works harder, my gas bill goes up but i still get nice warm showers.

 

[telectrix]

think it's down to the flow rate. if the flow rate is fast, then the boiler ain't got enough time to get it to temp. like it's going full blast but can't keep up. see, geordie, i'm learning. :earmuffs:

 

[Geordie Spark]

think it's down to the flow rate. if the flow rate is fast, then the boiler ain't got enough time to get it to temp. like it's going full blast but can't keep up. see, geordie, i'm learning. :earmuffs:

Good lad!

 

[adammid]

Ok Cheers, that will work fine with the bath as you can just turn the tap down and it will just take longer to fill up but if i did that with the shower I would just be left with a trickle.

 

[Geordie Spark]

Thanks guys. The boiler was actually replaced a few months ago as the old one had a dodgy diverter valve. When the hot tap was turned on, the radiators came on too. My girlfriend, who lived in the house before me, thought that was normal and had been doing it for a year or so. When I moved in and realised that wasn't right we got the plumber to come and he replaced the boiler.

Back to the current issue with colder hot water. I have turned the hot water stat on the boiler to max which is 60c but doesn't make much difference. it makes sense though, when you say the water entering the property is colder and therefore the boiler has to work harder to heat it up, but I would have thought that 60c is 60c and if thats what my stat says then that is how hot the water should be that comes out of the tap.

Yes i understand that the boiler has to work harder, but it should still be the same temp that comes out of the tap. It just means the boiler works harder, my gas bill goes up but i still get nice warm showers.

Yes, that *should* be the case providing the boiler has the power to cope with the lower temperature of the incoming water and the rate at which it's coming in.

For example, the boiler that was in my house when I moved in was a 24 kW job and did not provide me with a hot shower in the winter so I replaced it with a 37kW boiler which very easily copes to the extent that it can fill a hot bath in about 10 minutes which the "old" boiler wouldn't do even if I left it running all day !!

I would not advise anyone fitting a Combi rated at less than 30kW for this very reason.

 

[adammid]

so in theory, if i turned the main stop cock down to reduce the flow rate then the boiler should have time to heat the water? I'm not entirely sure what size the boiler is but I will check tonight?

 

[graeme210375]

It could be as simple as limescale. If electric shower remove the filter on the cold water inlet and clean it out. If the shower is fed via mixer taps, then remove them and there will be filters where the hot and cold feed into them. Limescale an rust from old steel pipes will reduce the flow rate at the shower if they have clogged the filter. A 5 min free fix. Worth a try.

 

[adammid]

Ok, but where will the isolation valve likely to be. If the boiler is upstairs and the shower is also, would it be likely for the pipes to run in the loft or under the floor. The shower is directly above the bath so i would assume that the hot and cold feed is tapped off the supply to the bath or vice versa. Could I just isolate at the main stop cock and remove the taps?

 

[Geordie Spark]

so in theory, if i turned the main stop cock down to reduce the flow rate then the boiler should have time to heat the water? I'm not entirely sure what size the boiler is but I will check tonight?

Yes that would work, but it would also reduce the flow to everything else in the house. Have a look underneath the boiler for the isolating valve on the cold supply to it & close that down a bit.