Central Heating system in old house - help needed!

I bought a house with 3 separate heat sources able to provide heating for the domestic hot water and/or central heating.

1 - Rayburn (heats hot water only) 2 - Standard Oil Boiler (heats hot water and central heating) 3 - Open fire with back boiler (heats hot water and central heating).

I have been using 1 and 2 simultaneously with little problem since November. I have been given to understand by the previous owner that to use the open fire w/back boiler I must go into the loft and "change the systems over" since running the back boiler with the oil boiler would obviously lead to overheating.

The systems are interconnected, but having had a look in both lofts, I can't quite see what is connected where.

There are:

2 standard hot water tanks (both in different loft spaces). 2 cold water tanks (of different sizes) (both in different loft spaces). 1 header/feeder tank for the central heating. 1 central heating pump next to the oil boiler in the kitchen. 1 central heating pump in the loft above the open fire.

All I really want is to understand how this is all put together, how it works, what can/can't operate simultaneously etc.

Whilst I realise that what I need is a plumber to come in and look/map out/explain the system, can anyone suggest any websites/books/information that would give me a start at understanding the maze of pipes in this house?

Reply to
argosgold
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Your plumber will roll his eyes and take in a big in-draw of breath, but what you need to have is a Dunsley Neutraliser in your back-boiler/ oil burner circuit.

Depending on how good your plumber is, will depend on whether a) he has heard of such and b) whether he is capable of installing such.

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Basically it is a microtank in which all the heat sources mix at a neutral pressure point. I've installed one myself 25 years in just your situation (wood burning stove but that's still a back boiler), and I've never had any problems, and certainly no need to switch things over. I suppose I could say this does that itself.

The one thing that you do need to look into is a system of switching off the oil burner when the back boiler water is hot - the logic behind the fire and boiler, programmer and thermostat, and CH and DHW is not that simple - I've a home brewed box for that. But then I'm an electronic engineer and look to find nice complex solutions for simple problems.

Come back if you want more info.

Rob

Reply to
robgraham

The purpose of the "changeover" is to prevent hot water from your oil fired boiler circulating through the open fire back boiler when the fire is not lit so wasting heat. (And vice versa.) There are several ways of achieving this with manual valves, so no-one else can help you without a layout diagram.

The likely valves are the ones intended for isolating the circulation pumps, ie these valves are only open when the pump is in use for that heating appliance when it is on and closed when it is not in use. (Only one valve per pump need be operated if this is the case.)

The tanks should be at the same height too, or the lower one could overflow.

Reply to
harry

BTW, the normal way to have multiple heat sources is to pipe in a non- return valve on each boiler/source. This prevents reverse circulation automatically in unused boilers without having to fiddle with hand valves

Reply to
harry

More bollocks. Will stop reverse circulation but doesn't stop circulation in the normal direction, which may not be wanted.

The correct solution is either Dunsley Neutraliser as already mentioned or all the primaries connected to a single thermal store. With the combination of heat sources the OP has I'd be looking at the thermal store approach.

Reply to
Dave Liquorice

Manual valves or anything that stops the gravity circulation from the solid fuel back boiler is not a Good Idea. As sure as eggs is eggs at some point the fire will be lit with the circulation prevented. Worst case scenario is a boiler explosion, not something desirable in your living room...

Reply to
Dave Liquorice

Only if there are valve on both flow and return. And there should also be a SV.

Reply to
harry

Bollocks yourself. A non-return valve will not be lifted by convection currents, only the pump pressure will lift the jumper/clack.

This is normal commercial/industrial practice with multiple boilers, started progressively and automatically as the heating load increases.

Reply to
harry

We have valves on the boiler and backburner circuits (which interconnect). Both have thermostats the boiler in the room and the backburner on the pipe coming from the backburner. This opens the valve when the water from the backburner reaches a certain temperature but is closed when the burner is off to prevent the boiler circuilating through the back burner. It is more complicated in our case as we have two heating zones, so two sets of valves.

Jonathan

Reply to
Jonathan

Exactly, boiler can be isolated. Never under estimate the stuipidity of harry's.

Reply to
Dave Liquorice

The solid fuel boiler loop should not have to rely on a pump and thus power for circulation.

We are talking domestic and solid fuel boilers not ones that can be shut down (relatively) quickly by simply closing the fuel valve.

Reply to
Dave Liquorice

Most advice is to include a towel rail or radiator in the gravity system for supply failure situations. Rather an odd radiator if it has to be above the coil in the thermal store and presumably plumbed in 28mm piping.

I have yet to do this but rather wonder how much energy could be absorbed by a towel rail covered in towel at say 90 deg.C?

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Reply to
Tim Lamb

So the moment that the back bolier would be really useful, like duringa power cut, you have to shut it down... OK you might not get much cirulation through the trads under gravity but you may get some. You will also have hot water.

Which is better arranged by a proper, passive, plumbing solution.

Reply to
Dave Liquorice

Lots of very useful information here - thanks to all.

Rob, re the Dunsley interconnector - I'm actually looking to get rid of the open fire with back boiler, and so rid myself of the problem. Information regarding valves etc was very useful and gives me something else to investigate.

Still looking to gather as much information as I can before phoning a plumber out to remove the old fire.

Is there a thread - 101 uses for an old back boiler?

Thanks to all!

ArgosGold

Reply to
argosgold

No but have you been following the various "energy crunch" threads? I don't think I'd be taking out a real fire place and back boiler, well I might to replace it with a stove with boiler.

Reply to
Dave Liquorice

You can get wax operated thermostatic valves with remote sensors. Have one that opens at 85 to 90 C with the sensor on the flow from the boiler. When it opens it allows flow through the heat dump radiator positioned at normal heights. You still have to be careful with the pipe runs though.

That's why I'd use a radiator... B-)

Reply to
Dave Liquorice

Start by mapping the system out. Until then its all guesses, except for one point: its not a well designed system.

NT

Reply to
meow2222

You really are a half wit. Why do you suppose SVs (safety valves) are fitted to boilers?

Reply to
harry

Once again, you are a half wit. Solid fuel boilers can't be shut down by closing a valve. Which is why there are extra precautions for solid fuel boilers over gas and oil boilers.

What do you do for a living? I hope it's nothing to do with heating systems.

Reply to
harry

A limited amount. Which is why there is a cold feed pipe and an expansion pipe. In emergency the boiler ejects water and steam over the expansion pipe into the header tank. A heat sink (permanently connected) is required for a solid fuel boiler. It's purpose is more to do with temperature overshoot due to the inertia in the system as the boiler is closed down/temperature reduced.

Reply to
harry

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