New boiler only gives 1 tap hot water at a time

[elpatcho]

Hi,

I was hoping for a bit of advice. I have just had a new worcester cdi27 combi boiler fitted which replaced a immersion heater, water tank and a back boiler. The combi was installed in the loft.

The issue is that now you can only run the hot water through 1 source at a time. As in, you can't have the shower on at the same time as the kitchen hot tap. This isn't a problem with cold water.

I queried this with the fitter and he said that it was due to low mains pressure even though I'm not sure he checked that. Also, he mentioned that 3 houses were run from one main.

Does this sound like the right explanation? Is there anything I could do to get it working through multiple sources?

Any advice would be very welcome.

Thanks,

e

 

[sooey]

It's normal for combis to only be able to feed one outlet. That should have been explained to you before choosing one.

 

[moggridgeplumbing]

If a combi tries to supply more than one outlet at a time then the mains flowrate will be shared between them, although water will take the easiest route. Before the combi was recommended and installed I assume the fitter checked your incoming mains flowrate (not the pressure) to ascertain if a combi would be suitable and which model would give you the optimum output?

 

[kevindgas]

24 kw = luke warm water
27kw = hot water if you're lucky
30kw = reasonably good hot water
37kw or higher = excellent hot water

all the above rely on the fitter ensuring that the gas supply is adequate, what size pipes do you have and approx length of pipe run from meter?
personally i never fit less than 30KW combi's

 

[SimonH2]

I have just had a new worcester cdi27 combi boiler fitted which replaced a immersion heater, water tank and a back boiler.

Well there's the problem, and why I personally wouldn't give houseroom to a combi without some very good reason - and I especially wouldn't replace a stored heat (ie hot water cylinder) system with one.. Unfortunately far too many plumbers think combis are the best thing since sliced bread and will "forget" to mention this limitation.
As others have hinted at, it's a basic physics limitation - it takes energy to heat water, so if you can't build up and store hot water, then you are restricted to how fast you can draw it off without it going cold. Just wait till winter when the cold mains drops in temperature and it gets even worse.

EDIT: The other problem the plumber will have forgotten to mention is that ... when it breaks down, you won't be able to get hot water using the immersion heater you no longer have. So you'll have no hot water as well as not heating.

Just for good measure, did he run the condensate drain outside ? If so, then (unless it's been done unusually well) look forward to losing heat/hot water when it's freezing outside

 

[ALEC1]

thats a bit unfair guys...

if the head of water above a cylinder is good then any one going to a combi is going to be disappointed...

the truth is that a 24kw combi does provide adequate hot water to one tap or a sensible shower all of the time...

thats much better than a cylinder with low head that needs a pump to make a shower work..

and yes incoming mains and gas pipe size do influence, but people can get used to anything...

 

[dcawkwell]

Sounds like a cowboy installed your system.
You should have stayed with a hot water tank.

Although the boiler you have will struggle to do anything more than
one tap at once with hot water.

 

[Mark Br]

thats a bit unfair guys...

if the head of water above a cylinder is good then any one going to a combi is going to be disappointed...

the truth is that a 24kw combi does provide adequate hot water to one tap or a sensible shower all of the time...

thats much better than a cylinder with low head that needs a pump to make a shower work..

and yes incoming mains and gas pipe size do influence, but people can get used to anything...

Yes, but the OP is complaining that the problem is when more tha one taps is being used.

Personally I would always try as persuade a customer not to have a combi if they currently have a cylinder