Hot water priority !!

[mysteryman]

Indeed. G3 actually says something on the lines of: 'a 2 port valve or some other device for preventing the flow of heat into the cylinder' and 'if the primary heat source is a boiler, the limit device may be in the boiler' and 'these recommendations are not binding. Any alternative means of producing an equivalent level of safety may be employed'.

 

[Dan Robinson]

As always MI's rule the roost, but the regulations want an "energy cut off" which technically can be the o/h stat of the boiler.

If you are fitting the cylinder made by the same company as the boiler, then invariably the control system is specifically designed NOT to have a 2-port valve to allow the boiler to operate at peak efficiency for longer.

Of course there are several boilers with integrated UV cylinders and nothing more than a mid-position valve and o/h stat internally.

 

[yodaveg]

As always MI's rule the roost, but the regulations want an "energy cut off" which technically can be the o/h stat of the boiler.

If you are fitting the cylinder made by the same company as the boiler, then invariably the control system is specifically designed NOT to have a 2-port valve to allow the boiler to operate at peak efficiency for longer.

Of course there are several boilers with integrated UV cylinders and nothing more than a mid-position valve and o/h stat internally.

Fair enough. But I think if you check out the MI for the
uniSTOR they ask for thier 2xport valve to be fitted, and don't give a wiring instruction for a 3 port.

 

[matt1e]

As always MI's rule the roost, but the regulations want an "energy cut off" which technically can be the o/h stat of the boiler.

I dont agree dan, maybe for direct heating but not for indirect

If you are fitting the cylinder made by the same company as the boiler, then invariably the control system is specifically designed NOT to have a 2-port valve to allow the boiler to operate at peak efficiency for longer.

but the 2 port used wholey as a safety device is open all the time so it makes no difference to the efficiency
its just that if you are on standard s-plan then you dont need to have an extra valve fitted (unless you are using momo's for control)

Matt

 

[Dan Robinson]

Perhaps I am used to systems that can modulate a three port valve in order to flow share depending on the level of need to hot water reheat.

Also, for systems that use a bus rather than simple on off where a zone valve may not be beneficial.


Not a particularly common set up I grant