Heating your pond using your existing combination boiler.
Firstly if your existing combi needs to be 240 volt throughout, some early combi boilers have low voltage external controls, which will not be suitable for pond use.
All combination boilers have hot water override so whilst your radiators, or pond are in demand, should the hot tap be opened, the boiler will automatically transfer heat from say pond, to the hot water tap.
Providing you consider your self competent, the following works can be carried out WITHOUT the need for a CORGI engineer, as the gas supply to the boiler is not being interrupted.
You will however require an electrician ( or get an electrician to check ) to make final connections, to comply with building regulation Part P.
The following specification, assumes that the pond is reasonably local to the house and that the existing central heating circulation pump housed within the boiler can be used.
You will need :
22mm Zone valve for existing central heating demand.
22mm Zone valve for pond demand.
House thermostat.
Pond thermostat.
Pond heat exchanger.
Pipework
Switch of appliance at fused spur – plug, then remove either fuse or plug from socket.
Drain heating system complete.
Cut a 22mm T’s into central heating flow and return pipework, these T’s should be near the boiler, or before the 1st radiator, as you wouldn’t want a radiator/s to heat when your pond is in demand.
Whilst cutting the flow pipework to install your tee off, fit one of the zone valves onto the radiator flow pipe, fit the other zone valve onto the newly install branch pipework.
You can know run your pipework to the pond heat exchanger, use plastic as this is easier for the DIY’er and has better thermal values than copper.
When you connect to the heat exchanger, install a automatic airvent at the top connect to the HX, this will save a lot of grief should air get trapped in the system.
Connect the return pipework from the HX into the T branch back at the boiler, refill the combi to a maximum of 1.5 bar ( on the small gauge normally on the front of the boiler ) and the easy part is done !!
TIP
When running the plastic down to your pond ensure the pipework is housed within 100mm UPVC ( 100mm soil pipe will do ) this will protect the pipework and provide thermal some additional thermal value.
Would be a good idea to pull through a 5 core cable at this point, as this will be needed for you pond thermostat.
Wiring
Fit wiring centre ( terminal box ) close enough to the zone valves to utilise the black 5 core leads.
At the wiring centre you should have a terminal strip with 10 connections, wire each lead from zones into wiring centre. The Earth, ( yellow & green ) Neutral ( blue ) Permanent live ( grey ) Switch live ( orange ) should be coupled, the motor lives ( brown ) MUST have independent connections within the terminal strip.
Run 5 core from boiler to wiring centre.
Identify, the live earth & neutral connections within boiler. Identify the thermostat connections within the boiler and disconnect thermostat wiring.
Please note
When identifying the thermostat, wiring, you are after the in & out ( common live & switch live ) serving the stat, the IN wiring will be from the timing arrangements ( most probably a plug in clock ) the OUT wiring, is the demand back from the stat to tell the boiler to fire.
At the wiring centre, adjoin the earth and neutrals, then take the boiler live to a separate terminal.
Loop the boiler live ( brown ) with zone valves permanent live ( grey )
Now wire the thermostat wiring, the demand from the stat joins the brown at the central heating zone valve, join return wire from the zone ( orange ) back to the thermostat terminal in the boiler, to act as the switch.
You can now test the central heating mode if you wish.
What is actually happening
When you turn your combi on as normal, the power from your existing time clock sends a signal to your room stat, this then return through the central heating zone valve before joining back at the boiler.
When the stat calls for heat the zone valve will open, which then sends a signal back to the boiler to fire.
Pond Heating
Connect the 5core wire that you have run down to the pond to the pond thermostat. The stat will require a live neutral & earth, together with a common live and a switch live to return back to the zone valve / boiler.
Make the same L N & E connections at the wiring centre, you then connect the common for the pond stat to the permanent life ( grey wire from zone ), the switch wire from the stat then connects to the brown wire of the pond zone to complete the wiring.
What actually happens ( part 2 )
When the pond stat asks for heat, the switch live send a signal down to the motor of the zone valve which then opens , this then activates a micro switch which send power via the orange wire to the thermostat demand terminal in the boiler asking for heat.
When the pond stat is satisfied, the zone valve shuts on a spring return, the micro switch closes turning the boiler off.
Whilst long winded, I believe this to be the most simplest way of achieving pond heating of an existing combi.
If you have a very modern combi, with built in controls, then we would need to address this on an individual basis, but the principal is the same.
Hope this helps.
If so then admin may want this post to become a sticky
Kind regards
Andy
Heating you pond via an existing combination boiler
Moderators: B.Scott, vippymini, Gazza, Manky Sanke
