Does This Microbore & Manifold Layout Sound OK?

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Good question. Just don't recall reading you should stick one in with a 3-port.
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if you have a 3 port valve you wont get heating only, you will get water only when you ask for water only (obviously) but when you turn the heating on the water side of the valve remains open, that is why if you want seperate water and heating you fit an s plan with 2 zone valves AND bypass, if you dont require heating only you fit a 3 port and no bypass and use the water circuit as a bypass route.
Eh on a mid position valve you do get CH only when selected
if you are right i stand corrected, but what is then the diff between a mid position valve and 2x 2 ports, i always thought a mid position valve was as i described and never closed fully to hot water
You surpise me kirk.
Nope its mid position when both selected when either is selected by its self then paddle moves to close port not req,
When demand ceases then you will always have one port open which is why sometines when you turn power off at fused spur you will hear motor return to rest position as it is de-energised.

S plan over Y plan gives a better flow to rad circuit when its a bigger system.

Which is why you cannot have trvs on every rad with a Y plan without still having a bypass
i'm still confused about this, the instructions for a honeywell v4073 definately say port AB (to water, always remains open) certainly when water is satisfied power shuts off boiler, and if demand is still on for heating paddle will move over to mid position (still leaving water route open) and powers boiler to heat rads
ok kirkie boy,

what happens when you have selected ch & hw and hw is satisfied

but ch roomstat is still calling for heat.

cmon mate yer letting the team doon!!!!!!!!!!!!!!
Think about it boiler stat on hi is 82 degrees so if heating was on cylinder would heat to this temp regardless of cylinder stat as opposed to the temp set on cylinder stat.
Read it again your missing something

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