Alternative to storage heaters in 15thc house?

[Penners]

Are there any limitations with a microbore system? For a given flow rate it must surely be less capable of transferring heat around a house than standard 15mm piping, or is a higher capacity pump required in order to circulate the water faster?

There certainly are limitations to the number of radiators that a microbore circuit can supply. The usual practice is to carry the flow and return circuits close as close as possible to the radiators in a larger bore (15mm or 22mm) and then use a manifold to take off microbore circuits supplying each of the rads.

Considering the distance that the water would have to travel between the heat source and the rads in your house, I'm not surprised that 22mm has been specified. But it should still be possible to run the 22mm, for example, under the floor, and then use manifolds for microbore supplies to the rads to emerge into the rooms.

 

[GK]

For a system designed to current standards, 10mm plastic pipe will carry up to around 1.2 kW (Hep2O say 1.5 kW); 15mm >5 kw; as long as the runs aren't too long.

Microbore systems are generally designed so that each radiator is served by its own dedicated pair of pipes fed from a manifold, so as long as the load of each radiator is 1.2 kW or less, then 10mm pipe is adequate.
Or you could install a ring of larger bore pipe and tee off for each rad.

Standard 15mm to ½" BSP rad valves may be used, just get a 15 to 10 compression adapter. Or if the pipes are hidden, increase to 15mm just below the floor and use copper or chrome plated pipe to the rad - it looks in better proportion than 10mm pipe. Radiator valves have never been metricated at the radiator connection thread so you can always bush an ancient radiator down to take any old (new) modern valve.

The makers of plastic pipe claim that the bore is smoother than copper and less susceptible to scale deposits. If you use plastic, make sure you fit oxygen barrier pipe for heating circuits. 15mm plastic pipe is a perfect sleeve size for 10mm pipe that goes through joists or masonry.

Polybutylene pipe takes tight bends more easily than the white PEX pipe though there was a post a while ago where someone said PEX was actually superior or had eternal longevity or something - apparently it can't be disposed of in the future. That's if the mice don't nibble it first.

 

[Penners]

15mm plastic pipe is a perfect sleeve size for 10mm pipe that goes through joists or masonry.

Which touches on a matter that I've been wondering about*.

The internal diameter of plumbing pipe (actually more accurately referred to as tube, because it's classified by its external diameter), doesn't seem to be considered when installations are planned. Yet the wall thickness of plastic pipe is noticeably greater than that of coppper, so its internal diameter must be smaller.
Is this sufficiently important to affect the specification of a plumbing system, or has the industry broadly agreed to ignore it, because it isn't enough to matter?

*Yes, folks, that's how boring I am.

 

[GK]

Well, I suppose if you want to plan your system to the Nth degree, you should refer to the manufacturers' velocity and flow tables for the pipe, sorry, tube you are actually using, if you do then you are considering the difference in internal diameter.

In practice the reduction in fittings and easier runs will compensate such that you can substitute one for t'other. Only when you're approaching the load limit of a particular pipe size might you go to the next larger size a little sooner than you might with copper.

Plastic pipe will also tolerate a slightly higher water velocity without vibration or noise so that's another thing that evens it all out.

 

[Flyfisher]

Or . . . in theory there's no difference between theory and practice, in practice there is :wink:

 

[borischarlton]

Ian
"I got what are called Munsen rings from B & Q and look great with cast iron rads
http://www.indanc.com/malleable_iron_pipe_fittings_107.php"

Yep they are like the ones I have used but in brass.

I will try to get a pick showing a pipe run and connection to a rad.

The megaflow has its own immersion for emergencies otherwise it is heated using the gas boiler. As long as there is no air in the system, it is more or less silent.
Rob
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[Ian Bond]

Thanks for that - Chris's pipe clips look good - I agree!!

Yep - without a central heating system I went for a direct cylinder - hopefully one day I will replace it with and indirect, and I think a backup immersion is sensible too.

 

[Penners]

...evens it all out.

Thanks, G. Useful to know. I confess I hadn't lost much sleep over the matter, but the brain tends to wander when it's idle...

 

[DaveBrigg]

We also started with a house full of storage heaters. Another disadvantage of them is the weight of the bricks inside, which had to be carried downstairs 2 or 3 at a time.
We went for the wood pellet boiler on environmental and cost grounds, and had a Czech model fitted in the garage, with a 1000 litre thermal store (basically a large hot water tank, with lots of insulation). Separate pipes take a direct feed into the house for hot water, and to a heat exchanger which transfers the heat to a closed central heating system. It needed to go in the garage because it is quite large, and we didn't want to add a modern flue to the listed house.
We were 'lucky' that the external walls all needed replastering anyway, so the pipework runs around the walls, and through the internal lath and plaster ones. It is 22mm plastic except where it emerges for the radiators, when copper is used. Some of the upstairs floorboards had to be lifted for the rewiring, allowing the pipes to run in the void. The plumber said that microbore would not work on a large pipe run.
The radiators work well, although the last one on the run needs bleeding most weeks, and those nearest to the heat exchanger are very hot even when turned down.
The wood pellet stove was not as straightforward as I was led to believe. For the first four months it overheated, and melted the plastic tube which feeds the pellets. The price of the wood pellets shot up, and one load that we bought had been shipped in from that model of sustained forestry, Argentina (on a hardwood pallet) Apparently most of the sawdust produced in this country is used for cat litter trays instead.
Having 5 tonnes of pellets delivered at a time was cheaper, but storage becomes an issue, since they must stay completely dry or they revert back to sawdust. I learned that 5 tonnes of pellets take up a lot more room than can be provided by 5 one tonne builders' bags. The last time I checked they were about £160 a tonne, although the price varies considerably.
After the five tonnes ran out in November we have turned off the pellet supply and burned wood instead. It gets through logs at a steady rate, but can also cope with bits of spare furniture, hedge trimmings, old SAT exam papers, Next catalogues and broken pallets.
Burning scrap wood to heat the house produces smoke, but I tell myself that it would all have gone to landfill otherwise, and it can't be as bad as oil. It also means a trip out to the garage every 90 minutes or so. If the boiler is not lit for a couple of days the thermal store goes cold, and it takes at least an hour before enough hot water is produced to get the central heating working again.
We have a wood supplier as backup for when no scrap is available. It has cost nearly £100 in the last month for hot water and central heating, but friends with a similar sized (and newer) house are forking out £140 a month on oil, so we don't feel so bad. Although our pellet burner has broken down several times, I know of another locally which has worked without any problems.