Instantaneous Water Heater

[RacquelDarrian]

I'm thinking of supplying my upstairs basin and kitchen sink with hot water via an instantaneous water heater.

Possibly a 9.5Kw one powered from my cooker outlet (I have a gas hob and oven).

Is this a good idea and can anyone give me any tips on the matter?

 

[DP]

20Kwatts gives you instant hot water at the rate of +9l per minute for a temp rise of 35 degrees C. Will only supply one tap with miserable flow rate.

9.5Kw will not be instantaneous and will certainly not be for multi supply (if indeed it is instantaneous)

Water heaters of this type usually have a spray heat for use at point of use only.

 

[RacquelDarrian]

The one I'm looking at is the Redring model in RS Components at £139.

"240Volt - 9.5kW. Operating pressure 15-150PSI / 1-10 bar.

Flow rate for 45C with 12C supply 4 l/min. 2 outlets. "

It's for use with normal taps.

 

[ChrisR]

I would suggest you consider a different sort of heater - see this thread
//www.diynot.com/forums/viewtopic.php?p=63017.

The heater will be a bit cheaper, (the electrical side would normally be MUCH cheaper because you only need a normal plug-in size supply), and you'll get the water out much faster. 15l is plenty for a sink - 10l would be ok, if you have the hot water hot enough that it needs some cold as well. There WOULD be a delay before you could take out another sink or basin full, but only minutes, especially if you have a slightly bigger one ( ie 15l) than you absolutely need.

The plumbing is a bit more complicated so it would cost more for the water side installation. Beyond some diy plumbers but not others.

Use a jug / milk container or summat to set a tap to 4 litres per minute, which is all you'd get from the instantaneous variety. Bear in mind that the water at that rate would NOT be hot enough for normal washing-up, so you'd have to slow it down to perhaps 3 litres per minute. It really is very slow indeed.


edit:
the flow rate you quote is misleading. You would get 4 litres/min with a 35º rise, divided between however many taps you like. They say 45º presumably assuming the mains comes in at 10ºC. But in the winter it can be 4º!

This is easy to work out from the laws of physics - all 9.5 kW heaters would be the same.

 

[RacquelDarrian]

ChrisR
You won't believe this but I have a 10L undersink water heater that supplies both my bathroom basin and kitchen sink already.

I plumbed it in myself.

My option was to install a similar heater under my kitchen sink to supply it only or an instantaneous water heater under my kitchen sink to supply sink and upstairs basin.

The 10L undersink heater is good when I'm on my own. I've got it on a timer to come on at popular times. If someone turns up to visit I have to rush upstairs to switch it on! This why I think an instantaneous water heater would be more practible.
I like the idea of hot water on demand and it sounds efficient.

I have a dishwasher for washing up and a shower for, umm, showering.
So all I need is warmish water to wash my hands after I've been gardening.

I'll take your advice and see what 4L/min looks like.

 

[ChrisR]

You don't need to turn them off - they are well insulated and have thermostats.
I hope when you installed yours you put in the tundish, pressure relief valve and discharge pipe, pressure vessel and two double check valves, possibly with a pressure reducing valve. Most don't, because they misunderstand the instructions. I've just installed 7 in one building so I've been round the loops!