Another Combination Cylinder question

[Mr Dallas]

Apologies for the basic questions, juts like to know in my mind what i want out of a new system before i bring a professional in to actully do it

2 up 2 down terreced house, bathroom and kitchen both on the ground floor, only hot water required (no central heating)

we want to use the loft space, and want to bin off the CWSC, and the fact we were allways going to replumb the house leads me to think about other ways of carrying this out and not using the loft space

1) option one is use and unvented direct cyclinder if the mains pressure is sufficant as per my last thread

2) this is what im wondering, if i used a direct combination cyclinder in the airing cupboard (upstairs) would the pressure be sufficant to supply the hot water outlets downstairs, also with regards to combination clylinders are these considered vented because of the built in CWSC placed on top of them, and therefore not as expensive to install/look after ?

any help would be brillaint

jr

 

[GQuigley67]

Hi there Mr Dallas, is your incoming mains low pressure and that is why your considering a combination cylinder ?? these are usually placed in the loft for better pressure(still poor) if your mains pressure is decent, go for a direct unvented cylinder and no matter where you place it in your house you will have good pressure at your hot water tap.

for a combination cylinder to work, in order to get 1 bar of pressure the cold tank on the top of the cylinder would have to be 10m above your hot water tap, 10m of height = 1 bar of pressure. Assuming the cylinder is in the airing cupboard upstairs and your taps are downstiars your looking at approx 2m of head(0.2 bar of pressure)

 

[Mr Dallas]

Many thanks for the reply, still waiting to find out the mains pressure from the water board, am i correct in thinking i would need around 2 bar for an unvented cyclinder to work ?

if the mains pressure is poor i take it a cwsc is my only option ?

 

[AWheating]

idealy you require 2bar of dynamic pressure and a 20litres per min flow rate for an unvented cylinder to work as designed. You can get away with slightly less but the lower the figure the worse the performance of course.

The water supplier only requires to supply 1bar and 9 litres per min at the road/stop tap connection, so if your values are above these levels they will not do anything to help.

On an open vented hot water system with a cwsc you will get an average of 0.5bar of pressure (2storey dwelling) with a flow rate dependant on pipework and fixtures.

 

[Plamber]

Thought of a thermal store cylinder if the pressure is poor?



http://www.mcdonald-engineers.com/thermalstore.html
some about them on here.

 

[Mr Dallas]

Brilliant, really appricate that link as explains it all so well, only thing im concious of now is the cost of purchasing the tank etc

Do the install costs vary much on the various diffrent systems ???