16 showers job

[seanadams121]

little bit of help needed lads
iv got a job on to install 16 thermostatic bar showers in a kind of hotel spread across one floor, the building is basically one level, no upstairs,
as I say its all over one floor, all pipework is to run above the rooms and drop down in stud work. each room has a bathroom, 16 in total with thermostatic bar showers, and obviously a basin and toilet.
I am arranging 2 x 32mm or one 63mm mdpe connections coming into property and a manifold.
There is no gas in property.
I am planning on fitting two large unvented hot water cylinders. Im not sure what size to go with, if I allow 8 bathrooms per cylinder, im unsure how to size cylinders correctly.
Iv read the average shower lasts 6 minutes so if the hot water cylinder was to provide 15 litres per minute and we say that the hot/cold ratio is 60/40 we are looking at 9 litres x 6 (minutes) = 54 litres per shower.
so my question is, how many would I allow for diversity? ideally each cylinder would be 54litres x 8 rooms so would be 432 litres but obviously this isnt practical or feasible. Im inclined to put 2 x 200 litre cylinders in with bronze circulators and make sure the cylinders have some kind of rapid reheat times with good immersion elements but any advice will be greatly appreciated from people in the know.

cheers

 

[ShaunCorbs]

What’s it being used for ? Hotel ?

 

[seanadams121]

What’s it being used for ? Hotel ?

yeah a hotel Shaun , the set up im installing though won't be used for the kitchen or communal areas however, just the rooms to be constructed

 

[ShaunCorbs]

As it’s random usage I would go 2x 400l in parallel per 8 with src circuit the problem is it’s direct so around an hour reheat time or commercial 3 phase cylinder but then you still be around 30-45 min on full depletion

Max immersion for a stnd cylinder 6kw

 

[king of pipes]

I'd go timed push shower controls done many a sports complex last one has 3 - 200 litre unvented cylinders and was heated by a commercial ideal gas boiler , heat recovery time using electric will be much slower .

 

[seanadams121]

As it’s random usage I would go 2x 400l in parallel per 8 with src circuit the problem is it’s direct so around an hour reheat time or commercial 3 phase cylinder but then you still be around 30-45 min on full depletion

Max immersion for a stnd cylinder 6kw

ahh right im with you mate so have 2 x 400l linked per 8 rooms. so just to clarify that would be 4 x 400 litre cylinders linked in pairs?

 

[seanadams121]

I'd go timed push shower controls done many a sports complex last one has 3 - 200 litre unvented cylinders and was heated by a commercial ideal gas boiler , heat recovery time using electric will be much slower .

yeah good idea that mate actually! would help massively if timed. Be a lot easier if gas was available in property

 

[ShaunCorbs]

ahh right im with you mate so have 2 x 400l linked per 8 rooms. so just to clarify that would be 4 x 400 litre cylinders linked in pairs?

Yep unless you can get sub 30 min reheat time

 

[ShaunCorbs]

yeah good idea that mate actually! would help massively if timed. Be a lot easier if gas was available in property

Lpg?

 

[king of pipes]

400 litre cylinders are huge check plant room dimensions and make sure you can get something that size in if you decide to go that big ??

 

[ShaunCorbs]

its the reheat time anywhere from 4-6 hours from cold

with gas you can put 30-60kw in depending on if use the solar coil as well with direct thats 6kw

 

[Chuck]

IMO, one-off jobs of this size need a consulting engineer to do the requirements and design. You really don't want to install 1600 litres of HW store and a 3x200A power supply only to find your guesstimate of 6 minutes per shower should have been 12 minutes and the rooms are all doubles not singles and breakfast is served from 0730 to 0830 so everybody wants their shower between 0715 and 0745.

 

[ShaunCorbs]

roughly 1280 L hot required for a single 10 mins shower added 25% for unaccounted things like basins etc / overhead

 

[Scott_D]

How will you maintain floe/pressure at peak times?

 

[Timmy D]

How will you maintain floe/pressure at peak times?

This was my first thought.

Let’s say peak, 8 showers running, 12lpm a shower, that’s gonna require nearly 100lpm!

Have you checked the mains water supply? Unvented could already be a dead option without a mains upgrade or storage/booster set.

You’re gonna struggle to get the required reheat time using domestic immersions. Do you know your available electricity capacity?

You’d be better off, installing indirect and electric boilers. You could also then wire the immersions with a temp sensor to turn on at a preset hot water temp to assist with high demand periods.

Edit: I also want to add (this isn’t an insult, we all need to gain experience/confidence), are you ready/comfortable with taking on this responsibility? If you get it wrong, it could cost a lot to fix. Have you thought about paying someone to run/design the job, with you taking a backseat and learning?