Hoffmans are to blame...Alternative?

Dooverdixon

I posted up here a few weeks ago and got some fantastic advice, but I need just a bit more help

My radiators have been hissing like crazy from the radiator vents (hoffman 1a). Typically they huff and puff while the rads are cool, which is fine, but once the rads get pretty warm they start making awful high pitched hissing/whirring noise even after the metallic "thunk" i assume is closure.

Here is the list of thing i already did to help the issue:
1) increased main venting from 1 hoffman 45 on each dry return by adding a gordon #2 to each (both running on an antler)
2) changed pressure on vaporstat to cut out at .5 psi and cut back in just before it reaches 0
3) skimmed (8 hours), blew down, and drained mud leg of the system

None of this has really helped to much with the radiator vent noise. Last night I decided to swap out a bunch of my 1a's for some old 40's i had lying around the house. The 40s were MUCH quieter, They still make some noise, its more of a hiss that sounds like its pushing a bunch of air (if it put my finger above it you can feel quite a bit of air coming out).

The issue/question now is vent capacity. As predicted based on the venting chart from "the lost art" these 40's have a much smaller capacity than my 1a's, and now all my rooms with 40's are 3-4 degrees colder than rooms with 1a's. This makes sense because obviously the faster venting rads are going to fill much faster.

So....What should i do here?

Can i buy a few more hoffman 40's and replace all the vents in the house with 40's and hope for it to balance itself out? or should i switch gears completely and get some Gorton D's for everything and quickly get the air in and out of my rads. My boiler is oversized (450 sq ft of radiation and the boiler is rated for 750) and with my new vaporstat settings all the rads get steam quickly, but the system will cycle on pressure after the rads are full. Will slowing down my perimeter venting cause the system to build up pressure too quickly and not work correctly. Or is there another venting option that i should consider. At this point i would even consider adding big main vents on ends of noisy lines if thats what it would take (my top floors are the hottest so im not sure this is necessary at this point).

or...is it possible im still under vented on the main. Adding the #2 didnt seem to help at all, but maybe im just not there yet and thats why my radiator vents are moving so much air?

Post script. You all recommended "the lost art" and I purchased and read the entire book. What a fantastic book, i was really surprised by how readable and interesting this book was, for what essentially is a owners manual.

Jamie Hall

It won't balance itself out -- unless you are extremely lucky. A better bet is to pick up some adjustable vents -- Vent-Rite #1's have a pretty good reputation -- and put them on. Then adjust them to get things in balance. Always remember that it is better to start by slowing down radiators which are too enthusiastic than it is to try speeding up slow ones.

Dooverdixon

Do you think the vent rite option will be less noisy than the hoffman 1a?

Jamie Hall

That I couldn't tell you.

ChrisJ

I went from 10 new 1As to all Gortons.

But your pressure still needs to be reasonably low

EBEBRATT-Ed

Sounds like you may need more main vents, but I didn't read your other post so maybe the main vents are fine.

You can vent the radiator with larger/more vents but venting too fast can cause noise issues

Dooverdixon

Ok I did some homework and measured all of my supply lines.  2" diameter (ID).  Measured from the header to the last run out.  
Leg #1 ~40 ft
Leg #2 ~45 Ft

Below is a photo of the vent setup.  If I'm still short main venting I'll buy more and run them.  

I just watched the system cycle for a bit and she never got above 0.5 psi and still hisses at the Radiators for 3 to 5 mins before it cycles off on pressure (runs for maybe 20 mins first).

Dooverdixon

Dumb question.  I only measured the 2" pipe to the last runout.  The pipe gets one size smaller at this point and returns to the boiler (dry return?)   This additional pipe is about 20 more feet per loop.  Should this be included in my main vent calculation.

Jamie Hall

Not really needed. You are concerned with getting the air out of the main so it can get to the radiator. Anything after that is gravy. That said, it gives you a variety of options for placing a vent, which can be anywhere along that pipe.

Like the bedstead, by the way!

Dooverdixon

Lol at the bed..basement apartment.  So thoughts on my main venting setup...adequate??

SteamCrazy

Agree great book.  Any other pics of system?

Dooverdixon

Sure!

nicholas bonham-carter

Are you measuring the pressure with a 0-3 psi gauge, or just relying the somewhat inaccurate pressure control.
When you have enough venting, the air will escape at less than 2 ounces, verified by the gauge.
Naturally, when all the air is out, then the oversize of the boiler will come into play, which may be possible to downfire, using a 2 stage gas valve.
Whoever sleeps in that bed will not like having a main vent in the same room, as you come and go at all hours measuring the timing of steam arrival! Put it next to the boiler and make sure the steam arrives at all Of them at the same time.—NBC

Dooverdixon

Hah. Yeah the boiler and all vents are in a separate room.  I do have a 0-3 psi gauge, vaporstat, and backup pressuretrol.  

I called the manufacturer, dunkirk.  They said that it could not be downfired.  That might just be CYA on their behalf.