wood burner, back boilers and gravity fed central heating

[soxer]

Hello, We are hoping someone out there can help and advise.
We have just put gas central heating in after many years of not being able to get gas where we live.
We have always heated the bungalow using a wood burner with a back boiler and a hot water tank (for the water!!) with a top up tank in the loft. The wood burner, boiler and top up tank remain as we would still like to use the open fire. We have been advised already to add a couple of radiators to the back boiler and we can then use this as a secondary heat supply on its own circuit - single pipe loop has been suggested as easier.
Can this be done without using a pump? Do we need to put any valves in for over heating?
Can anyone help?
Thanks

 

[g20]

is your back boiler only doing the hot water at the moment (like an old circulator) or are there rads already connected to it as well? If it is only doing hot water then it could be a direct hot water cylinder, if so adding radiators is not reccomended, as you'll be mixing the central healing water with your potable water.

Also a 1 pipe system is extremely inefficient and building regs don't allow these to be fitted anymore, You would almost certainly need a pump too, as gravity can only really be used where there is alot of rise an fall (as there will be on your hot water from back boiler to cylinder)

It doesn't sound like a sensible or ecconomic option to me

 

[muggles]

Almost right g20, although hot water isn't counted as potable, so mixing doesn't present a huge problem. Having said that, I'd be inclined to install non-ferrous rads if it is a direct system - there needs to be a heatleak somewhere to prevent the water in the cylinder overheating.

If the fire is going to be used anyway then I would say that using the heat to heat up the water is extrememly economical and very efficient. I agree that it would have to be a two-pipe system though (although of course if it's DIY then they will do what they wish and nobody will ever know).

Gravity circulation should work well providing it is piped correctly. Valves should be added for servicing but must be left on at all times, including on the rads, this will prevent overheating. The last thing you want to do is boil the water in your back boiler

 

[g20]

if they added a central heating circuit on to the hot water circs, then whenever the hot water came on then so would the rads, so if you are going to do this, then you would probably want to add zone valves, an if your doing this you might as well add a pump no?

an central heating water going through steel rads an possible some inhibitor or other chemicals in system, being added to hot water cyclinder? an are you sure your hot water isn't counted as potable i always thought it was

 

[muggles]

Agreed, but I got the impression that the gas boiler was being used for the central heating and that the idea was to use the back boiler to heat the water. As the back boiler would continually heat the water to boiling point, there needs to be a heatleak rad somewhere, usually in a bathroom, to dump the excess when the cylinder's up to temperature.

I said I'd use non-ferrous rads, IE ones not made of iron or steel that would therefore not rust. There are still some copper ones around...or copper/brass towel rails that would be fine in a bathroom. No hot water is not potable, potable water is fluid risk category 1, hot water is FRC2