Calculate main vent replacement requirements

umscheidt

I’m the proud owner of a new (to me) Weil McLain series 5 e-3 boiler installed in 1971 that is (somehow) still running.

I’ve read through We’ve Got Steam and the Lost Art of Steam Heat and making a few adjustments. I’m trying to make it more efficient and extend the life as long as possible before buying a new one - hopefully a few more years. 

To start I’m looking to replace my main vents, but I’m trying to calculate how to balance and which vents I need. 

Both runs are 2 inch pipes, but one is much longer, at 62 ft while the other is 27 ft. 

Is it best to buy different vents that would have them fully vent at about the same time? Or does it generally not matter? 

Based on my calcs: 

27 ft run:

This run serves 2 1st floor radiators 

Pipe Contains .54 cubic feet of air 

Current vent: Dole 1933 vents at .033 cfm, fully vents in 16.4 mins 

Potential replacement: Gorton 1 vents at .33 cfm fully vents in 1.6 mins

62 ft run:

This serves 3 first floor radiators and 2 2nd floor radiators. 

Pipe Contains: 1.426 cubic feet of air 

Current vent: Dole 1933 vents at .033 cfm, fully vents in 43 mins 

Possible venting replacements  

(1) Gorton 1 vents at .33 cfm , fully vents in 4.32 mins

(2) Gorton 1 vents at .66 cfm fully vents in 2.16 mins

(3) gorton 1 vents at .99 cfm fully vents in 1.4 mins 

(1 ) Gorton 2 vents at 1.1 cfm, fully vents in 1.3 mins 

First off, does this math look right? I used the balancing steam system venting charts for vent cpms and pipe cubic feet calculation.

I like the idea of using multiple #1s for redundancy sake, and their smaller profile vs going one singular #2

The current vents are on 6 inch by 1/2 inch nipples.

Based on the above calcs above I’m  leaning towards installing a single #1 on the 27ft run, while going with 3 #1s on the 62 ft run. That would provide better venting then my current set up, and both runs would vent within a min of each other. 

Is the way I’m thinking about it accurate or am I overlooking anything? Do I have to account for the fact that the longer run supports more radiators and therefore air?

I’ve also read the general rule is to install one Gorton 2 per 20’ of 2 inch, but that seems like overkill, at least per my calcs above. Is there any math behind that guide?

This site is awesome, I’ve learned a ton already!

ethicalpaul

I bet your math is right, but the real world might not show these numbers.

This is because the steam has to heat the main and that slows it down. This is even when the main is insulated and still warm. This is why I think that buying vents per some flow rate charts is a mistake.

For my dumb opinion, I'd throw a Gorton 1 on the short main and a Gorton 2 on the long main. You can then time it vs just the open pipe and see if you need any more, but I don't think you will.

umscheidt

Thanks, that’s a good point. This was going off just theoretical numbers, ignoring a number of variables (including pipe insulation, etc). I’m sure real world application will be different. 

I do like your approach.  I can install those, see how it’s working, and add more vents if needed

AdmiralYoda

Vent the mains with as much venting as space and budget allows. You won't over-vent them, you will just have more venting than you need.

I agree with Paul, a #1 on the short main and a #2 on the longer one at the minimum. But I'd just throw a Barnes and Jones Big Mouth on each one and call it a day.

Jamie Hall

I'd go with @ethicalpaul , while at the same time agreeing partly with @AdmiralYoda -- you can't overvent a main. Beyond a certain vent capacity the steam will just get there when it gets there, and you can't speed it up.

KC_Jones

As a separate piece of information they will not vent at the rate you are seeing in the charts, if you have enough, because you are starting at zero pressure, so the rate is automatically slower. Those charts are a great reference for speed comparison from vent to vent which helps a lot with vent selection, but for an actual rate on a real system, not so much.

Steamhead

@umscheidt , I'd start with @ethicalpaul 's suggestion. We're not just looking for speed, but also balance- we want the steam to reach the ends of both mains quickly and at about the same time. Try timing the system with the Gorton #2 on the long main and the #1 on the short one, and get back to us.

umscheidt

Thanks all - great points all around