Central heating ideas
Helen
We're in the process of renovating an outbuilding and are looking at
various heating options.The room we need to heat is 5mx7m with a
pitched roof which is 4m high at its highest point. We have water and
electric in the building but no access to gas or an oil tank. The room
is insulated and drylined. We're looking for some ideas for a primary
heating source for this - and are open to any sensible suggestions. As
we have capacity in our house central heating system it has been
suggested we drill holes in one of the house exterior walls and attach
pipes between the house and the outbuilding at approx 10 feet off the
ground. Anyone any thoughts on this - is it a viable option? What
would we need to lag the pipes with? Does anyone have any better
suggestions?
Many thanks
Helen
Peter Crosland
The first thing is to get the insulation sorted out. These days the
requirements are strict and you will need building regulations approval for
it. This should include details of the heating arrangements. Your local
building control department should be able to give you some pointers. Don't
expect it to be cheap though.
Peter Crosland
Christian McArdle
> suggested we drill holes in one of the house exterior walls and attach
> pipes between the house and the outbuilding at approx 10 feet off the
> ground. Anyone any thoughts on this - is it a viable option? What
> would we need to lag the pipes with? Does anyone have any better
> suggestions?
Yes, bury the pipes underground. Use MDPE, well lagged buried below the
local height required for frost protection. Your local water company can
advise on recommended burial depths for your local area.
The new system connect into your central heating using a plate heat
exchanger on its own zone. This separates the outbuilding primary circuit
from your main one, making servicing easier and ensuring that the house
system is not compromised if there is a problem in the outbuilding or
underground pipework.
There will need to be an signal connection between the outbuilding and the
house so that when the programmable thermostat calls for heat, it can open
the heat exchanger zone valve and fire up the boiler/house pump. The
outbuilding pump can be either in the house or outbuilding.
Christian.
Andy Hall
wrote:
I have done an exercise almost identical to this with a building
(large garage to be precise) used as a workshop. It's a little larger
than what you describe but of the same order.
Its a single skin brick construction with wooden doors at one end and
prior to doing anything would require 12kW in fan heaters to bring it
up to house temperatures of 18 degrees plus. In practice I didn't do
that and used 6kW of fan heater capacity which was always inadequate,
took a long time to warm up and was expensive to run. It's easy to
work out what.
My first task was to insulate it, in effect to about the equivalent of
the current requirements for a house - at least in terms of heat loss
through walls and roof. This was done using sheets of Celotex
insulation because it has a very low U value (heat loss factor) for a
given thickness. I used timber framing and a ply clad so that I can
fix things easily to the walls. I insulated the doors similarly
and draught proofed with sealing strips.
I had calculated what the heat losses would be after doing this and it
came down to around 3kW to maintain the desired 18-21 degrees with -1
to -3 outside. Following the insulation work, I did some
measurements using one fan heater, and the results were close to what
was predicted.
So this is really the first step. Take a look at the insulation of
the building and calculate what you will need in terms of heat. The
radiator manufacturers have claculator programs to help with this but
you need to know the nature of the insulation and the rest of the
construction to be able to plug in the correct heat loss U values.
Myson and Barlo both have reasonably good programs, although Myson's
is not on their site last time I looked. If you want to drop me an
email I can send it to you.
If you are using the building as habitable space, it is a Building
Regulations requirement to insulate it to certain defined levels. You
can find details of this in Approved Documents to the Building
Regulations on www.odpm.gov.uk. Look at Part L1.
I still didn't want to use electricity for heating because I wanted to
maintain a minimum temperature of 10 degrees to keep materials and
tools from becoming affected by damp in the air.
I found references to how to deal with the case of having a boiler in
an outbuilding on the web site of the Northern Ireland Building
Regulations web site. However it no longer seems to be there. I can
send you a copy if you like.
Essentially, the idea is to use PVCu pipe (e.g. soil pipe(s) of 100 or
150mm diameter) buried in the ground and to run the heating flow and
return carrier pipes in that, insulating them with fairly substantial
pipe insulation.
First one would have to check pipe run distances and diameters. For
me, 22mm pipes were enough, but the garage is only a few metres from
the house. If you have a long run, you may need larger diameter
pipes. For 22mm pipe, the recommendation was to use 22mm insulation
such as Armaflex. You can fit two of these in a 150mm duct. The
recommendation for the duct is to bury it at a depth of 150 to 500mm
and surrounded in sand or pea gravel. Each end is then brought into
its building.
For the carrier pipes themselves, copper could be used, but it is a
lot easier to use plastic barrier pipe for the purpose since it can be
bent more easily while assembling the duct.
This gets you the basic installation.
Even with the insulation methods described, there would need to be
some frost protection to prevent water in the carrier pipes from
eventually freezing - i.e. running the pump and the boiler for short
periods if temperatures fall
I felt that it was important, considering that this was an outbuilding
that *could* be unheated, to have a way to protect the integrity of
the house heating system from failure or freezing related to the
outbuilding, so I took a different approach.
The circuit for the outbuilding is run completely isolated from the
house one by the use of a stainless steel heat exchanger.
http://www.gea-ecobraze.com/
These are typically used for thermal stores etc. where it is necessary
to transfer a lot of heat quickly between separate bodies of water (in
that case heated water in a cylinder to a flow of mains tap water).
They cost under £100 and work very efficiently - i.e. for this purpose
do not limit the rate of heat transfer between circuits. FOr heating
purposes on this scale, it is as though the circuits were really one.
THe technique is also used for heating swimming pools.
The primary (supply side) of the heat exchanger is connected into the
indoors heating circuit as though it is a heating zone. Heating water
flow to it is controlled by a motorised valve according to Honeywell's
S-plan+ scheme.
http://content.honeywell.com/uk/homes/systems.htm#S%20Plan%20Plus
The valve is controlled by a flow switch (as opposed to a room
thermostat) fitted in the *secondary* circuit from the heat exchanger.
More of this in a moment.
The secondary circuit is filled and pressurised with a sealed system
vessel as though it was a conventional sealed CH system but with the
heat exchanger being the heat source (i.e. "boiler"). One could use an
open vented arrangement but there is no need.
I fitted the pump and a room thermostat/time controller in the
outbuilding. This is a simple arrangement and the pump runs and
circulates water in the secondary circuit when heat is needed. The
flow switch in the circuit, located near the heat exchanger in the
house, operates when secondary water flows, causes the motorised valve
feeding the heat exchanger to open and the boiler to fire. The
advantage of this approach is that there is totally separate control
for the outbuilding without the need to have control wiring back to
the house.
I didn't want to mess about with frost thermostats etc., so I used an
alternative approach of a corrosion inhibitor with antifreeze (Fernox
Alphi-11) in the secondary circuit. THis stuff is relatively
expensive which is another reason to have separate circuits. I added
sufficient to protect down to -20 degrees which should cover anything
in the UK at present.
Finally, I did size the radiators larger than needed to compensate for
heat loss. This is because I often like to go and use the workshop in
the evening and want it to warm quickly. Therefore there is 9kW of
radiator capacity, even though only 3-4 is needed in the steady state.
How does it work? Really rather well and this is the third winter.
Not an expensive solution in terms of capital cost either. THe
fiddliest bit was threading the insulated pipes through the duct work
on a cold day. Plastic pipe is not as flexible when cold as one might
like.
--
.andy
Andy Hall
<cmcar...@nospam.yahooxxxx.co.uk> wrote:
>
>There will need to be an signal connection between the outbuilding and the
>house so that when the programmable thermostat calls for heat, it can open
>the heat exchanger zone valve and fire up the boiler/house pump. The
>outbuilding pump can be either in the house or outbuilding.
>
Flow switch, Christian :-)
See other post.
--
.andy
vortex2
"Helen" <helen.r...@oracle.com> wrote in message
news:1135176855....@o13g2000cwo.googlegroups.com...
We have a room in our office that has a combined aircon/heat pump unit. It
is amazing.
They aren't expensive (example
http://airconwarehouse.co.uk/air_conditioning_shop.htm)
Relatively energy efficient
They cool as well
VERY "turn off and onable"
Don't freeze up.
Must be much less grief than messing around with plumbing.
David
Christian McArdle
Ah yes. I should have thought of that!
Christian.
Pete C
<dhe...@DELETE.firstsightvision.co.uk> wrote:
>We have a room in our office that has a combined aircon/heat pump unit. It
>is amazing.
>
>They aren't expensive (example
>http://airconwarehouse.co.uk/air_conditioning_shop.htm)
>Relatively energy efficient
>They cool as well
>VERY "turn off and onable"
>Don't freeze up.
>
>Must be much less grief than messing around with plumbing.
Hi,
What make and model do you have?
cheers,
Pete.
vortex2
>>
>>They aren't expensive (example
>>http://airconwarehouse.co.uk/air_conditioning_shop.htm)
>>Relatively energy efficient
>>They cool as well
>>VERY "turn off and onable"
>>Don't freeze up.
>>
>>Must be much less grief than messing around with plumbing.
>
> Hi,
>
> What make and model do you have?
>
> cheers,
> Pete.
Daikin FTXS 35 C
IIRC about £1000 installed. I think they're cheaper these days.
David
meow...@care2.com
> I still didn't want to use electricity for heating because I wanted to
> maintain a minimum temperature of 10 degrees to keep materials and
> tools from becoming affected by damp in the air.
Putting a humidistatic dehumidifier in instead of always heating would
save you a nice sum. Even if you add a 3kW electric fan to help bring
it upto temp when you go there in the evening.
NT
Andy Hall
I don't really want the wide temperature swings either. There is in
any case a dehumidifier which is used when needed.
Considering the average temperatures through the year and amount of
the time that it is below 10 degrees inside, I calculated it to be
about 300W of heating on a continuous basis. At 2p a unit, it's about
£50 a year which is fine as far as I'm concerned.
--
.andy