New C/H system - recommendations

[bernardgreen]

and of course the good old fashioned combi.

I missed that. Old fashioned ?, according to a boiler designer the combi is ( he was speaking in late 1970'S ) a new concept beimg developed to provide hot water in flats and modern compact houses where there is no space for cylinders and storage. I got to know him via the Philips Experimental House Project at Eindhoven.

Not when you're a professional, and not when you make specific claims like it "equates to a 48 kW combi boiler",

This sort of equates to a 48 kW combi boiler providing "instant" hot water for the shower.

30 minutes @ 16 kW = 8 kW hr
10 minutes @ 48 kW = 8 kW hr

You are correct in saying that my system does not give instant hot water for a shower, It does require the boiler to be fired up about 30 minutes before the shower. ( less early for a quick shower ). Amazing things time clocks and remote controls.

 

[Dan Robinson]

30 minutes @ 16 kW = 8 kW hr
10 minutes @ 48 kW = 8 kW hr

Irrelevant.

 

[Nozzle]

Losses my friends. You have more losses from a "slow and steady wins the race" setup than a "heat it now and leave it alone for 24 hours".

An experiment to prove it:

Get a pan of water.

Heat it on your gas stove. It'll boil in a few mins. Take the lid off, it still boils away.

Heat it with a fag lighter. It'll never boil, even with the lid on. Despite the high temperature of the flame, the pan can take more heat away than the flame can put in.

Okay, that's power alone - so to make it analogous to your set-up it needs to be about overall heat input.

Let's say the hob is 1000 times more powerful than the fag lighter - give the fag lighter a 1000 times the opportunity, time wise, to boil the water. It sill wont.

Result? The second set-up, though able to put just as much energy into a system, given enough time, has greater losses. The losses are so great in fact, that the fag lighter is limited in how hot it can get the water. Once the losses balance the heat input.. the water gets no warmer.

So quit this non-sense that it's better to have an under powered boiler would ya. It's a compromise at best.

Nozzle