Wood Burner with back boiler - heating installation questions
 

Firstly the wood burner is being installed by a qualified HETAS
engineer, so that is all under control.

It will be used to drive the central heating system and hot water.

My questions relate to the plumbing side.

I already have a hot water cylinder plumbed in to give hot water through
electric heating. It is an indirect cylinder and I have the indirect
coil plumbed "ready" for the woodburner.

However, looking at various web sites there seems to be a requirement
for a radiator in the indirect circuit to act as an additional load
(minimum 1kW). Does this radiator have to be at the same height (more
or less) as the cylinder or can it be lower? The reason I ask is that
(as you would expect) the hot water cylinder is upstairs but I would
like this "load" radiator to be downstairs.

Second question.

What is the physical make up of the back boiler? There are 4 tappings -
two for the hot water circuit and two for the heating circuit - are they
"commoned" inside" (it is not clear from any drawings or explanation).

Again, the reason I ask is that I have all the feed and expansion tanks
set up for the indirect hot water, when that is connected to the
heating, will the heating share the same feed and expansion or do I need
another tank in the loft!

Finally, is there a "best" place for the central heating pump? It is
shown in schematics as being in the return leg of the heating system,
but does it have to be next to the boiler or can it be a distance away?

Thanks in advance.

Peter

Second question.

What is the physical make up of the back boiler? There are 4 tappings -
two for the hot water circuit and two for the heating circuit - are they
"commoned" inside" (it is not clear from any drawings or explanation).

The four outlets are all commoned to the one water jacket.
There should be two near the top and two near the bottom of the jacket.

On my Bont ESSE Model Four I used the left hand two for the indirect
heating loop in the hot water cylinder. The top outlet to go to the top
of the heating loop and the bottom outlet of the jacket to the bottom
of the heating loop. The right hand pair of outlets were used for the
central heating (CH) circuit. The top (Hot) outlet had the circulation
pump fitted to it so that the pump pushed the hot water out to the
radiator circuit. The return (Cold) pipe went into the lower outlet of
the water jacket.

The cold water feed from your small 4 gallon header tank can connect
to the same pipe as goes to the bottom of the water jacket or the
bottom of the indirect heating coil.

My 'Leak' or 'Dump' radiator, which is not pumped, is on the same
level at the Bont ESSE. The cylinder is one floor up from the Bont
ESSE. The 'dump' radiator is effectively across the indirect heating
coil except in my case the cold, return from this 'dump' radiator,
returned to the pumped return pipe of the CH system. The reason for
this was because the cooler water output of the 'dump' radiator will
not go back up-hill to the indirect coil as that is virtually where it
came from in terms of water height.

Sit down and draw it. Remember the priciple of a 'U' tube, you can
NOT have a radiator higher than your 4 gallon header tank.

Chris.

Peter Sheppard wrote:
Firstly the wood burner is being installed by a qualified HETAS
engineer, so that is all under control.

It will be used to drive the central heating system and hot water.

snip

I appreciated you have already committed yourself to this configuration
but I will warn you, based on experience, that it does not work
whatever the stove seller says.

The problem is that the amount of heat you require to drive the CH
system requires the stove to be driven hard, and because the water
jacket does not totally encapsulate the flame as in a gas or oil
burner, there is a large amount of heat leakage with the result that
the room the stove is in gets uncomfortably hot. I considered using
hot air extraction and circulation to get round this but in the end
opted for an oil burner with the wood stove operating in parallel
through a mixer tank.

I will admit that I have never bothered with a bleed radiator and in 25
years have never had a problem.

Rob

Rob,
you could be right about the 'Bleed' or 'Dump' radiator in
normal situations but back in the 1983-84 Winter "We" had no
electricity for nine days and my dump radiator was the only one
working. I was giving hot water away to the neighbours and throwing it
down the drain. After three days when the house started to cool right
down I moved my bed next to the dump radiator and was glad I had
installed it.

Our lounge, with the Bont ESSE in does get real
warm............... nice.

Aberdeenshire and 24 inch think Granite walls.

Chris.