Just moved into a new (well to us, house was built in 1910) that has single pipe steam. Boiler was replaced 4 years ago by previous owner. The radiators in the house are MASSIVE in size...some of the biggest I've seen, especially for a modest 2,400 sq ft house. Our previous house was a 2-pipe system with radiators that are tiny by comparison, at least visually.
When we first moved in, the upstairs would be sweltering while the downstairs (where the thermostat is) would be cooler, and take longer to warm up. Checked the main vents, and both were ancient, one was clogged almost entirely (the one on the main servicing the first floor, go figure). I replaced the vents with big mouths, now all the radiators start to warm up at the same time...for the most part (upstairs still seems to get hotter faster just slightly). The pressure gauge on the boiler read 0, assuming I needed a lower pressure gauge, I replaced it with a 0-3 psi gauge, and it continues to read zero, even after being on for an hour. So pressure does not seem to be an issue, indicating that the boiler is always working to "fill" the radiators.
However, the radiators never heat all the way across, they reach half way at most after the boiler is running for an hour straight. They start to get hot after about 10 minutes, which seems adequate, but take a long time for the heat to "spread" across the radiator. I can pull the vents off the radiators with no change (can feel air coming out slowly). Eventually, the thermostat kicks off before the radiators are fully hot.
I know Dan says that heating was sized to be comfortable on the coldest day of the year, and since in Michigan we haven't hit the coldest day of the year yet (but soon), is it possible that the system is behaving as designed considering the size of the radiators? It seems to me the radiators should heat up faster than they are, so I'm wondering if the replacement boiler is potentially undersized? Any way to figure out if it's performing as intended?