Water pushing out air vents on condensate return lines

waterjet

Whenever I turn up our furnace two degrees or more, the system will build up pressure and water starts coming out the air vents on the condensate return lines above where they return to the boiler. The could be a couple of issues that I'm aware of, after reading some of "Greening Steam". First off, let me say that I have replaced all of the steam traps on the radiators with "new" ones I purchased on eBay. One issue could be "wet steam", because of the boiler only having one pipe going to the header. Another issue could be that there is no Hartford Loop in the return lines, they just drop down below the water line, go through a check valve, and into a pipe that connects with the wet returns, then goes up, over, and down back into the boiler. It also doesn't look like there is an "equalizer" coming down from the header to the return lines. The one positive, is that I don't have this issue during normal operation, when it is just maintaining a temperature setting and I have not increased it by two degrees or more on the thermostat. One more thing to mention, is that this system was originally for a coal furnace and changed over about 30 years ago.

Jamie Hall

The first question is... what pressure is your boiler set to cut out at? It should be no more than 1.5 psi. Just changing that will help a lot. You don't need pressure with steam -- at least not more than a few ounces -- and building any more pressure is just wasting fuel. And money.

So crank it down. Let the boiler shut off on pressure when you are coming out of a setback, it won't hurt it.

Without an equalizer, the boiler pressure is pushing water back up the wet returns. Which is another reason to crank the pressure down. At some point -- though I wouldn't do it right away -- you may well want to redo the near boiler piping to be more correct.

What do you have in the way of vents? Since you mention that the system works OK while maintaining temperature, this probably isn't an urgent concern at all, but it's something you may want to consider -- particularly if the system is "OK" but not as even as you might like.

I like the covers for the insulation -- cheerful!

waterjet

The furnace was shutting off around 3psi, but I just lowered it even more along with the additive setting as low as it can go. I should probably check the pigtail, to be sure that it's not plugged.

I would like to redo this piping, but not this time of year. May wait until furnace is replaced to redo near boiler piping. Do you think that check valve on the returns could be causing any problems?

The vents are new Hoffman 75 air valves. It did have 76As on it, which I believer are more for one pipe systems or coal furnaces. Which do you think would work the best on these return lines?

Covered up the old asbestos the best I could for now, but not very neat and tidy, I know. Would like to get the long plastic strips like I've seen in factories. Any idea where I may be able to find these?

Thanks for you input!

Fred

Hoffman 75 is the vent you want to use if you are staying with Hoffman. I use them too but you need more than just one on each main. A single Gorton #2 will vent the equavilent of two Hoffman 75's though, as long as you have enough headroom to install them (and you do). Measure the length of your mains and the diameter of the piping and we can tell you how many vents you need. Typically you want 1 Gorton (or two Hoffmans) for each 20 feet of 2" main. Do make sure your pigtail is not plugged with gunk.

DanHolohan

Another consideration: You have steam traps on the radiators. That means you need at least 30" of vertical height between the center of the gauge glass and the spot where your main vents hook into the main FOR EACH POUND OF PRESSURE on the boiler. Run too much pressure and the water will back up into the mains. This system needs a vaporstat.

nicholas bonham-carter

Why not clean the old vents and reuse them. They are vacuum vents, but if you have other conventional vents you won't have any problems.
Did you replace the crossover traps as well, if there are any?--NBC

waterjet

I did clean the old vents and three out of the four seemed ok, but I still had problems and thought they were not the correct vents for a two pipe system.

I only have traps on each radiator.

How is a vaporstat different from a pressure control switch? I'll have to check the distance for the vents. Is that from the water level or the middle of the sight glass?

Unfortunately, I read about the Gorton vents after I already ordered the Hoffman vents.

I'll do some measuring and get back to you.

BobC

A vaporstat allows control in the ounce range where pressuretrols are lucky to control anything much below two pounds. Vapor systems don't work very well that high.

Bob

waterjet

I'm gathering from this conversation that I may have too much pressure and not enough air vent capacity. Guess I may need to break out the tape measure and spend some more money

BobC

Yes it's time to free the moths, upsetting though it might be. They say a boat is a hole in the water into which you throw money, I think an old house is a hole on a lot into which you throw money.

Jamie Hall

There's absolutely nothing wrong with the Hoffman vents. They just don't have the capacity that the big Gorton #2 has. I'd go ahead and use them.

waterjet

This old house is a blessing and a curse, I suppose. For the money, it's much larger than we could have in a newer home, but it does require quite a bit of on-going maintenance.

I measured the two mains, that are 1 1/2" in diameter. The long one is 42' to the air vent and the shorter one is 16'. I suppose that I could keep a Hoffman on the shorter one and get a Gorton No 2 for the longer main and return line. The return lines are 1", going to 1/2" and even 1/4" from the radiators. Just the 1" section alone is 45', which doesn't include pipe going over to the riser and the risers. I suppose that investing in two Gortons' for the longer lines would be a good investment. What do you all think? Do you still think I should invest in a vaporstat? The piping, I probably won't change unless there is a leak; at least until the furnace is replaced.

DanHolohan

Again, you have to lower the pressure because of the steam traps. If water backs out of the boiler it will shut any air vents you install. You need 30" of vertical space between the center of the gauge glass and the bottom of the lowest return main for every psi on that boiler.

waterjet

Just measured the drop between the center of the site glass and where the return lines go back into the main and it's only 26". Also lowered the pressure control as low as it can go.

Would a Honeywell Vaporstat L408B-1081 work on my system? Saw it on eBay, but no info on it. On Honeywell's website I saw a model L408J1017/U that looked suitable. It doesn't have the little vapor tank on it, but it is for vapor heating systems with pressure up to 4 psi.

Jamie Hall

You will find, in time, that an old house, while a challenge, is a blessing.

On the vapourstat -- the model you want is L408J1009. I wouldn't trust anything from eBay -- sorry -- and the other one you mention is for a higher pressure range.

BobC

I've had pretty good luck on ebay, just make sure they say it's working. I bought a NOS mercury vaporstat in 2009 that is still working fine and I just bought a new Safgard LWCO for about the cost of a Gorton #2 vent.

There are some good deals, just make sure they say it's working, then if it doesn't they get to give all your money back and pay you to ship it back to them.

Bob

waterjet

Thanks for the advice on the vaporstat. What settings would I use on this model?

I don't think I'd order anything from eBay if I was doing work for someone else, but I take the risk for myself because it's saved me a good deal of money. You just have to watch, because the prices aren't always better than retail sites and the quality and shipping can be less than you'd expect from a retailer or wholesaler. Like Amazon, they do have a very good return policy, as long as you make sure that the seller will allow you to return it when you are purchasing the item.

Jamie Hall

All fair enough -- I'm just a pretty cautious old fashioned kind of guy...

As to settings, try it for starters with a 12 ounce cutout and an 8 ounce differential and go from there (unless you have a Hoffman differential loop on the system? I forget... in which case, it should start at 8 or 9 ounce cutout and a 5 or 6 ounce differential.

If it is the mercury variety, be really happy -- they are much better than the newer microswitch flavour. However, they are very very sensitive to being level!

gcp13

I would try to take the cover off the check valve and clean it. They always get full of sediment. If you had an equalizer you could and should take the check out.
It was installed so pressure wouldn't push back up the return. But now it is.
Not easy but if you tap the cover with a hammer for a bit it may come off. They are made of brass.

DanHolohan

gcp13 said:

I would try to take the cover off the check valve and clean it. They always get full of sediment. If you had an equalizer you could and should take the check out.

It was installed so pressure wouldn't push back up the return. But now it is.

Not easy but if you tap the cover with a hammer for a bit it may come off. They are made of brass.

There is no steam pressure in the dry return lines beyond the steam traps. That's why he needs a bit more than 28" of vertical space per psi of boiler pressure in that vertical return piping. I call it at 30" per psi. Using a vaporstat and very good venting to prevent short-cycling sould solve this problem. Back in the day, they didn't use equalizers. That's why we're seeing the check valve on the return.

gcp13

Vents off the 90's are problems too, they should be set back 12"-15"
From a cold start you may have too much condensate coming back hitting the elbows and pushing up out the vents

DanHolohan

He needs a vaporstat. The pressure he's using is just too high for this type of system. It's old-school stuff.

gcp13

Thanks Dan,
what I was thinking was that if he runs his boiler up in pressure it will push the condensate up toward the air vents if the check is stuck open.
I agree he needs that A dimension

DanHolohan

Thanks. It's actually a B Dimension in this case because of the steam traps. Think of it as a hydronic see-saw. There's excessive pressure inside the boiler, and only atmospheric pressure in the return line beyond the steam traps. The water stacking in the vertical space simply doesn't have enough static weight to overcome the high pressure inside the boiler caused by the pressuretrol. He needs a vaporstat that can lower the pressure. Vaorstats need very good venting to keep the boiler from short-cycling.

gcp13

Makes sense,I wish the vaporstats were more common. I could install one at least twice a week. Other then online I only have one source for them. I resort to tampering with set screw to lower the pressuretrols

waterjet

gcp13 said:

I would try to take the cover off the check valve and clean it. They always get full of sediment. If you had an equalizer you could and should take the check out.

It was installed so pressure wouldn't push back up the return. But now it is.

Not easy but if you tap the cover with a hammer for a bit it may come off. They are made of brass.

I have taken the cover off of this check valve and cleaned it out. Have also taken the plug out of the main pipe that goes down to the floor and flushed the lines from each air valve. There was and may still be quite a bit of junk in the wet returns. I'm considering one of "Utilities" products for cleaning the system, like "Dry Steam" or "Boiler Colloid".

That Vaporstat may have to wait until next year, because my funds are drying up. A new one is a little less that two hundred. The Gorton's are on the way and I'm hoping they help. I will try to pressurize the system after I get them installed and see if there is any change.

DanHolohan

Basic physics: High pressure goes to low pressure. Always. The problem will stay with you until you install the vaporstat, regardless of what else you do. Hoping isn't going to help.

waterjet

Are you saying that my system will be much less efficient until I replace the pressure control switch with a vaporstat?

DanHolohan

Yes, because the pressure is too high, the water can't get back into the boiler, so it rises up and closes the main vents. If the main vents are under water they can't vent the air from the system, so the system will be very inefficient. You're spending money on things that won't solve your problem until you get that pressure down.

Jamie Hall

waterjet said:

Are you saying that my system will be much less efficient until I replace the pressure control switch with a vaporstat?

In a word, yes...

waterjet

Thank all of you for your input on this. Once I get the larger air vents and the vaporstat installed, I will let you know how it's working.

DanHolohan

Sounds good. Thanks.

waterjet

I guess I don't have any need for a vacuum breaker, since I don't have zones?

DanHolohan

Correct.

waterjet

Besides the Gorton's and the Vaporstat, I'm also going to insulate those condensate return lines.

waterjet

Just installed the two Gortons on the longer mains and it's amazing how much they helped. Radiators heated up faster than before, without the pressure building up, so far. I need to do a true test with the heat turned down at least four degrees and then take it up to see if the system will work without installing the vaporstat. I have the vaporstat, but need a 1/4" nipple to give me room to install it away from the furnace. Just want to be sure that I truly need it.

Fred

Recovering from a 4 degree set back may cause the boiler to short cycle on pressure at some point before the thermostat is satisfied. That is fairly typical. in most cases a 2 or 3 degree set back is all you want to do if you want to avoid short cycles.

waterjet

Thanks Fred. That makes sense. I also want to see if water still comes out of the air vents on the condensate return lines. I'm assuming that short cycling is not a big problem, since you say that it is "fairly typical" when taking the temperature up more than 2 or 3 degress at a time.

I have another question that I'd like to ask. I had purchased four Hoffman Specialty No 75 Main Steam Vents. I am going to sell two of them. Three of them are painted green; it's the way they were made new, and one of them is copper. Do you think there would be any difference in how well the green or copper sell? I'm assuming the green ones were made for areas where people might be concerned about how they look, but don't really know. Any insight would be appreciated.

I also will be selling a No 62 Vacuum Breaker, that I never used and a 4A Quick Vent that is slightly used. All Hoffman Specialty.

Fred

The green Hoffman 75's are just an earlier production of the same vent. As a cost cutting measure they cut out the painting process. They all sell for about the same price (obviously on a secondary market you won't get what a supply house gets) Check out new ones on ebay for what they typically sell for. a used 4A, not likely to get you much

waterjet

Thanks Fred. They are all used now, only slightly, and I could save them if the other ones ever go bad.

waterjet

Happy Thanksgiving,

So, I turned the heat down three degrees and eventually the pressure built up to around 2psi and once again water came out of the air vent on the longer condensate return line. I can see that I still need lower pressure, but was wondering if I only turn up the heat two degrees or less at a time, or leave it set at one temperature, will the system still heat inefficiently without a vaporstat?

Also, how often should a pressure relief valve be replaced on a steam heating oil furnace? I think mine still has the original on it.