Hi

We currently have a 24kW Vokera combination boiler which was installed
in the early 90's.

I'm looking to replace it for many reasons not least of which is that
it is completely underpowered for our house.

The house is a four bed detached with two bathrooms. There are nine
radiators and two towel rails connected to the current system.

Current problems a-

1) The boiler is extremely noisy - needs a new / refurb fan
2) It can't heat the hot water to an acceptable temperature in winter
without reducing the flow to an unacceptable rate
3) The response time on the heating system is appalling - it takes
several hours for the house to reach an acceptable temperature.

Now I know I haven't gone into details about the sizing of each
radiator but my gut feeling is that 24kW - even if it was a brand new
boiler - is not adequate for a 4 bed / 2 bath house.

I am leaning towards either Worcester Bosch or Vailant. There is a
calculator on the WB website that recommends I get either a 37kW or
42kW boiler. Does that sound reasonable?

Thanks,

Steve

In an earlier contribution to this discussion,
stevelup wrote:

Hi

We currently have a 24kW Vokera combination boiler which was installed
in the early 90's.

I'm looking to replace it for many reasons not least of which is that
it is completely underpowered for our house.

The house is a four bed detached with two bathrooms. There are nine
radiators and two towel rails connected to the current system.

Current problems a-

1) The boiler is extremely noisy - needs a new / refurb fan
2) It can't heat the hot water to an acceptable temperature in winter
without reducing the flow to an unacceptable rate
3) The response time on the heating system is appalling - it takes
several hours for the house to reach an acceptable temperature.

Now I know I haven't gone into details about the sizing of each
radiator but my gut feeling is that 24kW - even if it was a brand new
boiler - is not adequate for a 4 bed / 2 bath house.

I am leaning towards either Worcester Bosch or Vailant. There is a
calculator on the WB website that recommends I get either a 37kW or
42kW boiler. Does that sound reasonable?

Thanks,

Steve

If the house is decently insulated, 24kW should be more than adequate for
space heating. If the current one can't cope are you sure that it's actually
producing 24kW, or is there something wrong with it?

If you want a lot of hot water in a hurry, *any* combi boiler is a bad
idea - but if you *must* have one, get the biggest one you can
accommodate/afford.

Don't forget to check the adequacy of your gas supply and internal
pipework - 42kW needs a *lot* of gas!
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

"stevelup" wrote

Hi

We currently have a 24kW Vokera combination boiler which was installed
in the early 90's.

I'm looking to replace it for many reasons not least of which is that
it is completely underpowered for our house.

The house is a four bed detached with two bathrooms. There are nine
radiators and two towel rails connected to the current system.

Current problems a-

1) The boiler is extremely noisy - needs a new / refurb fan
2) It can't heat the hot water to an acceptable temperature in winter
without reducing the flow to an unacceptable rate
3) The response time on the heating system is appalling - it takes
several hours for the house to reach an acceptable temperature.

Now I know I haven't gone into details about the sizing of each
radiator but my gut feeling is that 24kW - even if it was a brand new
boiler - is not adequate for a 4 bed / 2 bath house.

I am leaning towards either Worcester Bosch or Vailant. There is a
calculator on the WB website that recommends I get either a 37kW or
42kW boiler. Does that sound reasonable?

From info I have read on this group, I would expect that the size of a combi
boiler in this situation is likely to be governed by the flow rate of hot
water you want rather than its ability to heat the place.

I have a 1970s 4 bed property 1 bathroom 1 en-suite but opted for a
conventional system boiler install (retaining hot water cylinder - teenage
kids etc etc). Mine is a Worcester Bosch 24Ri which seems well upto the
job.
Took the opportunity to zone upstairs and down as part of the re-work.

HTH

Phil

On Thu, 20 Dec 2007 16:20:18 -0000, "Roger Mills"
wrote:

In an earlier contribution to this discussion,
stevelup wrote:

Hi

We currently have a 24kW Vokera combination boiler which was installed
in the early 90's.

I'm looking to replace it for many reasons not least of which is that
it is completely underpowered for our house.

The house is a four bed detached with two bathrooms. There are nine
radiators and two towel rails connected to the current system.

Current problems a-

1) The boiler is extremely noisy - needs a new / refurb fan
2) It can't heat the hot water to an acceptable temperature in winter
without reducing the flow to an unacceptable rate
3) The response time on the heating system is appalling - it takes
several hours for the house to reach an acceptable temperature.

Now I know I haven't gone into details about the sizing of each
radiator but my gut feeling is that 24kW - even if it was a brand new
boiler - is not adequate for a 4 bed / 2 bath house.

I am leaning towards either Worcester Bosch or Vailant. There is a
calculator on the WB website that recommends I get either a 37kW or
42kW boiler. Does that sound reasonable?

Thanks,

Steve

I have a 4 bed det house with 12 rads, double glazing, no cavity wall insulation, 100mm roof insulation, and a 18KW conventional boiler. The house is always toasty. Are you sure there isn't another problem?

On Thu, 20 Dec 2007 06:56:14 -0800, stevelup wrote:

Hi

We currently have a 24kW Vokera combination boiler which was installed
in the early 90's.

I'm looking to replace it for many reasons not least of which is that it
is completely underpowered for our house.

The house is a four bed detached with two bathrooms. There are nine
radiators and two towel rails connected to the current system.

Current problems a-

1) The boiler is extremely noisy - needs a new / refurb fan 2) It can't
heat the hot water to an acceptable temperature in winter without
reducing the flow to an unacceptable rate 3) The response time on the
heating system is appalling - it takes several hours for the house to
reach an acceptable temperature.

Now I know I haven't gone into details about the sizing of each radiator
but my gut feeling is that 24kW - even if it was a brand new boiler - is
not adequate for a 4 bed / 2 bath house.

I am leaning towards either Worcester Bosch or Vailant. There is a
calculator on the WB website that recommends I get either a 37kW or 42kW
boiler. Does that sound reasonable?

You current boiler is behaving really badly. A 24kW boiler should get
all 11 rads/rails untouchable in 20 minutes from a cold start.

I'd try not to go over board on a 37kW boiler. I think you'll find a 31kW
will be very acceptable and even a 24kW in working order will be a
welcome relief.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

On Dec 20, 8:44 pm, Ed Sirett wrote:

You current boiler is behaving really badly. A 24kW boiler should get
all 11 rads/rails untouchable in 20 minutes from a cold start.

I'd try not to go over board on a 37kW boiler. I think you'll find a 31kW
will be very acceptable and even a 24kW in working order will be a
welcome relief.

Hi

Thanks everyone for your replies. The hot water flow rate is probably
more important to us than the heating performance but unfortunately we
do not have space for a storage system.

It is possible (indeed likely) that the problems keeping the house
warm are more to do with the fact that it is poorly insulated and has
draughts coming through some ill fitting doors. I think that in the
new year I'll focus on getting the gaps plugged in the fabric of the
building!

I still intend on replacing the boiler because of its weak hot water
performance and noise, but I'll moderate the power output to something
more sensible.

The entire heating system has been constructed (not by me I must add!)
using Hep2O pipe, not copper. Will this be affecting the performance
significantly?

In terms of gas connectivity, there is a brand new 22mm supply pipe
running directly from the meter to the boiler (we have no other gas
appliances) which is approximately nine metres in length. I really
don't want to replace this - will it be adequate for a 31kW boiler?

Thanks,

Steve

On Thu, 20 Dec 2007 14:47:14 -0800, stevelup wrote:

On Dec 20, 8:44 pm, Ed Sirett wrote:

The entire heating system has been constructed (not by me I must add!)
using Hep2O pipe, not copper. Will this be affecting the performance
significantly?

No. Not even you know who thinks Hep2o affects performance.



In terms of gas connectivity, there is a brand new 22mm supply pipe
running directly from the meter to the boiler (we have no other gas
appliances) which is approximately nine metres in length. I really don't
want to replace this - will it be adequate for a 31kW boiler?

Is that 9m allowing for the bends and joints? If so you should be OK,
just.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

On Thu, 20 Dec 2007 06:56:14 -0800 (PST), stevelup
wrote:

Hi

We currently have a 24kW Vokera combination boiler which was installed
in the early 90's.

I'm looking to replace it for many reasons not least of which is that
it is completely underpowered for our house.

The house is a four bed detached with two bathrooms. There are nine
radiators and two towel rails connected to the current system.

Current problems a-

1) The boiler is extremely noisy - needs a new / refurb fan
2) It can't heat the hot water to an acceptable temperature in winter
without reducing the flow to an unacceptable rate
3) The response time on the heating system is appalling - it takes
several hours for the house to reach an acceptable temperature.

Now I know I haven't gone into details about the sizing of each
radiator but my gut feeling is that 24kW - even if it was a brand new
boiler - is not adequate for a 4 bed / 2 bath house.

I would recommend that you do this. Then you will know for sure what
power you need.

M

On Dec 21, 8:53*am, Ed Sirett wrote:
On Thu, 20 Dec 2007 14:47:14 -0800, stevelup wrote:
On Dec 20, 8:44 pm, Ed Sirett wrote:
The entire heating system has been constructed (not by me I must add!)
using Hep2O pipe, not copper. Will this be affecting the performance
significantly?

No. Not even you know who thinks Hep2o affects performance.

Thanks - I thought it was worth asking. As the rest of the system was
already Hep2o, all the bits I've added have also been done the same -
it seemed pointless to do otherwise. Literally the only bits that are
copper are the radiator tails and the first meter or so of pipe
leaving the boiler.

In terms of gas connectivity, there is a brand new 22mm supply pipe
running directly from the meter to the boiler (we have no other gas
appliances) which is approximately nine metres in length. I really don't
want to replace this - will it be adequate for a 31kW boiler?

Is that 9m allowing for the bends *and joints? If so you should be OK,
just.

The total length of pipe is 9M but there are 3 x 90 degree elbows:-

2M 90deg 2.5M 90deg 4M 90deg 0.5M.

Steve

On Dec 21, 10:53*am, Mark wrote:
On Thu, 20 Dec 2007 06:56:14 -0800 (PST), stevelup



wrote:
Hi

We currently have a 24kW Vokera combination boiler which was installed
in the early 90's.

I'm looking to replace it for many reasons not least of which is that
it is completely underpowered for our house.

The house is a four bed detached with two bathrooms. There are nine
radiators and two towel rails connected to the current system.

Current problems a-

1) The boiler is extremely noisy - needs a new / refurb fan
2) It can't heat the hot water to an acceptable temperature in winter
without reducing the flow to an unacceptable rate
3) The response time on the heating system is appalling - it takes
several hours for the house to reach an acceptable temperature.

Now I know I haven't gone into details about the sizing of each
radiator but my gut feeling is that 24kW - even if it was a brand new
boiler - is not adequate for a 4 bed / 2 bath house.

I would recommend that you do this. *Then you will know for sure what
power you need.

M

It's a little difficult to do though as I cannot directly identify the
radiators. If you think it is a worthwhile exercise, I'd could find
the nearest equivalent to each radiator in the Screwfix catalogue and
tot up the values.

I'm not convinced it is necessary though as the overall maximum power
output of the boiler is being selected to ensure the instant hot water
flow is adequate rather than the heating? Surely whatever boiler I
choose will be adequate from a heating point of view as much more
power is needed for the hot water than is needed to efficiently heat
the house.

If this is flawed logic, I'm willing to reassess.

Thanks,

Steve

"Ed Sirett" wrote in message
...
On Thu, 20 Dec 2007 06:56:14 -0800, stevelup wrote:

Hi

We currently have a 24kW Vokera combination boiler which was installed
in the early 90's.

I'm looking to replace it for many reasons not least of which is that it
is completely underpowered for our house.

The house is a four bed detached with two bathrooms. There are nine
radiators and two towel rails connected to the current system.

Current problems a-

1) The boiler is extremely noisy - needs a new / refurb fan 2) It can't
heat the hot water to an acceptable temperature in winter without
reducing the flow to an unacceptable rate 3) The response time on the
heating system is appalling - it takes several hours for the house to
reach an acceptable temperature.

Now I know I haven't gone into details about the sizing of each radiator
but my gut feeling is that 24kW - even if it was a brand new boiler - is
not adequate for a 4 bed / 2 bath house.

I am leaning towards either Worcester Bosch or Vailant. There is a
calculator on the WB website that recommends I get either a 37kW or 42kW
boiler. Does that sound reasonable?

You current boiler is behaving really badly. A 24kW boiler should get
all 11 rads/rails untouchable in 20 minutes from a cold start.

I'd try not to go over board on a 37kW boiler. I think you'll find a 31kW
will be very acceptable and even a 24kW in working order will be a
welcome relief.

He wants a decent DHW output.

In an earlier contribution to this discussion,
stevelup wrote:

On Dec 21, 10:53 am, Mark wrote:
On Thu, 20 Dec 2007 06:56:14 -0800 (PST), stevelup



wrote:
Hi

We currently have a 24kW Vokera combination boiler which was
installed in the early 90's.

I'm looking to replace it for many reasons not least of which is
that it is completely underpowered for our house.

The house is a four bed detached with two bathrooms. There are nine
radiators and two towel rails connected to the current system.

Current problems a-

1) The boiler is extremely noisy - needs a new / refurb fan
2) It can't heat the hot water to an acceptable temperature in
winter without reducing the flow to an unacceptable rate
3) The response time on the heating system is appalling - it takes
several hours for the house to reach an acceptable temperature.

Now I know I haven't gone into details about the sizing of each
radiator but my gut feeling is that 24kW - even if it was a brand
new boiler - is not adequate for a 4 bed / 2 bath house.

I would recommend that you do this. Then you will know for sure what
power you need.

M

It's a little difficult to do though as I cannot directly identify the
radiators. If you think it is a worthwhile exercise, I'd could find
the nearest equivalent to each radiator in the Screwfix catalogue and
tot up the values.

I'm not convinced it is necessary though as the overall maximum power
output of the boiler is being selected to ensure the instant hot water
flow is adequate rather than the heating? Surely whatever boiler I
choose will be adequate from a heating point of view as much more
power is needed for the hot water than is needed to efficiently heat
the house.

If this is flawed logic, I'm willing to reassess.

Thanks,

Steve

It is certainly true in most cases that if you size a combi boiler to give
an adequate water heating performance it will be more than adequate for
space-heating.

If there is a flaw in your logic it is in your assumption that even a new
24kW boiler wouldn't be adequate. It's a bit like convincing yourself that
you need a car with a 4-litre engine because your current 2-litre model will
only achieve 40mph, while ignoring the fact that the current car is only
firing on half its cylinders!

It would certainly do no harm to calculate the space heating requirements to
see what they *really* are. To do this you need to calculate the heat losses
for each room based on the construction, required temperature etc. - which
has nothing directly to do with the radiators which are currently fitted,
although you *will* need to assess their adequacy once you have calculated
the heat losses.

If your house is properly insulated (cavity wall insulation, double glazing,
thick loft insulation) I would be very surprised if the total losses
exceeded 15kW. If a 24kW boiler can't keep up with this, there's either
something drastically wrong with the boiler or else the radiators are far
too small and not utilising the boiler output properly. In my opinion, you
need to resolve these issues *first* - otherwise rushing out and buying a
new boiler may not solve the problem.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

"stevelup" wrote in message
...

High DHW output is your aim. Try:

Alpha CD50
Vaillant 937 (stored water version)
Worcester-Bosch 40 kW
Glow Worm 38kW

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
stevelup wrote:

On Dec 21, 10:53 am, Mark wrote:
On Thu, 20 Dec 2007 06:56:14 -0800 (PST), stevelup



wrote:
Hi

We currently have a 24kW Vokera combination boiler which was
installed in the early 90's.

I'm looking to replace it for many reasons not least of which is
that it is completely underpowered for our house.

The house is a four bed detached with two bathrooms. There are nine
radiators and two towel rails connected to the current system.

Current problems a-

1) The boiler is extremely noisy - needs a new / refurb fan
2) It can't heat the hot water to an acceptable temperature in
winter without reducing the flow to an unacceptable rate
3) The response time on the heating system is appalling - it takes
several hours for the house to reach an acceptable temperature.

Now I know I haven't gone into details about the sizing of each
radiator but my gut feeling is that 24kW - even if it was a brand
new boiler - is not adequate for a 4 bed / 2 bath house.

I would recommend that you do this. Then you will know for sure what
power you need.

M

It's a little difficult to do though as I cannot directly identify the
radiators. If you think it is a worthwhile exercise, I'd could find
the nearest equivalent to each radiator in the Screwfix catalogue and
tot up the values.

I'm not convinced it is necessary though as the overall maximum power
output of the boiler is being selected to ensure the instant hot water
flow is adequate rather than the heating? Surely whatever boiler I
choose will be adequate from a heating point of view as much more
power is needed for the hot water than is needed to efficiently heat
the house.

If this is flawed logic, I'm willing to reassess.

Thanks,

Steve

It is certainly true in most cases that if you size a combi boiler to give
an adequate water heating performance it will be more than adequate for
space-heating.

If there is a flaw in your logic it is in your assumption that even a new
24kW boiler wouldn't be adequate.

A good DHW output combi will be over 24kW

The message

from stevelup contains these words:

I'm not convinced it is necessary though as the overall maximum power
output of the boiler is being selected to ensure the instant hot water
flow is adequate rather than the heating? Surely whatever boiler I
choose will be adequate from a heating point of view as much more
power is needed for the hot water than is needed to efficiently heat
the house.

If this is flawed logic, I'm willing to reassess.

It doesn't matter how powerful the boiler is if the radiators are too
small. Other factors being equal doubling the size of a radiator will
double the heat output.

--
Roger Chapman

roger wrote:
The message

from stevelup contains these words:

I'm not convinced it is necessary though as the overall maximum power
output of the boiler is being selected to ensure the instant hot water
flow is adequate rather than the heating? Surely whatever boiler I
choose will be adequate from a heating point of view as much more
power is needed for the hot water than is needed to efficiently heat
the house.

If this is flawed logic, I'm willing to reassess.

It doesn't matter how powerful the boiler is if the radiators are too
small. Other factors being equal doubling the size of a radiator will
double the heat output.


It also depends on the house size and insulation

A masll house or flat with good insulatin may only require a Kw of heat
to keep it warm.But up to 30KW to run a shower.

OTOH houses that need 30KW to heat in winter are not uncommon. A case
for more insulation tho :-)

Mind you, such a house would be foolish to run the expected several
bathrooms of one 30KW combi...

In message , The Natural
Philosopher writes
A masll house

wpssat?

--
Si