Trying to understand my system, what is the purpose of my 2 motor valves, throttle valve, bypass valve, open vent system with close couple, oil???
Valve jobs???
- Thread starter Mexicanomal23
- Start date
Which of the above do you not understand?
what the close couple is actually doing and the bypass, would it not go ok without them?
Close couple
I assume you are talking about the close couple feed and vent pipes, which are connected to the flow from the boiler and have to be no more than 150mm apart.
The feed pipe is used to fill the system from the feed and expansion pipe and also allows the water to expand back into the tank when the water heats up. The vent pipe allows air in the system to escape and also acts as a safety device. Because the feed and vent pipes are only 150mm apart where they connect the boiler flow, the water level in the vent pipe is virtually the same as the level in the tank. If they were too far apart there would be a danger of the water level rising too far in the vent pipe.
By-pass
This is a pipe connecting the flow, after the pump, to the return.
It can serve two purposes:
1. If the boiler is the type where the pump carries on running after the boiler goes out (pump overrun), it ensures there is a path for the water to travel through if all the motorized valves are closed.
2. If the boiler manufacturer specifies a minimum flow rate through the boiler, the bypass will ensure this rate is maintained as thermostatic valves open and close.
A by-pass will always have a valve on it to regulate the flow. Originally they were gate valves, which meant there was always a flow through them. Regulations now specify that an automatic by-pass has to be fitted, which only opens when required.
That was a brilliant answer , thanks, get it now, just one thing, why would the vent flow over if they were to far apart, and the pipe goes on the feed from the f&e tank??
The order of components is: boiler, vent, feed, pump, rads.
The pressure at the bottom of the feed pipe is constant (called the neutral point), but is increased by the pump. It then drops slowly over the circuit and through the boiler back to the pressure at the neutral point. The pressure at the vent is therefore higher than at the neutral point. But, provided the distance between the vent and the feed is less than 150mm, the difference in pressure is not enough for the water to rise too far in the vent pipe and spill over into the F&E tank.
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