Secondary Circulation loop on a combi (2023 Update)

[Matt]

That's the output from the combi you fool.

No it doesn't, you have much to learn and so little time before you get locked up again.

[Doctor Drivel]

Have a flow switch on the lines to the toilets. When a flush the pump comes on. Or have an infra red sensor in the kitchen too. When occupied the pump runs. People in the kitchen tend to use water. Still have pipe stat when it reaches 40-45C.

Using a pipe stat in a well insuated loop would mean the pump would not cycle too often anyhow.

[Doctor Drivel]

Our space cadet is into the sun again. I wonder how much that Treki uniform cost him.

[Doctor Drivel]

Must an intergalactical combi.

..confusion has set in.

[Doctor Drivel]

If using a mains pressure system having hot water within 1 second at the tap mean that kettles can be filled with hot water reducing electricity consumption quite a bit. It pays for itself in more ways than one.

[Matt]

But the figures simply don't stack up and you can't prove it "pays for itself" True but sad.

[Doctor Drivel]

Yes, but. Me thinks Matt is not really Matt. Me thinks he is an old poster from here.

[mafj]

Recent research that in UK households with combis kitchen water use is 2.5 higher than other systems. (18L vs 7.2L per person per day). And the most likely reason pointed out is time for HW to arrive).

So secondary loop of any sort would seem to help alleviate this waste.

[mafj]

There is many ways to regulate the frequency I reckon e.g. hysteresis, timer). Nevertheless, adding some buffer close to the outlets could greatly help with cycling - e.g. couple of litres of pipe storage.

[mafj]

12L per person per day of waster water with combi on average. Immense time savings (3s vs 30s).

People can buy combi for 2000 or for 700, Implementing this loop would make 700 boiler surpass 2000 one with convenience at fraction of a cost.

[Dave Plowman (News]

Not sure circulating water within a potable supply is either allowed or a good idea. And just when were we short of water in the UK?

[Andrew]

More expensive combis have a setting that keeps firing the burners occasionally to keep the primary circuit hot. This allows faster hot water performance but uses more gas.

[nothanks]

DHW circulation is standard in larger buildings, without it there would be huge water wastage as people wait for hot water to reach the taps. I control mine with a pipe stat and a timer.

[Dave Plowman (News]

But that will be from a storage system. A combi is connected to mains water.

[nothanks]

True, I was responding to your comment and didn't spot that the subject was about combi boilers.

[Dave Plowman (News]

Didn't potable water give you a clue?

You can circulate a stored system in a house to give quicker hot from a tap. Whether it is worth it in cash terms, I doubt it.

[nothanks]

Errr ... my hot water is potable, is on a circulation loop, and is based on a 300 litre unvented cylinder. Search for <potable dhw circulation pump> for more info. I agree that it's probably not financially worthwhile to have a circulation loop, but in a large house (or hotel) it's a convenience that's worth paying for. My boiler and DHW cylinder are in a plant room (the old coal store) with quite long runs to the furthest bedroom and bathroom; when the circulation pump is off it can take a very long time to get hot water out of the tap or shower.

[The plumber man]

Yes can be done need a tiny buffer vessel with coil inside. The vessel is kept hot by cental heating to keep secondary loop warm. And boiler only fires up to warm up vessel or when hot water is drawn

[Brian Gaff]

Oh dear another disembodied post from home owners club. Brian

[fred]

The original thread is 17 years old