On Sun, 16 Nov 2003 22:54:49 -0000, "simon beer"
wrote:


Just moved house and we think the central heating could do with a once over
whilst we are redoing the kitchen, as boiler presently situated there.

We intend putting it in the garage, other side of the wall. We are going to
install a new boiler as we think the old one is prob inefficient and working
hard for the size of the house, although we put this down to its age. It is
an Ideal E Type 60N which we have been told is an ooold boiler.

System pipe work is also all in 15mm which could do with beefing up to 22 on
the main circuits if my thinking is right, any thoughts?

This really depends on the amount of heat that the pipes are
transporting. Before doing major surgery, it would be sensible to
calculate the requirements.

If it were me, I would work from first principles and not trust
anything already there. It seems that a lot of professional
installers work from fag packet rules of thumb and guess what is
required based on the area of the rooms multiplied by granny's
telephone number.

The radiator manufacturers have calculator programs which will do the
grunt work of heat loss calculations. Basically you measure all the
surfaces, choose the material type from a menu to determine the loss
factor or U value and then for each element multiply the temperature
difference across it by the area and the U value. The programs
simply tabulate and calculate it for you and add the results.
Look on the web sites of Myson and Barlo for examples. This is not
complex arithmetic.
You will end up with a heat loss for each room typically by choosing
-3 degrees for outside and appropriate temperatures for internal
rooms. The radiators need to make up for the heat loss. From the
heat loss in Watts you can refer to the radiator manufacturer's data
or the program to pick radiator sizes. This would be for an
installation from scratch. The radiators are connected generally
via 15mm pipe in groups, trunked to 22mm or in large systems 28mm for
connection to the boiler. Sometimes microbore in 8 or 10mm is used
and this generally connects to the 22mm directly at manifolds or other
junction points. The critical point is that the pipework is
adequately sized to carry the required heat. This is related to pipe
length and diameter and based on keeping the flow rate less than
1.5m/sec. If this is exceeded, the system will be noisy and/or not
enough water will flow to deliver the required heat.

There is a useful application note that you can download from the
Copper Development Association web site which gives data and worked
examples. www.cda.org.uk


If the system is otherwise heating the rooms adequately (you won't
know for sure because it hasn't been cold enough yet), then you can
start part way through and assume that the radiators are adequately
sized. In this case, find something looking the same on a
manufacturer's data sheet and determine radiators the same or close
in size to what you have. Take the output in Watts from that.
However, one point that is misleading in data sheets is that the
actual output, if you have a conventional UK spec boiler running with
82 degree flow and 70 return is that the actual output from radiators
is typically only 89% of the figures in the main table. This is
because the measurement method used assumes a higher water
temperature. Simply take the figures from the table and multiply
by 0.89 to get the actual output and the requirement. Then add
the figures of the radiators on given branches together following the
application note. You can get away with pipes being perhaps 10% or
so undersized, but much more than that and you won't get the heat
output.




Any way we are looking to change the current vented system to a sealed
system boiler, is this a good way to go?

Yes it is and very easy to do. Have a look at Ed Sirett's FAQ on
this. The only note that I would add is to make sure that you clean
the system very thoroughly (I've posted a way to do this a few times)
and be prepared to change the radiator valves as they may seep under
pressure. You are not talking about a lot of pressure - typically
2bar max. but it can be enough.



A couple of contenders on the list at www.discountedheating.co.uk are the
Worcester/Bosch SBI System Boiler 24SBI RSF or the Vaillant Thermocompact
RSF 624EH NG.

I would definitely consider going for condensing models from either of
these manufacturers. The Thermocompact and the Worcester Bosch SBI
only just scrape in above the minimum Building Regulation requirement
of 78% SEDBUK efficiency.

Installing these, although they are good makes seems a shame when you
can get a condensing model at about £150-200 more and achieve over
90%. The extra cost should easily be recoverable in the lifetime of
the boiler. There is discussion around raising the efficiency limit
to 86% from 2005 which would effectively take these lower efficiency
non-condensing products off the market.



I would appreciate some experienced input from those that know better than
me if these boilers are pretty much like for like. Do I need to buy extras
with one that I wouldn't with another; I notice there is also a price for a
SBI System Boiler Plug in Diverter Valve to go with the SBi do I need
something like this with either of them or does the Vaillant already have
it? Are there other boilers to seriously consider around this price point, I
should say that I not keen to go the combie route as I like to have the
stored hot water, just old fashioned I guess!!

Several people here have installed and been pleased with Keston
Celsius 25 which is a good value for money product,

If you do decide to stick with a vented HW system, and it certainly
does have a number of advantages, then it is worth changing the
cylinder for a fast recovery type to improve HW reheat performance
while you are at it.

Also the time clock is old
and playing up a little so thought better get one of the heating packs with
easy wire up panel, room thermostat & time clock etc. any recommendations of
names to go for.

Honeywell make good products as do Danfoss Randall. You may find
their RF products useful in eliminating wiring. There are also
useful features such as temperature set back for night use - the idea
is to drop the temperature about 5-6 degrees rather than turning off
the heat totally. This can be more efficient as well as being more
comfortable.



We also have an SMC Comet Controller Pump fitted next to our Grundfos pump,
what does that do?

Who knows. Perhaps there is one pump for the CH and another for the
DHW? I suspect that both of these will end up being chucked out and
a system of motorised valves used instead. The pump in a system
boiler should be able to do everything.





I'm sure I can come up with some more questions later but help with the
above will keep me going for now. I got her indoors breathing down neck to
get the boiler moved so I can get on with the kitchen as we have to
microwave everything at the moment!

Any body ever laid slate floor tiles?

Yes, and it is very hard work if you use the larger ones.




Thank for any imput



..andy

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