A friend has moved into a new small house and I was trying to sus out her
heating system as she has no independant control of her HW. It looks like
there's only one time clock that turns everything on & off.

I assumed at first that it would be on older system utilising thermosyphon
for the HW and pump for the CH but when I looked in her airing cupboard at
the tank, I discovered that the coil is plumbed with a mixture of 15mm and
8mm pipework and it has lots of right angled bends so I don't think theres
anyway that's working without a pump!

As far as I can make out, the boiler (a wall mounted open vented Baxi of
some sort) has only a single inlet & outlet.

My friend would like to be able to have HW only in the summer but it seems
that the only way to do that is to turn off all the radiators.

What would be the simplest way of achieving this? My first thought was to
add a motorised valve or two but finding where the CH system pipework
diverts from the HW tank circuit might not be easy. Alternatively, could
one add a second pump in the airing cupboard to circulate water just to the
tank (bearing in mind the 8mm pipework)? The radiators are all plumbed with
8mm pipes and the upstairs radiators are very slow to warm so there may be
sludging issues with the system. Some water I had to drain off to fix a
leaking connection was clear though.

Tim

On Dec 4, 9:53*am, "Tim Downie" wrote:
A friend has moved into a new small house and I was trying to sus out her
heating system as she has no independant control of her HW. *It looks like
there's only one time clock that turns everything on & off.

I assumed at first that it would be on older system utilising thermosyphon
for the HW and pump for the CH but when I looked in her airing cupboard at
the tank, I discovered that the coil is plumbed with a mixture of 15mm and
8mm pipework and it has lots of right angled bends so I don't think theres
anyway that's working without a pump!

As far as I can make out, the boiler (a wall mounted open vented Baxi of
some sort) has only a single inlet & outlet.

My friend would like to be able to have HW only in the summer but it seems
that the only way to do that is to turn off all the radiators.

What would be the simplest way of achieving this? *My first thought was to
add a motorised valve or two but finding where the CH system pipework
diverts from the HW tank circuit might not be easy. *Alternatively, could
one add a second pump in the airing cupboard to circulate water just to the
tank (bearing in mind the 8mm pipework)? *The radiators are all plumbed with
8mm pipes and the upstairs radiators are very slow to warm so there may be
sludging issues with the system. Some water I had to drain off to fix a
leaking connection was clear though.

Tim

You cant get much power through 8mm pipe. Only you can trace what
control exists and where the pipes go, to see if you can add a valve
on the CH.


NT

On 04/12/2011 09:53, Tim Downie wrote:
A friend has moved into a new small house and I was trying to sus out
her heating system as she has no independant control of her HW. It looks
like there's only one time clock that turns everything on & off.

I assumed at first that it would be on older system utilising
thermosyphon for the HW and pump for the CH but when I looked in her
airing cupboard at the tank, I discovered that the coil is plumbed with
a mixture of 15mm and 8mm pipework and it has lots of right angled bends
so I don't think theres anyway that's working without a pump!

As far as I can make out, the boiler (a wall mounted open vented Baxi of
some sort) has only a single inlet & outlet.

My friend would like to be able to have HW only in the summer but it
seems that the only way to do that is to turn off all the radiators.

What would be the simplest way of achieving this? My first thought was
to add a motorised valve or two but finding where the CH system pipework
diverts from the HW tank circuit might not be easy. Alternatively, could
one add a second pump in the airing cupboard to circulate water just to
the tank (bearing in mind the 8mm pipework)? The radiators are all
plumbed with 8mm pipes and the upstairs radiators are very slow to warm
so there may be sludging issues with the system. Some water I had to
drain off to fix a leaking connection was clear though.

That does sound rather odd. The section of 8mm pipe on the heating coil
circuit might just be a crude attempt to balance the flow between DHW
and CH.

AIUI with microbore which became popular in the 1970s radiators were
often supplied via a manifold to cut out long runs of very thin pipe
that didn't have much heat capacity anyway. The information I have from
that time refers to 3/8" and 1/4" pipe. I assume 3/8" is roughly
equivalent to 8mm which apparently had a heat carrying capacity of 5200
Btus and a maximum run of 50 feet. To put 5200 Btus into context a 24"
high single panel (no fins) radiator 73" long was rated at 4950 Btus/hr.

I would have thought that the 8mm pipe would have been bent into shape
without any actual elbows to cut down on drag but that is little more
than guesswork as I have never actually been involved with microbore.

--
Roger Chapman

NT wrote:
On Dec 4, 9:53 am, "Tim Downie" wrote:


You cant get much power through 8mm pipe. Only you can trace what
control exists and where the pipes go, to see if you can add a valve
on the CH.

As I said though, tracing pipes might be quite difficult (and disruptive).
I was interested in whether the second pump option was viable as it would
be easy to install in the airing cupboard. I'm just not sure whether it
would work given the 8mm pipework through the coil.

Tim

Tim Downie wrote:
(odd heating system)

This sounds exactly the sort of system that we had at my Mum's
house in the 1980s and in my house in the 1990s. The hot water
tank heat exchanger is "just another radiator", with a section
of 8mm piping to reduce the flow through it (Mum's house) or a
valve (my house).

Probably the simplest thing to do is add a motorised valve on the
radiator feed and change the controller. This relies on the hot
water tank being the first item on the system so you can put the
valve immediately after it:

--PUMP----+--VLV--+--------+-----+
| | | |
HWC rad other rads
| | | |
----------+-------+--------+-----+

You may find (as in my Mum's house) that the bathroom radiator
is before the hot water tank, eg:

--PUMP----+-------+---VLV---+-----+
| | | |
rad HWC other rads
| | | |
----------+-------+---------+-----+

JGH