WEhat size of unvented cylinder do I need?

[mysteryman]

It would seem reasonable to assume that mickyg works for Rinnai...

 

[Agile]

Well Micky did not work for Rinnai last week when I spoke to him.

But perhaps he has started a new job this week?

Good as the Rinnai are for some applications I still take the view that for the OP the two 300 li cylinders are the best solution.

I always work out demand at 50 li per person. Some others historically as low as 37 li per person but showering/baths now have increased hot water expectations. So the stored water would serve 12 people and reheating the remainder and the other applications. Washing machines should be used during the day so can be disregarded for peak demand.

I always work out water requirements based on the normally expected usage. But I am aware that this is often less than might be expected. The BBC used to have a Training/Conference centre and they seemed to get away with very little hot water storage.

Possibly this is because many people are either early risers or last minute risers and this seperates the peak demand by about an hour.

Tony

 

[DerAlteFritz]

Sounds like an excellent solution to me. So two boilers to get good heating and then a single 500 litre tank that actually fits into the low ceiling space.

What comments on the HRS Hevac semi-instananeous tank mentioned earlier. Is this directly heated mains supply with an additional storage tank? How is it different from an unvented?

The Rinnai gas heater option - what size are we talking about to deliver the 100 l/min demand?

 

[mickyg]

for 100 l/min you'd be looking at 4 or 5 units depending on how it was decided to plan the installation, but if one went down you'd still be left with 70-80 l/min . The units are smaller than your average domestic boiler but this type of system would ideally need a bit of room for a plant room style install and possibly shared flue system and quite a substantial gas supply. would probably be an expensive job too but would be my preffered choice of install if budget allowed. They also do storage solutions as well. Here's the brochure.
http://www.rinnaiuk.com/5_Downloads...2_Commercial_Hot_Water_Solutions_Brochure.pdf

 

[mickyg]

It would seem reasonable to assume that mickyg works for Rinnai...

well if you read through my posts you'll see me very rarely recommend any products unless I think there is a distinct advantage of a particular brand, ie in this case there is no one to rival Rinnai for banked water heaters.
If we look through your posts on the other hand we say you continually recommend Viessman at any opportunity.

 

[mysteryman]

I only give good advice, as I am sure you do.

 

[DerAlteFritz]

I welcome all suggestions, good or bad because it gives me a direction to look at and help in knowing the options out there.

I am warming to the idea of some stored water and some directly heated mains water. This seems to me to solve both the limited amount of space and the need for peak demand for only one hour a day.

This might be the best way to balance the limited storage and the limited ability to heat mains water.

 

[dumbrill]

Say 80 litres per bath at 60C, plus the showers at whatever design rate you've provided, all at once!

Wouldn't you apply a diversity factor in a similar way that would be done for sizing an electrical cable? I don't think ALL users would be on at the sametime.