Help me understand steam vent

jimdav

A bit context.
Toward the end of the main, I have two pipes back to back with each other going upstairs. One goes up to a room on the first floor and the other to two rooms on the second floor.

Second floor:
Room 1: 12 section radiator with size C vent
Room 2: 12 section radiator with size C vent
Thermostat is located in this room as it is the coldest room.

First floor:
Room: 14 section radiator with size 5 vent

Second floor Room 2(thermostat room) get warm up and reaches temperature but also cools down pretty fast. It takes 45 mins to reach desire temperature but calls for heat again in like 45 mins.
However, when first floor radiator vent was stuck, I notice Second floor room 2 gets warm up even quicker and stays hotter for at least 15 mins longer.

The first floor/radiator gets hot very well and the room usually get up to 78 degrees(i set the temp to 71). I have been thinking if I should reduce its vent to a size 4. If the second floor gets hot first, boiler stops, and the first floor radiator is only partially hot, will the steam from the second floor drop and rush to the first floor? I wonder if that's why my second floor radiator gets cold so fast. In that case, should I increase the vent size on the first floor radiator?

Jamie Hall

Decrease the size of the vent on the first floor. The vent controls how fast air can escape from a radiator, and thus how fast steam can get in and heat the radiator.

The steam won't "drop down" — once it gets into the radiator, it condenses almost immediately and there's none left.

ethicalpaul

Your question has some confusing things in it.

However, when first floor radiator vent was stuck

is it still stuck?

If the second floor gets hot first, boiler stops, and the first floor radiator is only partially hot, will the steam from the second floor drop and rush to the first floor?

No, when the boiler stops, so does all steam production. Steam doesn't travel anywhere after that, it all condenses and becomes water, the end.

I wonder if that's why my second floor radiator gets cold so fast. In that case, should I increase the vent size on the first floor radiator?

I'm not sure why you'd want to increase the vent size on the first floor when the first floor is already getting 7 degrees hotter than I assume you want it.

The only things that could make your second floor radiator get cold fast is if it is very drafty upstairs, or the radiator is small or not very massive.

jimdav

It's a problem that's been haunting me. Some times the unit is able to maintain heat and some times it doesn't. Some times it takes 30 min to heat up the unit some times it takes 50 mins and even short cycling on a warm day. This is comparing against similar temperature against last year's data. The whole house heats up fine except this unit.

ethicalpaul

There is still quite a bit that is confusing here, I will try to clear up my understanding, but no promises. Let's keep it very simple to start with:

What do you mean by "some times the unit is able to maintain heat and sometimes it doesn't"

Please don't say "it" or "unit". I think you are talking about a radiator, but I'm not sure.

dabrakeman

Put a 4 on downstairs and put the 5 in room 1.