Radiators, Slow Venting vs. Silent Venting and Boiler Run Time

gfrbrookline

For years I have been reading about venting radiators slowly and have posted several times to people advising them to do so. I had been a huge fan of Gorton No. 4's and Ventrites. Very good quality vents.

I recently tried a Hoffman 1A and found it too noisy, posted the results on the forum.

@acwagner after confirming my main venting was adequate suggested bumping up my radiator venting to larger Gorton's, which to me sounded like the equivalent of turning up the pressure on the vaporstat, heresy. That being said I like to tinker so I tried it and IT WORKED!

I swapped out the Ventrites #1's and most of the Gorton No. 4's with Gorton 5's, 6's, C's and even a D a week ago and the heat is even, the radiator's are silent and, most notably, the boiler run time is shorter. Previously I could always hear a slight hiss, not a tea kettle but enough to let me know the heat was on, now all I hear is the slight click of heat expansion if that. I used the Gill/Pajek calculation, which allows for venting the run outs and bumped up when the radiator was close to the top end of the vent capacity. I am averaging about 3 minutes less run time per cycle, that's about a 12 percent reduction.

My take away is you need to vent the radiators slowly BUT if your main venting is sufficient you can vent your radiators too slowly and make your system run less efficiently.

acwagner

@gfrbrookline thanks for trying it out and letting us know about your experience.

My theory, based on my own system, is that the ratio between total main venting capacity and the sum of the radiator vent capacity is the critical element. I think it needs to be at least 4 or 5 to 1 based on my own system. The more main venting you have, the faster you can vent the rads. The more venting capacity you have, the less resistance during venting and the lower operating pressure.

I am curious at other people's main to rad vent ratio. My own system has a few nuances, so perhaps it's not representative.

femaledog

acwagner, your comment about the ratio is thought provoking. On my personal (and very small) home system, increasing main venting seemed to necessitate faster venting of the radiators.

My experiments with smaller radiator vents of various sizes increased noise at the radiators, even at times creating gurgling, whereas larger vents run silently and heat evenly.

Like you, I am running super low pressure with a vaporstat.

SteamingatMohawk

What information do you use to calculate the ratio? I'm familiar with the Gill/Pajek report, but have not jumped into the calculations, just the comparison of venting capabilities. If you have read any of my threads, I mention the report and have attached a copy of the table and chart I made to show how the different vents compare in terms of capacity.

acwagner

@femaledog I'm curious--what's your main vent to rad vent ratio?

femaledog

That's a good question.

I have a big mouth and Gorton #1 as main vents.

On the rads I have a C, two Ds, a 4, a 5, and two very small but unknown convector vents.

How did you calculate your ratio - with the balancing steam systems using venting chart PDF figures?

edit: if so, I'm looking at about 2:1 main to rad ratio

SteamingatMohawk

I use mostly Vent Rites, some are set between the numbers, so estimating the capacity is a guess. The others are Heat Timers, which are even more difficult to estimate.

acwagner

Yes, I just use the balancing system PDF venting chart. Sounds like you're closer to 2.25:1 (not including the convector vents).

Are the big mouth and Gorton #1 on their own mains?

femaledog

The big mouth is on the large main and then there is a takeoff of shorter, narrower pipe that makes a 180 degree turn off of the large main to feed the radiators on the warm side of the house. That has the #1.

ethicalpaul

I don't really see a strong connection between the main vent capacity vs the radiation vent capacity.

The idea of this relationship as I read it above ignores the volume of the main piping, and that's the main determinant in my mind of the optimal main venting capacity.

The other thing would be the btu of the boiler (but hopefully that would be taken care of by proper main sizing, which would be related (ideally) to the size of the boiler (which is in turn ideally tied to the EDR)

And in my system where I have lazily not yet re-insulated my main, I require a lot less main venting because the steam gets slowed down significantly on its way to the vent by the cold pipes.

Now for clarity, none of what I've said above speaks to this issue, which may indeed be correct:

My take away is you need to vent the radiators slowly BUT if your main venting is sufficient you can vent your radiators too slowly and make your system run less efficiently.

acwagner

@SteamingatMohawk It looks like we posted about the same time. I just use the Gill/Pajek report. Barnes and Jones lists the vent capacity for the Big Mouth on their site. I've never measured the capacity myself. Did you measure the capacities yourself? I did a quick glance through your previous threads and didn't see a table, but I could have overlooked it.

So, looks like there's a big range for the ratio out there on @femaledog system.

acwagner

@ethicalpaul I'm proposing the ratio is a factor, not the factor. We say on this site to vent the mains fast and the rads slow, but what does that mean in actual venting capacity? I think it would be useful to understand what a general range for main to rad venting is (either too much or too little).

SteamingatMohawk

Here is the table and chart

SteamingatMohawk

What really opened my eyes was that Heat Timers at the SHUT position still vent at a #5 rate. I had been using them exclusively and ended up changing out most of them because I needed less capacity.

Sorry for the sidebar, but knowing the true capacity of the radiator vents was key to my being able to get the system balanced.

acwagner

@SteamingatMohawk I assume you could linearly interpolate the variable vents to come up with a rough venting rate for each setting. What kind and how many main vents do you have?

dopey27177

What amazes me is the stem velocity in properly designed systems is about 15 to 30 MPH. You cant make the steam flow faster than that because the pipe resistance wont allow it.

I remember in the old days before people started to replace vent valves because they were faster than the ones originally installed
Buildings with no problems until stupid became the now.

Jake

dennis53

On my system, 1 main is 5:1. The other main is 9:1.
All radiators get heat at the same time and give good comfort with no noise. I have a mix of MoM and Vent-Rites. The thermostat is in a room served by the 5:1 main, so I'm thinking increasing radiator venting on the 9:1 side won't decrease my run times.
I'm glad you brought it up, good question.

gfrbrookline

I am on day 2 and overall very happy with the results. I was afraid I would have pipes banging from creating condensate to quickly but it didn't happen. The only issue I have and it is very minor is with a bedroom radiator that makes a slight chuffing sound, similar to the sound an old fashioned style pressure cooker made but much quieter. The radiator is vented with a 6.

One question I have for folks is how do you mount your Gorton radiator vents? I see some people have them with the top pushed into the radiator and so with them completely vertical, does it matter?

@dopey27177 , I don't think I am necessarily trying to speed up the radiator, more like trying to allow the air to be vented out of the run outs, similar to main venting, and reach the radiator more efficiently. That is why I like the Gill/Pajek formula for sizing the vents.

acwagner

@gfrbrookline for what's it worth all my Gortons are installed with a slight tilt toward the radiator. I honestly haven't given it much thought--they appear to be that way out of the box.

gfrbrookline

Thanks @acwagner , my only thought about it, and I am probably way over thinking it, was that if it was vertical the pin would have an easier time seating at closing.

Mark N

If you haven't read this check it out. This is from 1935, the author recommended Main vents with orifices 10 times the size as the orifices on the radiator vents.

https://heatinghelp.com/assets/documents/116.pdf

Mark N

This one is interesting too.

https://heatinghelp.com/assets/documents/123.pdf

acwagner

@Mark N thanks for sharing! Interesting article. If it represents a real house, it has 20 units of main venting and 5 units of radiator venting, so 4:1.

gfrbrookline

@Mark N, these articles are I am guessing 70+ years old, unfortunately they could figure it out back them but the technicians now aren't being trained to understand steam. They think it's a pressure issue.

gfrbrookline

@acwagner tipped the vent towards the radiator and the chuffing stopped.

gfrbrookline

Day three, I raised my living room radiator by a 1/2" to add more slope to the manifold that feeds the radiator that was chuffing and eight others, also swapped out the C for a D on my living room radiator, largest and highest on this side of the building. Now there is one D on each main. The chuffing is now gone and the system is virtually silent.

ChrisJ

That's how it should be.

The loudest part of my system is the gas valve.

The Steam Whisperer

One thing that probably greatly effects performance is the boiler size compared to the radiation. When the boiler is oversized, bigger radiator vents work as long as the condensate can drain out against the rapid steam coming in. Also, I expect that running a properly sized boiler will require bigger main vents and smaller radiator vents simply because there is not as much steam to go around, so you need to coax it more to the end of the main. Probably one of the sharpest steam person around told me it is best not to insulate the dry returns after the last radiator take off. The uninsulated pipe creates a vacuum that helps pull the steam to the end of the system.

gfrbrookline

@The Steam Whisperer I am about 25 percent over sized, I have been able to overcome this with over abundant main venting. I have always been told to insulate the returns, which I did even though they were never covered in asbestos like the rest of the system. That might explain why it takes so long for the condensate to return to the boiler since I added the insulation.

This thread seams to have turned normal practices upside down.

Precaud

The Steam Whisperer said:

Probably one of the sharpest steam person around told me it is best not to insulate the dry returns after the last radiator take off. The uninsulated pipe creates a vacuum that helps pull the steam to the end of the system.

Wow. Interesting, indeed.

gfrbrookline

My returns were not insulated until I was told to do so on this site when I installed a new boiler. When the boiler was installed I had a huge issue with the water feeder overfilling the boiler because the condensate was slow to return. It wasn't an issue of the dry or wet returns being plugged since they were all new, I am now wondering if the added insulation was a large contributing factor. The only way it settled down was with massive main venting and a vaporstat.

gfrbrookline

As previously being someone who preached about slowing radiators down with Gorton 4's I am now a convert. If you max out your main venting and match your radiators and run outs to your connected load as described in the Gill/Patjek, adjusting here and there, you can have system that heats evenly, quickly, quietly and reduce your boiler run time. I am averaging a five minute or 20 percent reduction in run time, that is a measurable savings.

ChrisJ

I have my returns insulated with 1" fiberglass pipe insulation.
I've never had issues with condensate return or getting steam to the last radiator.

I'm a bit confused by that.
As long as I get steam to the last radiator before others steal too much, it creates suction on it's own, why do I need the dry return to do it?

I can see having to back off on radiator venting, but I'm not understanding how the dry return helps things. If anything, it would be consuming more steam making even less to go around?

ChrisJ

Here's my venting layout.

acwagner

@ChrisJ from your schematic it looks like your main to rad vent ratio is around 1.6 (assuming all TRVs are open).

ChrisJ

acwagner said:

@ChrisJ from your schematic it looks like your main to rad vent ratio is around 1.6 (assuming all TRVs are open).

Is that good, or bad for the theory?

It works fantastic.

acwagner

Neither, just more data points.

Why did you go with all Gorton #1's for main venting--limited by height clearance?

ChrisJ

acwagner said:

Neither, just more data points.

Why did you go with all Gorton #1's for main venting--limited by height clearance?

Yeah, very little height.
A big mouth will fit, but didn't exist when I did it.

motoguy128

> @The Steam Whisperer said:
> One thing that probably greatly effects performance is the boiler size compared to the radiation. When the boiler is oversized, bigger radiator vents work as long as the condensate can drain out against the rapid steam coming in. Also, I expect that running a properly sized boiler will require bigger main vents and smaller radiator vents simply because there is not as much steam to go around, so you need to coax it more to the end of the main. Probably one of the sharpest steam person around told me it is best not to insulate the dry returns after the last radiator take off. The uninsulated pipe creates a vacuum that helps pull the steam to the end of the system.

Bingo. I’m on the other extreme. Undersized boiler. All small vents #4 or vent rites. Most are set between 5-6 except one large radiator.

I run at 0oz. I suspect fractions of an inch (keep forgetting to put a manometer on it).

I’m now theorizing that lateral size and pitch become the main factor for steam balancing since there no pressure differential. Steam travels almost as much by gravity and vent provides just a Little resistance.

I can have two radiators one about 50% larger yet both set to 5 on a vent rite and heat at the same rate. But the lateral is larger on the bigger one. I think 1-1/2”‘instead of 1-1/4”. Other smaller radiators 1/4 that size of the larger ones are on the same setting but have 1” laterals and gate valves.

When I tried using large vents it was noisy and I struggled with balance. I then added more main vents , small radiator vents and then smaller boiler. The larger boiler ran around 1-2oz. It output was around 280k. Current Boiler around 160k.

The longer run times really even things out. The TRVs let me keep unused rooms cool but not too cold where there ice and moisture issues. Keep others from overheating.


I have to use a vacuum breaker on the main vent tree or I get horrible whistling on shut down. The main is about 100’ of 3” pipe.

If there was a cheap vacuum vent I’d use them. Would work great I think.

ChrisJ

@motoguy128 steam travels by gravity?

Horizontally?

motoguy128

The laterals rise up from the main.

Perhaps it’s more driven by vacuum. The larger the radiator the faster it cools as the steam hits it. So despite the vent being the same size a radiator 2x the size even with a well vented main heats at the same rate (2x the steam consumption).