DHW/ Cylinder connections

[notfocused]

Hi
I am currently trying to figure out the plumbing layout in my house, i have just successfully added a wireless programmable thermostat to my Ferroli optimax he 31s boiler, the temperature of the house was previously controlled by trv's in each room and this thermostat has made the world of difference to control.
I am now looking at adding a cylinder thermostat as my hot water temperature is controlled by the boiler temperature which is currently set a 75 deg, i know this is to hot for dhw which is why i would like to add a cylinder stat, i currently have one motorised valve situated at the top of my boiler
View media item 18652This valve on the right hand side of the pipework is to control central heating and is wired into the room thermostat and boiler, the pipe too the left of the valve i presume is the flow for the dhw to the cylinder, would this be the place to install a valve for the cylinder stat to control
Now for the confusing part, if i turn on the the hot water only ( i have a separate programmer for hot water only ) the first pipe to get hot on the cylinder is situated on the bottom of the cylinder and if i follow this back a little it is connected to the central heating 'flow'.
The pipe above this on the cylinder must be the return and has a bottle air vent on it, should this be round the other way ? All the diagrams i have seen have the flow going into the top and the return coming out of the bottom ?.
Also would i be able to add a cylinder stat if the dhw supply to the cylinder is connected to the central heating flow ? unless i put the valve on the flow to the cylinder after it joins the central heating.

Any help appreciated

 

[keego]

By fitting a zone valve to the cylinder feed you have changed your system to an S plan so you would also need to fit a bypass somewhere between the pump & the zone valves, do a search for S plans & you should get all the info you need.
As for the flow to the cylinder, it's standard to have the flow at the top connection but it wont make any noticable difference if it's piped up the other way.

 

[notfocused]

Hi Keego,

By fitting a by pass what do you mean exactly, the boiler already has an automatic by pass on it, will this do ?
Sorry i don't have an image but here's a link to my boiler manual

The s plan link is on page 15 and page 31 show the diagram with the automatic by pass

http://www.ferroli.co.uk/product_documentation/DOMESTIC/Optimax_HE_31_S_Manual.pdf

Cheers