why is my steam so slow?

danFromNJ

Sorry in advance for the long post...

I read these forums a lot and I've seen several articles talking about the amount of time for the steam in a system to go from the header to the main vents. It seems like the consensus around here is that with proper main venting, the steam should reach the main vents in several minutes. I feel my 1-pipe system takes too long. This system was installed by @Dave0176 a couple of years. As an aside, I love Dave's work and think he did a great job on my system. I attached a drawing of the system layout. You can also see pictures here (http://forum.heatinghelp.com/discussion/155731/another-replacement-with-an-added-hot-water-loop)



My house has 8 radiators totalling 193.5 edr. Before Dave installed the new boiler (Weil McClain EG30), half of the house was parallel flow and the other half was counterflow. After the new boiler, a main vent and drip to the wet return was added to both counterflow branches so they act more like small parallel flow mains.

The two short mains are each only a few feet long (1 is 2" and the other is 1 1/2"). They each have a Gorton #1 at the end. The long main is about 30' of 2" until it gets to the last radiator. It then reduces to 1 1/2" for 20'. This main has two sets of venting; after the last radiator it has 2 gorton #1s and just before it drops to the wet return it has 2 gorton #2s and a big mouth. This seems like more than adequate venting for the size of the system.

Today I was timing how long it takes for steam to make it to the vents. This was done when the system was already warm from a previous firing. I waited until the header got to hot to touch and I could see the water in the site glass start to bounce. It took 4 minutes to reach the vents on the 2 counterflow sections. It took about 6.5 minutes to reach the main vents placed after the last radiator. To reach the antler at the end of the dry return took almost 10 minutes.

The boiler is sized very well to the radiation in the house and it almost never builds pressure. Today when it was 15 out, I saw the pressure rise to 4 ounces. Usually I never see the dial on the 3psi gauge move off of 0psi. The system is pretty well insulated. Everything but the risers in the wall are covered with 1" fiberglass. The system also doesn't use much water. I have a VXT on it and it has used 3 gallons over the last 2 heating seasons.

Why does the steam take so long to reach the end of the 50' 2" main? Are the radiators over-vented and the steam is pulling into the radiators and condensing before the steam can reach the steam main? Most of the vents are Gorton 6s, two are 5s and one is a C.

Thanks is advance. Any help is appreciated.

Jamie Hall

You say there are no radiators after the reduction from two inch to inch and a half. At the risk of sounding like an idiot, the time it takes for the steam to get to the end of that 20 foot section of pipe is quite irrelevant to heating the house, no? The idea is to get steam to the radiators evenly and quickly -- which, it seems to me, your system is doing very nicely indeed. There is no purpose for the steam to get into that 20 foot section -- there's nothing out there to heat. Almost all of your steam is going quite happily into your radiators, which is where you want it to go, seems to me.

I wouldn't say the radiators are over vented -- nor the mains.

danFromNJ

Sounds sensible. Would it make sense to move the two Gorton 2s and the big mouth to just after the last radiator takeoff and plug the spot at the end of the dry return? Would the vents closing sooner cause steam to stop filling in the dry return and instead travel to the radiators faster?

Jamie Hall

Won't make much difference -- the resistance to flow in that inch and a half is trivial, and the steam will travel to the radiators as soon as it gets to the radiator runout.

EBEBRATT-Ed

I would leave it as is. It sounds like it is fine. Every system vents differently and most systems don't have "textbook piping" 100% throughout the system. 50' of 2" is a decent run. 6 1/2 min. to the end of the mains is not bad. Don't worry about timing the dry return getting hot that means nothing

Steamhead

danFromNJ said:

Sounds sensible. Would it make sense to move the two Gorton 2s and the big mouth to just after the last radiator takeoff and plug the spot at the end of the dry return? Would the vents closing sooner cause steam to stop filling in the dry return and instead travel to the radiators faster?

This is what I'd do. There's really no need to heat that dry return. Build a huge antler to hold the vents.

Just how long are those "short" mains?

danFromNJ

The short mains are both very short. A few feet each. They each have a 2 radiator take offs, one that goes to the first floor and one that goes to the second.

The 30' main is located along the front wall of the house (to keep the basement clear of pipes I believe) which makes the take offs from it very long. 3 of the take offs travel between 15-22 feet and are the last radiators to heat up. On the last radiator coming from the main, I followed the Gerety vent method from laosh and put a Gorton 1 before the radiators supply valve which helped it heat up a bit faster.

I get the feeling that with how I am venting now, I am wasting time moving steam through the dry return which should be going to those 3 slow radiators.

Steamhead

If they're only a few feet, they may not even need vents.

danFromNJ

Do you think I am over venting the short mains with a main vent and the radiator vents? Should I try to slow down these short mains while also trying to speed up the 30' main?

Steamhead

Quite possibly. You might try removing those vents and plugging the openings, and see what happens.

Gsmith

How is the heat distribution to the rads, and heat balance in the various parts of your house? If you are not having unbalanced room heating, then you are probably ok. But since you put a vent on one rad riser before the rad valve, I suspect at least that room was taking too long to heat. But again if the heat in the house is balanced then you are probably ok.

For sure you have more than ample main venting. I have a 150,000 but boiler with two mains one 25' and a 30' long , with one big mouth vent on each end, no vents on the dry return end, and it takes about 2-1/4 to 2-1/2 min to get steam to the main ends. But to do that and much more importantly to get even heat distribution in my house, particularly between floors, I had to slow down most rad vents so the fast ones were not stealing steam from the others. Remember you have a fixed volume of air in the mains, run outs and rads and your boiler puts out a fixed quantity of steam in cubic feet per minute , so if the venting is balanced and the mains vent faster than the radiators, the boiler will fill the piping in a fixed amount of time.
BUT, if you have fast vents on the rads, particularly on rads nearer to the boiler, the steam gets to the rads before it gets to the ends of the mains, and when that hot steam hits those cold rads it condenses, creating a vacuum which will cause more steam to be sucked to that rad until it is hot across and deprive the others . In one of Dans books, either LAOSH or greening steam he has an example of two rads on the same riser one gets hot the other never heats, all because the vent on one was much faster than the other.

So, long story short, if your house heats evenly and acceptably you don't need to do anything. If not and you have unbalanced room heating then look at the rad vents, slow down the hot room rads and speed up the cold room vents, till you get better balance. You have plenty of main vent capacity.