Is Main Vent (Vent-rite 75) large enough on this one pipe system?

Fred

During the coldest days of the year, the radiators should fill all the way and the boiler should run non-stop all day and stay below 1 psi, and all the while keep the each room in the house (no matter what the weather) comfortable.
If that were the case, it would mean the thermostat is never satisfied. No properly sized boiler should run all day. On the coldest day, it should/can run somewhere around 30 minutes per hour, give or take 5 minutes. If the radiators are hot all the way across, those radiators are going to be filled and the thermostat should be satisfied and allow the boiler to shut down, at which point it should be down long enough to provide enough time for the Mains and the radiators to breath (vents to open for the next cycle).
If a boiler runs continously all day, it is likely under-sized or the thermostat is poorly placed. In either case, imagine what your utility bill would be if it did run for 24 hours a day non-stop.

EDIT: Keep in mind, hot radiators are going to continue to give off heat well after the boiler has shut down.

Jack M

Is there a way to know if your system produces dry steam or wet steam? Can you look at the steam an tell?

ChrisJ

Jack M said:

Is there a way to know if your system produces dry steam or wet steam? Can you look at the steam an tell?

The only way I am aware of is to check the TDS of your return condensate. It should be practically distilled water.

I bought a fairly inexpensive temperature compensating TDS meter off of Amazon a while back. My wet return typically measures 1 to 2 PPM which indicates very dry steam vs the boiler's water which is around 500ppm.

ChrisJ

I think the TDS meter I have is this one.

http://www.amazon.com/dp/B00MD55M1C?psc=1

Jack M

How does the measure of total dissolved solids (TDS) in the condensate of the return line equate to a measure of the moisture saturation (content) in a volume of steam?

ChrisJ

Jack M said:

How does the measure of total dissolved solids (TDS) in the condensate of the return line equate to a measure of the moisture saturation (content) in a volume of steam?

Because wet steam means there's boiler water in the steam and it brings solids into the mains. Those solids then end up in the condensate.

Jack M

So a wet return with a TDS of 1 to 2 PPM and boiler water at 500ppm equates to .002 to .004 moisture content (well below 1%)?
When I run the boiler without the main vents attached (very carefully, just for a moment, to see) the invisible steam (gas and water vapor I'm guessing) quickly condenses in the cooler (lower pressure) basement air to form water droplets so small they look like a very fine mist or a cloud. If the steam is dry steam would I still see this misty cloud as the steam (gas and water vapor) cooled? I can see it; I can smell it; sense the increased moisture in the air, as it billows out quickly and condenses into this cloud.
I'm imagining (because I can't see what is happening inside the pipes) that the steam is always condensing in the cooler pipes and radiators and this would create a situation where the steam moving about would naturally be very wet. Is the temperature and pressure in the pipes so high that the steam (gas/vapor) has reached a saturation point and can no longer accept any more moisture (even as it goes flying down those wet pipes carrying the condensate back to the boiler(in this one pipe system)? Does steam by nature want to be in a dry state?