high recovery water heater

[hammers4spanner]

Have a job to do in a few weeks time which involves re jigging a cookery classroom . At present their is a gas fired water heater (vented) and if i recall about 180 litres feeding 16 sinks in two seperate classrooms.This currently is inadequate as the hot water constantly runs out and heat recovery is not quick enough .
Now they are adding an extra 8 sinks so more hot water draw offs making a total of 24 which will make it 12 hot water draw offs in each class.

I am considering dividing each classrooms supply but need something with a rapid hot water recovery , or if i decide to just alter what currently is in situ with a larger unit then again want an idea of something mains fed with quick recovery

 

[Keefy]

Is it going to be a secondry return setup for the hot draw-offs?

 

[hammers4spanner]

yes it will be

 

[happyflyer]

I would make up two systems that's a lot of taps on one water heater, if you use one system that will be a pretty long secondary run with two branches that will need balancing. You don't say if the water supply is mains or tank fed, whichever it it I would look at fitting water restrictors into the taps that will give you a better chance, some old sink tap have big holes in them, even 12 sinks is still a lot of water and there will be little in the way of diversity, as the classes end they will all wash up at the same time. If you speak to Andrews or AOC Smith or Hamworthy they have typical loads on taps against gas rating for their water heaters, this is what I do for a job, HVAC design even though I am nearly 70.

Good luck

BTW don't forget an expansion vessel for each heater, also watch the water temperature with children will they need a mixing valve,this will help you with your demand, part hot part cold you can raise the hot water storage temp a little if you are mixing it

[DLMURL]http://www.andrewswaterheaters.co.uk/documents/Sizing_Guide_Oct08.pdf[/DLMURL]

Try this for size:furious3:

 

[Dotty]

Download Baxi Size It - Baxi Commercial Division | Size-It is a Water Heater Sizing Program to be used to select from the Andrews Water Heater product range

Personally I'd go for one of these.

[DLMURL]http://www.andrewswaterheaters.co.uk/products_details.php?product=neoflo[/DLMURL]

 

[TBServices]

If there's gas, why not just bang in a big rinnai water heater or 2? Or unvented cylinders?

 

[vern]

Rinnai x 2 instantaneous which can have secondary returns also, being a school they will have to comply with legionella regs, being no stored water this is not a problem, they also have a burn program that raises water temps prior to the mixing valves to to further guard against pipework water volumes..

They wont run out of water, pay as you go!