Insulated heating pipes?

Talking recently to a supplier of gasifying log boilers about heating options for a detached annexe (sandstone barn) which I've been converting for part-time occupation, they came up with the suggestion that I could run both heating and water circuits from a combined heating system which would use the existing 90,000 BTU oil boiler as backup.

That sounded a good idea to me, given the savings I could expect on not having to install a separate heating system and having a renewable and cheaper fuel source for both. The existing boiler is more than adequate for heating the main 2 bed house and ultimately, I'd replace it with a higher efficiency device.

The log boiler will add a minimum 25KW to my total existing heating capacity, with the barn requiring only 12-15 KW.

I've got to dig up the garden anyway to lay the cold water supply along the same route , so I guess if there's a type of insulated heating pipe that could go in alongside that would be ideal. Perhaps I might also be able to deploy a heat exchanger/thermal store to deliver potable hot water?

Could anyone advise on where I might look for the kind of pipe I'd need to use?

Jeff

Reply to
Jeff Mowatt
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================== I don't know of any particular source but you might try 'googling' for 'district heating' which seems to achieve what you're looking for, although on a much larger scale.

Cic.

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Reply to
Cicero

Ah yes, that did the trick thanks Cicero.

I came across something quite interesting in Poland which looks like a massive investment in this technology.

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looks a bit tidier than a lot of Eastern Eur> >

Reply to
Jeff Mowatt

====================== I think you'll find other examples much closer to home, which is the reason I'm aware of the idea.

One item that caught my attention in the Polish example is the statement the no asbestos is used in the pipe lagging. Presumably they're using something with similar properties without the attendant danger of asbestos so if you can find out what they are using that would give you some idea of what you could use to lag your pipework.

Cic.

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Reply to
Cicero

Try and get hold of Andy Hall. He ran a similar system to his shed, isolated from the main system using plate heat exchangers to reduce leakage and draining issues. You may find a description with judicious use of Google Groups.

Christian.

Reply to
Christian McArdle

It's a workshop, and the story runs thus:

- Basic construction is single brick, tiled and felted roof etc. In the winter, this would require about 10kW of fan heater for some time to make it warm enough to want to work in it (i.e. 12 degrees plus.) It took ages to warm up. Expensive and not practical.

- First step was to insulate the whole thing with 50mm Celotex. This brought the heat requirement down to around 4kW to provide 18 degrees ambient in cold weather. Not bad but I wanted to reduce the cost and not use electric heating.

- One option which was ruled out was a separate boiler. Cost of laying on gas service made no sense.

- The other, was to use the house heating system to provide heat for the workshop, so I researched that.

There were a few design criteria:

  • Simple to add to existing system

  • No requirement for electrical connection between the buildings

  • Failure in the workshop system of any kind should not compromise the house system

  • Exterior heatloss should be minimised

  • Minimal risk of freezing.

Putting these together mandated a secondary circuit heated by the boiler primary. A stainless steel plate heat exchanger of 200kW rating is used. Although the load is nothing close to this, it minimises the temperature drop to the secondary circuit.

The secondary circuit is filled with a fairly concentrated mixture of Fernox Alphi 11. This is a corrosion inhibitor and anti freeze. Since it is relatively expensive, only using it in the secondary circuit saves the cost of filling the entire system. The secondary circuit is run sealed and pressurised and filled via filling loop as normal. Any failure in this circuit - bursts, leaks, freezing (unlikely) does not compromise the house system.

Control is achieved by having a timer/thermostat in the workshop operating a pump. In the house, there is a flow sensor in the secondary circuit. When the secondary water flows, this switch closes and operates a zone valve feeding the primary side of the heat exchanger. That in turn fires up the boiler.

Pipework is plastic barrier insulated in thick Armaflex. This is taped and fed through large diameter soil pipe running between the two buildings and buried. I've measured the pipe temperatures in steady state condition on a cold day and there is no measurable temperature drop on a 15m length of this, so I believe that any heat loss is not substantial.

The radiators in the workshop are deliberately over provisioned so that the room is warmed rapidly.

The same principle is used for pool and spa heating, so it's generically useful.

There's no reason why it can't easily be adapted to heat a complete house and HW system remotely. In effect the heat exchanger is a heat source like a boiler and can be turned on and off based on heat requirement at the remote end.

Reply to
Andy Hall

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