heating system design

[Andygasman2010]

Even thou the boiler has an internal by pass,its good practise to fit one externally,especially if the rads have TRV's fitted.

I was under the impression that the internal bypass is designed to give the minimum required flow rate through the heat ex, why would it also need an external one? Just go for a 3 port valve and you'll never have a closed port to worry about. Especially if you have towel rails open all the time too.

A dedicated return for the hot water is to prevent reverse circulation. If the cylinder return has to go past the return leg of any radiators there's a good chance it'll gravitate up and heat up the rad. You'll know if that happens because the return side of the rad heats up, not the flow. Just make sure the cylinder return is the last one before the boiler.

 

[Foobix]

Most manufactures instuctions will recommend an external by-pass if you are fitting TRV's to the radiators.If you were fitting a 3 port then it wouldn't be an issue but as you stated you will be fitting 2 ports then the choice is yours.A towel warmer without a TRV,but with 2 lockshields would add protection for the pump and the internal by-pass will satisfy the pump over run.It's always best practice to follow the manufactrers instruction so if they recommend one then fit one.As where to fit it,below the boiler before the zone valves will normally suffice unless otherwise stated.
Bring the return from the hot water cylinder all the way back down to the boiler and tee it in as the first connection on the return.This will prevent any radiators heating whilst on hot water demand.

 

[headzinbitz]

what a great site all the engineers having a go at each other Is it just me but does any 1 think the guys at ariston tec are a**holes?

 

[joe1234]

Thanks for all your help on this Just one thing apart from fitting a bypass what would be best two two zone valves or a three port valve which i still have to use a two zone valve which came with the tank thanks again Joe