water flow in a combi

[B.O.B DOLE]

this is a combi can someone tell me, when water flows from the mains to the boiler it goes through a flow restrictor, then the water flow switch tells the pcb the correct demand then primary water is diverted to plate heat xchanger
my question is if i turn on the hot tap, the water flows throu restrictor but does it then go to the 3 way valve and if so is there a switch which senses that the hot tap is on or does it go to where the flow switches are which send the signal to the pcb are is all of this bull..........

 

[Baxi-Remeha]

example 105e....

tap is opened, water flows through a preasure diff which makes the domestic flow switch....this in turn tells the boiler to fire up and the diverter valve to move over to dhw and send the water through the plate heat ex. the temperature is measured using the dhw ntc thermistor so if the water needs more heat, the thermistor tels the pcb, and the pcb modulates the gas valve accordingly. the flow restrictors are normaly used to slow the flow of water, as if it passes too fast through the plate heat ex, it wont have a chance to pick up any heat....

hope this helps...

 

[B.O.B DOLE]

example 105e....

tap is opened, water flows through a preasure diff which makes the domestic flow switch....this in turn tells the boiler to fire up and the diverter valve to move over to dhw and send the water through the plate heat ex. the temperature is measured using the dhw ntc thermistor so if the water needs more heat, the thermistor tels the pcb, and the pcb modulates the gas valve accordingly. the flow restrictors are normaly used to slow the flow of water, as if it passes too fast through the plate heat ex, it wont have a chance to pick up any heat....

hope this helps...

yes but where do the dhw and ch flow switches come into play are the flow switches on the 105 e built into the diverter valve?
as on a brittony 100 there is a seprate 3 way valve and it has 2 flow switches dhw + ch on a manifold whith the plate heat ex on it so with this set up how does the water flow

 

[Baxi-Remeha]

primary flow switch is incorporated into the divertor valve, when running the ch, the pump will start making the pin stick out of the primary presure dif which in turn tells the pcb that the pump is running, and it can go into ignition.

the dhw flow stitch just tells the boiler that there is a demand for dhw..


so in short, the primary flow swich is incorporated into the divvy valve(back), and the dhw flow sw is the big round thing stuck on the front of the divvy valve

 

[ChrisR]

Room for a bit of confusion there I think: Though the primary flow switch shares the same big brass casting which contains the DHW flow detector(diaphragm) and diverter valve, it needn't. They can be, and often are, separate.

Also, if you look at the hydraulics bit of the parts list on partsarena.com for the 105e, you'll see two thin pipes parts 96 and 97 which bring water over to be "sensed" by the diaphragm bit. So the flow sensor isn't really a flow sensor at all but a pressure sensor.
There are various ways the tap being open is detected by diaphragm mechanisms; some detect mains pressure when the tap's shut, some the flow of water past a small orifice which creates a negative pressure, and others. I used to be keen and work em all out, can't be bothered any more!

 

[Baxi-Remeha]

is getting a bit confusing........lol

on a 105 the dhw flow switch uses a preasure diff........(water passes past a venturi...and makes the preasure diff move across, this pressure diff is seperate from the divvy valve...

the primary pressure diff is housed it the divvy valve, just like chrisr said....

 

[B.O.B DOLE]

is getting a bit confusing........lol

on a 105 the dhw flow switch uses a preasure diff........(water passes past a venturi...and makes the preasure diff move across, this pressure diff is seperate from the divvy valve...

the primary pressure diff is housed it the divvy valve, just like chrisr said....

i see what you mean there are different mechanisms but at the end of the day they do the same thing

 

[B.O.B DOLE]

so what is the working sequence of the water supply as in once the hot tap is turned on from the mains it goes through the restrictor then where