Questions about a two-pipe steam system with pneumatic controls

loststeamnewb

Hi everyone,

I recently purchased a 1930's house, which came with a two-pipe steam heating system with (Johnson Controls) pneumatically controlled actuators in each room. Long story short, the original home owner/builder was a steam engineer, and placed in a very robust system that no one services in our area or seems to understand. At the very least it seems like our area (Rochester NY) has a dearth of steam heat professionals that are comfortable w/ two pipe systems with the pneumatic controls. The previous home owner ended up converting several of the radiators to manual actuators that don't use the pneumatics. We've had multiple HVAC/heating companies come out and take a look at our system, and most have recommended converting to individual manual actuators for each radiator. No one has had solutions with getting the pneumatics up and running.

I have read a couple of Dan Holohan's books (So You've got steam heat and the lost art of steam heat revisited) and have puttered around with the system over the past year, with a decent sense of the steam portion.

I'm wondering if anyone knows of someone in western upstate NY/Finger Lakes area with experience with a system like this. Also wondering if anyone has advice for trying to maintain the pneumatics vs just abandoning it and converting over? My preference is to maintain the original system, but it seems like a lost art in our area.

Thanks!

Big Ed_4

Any of the original owners stash of parts left around ?

PRR

The mid-Atlantic university I worked at, all the post-1960s hot-water heating was pneumatic control. Slim plastic tubes to a thermostat in each room, over to a pneumatic diaphragm in the the fan-unit or on a hot-water valve for baseboard. If you diddled the thermostat, or removed it, it hissed with air. No electric thermostat. Down in the basement was an air compressor which would start a BIG RACKET when it ran out of pressure.

And when I was leaving they were starting to re-wire EVERYTHING to get smarter (electronic computer) sense and control systems and save fuel. (Wudda saved more by just maintaining the gear they had, but not my union, not my job, not my business.) So maybe pneumatic IS a dinosaur, but hard to believe with all the inertia of a legacy university or other business campus.

I don't know where you find such techs or suppliers. **** Ah, Supply House has Pneumatic Thermostats: TP972A2036 TP970A2242

Pneumatics

Maybe the linked install sheets have clues. Yes, those are the exact system from the 1970s, apparently with many optional frills. The primary thing, if I read this right, is it recognizes two air pressures DAY and NITE, and can set different room temp accordingly. So the whole day/nite clock thing for the whole building/campus is in the basement, out of trouble.

PRR

Aside from thermostats, what I remember is the diaphragms. BIG housings with skinny tubes. I think that was the point: if you were not in an electric hurry, you could move large valves and dampers with very thin air-lines.

https://www.supplyhouse.com/Honeywell-MP953C1083-Pneumatic-Valve-Actuator-8-Diaphragm

mattmia2

They are pretty simple, the t-stat gets a line supply of air and outputs a proportional pressure to call for heat based on the differential of the setpoint and actual temp so the valves are modulating.

Residential contractors wont know it but they are very common in commercial buildings so some commercial contractors should understand it. If the system is old enough to be stem the pneumatic control lines will be copper. If they are leaking you'll have to find and fix the leaks. The thermostat bases usually have a service valve in them to close off the supply to the thermostat if you remove a thermostat.

EBEBRATT-Ed

Pneumatics are very simple and reliable. Occassionally the thermostats need recalibration. Keep the air compressor in good shape (drain any water from the tank)

Go online and look for a pneumatics control book you can easily work on this if your at all handy.

Anyone you call in to work on this will tell you to scrap the controls….no need to do that unless you have the money to spend.

You don't have to keep the system all Johnson either you can use Honeywell, Robert Shaw or any other brand controls they are all pretty much the same

Try KMC Controls in Indiania or Kele Associates in Tn

clammy

The death of pneumatics in systems is usually from lack of a good air compressor producing fairly dry air ,moisture in pneumatic system over time ruines the diaphragms of the valves plus alack of knowledge from those who have not been exposed or worked on them . I have ran into some large old homes which where equipmented w these system and well over time they just went into disrepair and all the valve just had vise grip holding the stem up very sad. I would really look at all my opts before jumping. I think i would also take a look at the boier and see w all this zone if the boiler cycles on pressure . For all we know it was installed to balance the system out in which possible orifing the supply valves would be a cheaper alternative to rebuilding and repairing the pneumatics w the same results . KISS

peace and good luck clammy

KarlW

Hi @loststeamnewb, I'm in Rochester with a two-pipe system (my guess is you live within a mile of me) from the 1920s, and share your pain. I've been through the phonebook myself in technicians. Look up some of my posts and you will see my troubles.

I've found that Triple O has an excellent (and surprisingly young, like under 30) steam technician, and would recommend them.

As to pneumatics, I can't help you much, as my house was all standard valves. But given the dearth of local technicians, I'd recommend one of two things:

1. Replace all of your valves with TRVs. I did this route, this allows for maximum control in each room, but you need to make sure you have a working Pressurtol/Vaporstat to get the most out of it. This is expensive, think a couple hundred per radiator if you hire for it. I've done all but one of mine at this point.
2. Replace them all with steam radiator "screw" valves as they fail. You can throttle these, but you don't have the control of a TRV.
3. EDIT: If it is Johnson Controls pneumatics, you could try some of the Commercial HVAC companies. I could give you some recommendations in this space as well, I think the problem will be giving you the time of day. I'm in the facilities business these days, and we have a bunch of pneumatic controls on our commercial heating systems.

I'm a (civil) engineer by trade, and not very good at the physical mechanics but I have taught myself quite a bit about my system and how to work on it. I've turned a post-Spanish Influenza-heat the house with the windows open system into an on-demand system. In the process, I have cut my heating usage by about 15% in the 12 years I've owned my house.

I'd be happy to discuss some tips and even stop by if you are interested, feel free to message me.