Secondary return hot options. Which way would you do it

[bigspark17]

Not just the return....the whole hot water pipework needs to be insulated as it obviously draws from the cylinder. There is a requirement for a secondary return if the HW won't reach 50~C in 30 seconds from a hot tap.

On most presurised system you have built into the cylinder stat an overload linked in series to the stat, i dont recall there being a satisfied terminal on these? How do you get around that?

 

[Leesparkykent]

On most presurised system you have built into the cylinder stat an overload linked in series to the stat, i dont recall there being a satisfied terminal on these? How do you get around that?

They have a satisfied terminal as you can still pipe it as a Y-plan. you just have add an extra 2 port on the cylinder coil flow for the series connection of the the cylinder thermostat.

Terminal 3 on a megaflow is satisfied.

https://www.heatraesadia.com/-/medi...n-manuals/megaflo-eco-installation-manual.pdf Page 21, 2nd diagram.

 

[bigspark17]

They have a satisfied terminal as you can still pipe it as a Y-plan. you just have add an extra 2 port on the cylinder coil flow for the series connection of the the cylinder thermostat.

Terminal 3 on a megaflow is satisfied.

https://www.heatraesadia.com/-/medi...n-manuals/megaflo-eco-installation-manual.pdf Page 21, 2nd diagram.

So on a y plan your saying youd have to add another motorised valve? I cant see this being an option.

Pic below of standard overheat/cyl stat on standard pressurised system.

 

[Leesparkykent]

So on a y plan your saying youd have to add another motorised valve? I cant see this being an option.

Pic below of standard overheat/cyl stat on standard pressurised system.

Yes you can. On a 3 port mid position valve you obviously have 3 ports....AB is Flow from boiler, A is to radiators and B is to the cylinder, between port B of the 3 port and the cylinder flow connection, this is where the two port motorised valve goes. Normally closed of the cylider thermostat connects to the brown of the two port valve, normally open of the cylinder thermostat connects to the grey of the three port valve and HW off, on the programmer like normal. All the two port valve does is work like a kind of fail safe so in the event of a fault on the three port and it starts letting by then the two port is closed blocking the flow to the unvented cylinder. It's a G3 requirement of a Y-plan system with unvented hot-water storage.

 

[bigspark17]

Wouldnt it be a whole lot easier to convert to s plan? I wired today a presuried cylinder s plan and noticed no satisfied terminal on the cyl stat. Y plan seems old fasioned and no brnefit to s plan apart ftim giving priorety to DHW.