Replace boiler because of rust

ilikebeans

I was told by the technician from the oil company that this boiler (the whole unit) needs to be replaced. Weil McLain p-366he-s. 

Here is a picture of the problem area:


He said steam might leak out of the rusted area on the black ribbed part and go out the exhaust instead of up into the pipe/radiators.

I'm looking for any opinions on whether the whole unit needs to be replaced. 

He said the worst-case scenario is that some water will just have to be added occasionally.

Thanks for any advice.

Jamie Hall

Well, the question is -- do you have to add water when it's running, and if so, how often and how much? If it ain't broke...

As a guideline, more than a gallon a week besides the low water cutoff blowdown (if you do that) is too much and suggests a leak -- though that might not be it.

EdTheHeaterMan

Weil McLain 66 series was replaced by the 68 series a long time ago. The 68 series was replaced by the GO series over 25 years ago.

I'm thinking that "if it is over 40 years old, why would you want to keep it".

On the other hand, I have had customer's boilers with that same blockage, in the flue passage cavity, tried to clean out that blockage with a "Soot Saw" tool, with only partial success, and left it there every year I tuned up and cleaned the boilers, for years. (boy was that a run on sentence, but you get the idea). There were no perceptible water leak. I believe that rust is from condensation of flue gas. It forms over a heating season and if not removed, it builds up into that crust.

As long as there is at least 70% of that flue passage free from soot and scale in each of the flue passages, you should be fine. Just make sure you have an exhaust temperature above 350° at the boiler flue outlet, so you don't create more condensation of flue gas. As old as that boiler is, you never know what energy saving measures were done in the 1970s and 1980s. It may have been under-fired for some time over its lifetime. Back then we called it Down Firing. It was supposed to save on oil. Boilers rated for 1.25 GPH were fired as low as .75 GPH, all in order to save on oil. If the boiler does not make steam fast enough at that low firing rate, it can actually cost more to operate.

The concept worked better on hot water boilers when looking at fuel savings. But the condensation of flue gas problem was often found too late. But it was probably time for a new boiler anyway.

ethicalpaul

Are you selling the house within 3 years? If so, replace it now with a correctly-sized and piped new boiler. You'll be able to say "it has a new boiler" and not get caught in the middle of winter with a leak.

Does the boiler leak water if you or your plumber overfills it to a level above the boiler? If so, it already has a leak. Replace it with a correctly-sized and piped new boiler.

Does the boiler perform well currently? Are you OK with the risk of probably-non-catastrophic failure during the cold season? If the answer to these questions is "yes" then roll the dice and let it ride. If the answer to either question is "no" then replace it now with a correctly-sized and piped new boiler.

If any of the above questions leads you to replace it, make very sure you find a trustworthy steam contractor to properly size and pipe your new boiler. In 4 years on this size I have seen dozens of incorrectly sized and piped boilers and it's not fun for those homeowners.

Oh and convert to natural gas if you can.

ilikebeans

ethicalpaul said:

Does the boiler leak water if you or your plumber overfills it to a level above the boiler? If so, it already has a leak. Replace it with a correctly-sized and piped new boiler. 

I overfilled it to above the sight glass. I didn't see any water leaking. How long would you leave it overfilled to be sure? I assume there's some insulation in there that will absorb some of the water before it starts coming out.

Jamie Hall said:

Well, the question is -- do you have to add water when it's running, and if so, how often and how much? If it ain't broke... As a guideline, more than a gallon a week besides the low water cutoff blowdown (if you do that) is too much and suggests a leak -- though that might not be it.

Is this still applicable when the boiler is just being used for hot water (summertime)? It's not noticeably losing any water except for the blow down.

mattmia2

If it is summer you could leave it for a few days. It can still make dhw while flooded, just don't try to make steam that way.

pecmsg

Tomorrow drain the entire boiler. Then fill it until the steam header gets cold. If water doesn’t appear on the floor then there wrong. 

ilikebeans

pecmsg said:

Tomorrow drain the entire boiler. Then fill it until the steam header gets cold. If water doesn’t appear on the floor then there wrong. 

Thanks for your comment. The header is supposed to be horizontal? Should the green or yellow circled pipe being getting cold? The insulated iron pipe goes straight up to the supply main. It has the copper pipe attached to the side.

I filled it for a for a few minutes past the top of the glass but didn't notice any temperature change in the pipes. No leaks either. 

Can you clarify which pipe should be changing temp so I can make sure I'm doing this test correctly. How long should the temp change take roughly? I have an infrared heat sensor I can use to see if pipe temp is going down.

pecmsg

When that vertical pipe gets cold it’s full!

mattmia2

The large black iron pipe is the riser, it should connect to the header. You can feel that large black iron pipe when it gets cold from the water. It looks like the near boiler piping is wrong, that copper pipe is trying to be an equalizer but it should be on the header after the takeoff to the steam mains, not on the side of the riser.

ilikebeans

The boiler keeps turning itself on as I'm adding cold water to it, so the black pipe is not getting cold. The new water is 70°F and the control on the side is at the 180 mark. The water must be cooling the heating coil too much? Does the water temperature need to be at 180? The hot water is traveling about 60' away.

I didn't turn it off completely because I'm not 100% sure about the procedure to get it working again. Another thing to look up. But the thermostat is off, so it shouldn't be making steam.

The far end of the supply main got to 141° and the end of the horizontal part of the dry return back at the boiler was 138°. The top of the riser was at 177°. Bottom of the riser was 141°.

I guess I'm just circulating hot water through the steam pipes. So, this means there probably aren't any leaks, correct? 

End of dry return:




All comments welcome, thanks.

Jamie Hall

You should certainly not be circulating water through the steam pipes. I dearly hope that is not the case. What is the water level in the sight glass (on the front of the boiler)?

And I hope that when you say you are adding water to the boiler, you don't mean it -- you mean you are running domestic water through the domestic water heating coil.

Something just doesn't add up here.

EdTheHeaterMan

pecmsg said:

When that vertical pipe gets cold it’s full!

This test is assuming that the electricity to the boiler is off. Since your boiler is used to make hot water, then any water that is going into the header or equalizer will be hot. So unless you turn off the electricity to the burner and wait for 8 hours or so, the "Cold Water Test" will not work.

Since you have Hot Water in the boiler then the test would be "When the header gets HOT"

The idea is to temporarily get the water above the suspected leak by about 3 feet. That is where the top of the basement supply pipes run out to the radiators. If you get the water too high then you risk water filling the radiators and maybe leaking out of a radiator vent. The pipes up that high will be basement room temperature when the boiler is not making steam. When the pipe temperature changes, that is an indication that the pipe has water in it. The change can be hotter or colder depending on the water temperature in the boiler.

Once you are sure that the water is high enough, then let it sit there for several hours. If you do not see water leaking, then there is no need to replace the boiler. After the test is completed you MUST remove water from the boiler in order to get the water back to the proper level in the gauge glass. Otherwise, you will have a very noisy steam boiler on that first day you need the heat in the radiators.

I hope this clears up your Query.

mattmia2

Oops, i guess we forgot the turn the disconnect switch off before you flood the boiler part(although it really wouldn't hurt anything if you do run it on the DHW aquastat while it is flooded as long as you don't fill it up to the vents. You might get some ghost flow and some heating from the hot water however.).

ilikebeans

Jamie Hall said:

You should certainly not be circulating water through the steam pipes. I dearly hope that is not the case. What is the water level in the sight glass (on the front of the boiler)? And I hope that when you say you are adding water to the boiler, you don't mean it -- you mean you are running domestic water through the domestic water heating coil. Something just doesn't add up here.

The glass was full while I was attempting the test but I emptied all the excess water out. So it's where it usually is - top two or so inches empty.

EdTheHeaterMan said:

When that vertical pipe gets cold it’s full!

This test is assuming that the electricity to the boiler is off. Since your boiler is used to make hot water, then any water that is going into the header or equalizer will be hot. So unless you turn off the electricity to the burner and wait for 8 hours or so, the "Cold Water Test" will not work. Since you have Hot Water in the boiler then the test would be "When the header gets HOT" The idea is to temporarily get the water above the suspected leak by about 3 feet. That is where the top of the basement supply pipes run out to the radiators. If you get the water too high then you risk water filling the radiators and maybe leaking out of a radiator vent. The pipes up that high will be basement room temperature when the boiler is not making steam. When the pipe temperature changes, that is an indication that the pipe has water in it. The change can be hotter or colder depending on the water temperature in the boiler. Once you are sure that the water is high enough, then let it sit there for several hours. If you do not see water leaking, then there is no need to replace the boiler. After the test is completed you MUST remove water from the boiler in order to get the water back to the proper level in the gauge glass. Otherwise, you will have a very noisy steam boiler on that first day you need the heat in the radiators. I hope this clears up your Query.

Thanks for the explanation.