No Main Vents.....Worth Installing?

AdmiralYoda

I've got a single pipe steam system that was probably original to the house which was built in 1899. The boiler is an electronic ignition gas boiler that was installed in the 80's. Everything works fine but as I've been educating myself I noticed one thing.....NO MAIN VENTS!!!

There are two mains coming out of the boiler. One main goes 4 radiators and the other main goes to two. I installed fiberglass insulation on all the pipes.

I'm wondering how much efficiency I would gain if I installed a vent on each main. For arguments sake lets say I spend $300 per month on heat in the winter. Would installing main vents help me save $5 per month? Or are we talking $50 or more?

Thanks!

Mark N

How is the air getting out of the system now? Do you have vents on the rads? How long does the boiler run per cycle? Main vents will drastically reduce run times speeding steam delivery. are you cycling on pressure?

KC_Jones

You should always have main vents. It's about getting the steam to your radiators. Think of it this way if the steam is just sitting in your pipes in the basement what is the steam doing to heat your house? The short answer is nothing. You are burning gas to make steam and let it sit in your pipes. There is also the comfort level. Is your heat perfectly even? Are your radiator vents silent? Do you know what pressure you are running at? The higher the pressure the higher the fuel bill. The main vents will lower your pressure. If you are talking about ROI of adding vents it's hard to figure exactly, but I would guess you would recoup the cost very quickly. If that theoretical number you threw out is even close to what you are spending I would guess you would save money adding vents. I have 7 radiators in my house and I can tell you I don't spend anything close to that to heat my house. Of course gas prices vary, houses vary so it's quite difficult to do direct comparisons. The bottom line it's your house your call, but for me it would be a no brainer I would put them in. Do you have any insulation? The big one would be insulating the attic that makes a huge difference. The walls are tougher in the old houses, but generally with walk up attics you can do attic insulation without too much trouble. Just the thoughts of another homeowner.

AdmiralYoda

Yes there are air vents on all the radiators now. I installed them about 6 years ago. They have adjustment knobs on them and are adjusted based on the size of the radiator.

Its hard to say how long the boiler runs per cycle because it is dependent on the temperature of the water in the boiler and how long it takes to heat it up. But I'd say it could stand to have shorter run times.

It does cycle on pressure. I have it set to cut in at 0.25psi and cut out at 1.25psi.

KC_Jones

AdmiralYoda said:

It does cycle on pressure. I have it set to cut in at 0.25psi and cut out at 1.25psi.

The lower the pressure the higher the efficiency of the system. The only way to really lower the pressure is to add main venting. For example my system currently doesn't even see 1 ounce of pressure. Vents really aren't that expensive in the grand scheme of things again if it was me I would add them.

AdmiralYoda

The radiators are not silent. No water hammer or bad noises, but you can tell when the steam is moving as the radiator air vents make some noise opening and closing while they vent steam.

The house is well insulated. Plenty of insulation in the attic and most of the walls have had insulation blown in. There is some more air sealing to be done but I'd say the insulation isn't too bad considering the houses age.

AdmiralYoda

I should also mention that we use a wood stove as much as we can to avoid burning gas. So its been some time since we had a full season burning gas. The house has had many efficiency upgrades since then...so it is hard to say what it would cost us monthly to run it full time now.

When we moved in 7 years ago we had an average winter. In the colder months it cost us $300 per month. That was keeping the thermostat at 55 when we were asleep or at work and 63 when we were home. But the house had very poor insulation at that time.

Mark N

Are there plugs where the main vents belong? If so can you get them out. When maintaining temp the boiler should run about 20 minutes and not cycle on pressure. The system should be silent. You should not hear the air being vented.

KC_Jones

If you add main vents those radiator vents should go silent. The bottom line is it's about burner run time. The less it runs the less you spend. If you are cycling on pressure you aren't at peak efficiency. It is my opinion that the pressuretrol should be viewed more as a high limit than a pressure control device. You should control normal pressure in the system with venting. The pressuretrol is a safety device more than anything. That is just my opinion, but I am not alone on that one.

AdmiralYoda

Wow...you guys are great! Thanks for the wealth of information! I can confirm that there are no vents installed. And no plugged holes where a vent used to be.

Thinking back I would say that the boiler doesn't run too long and generally doesn't hit the pressure limit when it is maintaining a temperature. Generally this occurs when it has to bring the house up to temp.

From cold it runs for about a half hour and gets to 1.25psi and then cuts back in at 0.25psi. This will cycle until the house gets up to temp.

Sounds like I need some main vents! Installing them will be a chore though. That pipe is pretty old!

nicholas bonham-carter

The purpose of the main and radiator vents is to let the air out of the boiler, supply piping, and finally radiator vents, as steam begins to rise. If you hear any of them working, it is a sign you are under-vented. Steam, in a vacuum, will travel quickly, because there is no air in its way.
As we don't have a vacuum in our one-pipe systems, we must let the air out, with as little resistance as possible. Radiator vents are sized to handle the air in the radiators, and not the whole system, so likely, you have been burning extra fuel to squeeeeeeeeze the air out of the constipated little rad vents. This is noisier as well.
I would put main vents on, for better economy, and comfort.--NBC

KC_Jones

I would also add you should be careful about setbacks. A lot of times with high mass systems like this setbacks cost you more money than they save. You shouldn't assume a setback is a savings. Anything more than about 4 degrees is getting risky. You should experiment with this in your house to see what works best. Basically what happens is the house cools off so much that the boiler runs longer than it would have to just maintain temperature. Remember it's not just heating the air in your house it's overcoming every single cold surface in your house as well. If you had scorched air it would be a little different.

KC_Jones

AdmiralYoda said:

Wow...you guys are great!

I will say if you hang out here for a while you will probably find this is one of the best help forums on the net. I haven't been here for too long, and I love it. I was able to replace my own boiler thanks to the books and all the advice I received here!

AdmiralYoda

KC_Jones said:

I would also add you should be careful about setbacks.

Thanks for the good info. Although the steam is technically our main source of heat we are currently using it as our backup as we use our wood stove as much as possible. Generally the only time the boiler gets used is to maintain a minimum temperature while we are away for extended periods of time and to help bring the temp of the house up when we come back.

Mark N

Do you have access to free wood? With Natural gas being so cheap per therm, it wouldn't be worth the effort unless the wood was free.

AdmiralYoda

Yes. I get all my wood for free and 100% agree with your comments. My neighbor is a tree guy and gives me the wood he doesn't feel like dealing with. My parents have a large plot of land with plenty of hardwood from downed trees.

But our house is much more efficient than it used to be so running the heat wouldn't be a huge problem. I just want to get my steam system as efficient as possible.

Mark N

Get yourself a copy of "Greening Steam" available here. Steam can be run very efficiently and very economically. According to my records last with I spent $648 on gas for the heat to keep my house at 70 degrees from 10/15/13 to 4/15/14.

AdmiralYoda

Wow thats not bad! If I may ask...how big is your house and how well insulated is it, how old is your boiler, and what part of the country do you live in?

Mark N

My house is 1350 sq.ft. the attic is insulated. The walls are mostly uninsulated. I'm located in central New Jersey. My boiler is 6 years old, it is a Burnham IN-4. The EDR of the rads is 260 sq.ft. The boiler is rated at 271.

DuggieFresh5

AdmiralYoda said:

I can confirm that there are no vents installed. And no plugged holes where a vent used to be.

My system had only one vent in place on the return side (2-pipe steam). Even though the boiler wasn't original to the house, the venting was. Sounds like you may be in a similar situation.

I found a union in the piping where I could work backwards from and install vents. It was a bit of a challenge to break the fittings loose, but not too bad. I picked up some decent tools on Craig's List, so the investment was modest.