I have this old oil fired boiler (which apparently has an 83% efficiency rating) that produces steam heat.
All seems good with the boiler, but the radiators hiss really loudly for long bursts, especially as the heat comes on. The sound is really loud - similar to a trucks hydraulic brakes. Not sure if it means anything but the radiators have these odd looking valves on the side of them that look as though they were added as an afterthought.
Surely if I have steam heating I shouldn’t be hearing all this hissing as that signifies escaping steam?
You might want to have someone look at it. It could be that you have air trapped in your radiators. It’s pretty simple to fix, but I’m overly cautious about home maintenance, myself and always have someone else look at it.
You probably have air in your radiators. The past 3 apartments I’ve lived in had steam heat, so I’ve gotten used to it. Last year the radiator in my bedroom never seemed to get warm, even when the main control valve was opened all the way.
I did some googling on steam heat and discovered that air in the radiator is the cause of those loud noises and can prevent the radiator heating up properly. If you look on your radiator, you should see two valves on opposite end. One controls how much steam gets into the radiator (and thus, how hot it gets). The other is the bleed valve. It lets you bleed any trapped air off. Yes, you may lose a bit of steam, but once your radiator warms up, you can close it.