Secondary return hot water

[Madrab]

Yes, you can also reverse circulation due to convection, depending on the layout.

 

[fixitflav]

Reverse circulation, as in when the pump is off if on a timer. The secondary pipework could draw water out of the cylinder, if no check valve?

See #11

 

[Matt887]

Thanks sure when I worked at a place before they didn't fit a check valve after the pump. Somewhere else they do. Wondered on the reasoning.

 

[Madrab]

Thanks sure when I worked at a place before they didn't fit a check valve after the pump. Somewhere else they do. Wondered on the reasoning.

You can fit them before the pump so it's on the negative side which may limit pressure jumps on initial startup but TBH it's just about limiting the flow to one direction.

 

[Matt887]

Tha k yes if fit on the negative side of the pump this would help the pump i.e less resistance?

 

[fixitflav]

Tha k yes if fit on the negative side of the pump this would help the pump i.e less resistance?

It's a closed loop so the pump differential pressure is the same whether the NRV is before or after. In theory it's better after the pump, as that gives higher suction pressure (no NRV pressure drop) but in your case there is plenty of pump suction pressure either way.

 

[Fredstudio]

It's a closed loop so the pump differential pressure is the same whether the NRV is before or after. In theory it's better after the pump, as that gives higher suction pressure (no NRV pressure drop) but in your case there is plenty of pump suction pressure either way.

Thanks all sealed systems are closed loop?

 

[fixitflav]

Thanks all sealed systems are closed loop?

Not just sealed systems, open vented systems as well.
Edit - I suppose you could say in this setup it's a closed loop when there's no HW drawoff. When there is drawoff it's a bit of both. But it doesn't make any difference, why do you ask?

 

[Elsa TLC]

Secondary circuit must be run in copper, you shouldn’t use plastic pipes

Not necessarily we use tectite metal (aluminium layer in it) with tectite classic fittings and correct insert)
Other makes are available.

Butline can also be used, if a timer is incorporated.