honeywell vaporstat and hissing vents - 1 pipe steam system

DomesticEngineer

I am trying to eliminate some of the noises from my radiators. The pitch of radiators is maybe slightly off level so I don't think that's the problem. More vent hissing than water hammer.
Knowing the empire state building can be heated with 2psi, I've tried to reduce the pressure in my home (1.5 story 1800 sqft). Is 2 psi still optimal? if 2psi is optimal how can I quiet my hissing vents?

I find my vents hiss and spit even around 0.5 psi. I just cleaned most of them with vinegar but they are at least 10 years old. I've learned that steam vents should close, but I'm having a hard time finding a vent that closes at lower pressures.
I'm sure there are already posts on here that would help but I'm having trouble locating them.

My vaporstat is 'Diff is subtractive'. I have diff (oddly only in oz and kPa not psi) set around 3oz/1kPa ( = ~.2psi) and main at ~0.5psi but maybe the marks are off because it also looks like only 1-2kPa not 3 that I think is the math equivalent.
Anyway, I tried to get it to run lower than .5 psi but found that it had trouble turning back on if I fussed with it much.
Pigtail has it slightly unlevel - possibly adding into fine tuning difficulties.

Possibly an oversized boiler but I have no idea how to know 'what size' my boiler is nor what size I "need". And replacing it really isn't an option. I do have all the vents open including the upstairs (dormer) vent.

I know my minimum water level was fine when pressure cut off the boiler but I am not sure what constitutes "shortcycling." I think it's cycling per settings but looking for a quieter outcome.

(Yes, the house seems to heat just noisy.)
Thanks in advance!

nicholas bonham-carter

What sort of main vents have you got on the dry returns?
Have you verified those vaporstat settings with a low pressure, (0-3 psi) gauge On the same pigtail?—NBC

acwagner

2 psi is not optimal--it's considered the upper end of operating pressure for residential steam. You should be able to operate at much less. Venting will dictate the operating pressure until the radiator vents start closing. The vaporstat is really just there to prevent things from getting out of hand.

To start, some questions:

Do you have any main vents? If so, what kind and how many?

What kind of radiator vents do you have?

What kind of pressure gauge do you have?

Some photos of the boiler setup including the pigtail/vaporstat/pressure gauge will help.

Edit: NBC beat me to some of the questions.

Fred

Also, understand steam vents, both radiator and main vents don't close on pressure. They close when steam hits them, if they work.
Radiator vents typically hiss because there are no main vents on the system or, if there are, there aren't enough or they are stuck closed.
Is the Vaporstat a mercury switch or the microswitch version? If it is a mercury switch, it must be level.

Jamie Hall

On the other hand, if it is a mercury switch and carefully levelled -- it won't need calibration.

DomesticEngineer

NBC: I'm at a loss of what a "dry return" would be on a 1 pipe system. Isn't the steam in all the pipes? I do have a 0-5 psi Trerice gauge on the same T as the vaporstat. It is that reading that I base the "0.5 psi" cut out for my system.

AC Wagner: I am not aware of any "main vents" on my system. There are six radiators of varied size on main floor and one going to dormer. I'll go look things over closely and update this if I do. I currently have Hoffman 1A, 10psi max vents of unknown age (moved into house in 2008).

Fred: I believe the vaporstat is a microswitch. I do not know the age of the radiator vents, but if they are hot and hissing steam, even after cleaning, I probably need to replace them?


The picture doesn't show the pigtail loop, but it does go front to back not side to side. If I remember right, the larger pressure gauge in the pic comes right off the boiler - just a weird camera angle.

Honestly, the little I've just read about "main vents" still has me baffled. The "last" radiator of the house takes slightly longer to warm but as long as there is enough water in the boiler, it heats without a problem. In the middle of the winter I find I need to refill my boiler ever few days because of steam loss. I would think the steam would need enough "pressure" to close a radiator vent and am confused as to the nuances in difference in how they operate.

I can take better pictures tonight.

Jamie Hall

Vents -- radiator or main -- do not close on pressure. Rather they contain a thermostatic element and, in most cases, a float. The thermostatic element will close the vent when it senses steam temperature -- if it's still working -- and on the ones with a float the float will close the vent if water is present. Once they are closed, excess pressure -- usually anything over about 3 psi -- will hold them closed indefinitely. It may also destroy the thermostatic element so that they will never close on steam again.

The purpose of main vents -- which are like radiator vents, only larger -- is to let the air out of the steam mains when the boiler starts. This lets steam get to all the radiators more evenly and more rapidly. They should be locate on the steam mains beyond the last radiator take off from the main. Radiator vents, on the other hand, are intended to let air out of the radiator to which they are attached, so steam can get in and heat the radiator. They can also be used to control the amount of heat a radiator will produce (within limits), but they should not be asked to do the job of letting air out of the mains rapidly.

On steam mains, "dry" returns, true dry returns, and wet returns. There is ongoing confusion about these terms. A steam main is defined as a pipe which conducts steam to more than one radiator (if it's just one radiator, technically it's a runout, not a main). A true dry return is located above -- usually well above -- the water line of the boiler, and allows air exhausted from the radiators and any condensate from the radiators to return to the boiler or to a drip. They are not connected directly to a steam main anywhere, except through crossover traps which allow air to go from a steam main to cross into the dry return. Wet returns are located below -- usually well below -- the water line, and allow condensate to flow from various drips -- vertical pipes from steam mains or dry returns -- back to the boiler. Now. "dry" returns are found on many parallel flow one pipe systems, and are extensions of the steam mains running back to the boiler. They allow condensate from the mains and the radiators to get back to the boiler, but serve no other purpose. In many older systems the only main system vents were on these near the boiler for convenience, but as noted above so long as the main system vents are located beyond the last radiator runout they're fine. One problem sometimes encountered with these is that if there are two or more of them the must not be joined at the boiler above the water line -- each one must drop individually below the water line before they join and return to the boiler.

DomesticEngineer

I'm finding out many things about my system today. I have 2 main vents
Hoffman vacuum valve no 16. Really hard to get to them but that's all I can really make out as far as a model type.

One (paint covered) was much colder than the other which might correlate with the colder register.

I have a wet return from the main vents. I have one runoff (or maybe just an immediate branch from a main) and 2 steam mains.

Is there a way to tell if a vent closes and reopens properly or do I just assume I should change all 7 radiator vents and both main vents? (Or just the one problematic main vent?)

Should I just stick with Hoffman 1A's?
I can't find the same main vents online. How do I find the equivalent of the vacuum valve #16?

Here are the other boiler system photos.
Thanks everyone!
The gauge glare is the 0-5psi gauge.

Ps does anyone have any good go to sources as to how to adjust pilot lights for the thermocouple?

Fred

Wow,
That piping is messed up! I'm sure there has to be water hammer. I would say changing the vents won't fix your problem.

acwagner

Those main vents are curious since they are vacuum vents. Before I recommend a replacement I'd like to know what kind of radiator vents you have.

DomesticEngineer

Acwagner I assume u are asking for something other than the Hoffman 1A but not sure what you mean.
https://www.supplyhouse.com/Hoffman-Air-Valves-301000?gclid=Cj0KCQjw6KrtBRDLARIsAKzvQIGykyy67f-FuFB-qyNrDvt6Zkf-kXPnWfCcReEzQ6izCTNYXDVDl-AaAhN4EALw_wcB

acwagner

Sorry, I missed on an earlier post that you have Hoffman 1A vents on your radiators.

Your current main vents are obsolete and no longer produced. In any case, they are undersized for what your system needs.

You'll probably want to use a Gorton #2 vent on each main.

How long are your two mains from the boiler to the main vents?

DomesticEngineer

27 feet for short run, almost 60feet for long run (they basically make a rectangle, one is 3 legs, one just runs down the one wall.) The long run is the one with the problematic/slowest heating register. Im assuming that is also the painted vent that felt cooler than the other (heat had already kicked off before I felt them).

acwagner

This is an article about venting one-pipe systems that will be helpful:

https://heatinghelp.com/systems-help-center/balancing-one-pipe-steam-systems/

This PDF also has a narrative describing a venting strategy, and a table of venting capacities for various vents at the end (both mains and radiators).

https://heatinghelp.com/assets/documents/Balancing-Steam-Systems-Using-a-Vent-Capacity-Chart-1.pdf

Ideally, you'd get steam to reach the end of both the mains at the same time by varying the venting capacity on each. Given the disparity in length between the two, there might be some trial and error to get to that point. I'd start with a venting radio of 3:1 in terms of venting capacity between the long and short mains. You could start with a Gorton 1 on the short and Goron 2 and see how that improves things. If you're willing to spend the money, can put multiple vents on each main. That's called building an "antler". You can search for that term on this site and see some example photos.

I personally prefer Gorton main vents. But, Big Mouth vents are also a good choice and vent much vaster than a Gorton 2. So more bang for your buck.

In any case, I'd focus on your main venting for now. It'll help with the slow radiator and should drop your operating pressure.

nicholas bonham-carter

You will need one Gorton #2 for the short run, and probably 3 for the long run. Install a low pressure gauge to verify the back-pressure to be less than 2 ounces, while the air is being pushed out.—NBC

DomesticEngineer

Fred: Way less than helpful.
Nicholas: Thank you.

ACWagner: The last radiator is in a room that isn't very used, I thought maybe I had turned off the valve to it, turns out the vent on it is completely blocked now (i'm sure it had some air flow last winter). I'm sure that was part of the problem.
I'll use the detailed links you provided to help determine what vents to replace the spitting non-closing vents on the radiators. Probably a combination of #4, #5, and 6 or C.

I'm confused as to this: If a Gordon #2 is to vent faster than a #1, why does the #2 have a half inch connection rather than the 3/4? A 3/4" hole restricts flow less than a 1/2". If I go with the Gordon #2, I'm almost positive that I'll have to put a reducer on the current threading for the main vent. By the chart, a Gordon #1 with 3/4 in connection would still vent 4 times faster than the old Hoffman 16 vent without having to use an adapter. The colder room is a spare bedroom, even when in use, I don't mind if it runs cooler than the rest of the house. That's what blankets are for.

I just hope I'm not opening a can of worms as far as overall balance goes.

dopey27177

I used 1 main vent (Gorton # 1) in many buildings. here picture shows 2 vents so replace each on wiht a Gorton vent valve.

Key to venting a radiator. Using the Hoffman 1 vent you need a drop back pressure of 1.5 psi. which means your system pressure has to drop below 1.5 psig.

Sometimes setting steam pressure with a differential can be a problem.

My suggestion to you is to set the boiler to 4 psig with a 3 psi differential for a test.

Hopefully steam will fill all the radiators. and the vent valves will close due to the heat of the steam.

Do not worry about which radiator gets hot first, that can be dealt with later.

If this test works lower the pressure to 3 PSI with a 2 psi drop.
If this works leave the pressure alone.

If you want to spend money replace the Hoffman 1 valve with a Hoffman 1A adjustable vent valve. do not do this all at once, you may only need 2 or 3 of these vent valves.

Your building originally was supplied by a coal fired boiler because going by the vent valves your system was a 1 pipe vacuum steam system.

Looking at the picture of your pressure control I would remove it from the LWCF. and install it where the pressure gauge is with a syphon tube. The pressure control must be installed at the a location where boiler crud will no clog it.

Jacob Myron

I wrote a book on steam heating (Steam the Perfect Fluid for Heating and some of the Problems)

Available at Dan's library, Barnes and Jones, Amazon and Dorrance Publishing of Pittsburgh Pa.

Fred

@DomesticEngineer , Sorry if you don't like my response but it is what it is. I really do not expect venting to make the difference you are hoping to achieve. Sometimes we look for and expect the lowest cost solution to fix our problems. Many times it will not and we have spent a lot of time avoiding the real problem. From what I can see, there is no proper Header (Equalizer on the wrong end), which, by itself leads to wet steam (that affects if/how vents work), I see what looks like two mains tied together off of one riser, not the best for steam distribution (if one has larger radiators or more/larger vents on it, that main will feed steam first and, unless the boiler runs long enough, the other main/radiators may not get steam during a normal cycle and before the thermostat is satisfied). Also looks like there is a third standalone main (2 going is one direction and the third going in another direction. If so, there should be a third vent somewhere towards the end of that main.

Deltat210

I installed a new steam boiler, and had problems with radiator vents. I dont have any main vents, never did. Well, I bought the cheapies from H.D, put them on, pressure was high, and promptly blew them out. Readjusted, bought hoffman 1A's, system runs awesome, dont buy the junk at the home stores..

Hap_Hazzard

Deltat210 said:

I installed a new steam boiler, and had problems with radiator vents. I dont have any main vents, never did. Well, I bought the cheapies from H.D, put them on, pressure was high, and promptly blew them out. Readjusted, bought hoffman 1A's, system runs awesome, dont buy the junk at the home stores..

I've bought Maid-o-Mist vents at Home Depot that work fine. You just need to open the box and make sure they are what it says on the box and that they're not "slightly used." Apparently they let people get away with returning their old vents for a refund.

My system didn't have main vents when I moved in either. What had happened was that they added some radiators at the end of each main to heat the new addition that was added back in the 60s, and they didn't replace the vents.