Could I be venting the radiator too quickly?

jch1

I have recently installed new vents on my dry returns (1 pipe steam) and have 3 Gorton 2s and a Hoffman 75. I also have a mix of Hoffman 40,ventrite 1, and varivalves on my radiators. One radiator, which previously made a lot of knocking noises prior to me realizing the vent was not fully open, has began knocking again since I put all these components on my system. I have a varivalve on that radiator. I also put a thin piece of wood under the vent side to raise it slightly. I'm thinking that this radiator is venting way too quickly, hence the knocking. The problem is that i used this vent because that room does not get very warm.

Any advice would be appreciated.

nicholas bonham-carter

There must be a pipe slope problem below, trapping water, thus interfering with the flow of air out of the pipe. Use a level and follow the main from the boiler to the end of the dry return, checking the pitch of the pipe. It helps to put on pieces of tape, marked with arrows showing the direction of flow. When you have arrows pointing towards each other, Bingo, there is the low spot, which needs adjustment.--NBC

jch1

So you think it's a problem with the pitch of my main and not the radiator itself? Should I use a standard small level or do I need to get a longer one? If I do find an issue, is there an easy way to fix the pitch?

Fred

More likely to be a pitch problem with the pipe that feeds that radiator. If it were the Main, I'd expect hammer in the Main, not at the radiator. It could also be the venting is to fast on that radiator allowing steam to hit a very cold radiator. It could also be a combination of the two problems. Check the pipe that feeds that radiaator for pitch, back to the Main.

jch1

Unfortunately, I can't check the pitch because it's on the second floor and immediately goes under the floor and I don't know where it travels before getting down to the main in the basement. Though thinking about it, I suppose the pipe does traverse the room at least partially because there is a warm section of (wood) floor near the boiler during heating.

It seems like I may be out of luck on this one, yeah?

JUGHNE

You could raise both ends of the rad maybe a 1/2" with your added shim under the vent end. That 1/2" lift on the valve end might add enough slope to the horizontal pipe under the floor to correct the problem. Of course the entire rad needs to drain towards its valve.

Fred

jch1 said:

Unfortunately, I can't check the pitch because it's on the second floor and immediately goes under the floor and I don't know where it travels before getting down to the main in the basement. Though thinking about it, I suppose the pipe does traverse the room at least partially because there is a warm section of (wood) floor near the boiler during heating.

It seems like I may be out of luck on this one, yeah?

Not really out of luck (at least not yet) If you can raise the entire radiator a half inch or so you may be able to restore the pitch. You can put wood blocks under each leg of the radiator and then repitch the radiator back towards the inlet pipe.

agurkas

That is what I had to do, I had to raise entire radiator by an inch and it worked. Did have to widen the hole in the hardwood floor, so the union below it could pop up.

jch1

That's a brilliant idea. I'll do that and report back. I suspect that it may be a bit difficult to actually lift the valve end.

agurkas

I used a car low profile car jack to sloooooooowly and carefully lift the radiator. I was going 1/4" at a time.

agurkas

Harbor Freight usually has those for cheap :-)

jch1

I've got some new findings. After being off for at least an hour the boiler just fired up again and I attempted to trace the source of the knocking. It's definitely below a radiator on the 2nd floor (I guess obviously), but importantly it sounds like it is either coming from the 1st floor ceiling (corresponding to the floor in that room) or it is coming from a vertical wall somewhere close to the ceiling. In fact, I had my hand on the wall and could feel the knocking on the wall when it occurred. I will buy some of those stackable furniture risers to raise the rad up.

In other news, I'm pretty happy with the heat I'm getting. I need to figure out what to do with basement insulation and how to heat the finished part, test the pH, and vent some rads on the second floor in unused rooms (no kids), but that's not a priority. The biggest thing is trying to figure out how to heat the basement. I was told that my boiler could use a loop of some sort combined with a pump, but I'm not sure how much that would cost and whether it makes sense to even do that.

Fred

It definitely sounds like the supply pipe under the floor has lost its pitch. When you raise that radiator, I think you will be good to go.

jch1

Great, thank you all once again. I'll add this to my list of weekend projects, which includes cleaning the boiler with a steamaster tablet or two.

jch1

We have two radiators in our master bedroom on the second floor. One has a ventrite #1, the other has a varivalve on it. The bedroom is heating much faster and warmer than the rest of the house. At first, I figured it would be best to just slow down the venting to these radiators, but I'm wondering if it makes more sense to speed up the venting of all of the others? Maybe there isn't really a difference between the two options.

I have a combination of hoffman 40s, ventrite #1s, and varivents on radiators throughout the house. I'm thinking that I will purchase a few Hoffman 1As to vent faster than the ventrites (and replace the varivents eventually), and/or some gorton 6, C, and Ds. Frankly, there are just too many options here.

Fred

The tried and true venting for steam systems is vent the Mains fast and the radiators slow. Put slower vents on your Bedroom radiators or TRV's if you can't slow the venting down enough.

jch1

I had Hoffman 40s all around, but I ended up with no hot radiators on the second floor. I may play around with things, but I know that I need to keep the vent on the radiator by the thermostat at a slow(er) venting rate than the ones on the second floor.

Fred

I use the Hoffman 1A's just so that I can get the radiators balanced the way I want them. Once you find a combination that works, you don't have to mess with them anymore. Typically the ones furthest from the boiler need to vent a little faster because of the volume of air in the run-outs, risers and radiator just not so fast as to feed that radiator faaster thn the others in the house.

jch1

I thought I raed on here that some people have difficulties with adjusting the 1As, which is why I went with Ventrites. Since the max vent rate for the ventrite is quite a bit less than the Hoffman 1a, I was planning on buying the faster-venting gortons for the high end if needed. If you're happy with your hoffmans, perhaps I'll consider a few of those instead of guessing with the gortons.

Fred

There are those that say the cap on the Hoffman is sloppy enough to affct the settings and, truth be told, that is the case but if you simply hold the cap and tighten the cap screw by hand like you are suppose to, there is no problem. I have used 1A's for 25 years and never had a problem. It always boils down to personal preference. I'd suggest you buy one and draw your own conclusions.

BobC

You won't find a better built vent than the Ventrite 1A. The Hoffman is also well made but has to be operated with care.

Bob

jch1

I guess my only concern is the maximum vent rate of the ventrite. According to the capacity chart, its maximum is half of that of a Hoffman 1A, thus my concern is not having vents that are fast enough.

BobC

That's true if you need that extra capacity the Ventrite won't work.

Bob

jch1

All,

I just timed how long it took for steam to reach the end of a portion of the dry return just before my venting stack (3 Gorton 2, 1 Hoffman 75). It came out to 7 minutes, 51 seconds. This is a single, 2.5" or 3" main that travels about 80 feet. I'm going to remove the hoffman 75 in an hour or two and time it again.

8 minutes seems pretty high, doesn't it?

Fred

You really should also time it to the end of the Main, just after the last radiator run out. 8 minutes might seem like a long time when you compare it to what others are quoting but most of us don't time it all the way at the end of the dry run. If it's 4 or 5 minutes to the end of the Main, that's pretty good. You have enough venting on there (assuming the antler is 3/4". If it's 1/2" the venting may be constrained by that 1/2" opening.

jch1

The clock started when my hand told me I need to remove it from the header.

My main is one large loop. The distance from last radiator to the antler (just before dropping down to the wet return) is about 10 feet. I'm not sure this would make that much of a difference, but I'll re-time it again with the vents on.

jch1

It just took 6 minutes 16 seconds to get to a section that was just after the last tee for a radiator.

Here's how my system is sized. Like I said, it's all one large loop, and until it gets to last leg of the loop, it has a circumference of 8.75". At this short section (as well as the dry return), it has a circumference of 7 7/8". Hope this is helpful. I'll measure again with an open vent later.

Fred

You have 2.5" Mains and at 80 ', that 2.4 cubit feet of air that needs to be vented. The venting you now have on there should be fine and 6 minutes, 16 seconds isn't bad for 80 ft. You want it to vent as quickly as possible and when you get to "as quickly as possible" you have to reconize that.
Besides that, the time it takes to get steam to the end of a Main is going to driven by other factors, like how hot/cold the main is when the steam starts. On a cold main, some of the steam is going to condense in order to generate the heat necessary to heat the main.

Fred

Is the vent pipe off of the Main 1/2" or 3/4"? If it's 1/2" adding another Gorton #2 isn't going to improve anything. If 3/4" it might/could. but with 3 Gorton 2's and a Hoffman 75, you are very close to the capacity of a 3/4" pipe.

Fred

I think 4 Gorton 2's will about max out a 3/4" pipe.

jch1

All,

It's a 3/4" tapping off the return. I have a 3/4" nipple that is reduced to .5" for the vents. So I'm close to capacity?

KC_Jones

According to Gerry's venting chart a 1/2" pipe can do 2.6 CFM @1oz of pressure. A Gorton #2 can do 1.1 CFM @ 1oz of pressure. Basically 3 Gortons will exceed what the 1/2" pipe is capable of. If you want more you would need to open it up to the full 3/4" tapping that you have available. I feel so lucky on my system I have 1" on one main and 3/4" on the other and my longest main is about 32'.

Fred

Hatterasguy said:

If a 1/2" pipe can do 2.6 CFM, a 3/4" pipe can do 5.85 CFM. It's not on Gerry's chart but it can be extrapolated.

Yes, That's at 1 oz of pressure but when we start the boiler, we have 0 pressure, remember? (I got that feedback from you )

jch1

Looks like I have to repipe it. Currently, it's on a reducing tee which goes from 0.75 on one end of the tee to two 0.5 inch outlets. One of the outlets has a Gorton 2 right on it, and the other branch has the antler with 2 g2s and Hoffman. Will that make a big difference changing everything to 0.75?

KC_Jones

I don't think it will make a big difference. Honestly the way you describe it you are probably fine. You are still feeding all 3 with a 3/4" pipe essentially. Personally when I built mine I only reduced at the vent just to maximize everything. Overkill perhaps, but that's the way I roll. I don't think I would change it unless you plan on adding more vents.

Fred

I agree with what @KC_jones is saying and I'm willing to bet adding another Gorton 2 will only improve steam time by 5, maybe 10 seconds. Just not worth the cost of another Gorton #2. You're getting steam down an 80 ft. run in 6 and a quarter minutes. Maybe you can get to 6 minutes but that simply isn't going to have an impact on how your system runs.

Fred

Hatterasguy said:

Fred said:

Hatterasguy said:

If a 1/2" pipe can do 2.6 CFM, a 3/4" pipe can do 5.85 CFM. It's not on Gerry's chart but it can be extrapolated.

Yes, That's at 1 oz of pressure but when we start the boiler, we have 0 pressure, remember? (I got that feedback from you )

Correct.

However, that's the data point. The pipe and the vents (5 of them) can do 5.85 CFM at one ounce. If you reduce the pressure, both the pipe and the vents will do less, but the vents are not compromised by the pipe due to the reduced pressure.

With 1/4 ounce, the pipe and the vents are doing about 1.5 CFM as a guess.

Agreed, however, at that 1/4 ounce of pressure, it's going to take about 1.5 minutes to vent the 2.4 cubic feet of air in that main, regardless of how much more venting he puts on. In theory, 2 Gorton #2's should suffice.

Fred

It really doesn't seem to be a matter of how many vents it might take @ 1/4 ounce of pressure. If the air can't be delivered to the vent pipe any faster than 1.5 Cubic feet per minute, then it seems as long as there is adequate venting capacity to vent that 1.5 Cubic feet/min, he's not going to get any better.
EDIT: Two Gorton #2's should be sufficient. Those vents aren't metered in any way. They will take whatever air is given them, up to the capacity of the ports on them.

Fred

Those vents aren't metered in any way. They will take whatever air is given them, up to the capacity of the ports on them. They are wide open until the steam starts to close them.

Captain Who

The Heat Timer website suggests that a Gorton #2 can do 0.8CFM at 1" WC, which would be 0.57 oz/ sq in. If it were linear that'd mean 0.35 CFM at 0.25 oz/sq in. It probably isn't linear but I think at least 0.25 CFM.

Fred

Captain Who said:

The Heat Timer website suggests that a Gorton #2 can do 0.8CFM at 1" WC, which would be 0.57 oz/ sq in. If it were linear that'd mean 0.35 CFM at 0.25 oz/sq in. It probably isn't linear but I think at least 0.25 CFM.

Gerry Gills publication says 1.1 Cubic feet at 1 oz. which is in that ball park. But I contend they have the full capacity to expel air, up to the capacity of the port on them so the limiting factors are the amount of pressure available to push air down the mains and at what temperature the venting capacity deminishes to a level below 1.5 Cubic feet per minute (in this case) where he has 3 Gorton #2's and a Hoffman 75.