Unvented cylinder size for 6 ensuites

[Tony Moore]

Guys, I and another 3 engineers are perplexed.
We have a 4bed 4floor house being turned into a 6bed HMO.
We've calculated 45k btu for htg, and know that we are goin to have a system boiler and 300l unvented cylinder.. But 300l surely won't be enough water should, theoretically, all 6 showers be used at once and say the washing machine and kitchen taps? Would an accumulator be needed and what size? Any thoughts?

 

[Harvest Fields]

Guys, I and another 3 engineers are perplexed.
We have a 4bed 4floor house being turned into a 6bed HMO.
We've calculated 45k btu for htg, and know that we are goin to have a system boiler and 300l unvented cylinder.. But 300l surely won't be enough water should, theoretically, all 6 showers be used at once and say the washing machine and kitchen taps? Would an accumulator be needed and what size? Any thoughts?

Put 2 in. (Unvented cylinders that is).

 

[Harvest Fields]

never fitted to together myself but have seen it done before

 

[ShaunCorbs]

Well that's 60lpm hot only around 35lpm so any more than 10 mins or a sink and you've run out

What's your mains flow and pressure (cold water mains)

 

[Tony Moore]

2.8 and 13 lpm

 

[Tony Moore]

Or would putting 1 small unvented on each floor be a better way? A 24kw system boiler should suffice..

 

[Scott_D]

2.8 and 13 lpm

that's going to be a problem

 

[chris watkins]

Hi Tony
What flow rate are you after (shower deliver)? What can the mains supply pressure & flow? What recover rate are you allowing for above the heating load? Is there a secondary return?
What space is available for plant?

Just of a few important questions someone designing the hot & cold water systems would need answering before providing sensible answers to your question.

It needs designing properly, it can't be treated like a normal house albeit a large one on the existing mains supply.

 

[Tony Moore]

This is what I've told the guy.. I'm not a "plumber" so flow rates and heat loss aren't my thing, so I've suggested he call a "professional" company that deals in unvented systems to size it properly for him..

 

[Gasmk1]

think you need a professional definitely as you will probably need a new main or a pumped supply and 2 cylinders would it not be better to supply 3 from one and 3 from the other letting one do the kitchen as well. i wopuld say pass on the specifaction as you have intimated, then the onus is not on you

 

[Scott_D]

This is what I've told the guy.. I'm not a "plumber" so flow rates and heat loss aren't my thing, so I've suggested he call a "professional" company that deals in unvented systems to size it properly for him..

What's your role in the job?

 

[Tony Moore]

Gas/boiler fitter..

 

[Harvest Fields]

Gas/boiler fitter..

You going Floor standing?

 

[Tony Moore]

Was hoping to. Next to load bearing wall. Builder has already strengthened th floor

 

[oz-plumber]

Contact Rinnai UK.

They will size the and design the system for you free of charge - or may reimburse you if you purchase the system.
They've done it before for me over here

Too many variables for you to have a stab at without having an understanding of sizing hot water systems.
Too much liability for you if you install something you designed and installed

 

[Welder]

Was hoping to. Next to load bearing wall. Builder has already strengthened th floor

Personally I'd go OSO. Absolutely top draw in terms of HONEST advice (even to point of refusing to quote on one job cos it would not work) and service...

Upgraded main's a banker. I'd also be very careful about showers fitted. All too often these people think they can fit rainheads and of course when 2 plus using it simply dribbles.

Def get a firm it to advise. This is small hotel territory.

 

[Johny1092]

Guys, I and another 3 engineers are perplexed.
We have a 4bed 4floor house being turned into a 6bed HMO.
We've calculated 45k btu for htg, and know that we are goin to have a system boiler and 300l unvented cylinder.. But 300l surely won't be enough water should, theoretically, all 6 showers be used at once and say the washing machine and kitchen taps? Would an accumulator be needed and what size? Any thoughts?

I had done few houses ranging from 3-8 en-suite ,
Some have larger cylinder s (but not over the top)-6shower -300l,
some have small cylinder but quick recovery type 140l - 7showers , not a problem with any for few years

But low loss header maybe the way to go or HW priority , or both -and boiler no less then 35 kw,
But most important it’s water main supply upgraded to 1,5”and internal pipe work on cylinder it need to be 35mm in /out ,

 

[Chalked]

2.8 and 13 lpm

Your going to need a big break tank and booster pump.
13 lpm is borderline for one bathroom,