For those of you who aren't familiar with a boiler the basic parts consist of the Boiler itself, a pump, an Air release, and Zone Valves. There are a few other parts, but these are all you need to understand the basic functions. When the thermostats call for heat the Boiler heats water and triggers the pump to circulate water. The Zone valve opens allowing water to flow to the zone and that area of the house heats up. A zone is an area of the house that is controlled by a thermostat. This can be defined in any way, but in most homes it's usually by floor of the house. Newer furnace homes have this feature, but adding it to a forced air system is expensive requiring specialty baffles or even a second furnace system. Boilers just require a thermostat and zone valve. As for the air release that knocking and banging you hear in public buildings with old systems is due in part to air being in the system. Home boilers have air releases that help purge this out of the system allowing them to run almost perfectly silent.
One particularly cold day this winter I woke up to find it 64 Degrees Fahrenheit. Not too bad, but out of the norm considering my thermostat stated it was set to 70. Heading downstairs I could notice a temperature change immediately and the main level was 70. I immediately know either the thermostat or zone valve has died as I have heat in the lower level. Heading to my boiler room I find the zone valve buzzing which usually means the motor has died. Flipping the manual switch I immediately find heat restored to my upper level.
A little research on the subject via Google I learn two things. First over time the motor in a zone valve does give out. Looking at the manufacture date on the valve and noticing that the parts are all original my valve (a replacement part requires wire splicing which my unit did not have) has been operating almost 60 years. A good run for a motor that isn't constantly exposed to temperatures over 100 degrees. Secondly a zone valve consists of two parts. The valve itself which is a ball valve and is designed to outlast the rest of a boiler heating system, and a power module consisting mostly of the previously mentioned motor and some gears and springs. The power module is designed to not only be replaceable, but also easily repairable in place.
Unfortunately while the zone valve was designed to be both serviceable and replaceable, parts are not easily located. After calling a number of plumbing and heating supply companies I found that any store that actually had it in stock would only sell the part to a licenced contractor. I also found that the price they were charging was more than double (and in some cases triple) what the same part could be had for online. Luckily my zone valve started working again and as such enabled me to overnight the part I needed. Once it arrived it was only a 20 minute install including the time needed to gather the needed tools which were a wire stripper, a torx wrench, a philips head screw driver, and some electrical tape.
I'm not sure what this heating repair would have cost me exactly, but I know the average rate for a service call to get a tech to your door is $75-100, and the average cost of the part at a shop was over $80 so you could very easily have a bill of over $200 for this repair. The cost of a OEM part from amazon was $27. The included paper instructions were enough to get the job done, but a number of people have shown how to do this repair on Youtube making it a great easy to do repair.
Now as I stated before I have two zones in my home. As such when I placed my order I specifically ordered two motors. One for the immediate repair, and one to keep on the shelf for a future repair. As these don't go bad over time I figure I'll keep it boxed near the boiler for a future repair. If you live in a home with a boiler like I do you might want to consider doing the same even if you're not in immediate need of a repair. Buy two motors and have them ready.
Here are links to everything you'll need for this repair.
The OEM Motor (This matches my zone valve. A honeywell v8043. Check to see if this matches your valve, or search google for the motor you need)
A Wire Stripper
A Screw driver set that includes Torx bits.