Originally Posted By: janderson This post was automatically imported from our archived forum.
I recently did an inspection in a multiple dwelling building. The building has a hot water (boiler) type heating system and small baseboard radiators located throughout. While inside several of the units I could hear a loud banging noise when the heat cycle kicked in. That is, when I positioned the thermostat in the unit to ask for heat a loud banging noise occurred immediately after the zone control valve opened.
The owner stated that several of the zone valves had been recently changed out and some air had gotten into the system--they explained that they had bled the air out of the system and basically told me their was nothing else they could do about the noise. This is a 17 unit building and several units were doing this.
I recommended further evaluation by a specialist. However, for my own learning purposes, does anyone out there have any other ideas about a possible cause for this banging noise? Is the owner full of BS and needs to bleed more air out of the system?
-- Within the seeds of ignorance lie the fruits of denial
Originally Posted By: jmyers This post was automatically imported from our archived forum.
Jeremiah,
I would have to say he is just too darn lazy to bleed the rest of the air out of the system, most likely because he would have to do it in all the units.
Loud hammering is typical of air in those systems, although light hammering is typically caused by expansion of the pipes, more of a light tap.
Either way, it can be remedied, just takes some time and a little patience. 
Originally Posted By: jsavino This post was automatically imported from our archived forum.
Jeremiah,
It could be air in the system. Air in the system may give you uneven heat in the radiators, or no heat at all. You may hear the water running through the piping and the radiators. It sounds to me that the problem is in the circulator. Either a bad bearing assembly or a bad drive coupling.
Check the pumps.
Originally Posted By: jsavino This post was automatically imported from our archived forum.
The air chamber is not the answer to your problem.
When there is a call for heat, the zone valve opens. When the valve is fully opened, contacts made to the end switch that is inside the zone valve. That starts the pumps. That switch is wired either to a circulator control or to the circulator directly. If the drive coupling springs (depending on the pump manuf.) are broken the drive coupling is then not balanced. The same as a universal joint on a drive shaft when they go. The bearing assembly has a shaft that connects to the impeller. If the B.A. is not lubed, it can be noisy.
The sound will carry through the piping.
Water hammers are made to be put on mains to absorb the pressure bounce when a valve is shut, (washing machine, dishwasher) anything with a solenoid valve that closes fast.
Originally Posted By: cbottger This post was automatically imported from our archived forum.
You guys are scaring me again.
The banging you hear in the heating supply line is call a water hammer this is not something that is installed but rather created by the contact of hot water to the colder dormant water that was lying in the lines when the control valve was satisfied. The water Hammer arrestor shown above is an example of what can be used to defer or absorb this noise. This noisy will also go away when the lines all become the same temperature.
Bottom line temperature differentials create water hammers and water Hammers are very annoying.
Originally Posted By: phinsperger This post was automatically imported from our archived forum.
janderson wrote:
This is a 17 unit building and several units were doing this...... I could hear a loud banging noise ....... However, for my own learning purposes, does anyone out there have any other ideas about a possible cause for this banging noise?
Sounds like this is a motel and the banging from several units was patrons of the motel occupied in a profession much older than ours. 
Originally Posted By: jsavino This post was automatically imported from our archived forum.
In all my years of installing heating systems, working on heating systems, and installing zone valves on everything from single zone to milti-zone, to steam zone controls, to forced warm air zone controls, I have never heard of a water hammer arrester installed on a heating loop to absorb noise. Granted, when hotter water hits a cold pipe or cooler water, you may get an expansion noise, but that will stop when the radiator warms up. A water hammer arrester will not stop that expansion noise.
Originally Posted By: jsavino This post was automatically imported from our archived forum.
John
If the expansion tank is full the relief valve would blow off when the boiler was firing. The expanded water has no where to go. And on commercial application the tanks are very large and drainable. Here in the northeast most houses and commercial buildings are heated by water. Most old style expansion tanks, that hung between the floor joists have been replaced with the non-drainable type (Extrol) mounted on the boiler.
So to answer your question, the expansion tank is not the problem.
Originally Posted By: dedwards This post was automatically imported from our archived forum.
In my humble opinion you did exactly what you should have as an inspector. Report what you found, or heard in this case, recommend further evaluation / repair by a licensed professional. Never be afraid to say you don’t know if you don’t. As you can see there are more than one possible reason for water hammer / noise. I refuse to troubleshoot systems for the same reason I don’t perform maintenance while doing an inspection. If I do I just became responsible for it if something malfunctions down the road.
Originally Posted By: jsavino This post was automatically imported from our archived forum.
These posts are made for us to share knowledge. If W. H. are used for different reasons in other areas then so be it. I stopped troubleshooting also, and I agree, report your finds and move on!
