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BMelectrics

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Evening gents (and ladies)

I was doing an S-plan boiler house setup this week and after I had done it, I started to think about the flow of electricity to the point of insanity.

Imagine in the S-plan setup, a 2 chanel controller, controlling a cylinder stat and a high limit stat.


The cylinder stat controls the CH and the high limit controls the HW.

Now, when a person presses the CH button on the controller, the current flows through the cylinder stat, to the CH valve, when this valve is open a switched live from it is sent to the boiler and external pump.

Everything is fine so far, if the person presses the HW button on the controller, the current flows through the high limit stat, to the HW valve, when the HW valve is open, a switched live is sent to the boiler and exernal pump.

Now here is where I am being stupid .

When BOTH the CH and HW buttons at the controller are presses at the same time, both valves will open, and BOTH valves will send a switched live to the boiler. Does this not create 400v?? two phases together??

I may be just missing a simple explanationView attachment Sundial-S-Plan-Reference-Guide.pdfView attachment Sundial-Wiring-Rev1d-2nd Edition.pdf

I have provided the diagram

Thanks in advance
 
G

Guest123

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  • #2
Evening gents (and ladies)

I was doing an S-plan boiler house setup this week and after I had done it, I started to think about the flow of electricity to the point of insanity.

Imagine in the S-plan setup, a 2 chanel controller, controlling a cylinder stat and a high limit stat.


The cylinder stat controls the CH and the high limit controls the HW. Not quite. Thr cylinder stat control the temp of the HW, while a roomstat will control the temp of the CH.

Now, when a person presses the CH button on the controller, the current flows through the cylinder stat, to the CH valve, when this valve is open a switched live from it is sent to the boiler and external pump.

Everything is fine so far, if the person presses the HW button on the controller, the current flows through the high limit stat, to the HW valve, when the HW valve is open, a switched live is sent to the boiler and exernal pump.

Now here is where I am being stupid .

When BOTH the CH and HW buttons at the controller are presses at the same time, both valves will open, and BOTH valves will send a switched live to the boiler. Does this not create 400v?? two phases together?? No because both switched supplies originate from the same point on the same phase. If you were to place a volt meter across both these switched supplies at the wiring centre, your meter would read 0V as there wouldn't be any PD across them.

I may be just missing a simple explanationView attachment 13397View attachment 13398

I have provided the diagram

Thanks in advance
In blue.
 
B

BMelectrics

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  • #3
thanks for the response Lenny, forgive my ignorance, but if the 2 switched lives are connected to the L in the boiler (joined in connector block, then a brown to the L in the boiler) there may be no potential difference between the 2 orange cables from the valves(s/l) but what would i get if i placed a volt meter across L and E in the boiler???

Am i right in saying that if the 2 S/L's are coming from the controller at the same time to the boiler, the 230v is split between the 2????

its been a long day!!!
 
B

BMelectrics

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  • #4
One more thing, there isn't a room stat being used! its controlled by the radiator valves.

How would I get the CH valve to operate without a room stat to send a signal to it?
 
G

Guest111

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  • #5
to get around not having a room stat simply put a link in the wiring box where it it marked room stat.
 
G

Guest123

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  • #6
One more thing, there isn't a room stat being used! its controlled by the radiator valves.

How would I get the CH valve to operate without a room stat to send a signal to it?
Directly from the timeclock.

If you were to measure between L&E at the boiler, providing the supply was energised etc, you would read 230V

Also, each of the orange S/L's will read read 230V to earth when energised.
 
S

sedgy34

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  • #7
isnt the heating circuit controls on a single switched fused supply 230v??
 
B

BMelectrics

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  • #8
thanks guys, Im back on track!!
 
S

Spark1979

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  • #9
Thought you had to have a room stat now for building regs
 
G

Guest123

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  • #10
Thought you had to have a room stat now for building regs
Technically, you should have more than one roomstat as again, technically there should now be a minimum of 2 heating zones for houses of i believe up to 1500M2 floor area ( you'd have to double check Part L for clarification).
 
Technically, you should have more than one roomstat as again, technically there should now be a minimum of 2 heating zones for houses of i believe up to 1500M2 floor area ( you'd have to double check Part L for clarification).

Absolutely correct Lenny and Darrenburton.

But not only must there be a Room Thermostat under Part L for Dwellings up to 150 Square Metres in area - any Heating System that does NOT have this aspect of `Boiler Interlock` would result in the Boiler Firing / `Cycling` to keep the Boiler Thermostat satisfied - this would obviously be prohibitively Expensive on Gas / Fuel !


Chris - Heating Engineer
 
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