Benefits of one large hot water tank over two in parallel?

[Helenw]

A friend is building 5 en-suites above his pub. An advisor has said he needs a 64kW gas boiler to heat 7-8 radiators and an 800-1000 litre water tank to make sure guests have hot water when they need it. This seems way over the top to me - especially as it's not guaranteed that there will always be 5 guests. Is it possible to run two 300 litre tanks in parallel for example so that the second is only heated up if needed? If he did run two in parallel, would he still need a 64kW boiler? Any ideas welcome. Thanks

 

[ShaunCorbs]

bin the advisor and carry out a heat loss to calculate your heating load and go from there

 

[Knappers]

Hi, it doesn't sound ridiculous.
You should design for max load and with a 1 bath house usually having 200l + then that's prob about where it should be.

You couldn't safely have a cylinder that you sometimes use because of legionella rules.

In a larger hotel then you could get away with less per room as would be greater diversity in its use.

You could look at maybe a couple of 300l cylinders running at a higher temp with blending valves. Then you could run up to 60 every day, maintain at over 50 and crank up to 70 for a big group.

Boiler size would link mostly with recovery time and heat input of chosen cylinders.

Another major cost would be cold water storage and booster set.

If there is the space for it then gas fired water heaters from 'andrews' or 'ao smith' offer a fast recovery and allow reduced capacity.

 

[Timmy D]

Low loss header, plate heat exchanger and buffer vessel. Smaller store but quicker recovery when needed.

 

[ShaunCorbs]

Low loss header, plate heat exchanger and buffer vessel. Smaller store but quicker recovery when needed.

Exactly 250-300l hot water cylinder on priority hot water with a de strat pump easily handle the load

Eg 7lpm hot per shower normal shower 10 ish mins = 420l of hot water required if all running at the same time

30 kw boiler will reheat within an hour easily

 

[Enthalpy]

The Gledhill STAINLESSLITE PLUS UNVENTED INSTRUCTION MANUAL has a selection guide on page 12:

https://www.gledhill.net/uploads/StainlessLite-Plus-Manual.pdf