Unvented cylinder size

[TFGplumbing]

Hiya guys

I currently specing a job for a 5 bedroom house with x5 ensuites. Could anyone advise me on sizing cals for unvented cylinders.

Thank you

 

[ShaunCorbs]

showers baths ? spec

water mains flow and pressure static and dynamic

 

[TFGplumbing]

Hiya Shaun

6.5 standing

6 dynamic

22litre per min plus - it over flowed my guage

25mm mdpe main

x1 bath x 4 mixers

 

[ShaunCorbs]

ta last q how many outlets are they planning on using at once /demand like 4 showers each morning etc

 

[TFGplumbing]

I want it to work under load so lets say 4 out of 5

 

[ShaunCorbs]

400l or 300l fast reheat

4 showers lets say 12lpm

60/40 split

8 hot / 4 cold

average shower 10 mins

so total per shower 80l hot / 40l cold

over 4 showers 320l hot / 160l cold

if you allow this for cylinder temp will give you a bit of wiggle room as people dont have 60dc showers

 

[TFGplumbing]

Thanks Shaun thats very helpful.

What sort of heat loss should allowing for a cylinder of this size?

 

[ShaunCorbs]

i would allow a good 25kw for a high recovery

10kw for re heat within 90 mins is you can add more if the coil will take it eg 20 kw for 45 mins etc

 

[TFGplumbing]

Okay so I've got a Heat loss of about 24 kw for the rads including a 15% margin for pipework etc etc

The system will be run from a oil boiler, initally I have thought a 32kw would be suitable. The coil on the propsed 300 litre cylinder is 39kw.

Whats your opinion on fitting a larger boiler?

 

[ShaunCorbs]

depends stagger the hot water times then you can go with a 28kw

if they want them both on the same time around the 40 kw mark

 

[Welder]

How about putting in a flow switch & timer device so that after so many mins of HW flow, the boiler automatically initiates HW reheat? That could operate in parallel with the std HW schedule.

 

[ShaunCorbs]

How about putting in a flow switch & timer device so that after so many mins of HW flow, the boiler automatically initiates HW reheat? That could operate in parallel with the std HW schedule.

you could do how water priority ish

 

[TFGplumbing]

with regard locating this beast of a cylinder, 300kg odd is alot of weight do you guys do load cals for placing units like this on joists

 

[ShaunCorbs]

normally try and get it close to a load bearing wall or add extra support in

 

[TFGplumbing]

Thanks for your replies

 

[Welder]

with regard locating this beast of a cylinder, 300kg odd is alot of weight do you guys do load cals for placing units like this on joists

As Shaun says, get close to a wall first. Personally, I've always put mine on 25mm ply spanning joists and screwed through into them to distribute weight as much as possible. 300KG isn't that bad. Tis only three rugby players in a huddle

 

[Riley]

Depends which rugby players

 

[Welder]

Depends which rugby players

Prop-er ones...

 

[Welder]

you could do how water priority ish

Sorry Shaun. Have no idea what thats supposed to say

 

[ShaunCorbs]

Sorry Shaun. Have no idea what thats supposed to say

hot water priority

 

[TFGplumbing]

what size circulator should I be looking at its a five bedroom home with x2 heating zones and 22 rads approx

 

[Welder]

hot water priority

Sorry pal, youll need to expand

 

[ShaunCorbs]

Sorry pal, youll need to expand

w plan system

Hot water priority, if there is a demand for hot water & heating, the hot water is heated first

 

[Welder]

w plan system

Hot water priority, if there is a demand for hot water & heating, the hot water is heated first

Ahh. Sorry, bit of a thick day!
My point was to try to add a bit more monitoring of HW use rather than rely on fixed stat hysterisis alone. Ideally, one would replace the stat with a sensor so the two can be used in parallel. It would however require a microprocessor & programming to deliver...