how to set the pressuretrol low enough and boiler flooding issues

diamond67

I’m a homeowner with a one-pipe steam boiler. The quick and short is that I think the technician set the pressure too high during my recent annual service. (I’m not 100% sure he changed it, and if so, I’m not sure why either.) The pressuretrol (Honeywell PA404? or similar) is set to cut in at 2 psi and I’m not sure of the differential. But the pressure gauge was showing 5 psi.

Based on what I’ve read, the pressure only needs to be 0.2 to 0.5 psi for a small residential system, but how can I set the pressuretrol this low? The lowest setting for cut in is 0.5 psi. If I set this as low as possible, how low should I set the differential? Also as low as possible (~ 1 psi)?

Here’s the bigger picture…

We’ve had the house for four years now and the system has been relatively trouble-free. It’s a weekend home, so it’s just kept at 50F when we’re not there. We’ve had some leaking vents and a leak at a connection that were easily fixed. We’re planning on replacing the entire system soon but need this one to work in the meantime.

The oil-fired Weil-McLain SGO boiler was installed in 1995 but the distribution piping is older. (It has asbestos insulation.) The house is from 1830 so none of this is original. It’s not a precious historic house; it’s just a small farm house that somehow never burnt down. The radiators and pipes all have good slope (and some of the floors do too.)

I recently had the boiler serviced, and now it’s conducting some New Age musical number and the system is flooding to the point where water was spurting out of an old vent. I think this is due to the pressure being set too high. Could I be on the right track?

The boiler is definitely sending up very wet steam to the point where the water level in the boiler is dropping and the automatic feed is coming on. After running for a while and then turning off, all the returning condensate fills the boiler to over the glass gauge. I’ve drained the water down to the water line and this just repeats itself.

Skimming seems to be one of the first things to try, but I don’t think I would be able to get plug out since it’s so rusted. I also don’t think this is the problem. The water in the gauge glass is very clean. There are no signs of oil and there’s no reason why the system would suddenly get dirty or oily.

That leads me to think that the pressure was adjusted and set too high. When I first saw the 2-psi set point and 5-psi operating pressure, I didn’t think anything of it because my memory was off by a factor of ten and left out the decimal point. From what I’ve read, it should be 0.2 to 0.5, which leads me to my question at the top: how do I set the pressuretrol low enough?

A couple other things I’ve noticed: The boiler is rated for 100,000 Btu/hr for steam but the installed radiation is only 47,000 (5 radiators varying in size) plus piping etc. There are no main vents but I’m not sure if they’re necessary since the longest horizontal run is about 25 ft; the rest are about 10-15 ft long. Since the system was running ok for the past few years, I don’t think these are problem right now.

I’m interested in what you all think.

I have a few more questions if anyone has any answers?

Why would they put the skim port immediately above the electrical service shut-off switch? And why doesn’t this come with a valve so you can readily skim this? The literature says to have a qualified technician skim the boiler, but then I’ve read here to do it every day, week, or month for certain conditions.

Why doesn’t the pressuretrol’s typical operating range match the operating range for the system? My unit goes from 0.5 to 9 psi. It seems this model is common on lots of one-pipe systems even though they don’t need pressures that high.

Why would they install a pressure gauge that ranges from 0 to 30 psi when the system only needs less than 1 psi?

ethicalpaul

That's a lot of great questions. I swear I'm going to create a flowchart to help folks in your shoes, but in the meantime we just have to type responses

I'll number the answers so you can refer to them later if needed.

1. You can set it to as low as the indicator will let you. Don't keep spinning the screw past that though. That will be a nominal .5 but in practice will probably be more like .75-1, it's the nature of the beast. Don't worry too much just set it there. Open the cover and look inside for the white dial and make the "1" face the front, that's the differential. Now it should cut out at about 1.5-2 and cut back in at .5-1ish. Keep your eye on that tech.

2. When you replace it make sure to use a contractor from this site's "find a contractor" section and make sure he or she sizes the boiler to your actual radiation. (EDR)

3. Yes the pressure could be involved but your near boiler piping isn't helping. I can't quite see the whole picture but it looks very wrong. Make sure your replacement contractor (when the time comes) shows you the picture in the installation manual that he is using to build the new piping. Did the tech add any water treatment that might have increased the frothing/surging I wonder? You can try skimming. I don't know why the installer put the skim port there...why didn't he make the pipes correct would be a bigger question! The real skim port I believe is that higher one to the right.

4. I would go ahead and add Gorton main vents. You'll need their water-tolerant nature and you want to give this boiler every chance to do the right thing for you.

5. I did put a skim valve on mine, but honestly a cap is good enough. It's not an every day or every month thing unless like me you are constantly messing with your piping.

6. The pressure troll is meant as a safety limit, not a fine operating control. But since your boiler may be twice or more what it needs to be, it will definitely be operating. But don't worry, a 1.5-2 cut-out is fine. This system is not going to be in the low end pressure-wise anyway being apparently so oversized.

7. The pressure gauge is mandated by code to have twice the capacity as the 15psi Safety Relief Valve, that's why it goes to 30. You can add one with a more sane range like 0-3 or 0-5 psi.

I hope that helped and others will jump in with their own ideas. Sift out the ones that multiple people mention and focus on those

Hap_Hazzard

A cut-out of 1.5 is as low as you can get with a Pressuretrol. To go lower you'll need a Vaporstat. But your pressuretrol isn't set to its lowest setting. The cut-in looks like it's set to about 3 (but it's hard to tell from the picture), and I can't tell what the differential is because it's inside.

To set your pressuretrol to its lowest possible setting,

1. turn the screw on the top of the unit counter-clockwise until the pointer is at the bottom of the scale,
   
2. remove the cover and rotate the white thumbwheel to the right as far as it will go. (The number 1 should be visible in the middle of the visible portion of the thumbwheel.)
   

Replace the cover.

You should observe the next heating cycle to confirm that the burners are turned off when the pressure reaches 1.5 psi and back on when the pressure drops to 0.5 psi (assuming the thermostat is not satisfied). If this is not confirmed, one of the following could be at fault:

1. The pressure gauge is not accurate.
   
2. The siphon tube (or pigtail) is clogged and preventing the pressure from reaching the Pressuretrol and or pressure gauge.
   
3. The Pressuretrol is defective.
   

diamond67

Thanks, guys.

I'll reset the pressuretrol this weekend when I'm back up there and see how that works.

When we replace the system, we're going to redo the whole house and probably go hydronic. There are just way too many changes that we need: move radiators, add some more, rebuild an old addition...

Paul, your comment #6 shed some light for me about boiler sizing. I guess if this causes my boiler to cycle on and off, that will save some fuel (versus running all the time), but it would really be best to have a boiler sized to the radiation.

I'll let you know what happens.

Hap_Hazzard

Don't count on using existing piping for hydronic. It usually leaks when you try to run that much pressure through it.

ethicalpaul

I think it's unlikely that having an oversized boiler is a fuel savings, more probably the opposite. But many many people have them, it's not the end of the world, especially if it's on short time.

Even rather oversized boilers can operate without much cycling, especially if the thermostat setting is static. Setbacks are a challenge.

diamond67

We have no intentions of reusing the piping. There's only one radiator in a decent location and even that one will likely get moved.

An oversized boiler is not a fuel saver. Getting it to cycle more often will probably save a little compared to what we have going on now. But having a boiler half the size that actually matches the radiation would be best.

ethicalpaul

Oh I see what you are saying. Yes, correcting the cut-out will be better than running at high pressure for no gain.

JUGHNE

When the boiler is cool, you can take the pressure gauge off and see if you can blow thru the pigtail. You should feel a little pressure until you get the water out of the loop back into the boiler. Fill the loop with water when you are done.
If you can't blow thru it then it is time to remove it for cleaning. This should be part of annual service.........

Fred

Once you get the Pressuretrol set properly, you need to watch the boiler, in operation. If the water still leaves the boiler and the auto fill adds more water, you need to find a pace on that boiler that you can skim from and do a skim. Since this is not your full time residence, I doubt that you will want to visit it and find that the water level has risen enough that it pushes water out of the upstairs radiator vents and ruin ceilings and walls and floors.
Make sure that McDonnell Miller Low water Cut off is working properly too. They should be taken apart and scraped out every couple years. It is alo possible it is so gunked up, inside that the float isn't able to move freely allowing the auto fil to add more water than needed.
Finally, find a service guy/company that knows steam! Use the "Find a Contractor" tab at the top of this page and enter your zip code.

Canucker

@diamond67 consider your stated usage of the building while you make a decision regarding the switch to a pumped water system. If the building is used periodically, leaving it as a steam system would be good insurance against burst pipes in case of an extended power outage. All the water would make its way back to the boiler during the off time. If you can find an expert on this system, you should be able to spend fewer dollars and have the rads placed where you want when compared against the cost of converting. Personally, I would keep it steam and find a knowledgeable contractor to help me do that, if it were my money.

diamond67

Fred, thanks for the reply.

The blow down valve on the LWCO was just replaced and I blow it down when I'm there. The auto feed also appears to be working correctly and fully shuts off. (I've watched the pressure gauge on the well system.) We can hear when the boiler is running and the auto feed kicks on.

Trust me, I've searched on the "Find a Contractor" tab and there isn't anyone within 30 miles. We're in the Catskills and the closest ones are in Massachusetts and New Jersey. I've been using the oil company for service, but I think their expertise is only on the oil side, and I'll need to figure out the steam side.

BobC

If your inclined to learn more pick up a copy of TLAOSH - The Lost Art of Steam Heating. Even if you don't want to spin the wrenches yourself it will give you the knowledge to direct the guy that does spin the wrenches.

Bob

diamond67

Bob, I have that book and the "We Have Steam Heat" one. I read them both about ten years ago. I probably remember enough to really screw things up!

I have a pretty good handle on how these systems work and a great deal of respect for the dead men that figured all this out (before electricity!)

I have a harder time with implementation, hence the question on setting the pressuretrol.

I still don't get why they used a presseretrol instead of a vaporstat--probably the $100 price difference, but they probably could have saved that by right-sizing the boiler.

srmaietta

Diamond, you can skim from the top port of the sight glass. It is a bit touchy messing with the sight glass etc, but it will probably be a lot easier than cracking that big rusty plug out.

Turn on your water feed slightly and when the water is really close to the top of the glass, turn off the feed. Close the bottom sight glass valve, loosen the glass, remove the glass (bit of dripping here) then set up a funnel under the top sight glass port. Turn on the feed water as slow as you can and you should within a minute or two get a dribble out of the port and into the funnel. When you’ve done enough (bucket full) drop the water a bit via the lwco, and reassemble.

Using a chemical for a heat cycle before this can’t hurt but may break up more funk than you want to deal with.