OV/CF: close coupled or combined?

[Twinker]

Hi. I'm refurbishing an old working system that still has a soon-to-be-replaced Netaheat heat only boiler.

The old system has a tendency to suck air and develop stubborn air-locks. One reason being the rather long horizontal pipe runs. But the system design may also be at fault. I have recently cleaned the system using X800 and all rads were removed and cleaned at mains pressure.

Here's a diagram sketched in Corel to give an idea of the system.

Netaheat System Diag

• Twinker
• 13 Apr 2011
• 1

This may need to change

Can I improve the system now by changing the OV/CF connections?

Would a combined F&E layout help prevent sucking air? Should I close couple the CF and OV - and if so where; near the pump or under the floor (over the boiler)?

The current place where the CF joins the return near the boiler has been a stubborn site for magnetite to collect.

Thanks

 

[BlueMoonMole]

I'd be tempted to sort the pipework out whilst you have the chance.

It looks like a more traditional setup, with the cold feed coming in on the return. So I'd be tempted to put the cold feed on the flow, after the open vent and before the pump. If my memory serves me right, it should be within 150mm?

I'd also be thinking about sticking a bypass in after the pump, but before the zone valves, into the return.

Perfect opportunity to advise a Spirovent Magnabooster2 aswell, to protect the system further.

It all depends on what your doing though, does the customer still want that style of system?

 

[Twinker]

Thanks for that.
I had thought to make CF/OV changes myself as I have floors up - but it looks like I don't need to do anything under the floor, except perhaps cap of the old insert points of the CF and OV.
Here's a revised drawing showing my take on a close coupled solution with a three port diverter valve (default to HW).

Untitled

• Twinker
• 15 Apr 2011
• 1

The space is cramped in the airing cupboard, but its doable.
What I'd like to know now is:
1) Can the combined F&E solution (simplest) work? If not what problems does it cause?
2) Can the Spirotech be placed in the airing cupboard on the flow? The return is not accessible above the floor.

Thanks again


P.S. I like the Viesmann, but not many installers have suggested it.

 

[twgas]

I'd say stick with S-plan, you may or may not need a by-pass.
The Neteheat 16-22 needs one but the smaller ones don't.
A lot of new boilers do, check the MIs of whatever you're thinking of (having) fitted.
A better option, than combining feed and vent, is to convert to a sealed system but not on the present boiler, unless there is a ss kit fitted, which is rather unusual.