A properly mounted gravity (gravity) system does not require a circulation pump in its design. The pump deprives the entire system of the main meaning, non-volatility, when the power is turned off.
But if you wanted forced circulation, ask why you need it?
There are three reasons:
1) To increase the efficiency of the boiler, the fact is that gravity requires high temperatures, only at high the temperature of the coolant begins to move effectively in the system, warming up the far corners of the system, about this spoke here. If the boiler temperature is high, then most of the energy is sent to the atmosphere. This cannot be avoided. And the installed pump allows the system to operate at low temperatures.
2) So as not to overheat the boiler in spring and summer, when a high temperature in the registers is not required, and the coolant must be made to move.
3) Correct the installation jambs, incorrect slope and small pipe diameters.
A very important issue in gravitational heating is the correct installation of the circulation pump. So that it works in the presence of electricity and does not interfere with gravity in the absence of it.
Installing a circulation pump on the bypass line
Standard installation of a circulation pump in front of the boiler on the branch line:
When the pump is running, the flow does not move directly into the boiler, but by compulsion through a filter and shut-off valves. In this case, the ball FULL BORE the valve on the main line is closed.
Power outage, what should I do?
We close the bypass taps, open the FULL BORE valve on the return. The liquid independently begins to move through the pipes.
The disadvantage of this system is manual switching of modes with and without a pump.
Installation of a circulation pump on a bypass line with non-return valves:
One option to simplify a gravity system with a pump running automatically is to install check valve instead of a full bore ball valve.
If the pump is closed or does not work, then the flow opens the valve and moves directly.
For gravitational systems use a "poppet" or "petal" is all the name of one and the same. The principle of operation in it is based on the movement of the suspended plate by the flow of liquid. Naturally, the use of spring valves is not recommended, they have a lot of resistance.
When the pump is running, the valve is supported by the flow from the pump. The fluid works through a bypass.
Great option, in theory. But as practice shows, there is often a problem with the valves. They can stop functioning due to the presence of sludge in such systems, which can get on the valve seat. Accordingly, it ceases to fully fulfill its function. And the circulator begins to rotate part of the coolant in a small circle.
Installation of a circulation pump on a gravity system without a bypass, bypass line. Directly.
There are some installers who, in principle, do not install a bypass line. And the pumps are installed on a straight pipe. Naturally, the question arises, how does the gravity system work with such an installation?
When the pump is running, the heat carrier naturally moves. But what happens when the electricity goes out. Oddly enough, but the coolant passes perfectly through the "snail" of the pump, without stopping the system. This feature can be noticed by the owners of gravitational systems with a bypass line when the power is turned off. When the pump does not close and the full port valve does not open. The system continues to work through the "volute", the impeller of the pump.
The question arises, then why block the bypass, if everything moves perfectly straight through the impeller of an idle pump. The only thing is to monitor the cleanliness of the coarse filter and put a mesh with large cells in it. Otherwise, the drift will stop working because of this. It will also not be superfluous to have an "insert" instead of a pump, a kind of straight threaded pipe installed in place of the circulator during its repair or for other reasons.
Such a system will work even if the electricity is turned off and the owners are not at home. Gravity will perfectly cope with the resistance of the impeller of the circulation pump.