More than once I watched debate and debate between plumbers about the correct installation of the circulation pump in the heating system. Many copies have been broken in these disputes. For myself a long time ago I made certain conclusions, as it should be correct. After organizing my thoughts and drawing up illustrations, I will tell you about them.
Should the circulation pump be installed only on the return line?
If popular, then it is installed in front of the entrance to the boiler. Is it so? Experts who insist on this thesis argue their choice with several factors:
1) The pump operates at a lower coolant temperature than in the supply, accordingly its resource is higher, it will work for more time. In fact, the circulator is designed to operate at temperatures over 100 ° C. And it doesn't matter to him whether he works at 50 ° C or at 80 ° C. The runaway in temperatures is small. Accordingly, there will be no significant effect on the operation of the device, or if it does, it will be quite minimal.
2) The efficiency of the pump is higher if it pushes the coolant into the boiler, rather than pulling it out. And in reality, in closed systems, with an unbreakable jet, there is no difference for the pump, pushing the coolant into the boiler or pulling it from there. The pump does not improve or degrade performance from location. The only thing is that the circulation pump must stand between the boiler and the radiator network. Putting them between the registers is impractical and damages the heating system. As in the illustration below:
3) The cooled coolant has a higher density, respectively, the pump impeller will pump more liquid. But in fact, with a temperature difference of 20 ° C between the supply and return, the water will expand by less than one percent and such data should be neglected, when choosing a location, because it is insignificant.
If we discard all of the above arguments, then it turns out that a circulation pump can be installed anywhere, before or after AOGV. But this is not the case. There are times when it is worth installing the pump either in front of the boiler or after. Let's take a look at them:
Solid fuel boiler, install the circulation pump only on the return line
Why should you do this? In unregulated or high-energy boilers, which are boilers fired by coal, wood, pellets, etc. there is a high risk of overheating of the coolant. Consequently, steam can be generated, displacing the liquid from the pump. The impeller will not be able to push the liquid and the superheated steam will build up pressure in the combustion chamber and the system, which will lead to the explosion of the boiler or the activation of the safety group. If the circulator is installed in front of the boiler, then it will delay the moment of maximum overheating and there are less chances of shutting down the system in emergency mode.
Low pressure boiler, install the pump only on the supply
The circulation pump can raise the pressure in its flow line, about 0.2 bar, this moment should be taken into account when calculating the system, especially if there is a low pressure AOGV. Excess pressure in such boilers, if the pump presses into the boiler, leads to the leakage of the emergency valve when the circulation is started. In such cases, the circulator should be moved after the heating unit.
As a result, in a solid fuel boiler, the pump should be mounted on the return line, in boilers with low supply pressure. In other cases, we place it where it is convenient to carry out maintenance.
How to effectively connect heating radiators, consider all the options