Switch to a vaporstat on 2 pipe steam?

Gary Segal

Hello all, We have a 1938 vintage detatched 2 story home with 2 pipe steam (gravity return). We replaced the boiler when we bought the house 10 years ago (Slant Fin L40P2). I'm pleased to say I do not have any horror stories to report - all radiators get heat and the system is quiet.

However, I believe the boiler is running more than needed. I have the Pressuretrol set (PA404A1009) to the lowest cut in and differential values, but the boiler cuts out at 2 psi on the gauge (if one can believe 2 psi on a 30 Psi gauge) and the boiler seems to run a good 10 minutes after the most distant radiator gets steam. I'd guess that once it reaches cutoff, it cycles every 10 minutes or so until the house is at temperature.

So my questions are:
1. Is it worth switching to a vaporstat? I'd be happy with a 2 year payback (we used 650 gallons of oil last year)
2. Which vaporstat would be the best choice? The current pressuretrol opens the circuit at pressure cutout, , so I assume a L408A series or L608A Vaportrol will work. I'm just not sure whether to go for the 0-16 oz range or the 0-4 PSI range.

Thanks,

Gary

gerry gill

any steam system for a house

can use a vaporstat and work well..that said, it sounds like your system is working fine..you may want to invest in windows and insulation for a better payback...the vaporstat would make the system cycle more often..lower settings.. so there would be more to do..tweaking, balancing, perhaps venting differently, adjusting the firing rate..many things go into steaming a boiler at ounces and not cycling on the vaporstat but the thermostat..its a lot more difficult than it sounds but around here we have MOUAT systems designed to fire at 3 ounces AT THE BOILER..it can be done but if you change your pressuretrol to a vaporstat and dont do the other little things you will cycle often on pressure for sure..no efficiency there..

Steamhead

Generally a good idea

What variety of 2-pipe do you have? Do the radiators have traps on the return connections? Have you found any manufacturer's info on any of the system's hardware? The answers will give us an idea of what pressures to run. Take some pics and post them here if you can.

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Gary_10

type of 2 pipe steam

Thanks for the replies. Unfortunately, I do not have any information on the equipment other than the boiler. The house actually has convectors throughout most of the house, with two radiators that were added after the original house was built. All have steam traps on the return.

I will be glad to shoot some pics and post them. It will take me a few days - the digital camera is on my post holiday shopping list!

Gary

Mad Dog

Very good points Gerry

Mad Dog

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Steamhead

That's probably Vapor

the Cadillac of heating- can't wait for the pics!

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Gary_10

Here are some photos

Here are some photos of our steam system. They were shot with our camcorder, so I apologize for the less than perfect crispness. I should also note that the inlet to all the radiators and convectors is at the bottom of the unit; none come in at the top as depicted in “The Lost Art of Steam Heating”.

Also, last night, I studied the timing that the radiators and convectors heated up from a cold start. Most were hot at less than 1 PSI, if one can really believe that level of resolution on a 30 psi gauge! There was one exception that did not make sense. It was a convector on the second floor, which had a relatively short supply run. For some reason, it was one of the last to heat up. It was only half warm when the boiler cycled off at approximately 2 PSI.

It’s possible that the supply valve is almost closed on this convector. Most of the supply valves in the house are frozen in place. I tried to rebuild one of them a while back to make it operational, but I had a fit stopping it from seeping, so I never tacked the rest of them!

List of photos
1. Convector – a typical convector. They vary in size. The house also has 2 large radiators that were added after the original system was installed
2. end of main and end of drain 2 – this shot shows the various devices at the end of the supply line and at the end of the return line. Note that there is a thermostatic trap located at the end of the supply line that is fed from the end of the return line. I am not sure what it does or is supposed to do. The inlet to the trap is always cold and the vertical return line from the supply line heats up quickly. Then again, I see no reason why it would not. What’s to keep any steam remaining in the line from entering this return line?
3. end of main and end of drain – a similar view to photo 2
4. end of main – shows the piping going back into the boiler
5. pressuretrol – the pressuretrol and pressure gauge installation
6. return piping front view – the left pipe with the white insulation is the return from the start of the supply line. The angled pipe to the right with the white insulation is the return line at the end of the supply line
7. Return piping – typical return lines from the convectors
8. side view showing main line – a side view of the near boiler piping showing a broader view than in photo 6
9. sun room feed – this line feeds the last radiator added to the house. It was the most problematic in terms of noise since the rise to the radiator is very slight. Eventually, I propped up the inlet to the radiator to eliminate the hammering.
10. Supply piping – shows the lines coming off the main going to the convectors
11. trap at end of supply line – shows a close up of the trap at the end of the supply line. The end of the supply line is close to the galvanized steel support strap hanging from the ceiling

I look forward to your observations, comments and suggestions!

Gary

Steamhead

It's definitely Vapor

but I'm not sure if it's a Webster, Dunham or what. The convectors look similar to the Herman-Nelson "Paneled" type Invisible Radiators, which you can see by following this link:

http://www.heatinghelp.com/pdfs/220.pdf

The radiator trap crossing over between the steam main and dry return acts as an air vent. Air from the main is routed into the dry return and out the (green) vent on top of the Float Trap/Air Eliminator, the same as air from the convectors. When steam reaches the trap it closes. The connection to the steam main should be hot, and that to the dry return warm but not hot. If this is not the case, the trap is probably bad. BTW, the inlet to the trap is on the side, and the outlet is on the bottom.

There should be no steam at all in the dry return. If there is, follow it back to the convector with the bad trap. Replacement trap innards are still available for about any brand of trap out there.

That green vent might be too small. This is the only vent in the entire system, and must have plenty of capacity. I like to use Gorton's #2 vent on this type of system.


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Gary Segal

Thanks for the analysis

I looked at the Invisible radiator catalog. Our convectors are similar, but not identical. The front of the convector is actually exposed (and painted) on ours.

I replaced the green vent once, before I knew anything about the system. At that time, it was spewing hot water out of the vent - sytem pressure was set to 5 PSI - the same setting it always seemed to be set to after a boiler tune-up.

Steamhead - I see you are in the BAltimore area. My house is in Ellicott City. If you do residential service, I would love to talk with you.

Thanks,

Gary

Steamhead

Check your e-mail, Gary

This will tell you how to find me.

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