Please see other post
right now i am listening to a high pitched whistle the is coming from my oil fired hot water system.
It seems to happen most often when we use the hot water
When you use hot water it drops the temp in the tank and kicks on the burner assembly.
Please keep in mind I am going by my own experience with sounds and oddities with equipment, and can not tell you 100% what your problem is.
What I do know is I have heard oil burners whine quite often. I do not know how often you have it serviced but you may want to at least check the oil filter. Some units whistle from restricted oil flow. The pump is trying to pull oil and if anything slows it down, like a plugged oil filter. it will make even more noise.
Now that is odd!!
Is this strictly domestic hot water or also home heating?
It is alos home heating
I have 4 zones on my system, One of which is the hot water tank
Ok, so here is what my process when researching noises -
Noise can be caused by mechanical components during their operation, and can also be related to pressure and liquid flow.
I identify every pump, motor, zone valve, blower etc. One by one I eliminate them.
2nd, I check pressure relief valves for signs of blow off, ant leaks in the system, and any sign of unit running a higher temp than desired.
Once in a great while something is found to simply be from design..
But in your case I would check circulating pumps, zones, and pressure relief.
One by one you can eliminate items.