No mains on one pipe counterflow system - what about a large vent on the radiator?

stevep

There are no main vents in my system so I'm experimenting a bit. I installed adjustable Maid-o-Mist vents on a couple of our downstairs radiators and have them running with the largest orifice. The radiators get HOT all the way across within minutes of the boiler steaming. I've been running it all day (working from home today) and I haven't seen a single problem so far, and I like how quickly these radiators are heating. The large vents are allowing the mains in the basement to quickly fill with steam which is also helping the upstairs radiators get hot when needed (the upstairs radiators don't run as much because I have them cranked down with TRV's so the bedrooms stay cool).



I recall you guys saying that large vents on radiators are a bad idea but I really like the way the system is running with them. Is there anything I should be watching for to make sure everything is ok?

BobC

Wait for the cold

We have not had really cold weather yet and it's not unusual for radiators to not heat all the way across at this time of year. Watch how the system works when we get a good prolonged cold snap to make sure you don't have to adjust the venting. The heat would probably be more even if you could find a spot for a main vent but see how what have now works out.



I've used the MOM's for a while now and find they operate fine for me.



Bob

stevep

Cold weather

Bob,

These radiators are in our family room where we sped most of our time. During normal operation they don't get hot all the way across, but when it gets very cold they do. This is the room where we want as much heat as we can get. This is also where the thermostat is located. These larger vents are giving me some major heat right where I want it. I'll keep an eye on it as you suggest as the temps fall this season.



The thought of adding mains has crossed my mind but the system is so well laid out and plumbed that I have to believe the "dead man" knew what he was doing. Maybe they ran it this way back then? I'm very curious to see how it behaves as the season progresses.

Hap_Hazzard

If you want more heat in the room where the thermostat is located,

you'll have to turn up the thermostat. If you vent the radiators faster, they'll just shut off the thermostat sooner, leaving the rest of the house cooler. But if you can make the whole house uniformly cool, notching up the thermostat should make the whole house toasty.

BobC

In the end

all that counts is that the system operates the way you want it to. Just monitor it when we get those frigid blasts we all know we are in store for; if it still works they you want your done.

My house has a very short main that just goes around the chimney in the center of the basement. That means my shortest radiator runout is 9 ft, the ones on the second floor are 16 to 20 ft. I use faster than normal venting on my radiators because i have a lot of air in those runouts but I have the system working the way I want for my specific conditions.



Bob

stevep

Thermostat

The thermostat being located in this room is a win. My wife likes it warm and she'd keep the house at 75* if she had her way. I am the exact opposite - I like it cool. So, we compromise by keeping this area of the home warm. By pumping the heat into this room I can keep it nice and toasty, and the rest of the house a little cooler. In the past we'd use a small space heater in the family room but I'm thinking with the large vents we won't have to this season.

MDNLansing

Thermostat Vision

I used to be obsessed about the temp the thermostat was set at. It took a 70 year old steam guy to make me realize the thermostat represents the temp pf about 10 square feet of your house. It's better to set the thermostat at whatever temp it takes to make you happy and comfortable. Setting it at 71 only ensures it's 71 degrees right near the unit. The rest of the house might, and surely does, vary. Thermostat is just the device to ensure you're comfortable. Now, I only use it as a reference for the numbers and ignore the temp it reads.

nicholas bonham-carter

Unvented counter flow system

The old dead men knew that the system would have a coal fire built in the boiler at the start of winter, and it would be kept burning until spring, so no main vents were needed. Modern on-off burners need to get the air out many time during the day.

The fuel companies who may have installed successive boilers knew that a poorly vented system burns more fuel in squeezing the air out of the constipated little radiator vents, so a win-win situation for them.

You can sometimes compensate for the lack of main venting on a counter flow system by putting a very fast vent on the radiator fed from the end of the main(s), and slower ones on the others. This may cause water hammer in the radiators.--NBC

stevep

NBC I think you're on to something...

This house was built in 1934 and it never even occurred to me that it could have had coal at one point. What kind of evidence would suggest coal was used? Here are a few pictures. The boiler sits up against the chimney, and on the other side are two cast iron 8x10 cleanouts (there's a fireplace directly above it). Two mains run from the boiler room to either side of the house; one splits again into a tee and the other makes a 90* turn.

stevep

Couple pictures of the floor

Please forgive the wooden shim, been meaning to replace that with copper. The previous boiler was an oil fired Burnham installed horribly incorrect. It was sitting on two cinder blocks so I don't know the history of any concrete floor modifications as they were done well before we owned the home.

Blaine

total rookie here, but I have a quick question.

can you see all of the main in your system? the reason i ask is im in an early 1900's Dutch and like many houses in this neighborhood its been remodeled several times. one of our neighbors had venting problems and her handyman told her that she didnt have vent on the main either. she did in fact have them and they wound up being behind a wall that was put in.

Blaine

nevermind

sorry, i see now you said no main, i thought you said no vent on the main. didnt realize they made systems with no mains (told ya i'm a rookie).

MDNLansing

Chutes

Most house still have the old coal chute doors on them. Its an iron door on an exterior wall mounted right at grade level. It's the door they would open to throw the coal in to pile in the basement. Coal or not, if you have no main vents you either have to install some, or vent the air through the radiators. This will work, but isn't as efficient and might cause some water hammer and gurgling. If it works and you're happy with it, i'd leave it alone until spring. Then, get some vents on the mains over the summer.

stevep

Door

I always wondered why the basement walkout door was so short. Initially I thought it was a walk out bulkhead which was later modified, but eventually discovered it was part of the original foundation. Maybe this is where the chute was located. I'll poke around a bit.

stevep

Mains

Blaine, I'm considering the horizontal plumbing in my basement the main. It's a relatively small house (26' x 36') floor plan with a centrally located boiler, so maybe mine is different than yours. There have been two radiator modifications that I'm aware of which occurred over a major kitchen and bathroom renovation. One radiator was removed and the pipe was capped, and the other radiator was swapped out for a smaller hot water radiator so it would fit in the half-bath. The hot water radiator heats in a very odd pattern but it's so small, and first in line from that main, that it's going to get hot no matter what.