To install the new pump, clean the old gasket material from the flange and install the new gaskets on the new pump. Carefully insert the new pump with gaskets into the flanges. Be careful not to damage the gaskets and pay close attention to the arrow on the side of the pump which shows the direction of the water flow. Make sure the new pump arrow is pointing in the same direction as the one you removed.
Then install the 4 bolts that hold the circulator pump in place. Tighten the bolts just so they are snug and not too tight. If they leak a bit you can always make them a bit tighter to stop the leak. Too tight may damage the gaskets. Hook up the wires to the pump motor again. Open the valves back up and check for leaks. Adjust bolts as needed. Apply power to the system and start the motor to check the operation of the circulator pump. The hot water should start to flow through the pipes and radiation to deliver heat to the house.
Circulator Pumps are the heart of a hot water heating system. Without the pump circulating the water, there is no heat. The very first thing you need to know is the water temperature in the boiler. If the water is hot, 140F or above, than the problem is not the boiler. It is heating the water. The next thing will be to see if there is power coming to the circulator pump. Either take the electrical cover off of the circulator pump motor, or check for voltage at the source of the wire going to the circulator pump. If there is no voltage, usually 110 volts for the US, then you have to look at why the motor is not getting power. I will do another article on that issue at another time.
So now we have established that you have power coming to the motor. There is hot water in the boiler however the pipes going to the radiation are cold. The next thing to look for, are zone valves. They are little motorized valves that open and shut to direct the flow of heat to different parts of the house or building. It is possible that one of them could fail and the circulator pump is running and moving no water. Usually the circulator pump will be making a noise and often be very hot if this is the case. Of course then you need to check the zone valve. That, we will also cover later.
Changing the pump is not always an easy process. I will attempt to explain some of the possibilities for changing out a circulator pump. First of all I would recommend that if you are reading this and you do not have an extra circulating pump in the basement beside the boiler. That you stop by your local heating and air conditioning supply house and buy one. For under one hundred dollars it will be cheap insurance.
If you had a responsible installer do your heating system, then you will have valves in the piping on either side of the circulator pump. These valves will isolate the pump from the rest of the system and changing the circulator pump will be fairly painless. If you do not have valves close to the pump, then you will need to find the valves that will be the closest to either side of the pump and close them. For some older installs there may not be any valves and you will have to drain most of the water out of the system to change the pump. This can get very complicated and professional help may be needed. The hardest part may be refilling the system and getting the air purged back out of the piping.
A very important thing you need to do to before changing the circulator pump, is to make sure that the electricity to the circulator pump motor is turned off. Verify that the power is off before touching the wires. The wires then need to be disconnected at the pump motor. Then the 4 bolts that hold the circulator pump in place need to be removed. Save these bolts, they may be needed to install the new pump. Carefully remove the pump from the flange. A pry bar or screw driver may be needed to break the pump lose from the old flanges. Be careful of the motor, depending on the type of failure, the motor can be very hot.
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