Hi i'm looking at adding 3 radiators to my heating system, the boiler
is a combi and only 18months old. It can take 14 radiators. I will
check the max btu it can take, and make sure it's all ok. I only have 6
radiators on the house at the moment.

Now i have looked in the kitchen attic and the boiler has 2 22mm pipes
coming out (F&R) and they then go into a 15mm (F&R) pipes ones goes
left the other right, now the one going rights feeds 2 radiators the
kitchen and bathroom. And the other on feeds the whole of the house,
bed1, bed2 then comes downstairs and feeds the living room and dining
room.

Now i'm looking at adding 2 upstairs in Bed 1 and landing and one
downstairs the hall (this will come from upstairs.

Now i know you should really only have 3/4 radiators off 1 15mm run so
i'm maxed out coming off the run that's there.

How do i go about making a new return and flow so can feed the new 3
radiators i require?

I've done a little reading, is it just cutting into the 22mm with a
15mm 't' joint and then feed that up and then feed each radiator, and
doing the same with the return?

I know i need to drain the system aswell.

Any help would be great

On Thu, 29 Dec 2005 08:43:53 -0800, htmark98 wrote:

Hi i'm looking at adding 3 radiators to my heating system, the boiler
is a combi and only 18months old. It can take 14 radiators. I will
check the max btu it can take, and make sure it's all ok. I only have 6
radiators on the house at the moment.

Now i have looked in the kitchen attic and the boiler has 2 22mm pipes
coming out (F&R) and they then go into a 15mm (F&R) pipes ones goes
left the other right, now the one going rights feeds 2 radiators the
kitchen and bathroom. And the other on feeds the whole of the house,
bed1, bed2 then comes downstairs and feeds the living room and dining
room.

Now i'm looking at adding 2 upstairs in Bed 1 and landing and one
downstairs the hall (this will come from upstairs.

Now i know you should really only have 3/4 radiators off 1 15mm run so
i'm maxed out coming off the run that's there.

How do i go about making a new return and flow so can feed the new 3
radiators i require?

I've done a little reading, is it just cutting into the 22mm with a
15mm 't' joint and then feed that up and then feed each radiator, and
doing the same with the return?

I know i need to drain the system aswell.

Any help would be great

You're heading in the right direction.



--
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

So if i go ahead it will be ok?

Whats the rule about plastic pipes and how close from the boiler it can
be?

Never done any soldering before so try and avoid that if i can.

On 29 Dec 2005 08:43:53 -0800, "htmark98"
wrote:

Hi i'm looking at adding 3 radiators to my heating system, the boiler
is a combi and only 18months old. It can take 14 radiators.

That doesn't mean an awful lot. What is important is the size and
hence heat output of the radiators.


I will
check the max btu it can take, and make sure it's all ok. I only have 6
radiators on the house at the moment.

If you can provide the make and model of the boiler, then it should be
easy enough to find its range of heat output in kW.



Now i have looked in the kitchen attic and the boiler has 2 22mm pipes
coming out (F&R) and they then go into a 15mm (F&R) pipes ones goes
left the other right, now the one going rights feeds 2 radiators the
kitchen and bathroom. And the other on feeds the whole of the house,
bed1, bed2 then comes downstairs and feeds the living room and dining
room.

Now i'm looking at adding 2 upstairs in Bed 1 and landing and one
downstairs the hall (this will come from upstairs.

Now i know you should really only have 3/4 radiators off 1 15mm run so
i'm maxed out coming off the run that's there.

No that isn't true. What actually matters is the flow rate through
the pipe - there is a maximum for that which should not be exceeded so
that turbulence and noise from the pipework doesn't happen.
It is related to the diameter and length of pipe.

When a heating engineer designs a system, he takes (should take) into
account first of all the heat required for the room in order to keep
it at the required temperature inside when the temperature outside is
low. (-3 degrees outside is used to work out the worst case.)
From that, he sizes the radiator(s) required to achieve that.

Once that is done, the flow rate for each radiator can be calculated
(the more the output, the greater the required rate).

Pipe runs can be determined from that, and must be adequate to support
the required flow. If the pipe is inadequately sized, the flow will
be inadequate and so will the radiator heat outputs.

So before you start....

- You need to know the required outputs for the new radiators. This
can be done by measuring the rooms and working out the heat loss
through the different surfaces. You also have to account for air
changes in the room and heat the replacement air.
This can be done with a calculator and a table of U values that can be
obtained from the Approved Documents to the Building Regulations
(www.odpm.gov.uk) or you can download a program for doing it all from
www.barlo.co.uk

- Don't be tempted to guess what's needed or to work from a rule of
thumb from a leaflet picked up in B&Q. Houses vary enormously in
terms of insulation and heat required also varies considerably for a
given size of room.

- Once you know the heat required in kW, you can go to any of the
radiator manufacturer web sites and pick your radiators. Don't forget
that you need to apply a correction factor of 0.9 to account for a
difference in the measuring technique used by the manufacturers and
the practical temperature of water from the boiler. Do this by taking
your heat requirement, dividing by 0.9 and using that figure to pick
the radiators.

- Measure the sizes and determine the types (number of fins and
panels) of the existing radiators on each 15mm section. Look these
radiators up in the data sheets (near as you can) to determine what
their nominal output is. Multiply these by 0.9 to determine real
output.

- At this point, you can either be scientific or use a rule of thumb
to determine whether the pipes are up to providing the flow.

The scientific way is to calculate the flow required for the relevant
radiators using (heat emitted = mass x specific heat x temperature
fall).
Temperature fall is temperature difference across radiators which
should be around 12 degrees.
Specific heat for water is 4.2 J/g.degC
Heat is in watts.
If you plug in the numbers, you will get a flow rate in grams/second.
Knowing the diameter of the pipe and that 1 litre of water weighs
approx 1kg, you can calculate the flow rate required through the pipe.
This should not exceed 1.5 metres/sec.
There is an application note on the Copper Development Association web
site which explains all this and also gives tables to make the sums
easier.

The rule of thumb way is to say that 15mm tube over distances of less
than about 10m or so, can support the flow needed to provide 6kW of
heat output in total.

If you do this work, which takes less time than it sounds, you may
find that you can add your radiators onto existing runs.



How do i go about making a new return and flow so can feed the new 3
radiators i require?

If your existing 15mm runs would be exceeded by adding more radiator
capacity, then you have two options.

- Upgrade sections of the 15mm to 22mm to take the 22mm closer to the
point where you want to branch off

- Run 15mm sections all the way from the 22mm.




I've done a little reading, is it just cutting into the 22mm with a
15mm 't' joint and then feed that up and then feed each radiator, and
doing the same with the return?

Basically yes, with the caveats above.




I know i need to drain the system aswell.

Yes you do, and when you refill it, please do remember to flush it
well to remove any flux residue and then to add a good quality
corrosion inhibitor.




--

..andy

On 29 Dec 2005 09:03:10 -0800, "htmark98"
wrote:

So if i go ahead it will be ok?

Whats the rule about plastic pipes and how close from the boiler it can
be?

Never done any soldering before so try and avoid that if i can.

At least 1 metre is normally recommended.

Soldering is really not difficult though.....

Also, by the time you've paid the extra for the pipes and fittings for
plastic, you will have enough to buy a blow torch and the other items
for copper plumbing.


--

..andy

Many thanks Andy, Gonna work all that out later.

One of our radiators in the bedroom is already making a 'banging' noise
so i think that may be a sign that there are too many rads on the run
already.

It terms of BTU i've worked it out (approx) to be

Rad 1 (600x1600) 6145
Rad 2 same 6145
Rad 3 same 6145
Rad 4 (500x1000) 3275

Total BTU 21,710 off one run going left now the 22mm goes into another
run (so only 1 pipe really)

I will do the sums later and work it out right.

Again thank you for all your help

In an earlier contribution to this discussion,
htmark98 wrote:

So if i go ahead it will be ok?

Whats the rule about plastic pipes and how close from the boiler it
can be?

Never done any soldering before so try and avoid that if i can.

If you use plastic pipe, it *must* be barrier pipe, and must not be within 1
metre (as the pipe runs rather than straight line) of the boiler.

The limit to what you can run off 15mm pipes is defined in terms of heat
throughput rather than number of radiators. In other words, you can have a
couple of big ones or lots of little ones. The general rule of thumb is a
max of 6kW. [I would recommend that you work in kW rather than out-of-date
and deprecated BTUs].

You appear to have one 15mm branch which is much more lightly loaded than
the other one. Can you tap into that - or does it go the wrong way?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

On 29 Dec 2005 09:46:25 -0800, "htmark98"
wrote:

Many thanks Andy, Gonna work all that out later.

One of our radiators in the bedroom is already making a 'banging' noise
so i think that may be a sign that there are too many rads on the run
already.

Does it have a thermostatic valve? If so, it might be fitted the
wrong way round.

It terms of BTU i've worked it out (approx) to be

Rad 1 (600x1600) 6145
Rad 2 same 6145
Rad 3 same 6145
Rad 4 (500x1000) 3275

Total BTU 21,710 off one run going left now the 22mm goes into another
run (so only 1 pipe really)

I will do the sums later and work it out right.

It's best to stick to one unit of measure if you're doing the sums.
When something is out by a factor of 10 it's usually obvious, but so
many of the conversions between imperial and metric are 3s and 4s and
it's easy to go wrong.

For the above you can divide BTU/hr by 3412 to get kW, so 6.4kW for
the 21710. That's about the limit.





--

..andy

It goes the other way,
Both the flow and return are like this

22 (from boiler apx 2.5m of pipe)
I
(this feeds 2 rads) 15mm -------I------- 15mm (feeds 4 rads) *

*This is the way i want the extra 3 rads

Cheers Andy, i think i have the other feed on the same line aswell,
diagram sort of above.

So working out the other rads aswell i got about 7.9k off one line if
what it looks like is right, now what is the best way to get this
sorted. aswell as running the new rads?

It goes the other way,
Both the flow and return are like this


22
I
(this feeds 2 rads) 15mm -------I------- 15mm (feeds 4 rads) *


*This is the way i want the extra 3 rads

Done a quick diagram for you

http://img517.imageshack.us/img517/1900/22mm1il.png

On 29 Dec 2005 12:14:25 -0800, "htmark98"
wrote:

Cheers Andy, i think i have the other feed on the same line aswell,
diagram sort of above.

So working out the other rads aswell i got about 7.9k off one line if
what it looks like is right, now what is the best way to get this
sorted. aswell as running the new rads?

Basically I think there are a couple of options, considering that you
are at or above the limit of the existing 15mm branch that you had
hoped to use.

1) For least disturbance of existing. Check that the three new
radiators that you will need together don't exceed 6kW. Assuming this
to be true, then plumb them up and run the new pipes all the way back
to the 22mm section and connect onto there. Obviously if the new
radiators exceeded 6kW you would need to run in 22mm for the first
section and branch to 15mm at the first one - basically to make sure
that 15mm runs are not being expect to carry 6kW.

2) For less pipe and possibly less work. Work out the existing
layout of radiators and pipework and the amount of heat in kW going
through each section. For example, if there is a final run in 15mm
covering two radiators each of 1.5kW, then you would have 3kW in the
common section and so on.
Now add in the new radiators on your sketch with pipes connected to
the locations on the existing 15mm run that are most convenient for
connection. Again add up the figures and determine the point where,
going in the direction of the boiler, the load exceeds 6kW. From that
point, back towards the boiler you will have to change for 22mm.

Have a look at this and all will be explained.

http://www.cda.org.uk/megab2/build/Pub150%20UKCB.pdf



--

..andy

Thanks for the link andy.

will probally do the 1st choice as i'll do all 3 and work back to the
22mm then.

Now as the run of the 15mm goes straight across the 22mm and feeds 6
rads, would it be better to cut the one feeding 4 rads on it's on run
to be sure.

Is there a rule how many times i can cut into 22mm pipe? the pipe is
only about 2m long.

Thanks for the link andy.

will probally do the 1st choice as i'll do all 3 and work back to the
22mm then.

Now as the run of the 15mm goes straight across the 22mm and feeds 6
rads, would it be better to cut the one feeding 4 rads on it's on run
to be sure.

Is there a rule how many times i can cut into 22mm pipe? the pipe is
only about 2m long.

On 29 Dec 2005 13:29:39 -0800, "htmark98"
wrote:

Thanks for the link andy.

will probally do the 1st choice as i'll do all 3 and work back to the
22mm then.

Now as the run of the 15mm goes straight across the 22mm and feeds 6
rads, would it be better to cut the one feeding 4 rads on it's on run
to be sure.

You can apply exactly the same rule for 22mm pipe as for 15mm - I
forget what its maximum carrying capacity is - but you can work it out
from the CDA paper. As a clue, it's only in pretty large
installations that it is necessary to exceed 22mm for the first run
from the boiler, so you can work it the other way based on boiler
output.



Is there a rule how many times i can cut into 22mm pipe? the pipe is
only about 2m long.

No it's OK. Bear in mind that you need to keep a metre or so from the
boiler if you use plastic.

Once you have finished, it's quite likely that you will need to
rebalance the system as a whole to achieve correct water flows and
temperature drops across all the radiators.

There are two ways to do this in the group FAQ.




--

..andy

Cheers andy will look at those, i roughly know how to drain the system,
but people recommend to clean the system, how does one do this?

On 29 Dec 2005 13:51:09 -0800, "htmark98"
wrote:

Cheers andy will look at those, i roughly know how to drain the system,
but people recommend to clean the system, how does one do this?

The simple way is to successively drain and refill the system.
However, this will only dissolve and remove chemicals such as flux
from soldering. You can add a flushing agent and run the system hot
for a week or so and then drain, flush and refill, adding inhibitor.

If the system is reasonably new and clean and no sign of sludge, black
water or other crap, then that would be good enough.

If there is sign of crud in the system, then plan B is to flush at
each radiator.

Here are the steps:

- Drain the system.

- Take radiators off one at a time by undoing valve unions. Close
valves. Place containers under each radiator valve union. Make sure
you use plenty of old towels, newspaper and a plastic sheet. Sludge
contains iron compounds which dye indellibly. Tip remaining water in
radiator carefully into tray and then attach a plastic bag to each
tail with a rubber band.

- Take radiators outside and flush with a mains hose or pressure
washer, tapping them gently as you do to loosen any crud inside.

- Put small containers under each radiator valve and turn on the water
slowly. Check that there are not any which leak badly.

- With water still on and larger container under radiator valve (cat
litter trays are good for this), open the valve and allow flushing out
until water is clear. Close valve and repeat for all valves. The
benefit of the approach is that crud can only leave the system, not be
circulated.

- Refit radiators and refill system adding inhibitor.

An alternative is to rent a power flushing machine. This avoids
needing to remove the radiators.....



--

..andy

It's only 18 months old the boiler that is. thanks for all the advice.

Now how to solder is my next step as figure it will be cheaper than
plastic and compression joints.