Weird heat levels from different taps

[peterb20]

24kW is the lowest power combi you can buy, so it shouldn't be too surprising that it's struggling to keep up with high flow rate fittings. As with your bath, does the shower temperature also improve if you reduce the flow rate?

We have no high flow rate fittings

 

[peterb20]

And maybe a *slight* Improvement in the shower, but nothing to write home about.

My confusion lies in the two outlets producing scolding water and the other two lukewarm - even though they are the same flowrate.

 

[muggles]

We have no high flow rate fittings

Higher flow rate then, if you want to be awkward. The point still stands - your bath and shower are outstripping what your boiler is capable of delivering, resulting in cooler water than you'd like. Reduce the flow rate through them and all will be well

 

[muggles]

My confusion lies in the two outlets producing scolding water and the other two lukewarm - even though they are the same flowrate.

Have you actually measured the flow rates and temperatures produced at each outlet, or are you just guessing by eye and feel?

 

[John D v2.0]

Have you actually measured the flow rates and temperatures produced at each outlet, or are you just guessing by eye and feel?

Agree, everyone should have a big bowl and stop watch for a basic relative measurement. Temperature more tricky, even a digital meat thermometer or an IR thermometer would get an accurate enough temperature if you have one.
Op, Also measure the temperature of the cold tap after running it for a minute.

 

[peterb20]

Ok right so, I dialed the rising main down to a less powerful flow as an experiment, so these figures are based on the reduced flow due to that:

Kitchen 6.5l/m flow rate, 13deg cold, 54deg hot
Bath 7.3l/m flow rate, 43deg hot.

I see the higher flow rate means it will be colder, but both flow rates are well within the 12.4 flow rate the boiler is rated at.

With the bath at 43deg, it would need a bit of cold added, but at that flow rate would also take hrs to fill!

Oh and the boiler is 30kw for dhw, rather than the 24kw I stated earlier.

 

[John D v2.0]

Bath 7.3l/m flow rate, 43deg hot

Yes 7.3l at 30c rise doesn't sound good. For 30kw I'd have to work it out and that's the heat input, but you should get more than that.

 

[peterb20]

Yes 7.3l at 30c rise doesn't sound good. For 30kw I'd have to work it out and that's the heat input, but you should get more than that.

So are you saying their is a possible boiler issue too? Still doesn't explain the difference at different outlets though!

 

[Newboy]

Your boiler should be producing a 35°C rise (between incoming main & temp at a tap) @ 12.4 l/min so the performance you're reporting doesn't seem right.

Still doesn't explain the difference at different outlets though!

Yes it does - higher flowrate = lower temperature rise.

 

[John D v2.0]

So are you saying their is a possible boiler issue too? Still doesn't explain the difference at different outlets though!

Yes sounds like a boiler issue or a gas supply issue.
Energy transfer is measured in kW or alternatively degrees per litre per second. Increase the litres per second and the degrees decreases. If you multiply them together you should get a similar figure.
7.3x30 = 6.5x41 in theory
However it seems your boiler has an issue so it may be getting incorrect readings from one of the temperature sensors.
Try putting both the taps on full blast and then gas rate the boiler using the gas meter.
Ie take a reading of the smallest digit or spinning dial, wait a minute and take it again, then input into one of the online calculators.

 

[Newboy]

So are you saying their is a possible boiler issue too?

Do you have the benchmark from the boiler installation?

 

[peterb20]

Do you have the benchmark from the boiler installation?

I do, it states 18deg in, 58deg out @ 18l/min

So this is how pointing towards the boiler not working quite as it should be to have such a drop in output, correct?

 

[John D v2.0]

So this is how pointing towards the boiler not working quite as it should be

Yes or lack of gas,see below

it seems your boiler has an issue so it may be getting incorrect readings from one of the temperature sensors.
Try putting both the taps on full blast and then gas rate the boiler using the gas meter.
Ie take a reading of the smallest digit or spinning dial, wait a minute and take it again, then input into one of the online calculators.

 

[peterb20]

Yes or lack of gas,see below

I will get the installer in then and get it serviced. We've had a new meter installed recently and the guy who did that didn't go out to the boiler so maybe the gas flow has been changed during Ng that to affect it. I'm in over my head now but appreciate everyone's help in pointing the finger towards the boiler being the problem

 

[John D v2.0]

Interesting, it may be that the new meter has an issue or has caused an issue. Definitely a good idea to call someone in, they can check the working pressure at the meter (and at the boiler) very quickly and easily and narrow down the problem if any with the supply