Do I have a steam boiler?

9310triola

American Standard Model G26 DPG, Series 6B J5. I have had HVAC/plumbers tell me different things: some say it's steam, some say it's hot water.

bburd

That is a hot water system, originally designed for gravity flow but probably now pumped, though we cannot see the circulator. It is not steam.

The most obvious difference is in the boiler trim: the presence of a combination temperature and altitude/water pressure gauge rather than a steam pressure gauge, and the absence of the gauge glass required to show the water level in steam boilers.

JUGHNE

Because of the gauge on the front that shows pressure/height of water/temp I would call it a water boiler.

Do your rads have an air bleeder near the top on the side?

I do not see a pump anywhere so this could be a gravity flow system.
That could be why some think steam.

Somewhere there is most likely an expansion tank; maybe hanging near the ceiling. Or if an old system an open air tank in the attic or on high 2nd floor attic.

9310triola

Yes, my radiators have an air bleeder, and I have had them bled before. But the people who have come out have said they don't see a pump. Is this the expansion tank?

bburd

Yes, that is the expansion tank. Your system may still operate by gravity flow, with no pump. Most of those have been converted to forced circulation, but certainly not all of them.

9310triola

Here is a close up of the gauge.

ChrisJ

bburd said:

Yes, that is the expansion tank. Your system may still operate by gravity flow, with no pump. Most of those have been converted to forced circulation, but certainly not all of them.

What are the reasons to convert a gravity flow system to a pumped system?

bburd

@ChrisJ as gravity systems age, the gravity circulation slows down due to  increased friction in the pipes from corrosion. This makes the system slower to heat and reduces its efficiency. Adding a small circulator pump improves both situations. Also, some modern boilers with compact heat exchangers have a minimum flow rate and require pumping.

If the boiler also provides domestic hot water, pumped circulation with a flow control valve allows heating tap water independently from space heating.

The Steam Whisperer

Those are very good boilers. That model probably dates from around 1965. If you clean it well and maybe add a motorized stack damper, it just about as efficient as a modern cast iron sectional boiler. It is probably oversized, since that amount of Btu/hr capacity can heat an uninsulated 2500 sq ft home Northern Illinois climates right down to -20F outdoor temperature.

9310triola

Thank you, everyone, for your comments. I also have a very old (1980s) hot water heater that I am looking to replace, so I was considering replacing both the boiler and the hot water heater with a Navien combi NCB-240/110H. House has three bathrooms, four people, and is about 2000 sq. ft. in Washington DC. Would the combi work with my gravity flow system? Would the heating on the NCB-240/110H (13k to 110k BTU) be oversized and lead to problems? Any alternatives that you would suggest? Going with the combi will save a lot of space, which is nice, but I have the space for something bigger if that will work better for my needs.

ChrisJ

9310triola said:

Thank you, everyone, for your comments. I also have a very old (1980s) hot water heater that I am looking to replace, so I was considering replacing both the boiler and the hot water heater with a Navien combi NCB-240/110H. House has three bathrooms, four people, and is about 2000 sq. ft. in Washington DC. Would the combi work with my gravity flow system? Would the heating on the NCB-240/110H (13k to 110k BTU) be oversized and lead to problems? Any alternatives that you would suggest? Going with the combi will save a lot of space, which is nice, but I have the space for something bigger if that will work better for my needs.

My suggestion is do not do a combi.

Not because of your system, but because it'll be oversized, not work great for heat, and not work great for hot water. They're a "one size fits all" less than spectacular solution that is expected to work "good enough" at best.

You'll be better off with a proper water heater and a boiler.

9310triola

Given that my current boiler is already oversized, would I notice a difference in the heat? My heat is perfectly fine right now.

ChrisJ

9310triola said:

Given that my current boiler is already oversized, would I notice a difference in the heat? My heat is perfectly fine right now.

I don't think I can answer that honestly.

But if I was you, I'd leave the heat alone and fix the water heater side of things.
A combi isn't a good tankless heater from everything I've heard.


So you end up with an oversized boiler for your heating, and at the same time and up with a very poor performing "tankless" heater for your hot water.


There's many on here that know far more about these than I do. @Burd and @The Steam Whisperer for example. Perhaps I'm wrong, but I've got a feeling I'm not.

mattmia2

I'd do a mod con and an indirect water heater sized to your hot water load with a boiler sized to your heating load if I were to replace the boiler.

A mod con will deal better with the mass of the gravity system and quite possibly can run pretty low water temps in the system. If you put a conventional boiler on that system with a circulator you will need return water temperature protection to keep the conventional boiler from condensing because of the mass of the system.

I would just replace the water heater and keep the boiler until it leaks which could be 50 years from now or tomorrow. It is very possible that boiler will outlast a new boiler you install today.

@ChrisJ the biggest reason to convert gravity systems to pumped systems is that when this boiler was replaced was around the last time you could buy a boiler that was designed for gravity circulation.

9310triola

@mattmia2 what is a mod con?

ChrisJ

mattmia2 said:

I'd do a mod con and an indirect water heater sized to your hot water load with a boiler sized to your heating load if I were to replace the boiler.

A mod con will deal better with the mass of the gravity system and quite possibly can run pretty low water temps in the system. If you put a conventional boiler on that system with a circulator you will need return water temperature protection to keep the conventional boiler from condensing because of the mass of the system.

I would just replace the water heater and keep the boiler until it leaks which could be 50 years from now or tomorrow. It is very possible that boiler will outlast a new boiler you install today.

@ChrisJ the biggest reason to convert gravity systems to pumped systems is that when this boiler was replaced was around the last time you could buy a boiler that was designed for gravity circulation.

What about the boiler cares if it's gravity or pumped?

mattmia2

ChrisJ said:

What about the boiler cares if it's gravity or pumped?

I'm not completely certain but likely larger water passages and tappings to allow its full output to move out by convection and probably a larger water content.

9310triola

If I keep the boiler would it make sense to do a tankless water heater?

9310triola

Or can I have an indirect water heater with my existing boiler?

mattmia2

9310triola said:

@mattmia2 what is a mod con?

A modulating condensing boiler. It varies its firing rate to match the supply water temp instead of cycling on an off during a heating cycle and if you give it a low enough return temp it condenses the water that is produced in combustion out of the exhaust gases so it recovers the heat that was used to vaporize the water(or at least some of it).

NCB boilers are mod cons. A combi is a mod con with some sort of a diverter valve and a heat exchanger built in to make domestic hot water.

9310triola

@mattmia2 so then what is the advantage of doing a mod con + indirect water heater versus a combi?

Steamhead

@9310triola , you clearly need the advice of a good contractor. Give @Dan Foley a call, here:

https://heatinghelp.com/find-a-contractor/detail/foley-mechanical-inc

mattmia2

9310triola said:

@mattmia2 so then what is the advantage of doing a mod con + indirect water heater versus a combi?

Smaller boiler that can better match the heating load. Less complexity in the boiler itself so there are fewer proprietary parts to break that you have to get from the boiler manufacturer. Can size the indirect to however much hot water you need instead of possibly being limited to around 2 gpm if you are in a cold climate. Hot water is available immediately(though some combis solve this by having a small indirect inside).