Best option for heating a basement off a 1-pipe steam system

stormbytes

In the early stages of a soup-to-nuts redo of a 100 year old steam system in a NYC 2-fam. I'm trying to work through some heating options for the basement/garage and would love some input. I'm already set on installing a steam system so please address my question in that context. I'm not an HVAC professional. I'm a DiY'er with years of experience as a technician, tooled and comfortable working with pipe, water and gas. I'm looking at this **practically** so please criticize constructively, understanding that I'm just doing the best I know how.

System consists of a steam boiler, two main trunks (north and south) and a fully exposed (brand new) wet return that runs along the exposed basement walls. I'm considering the following options:

1. Running the wet return through some baseboard water radiators

2. Mounting steam radiators on the wall, above NWL. Steam would feed through one side and the condensate would come out the other (rad would be pitched accordingly) and piped to the wet return directly below.

3. Running several 2-1/2" horizontal branches (vented) off the main trunk, that would 'act' like radiators. Think: Old rooftop TV antenna. I realize this is sub-optimal, but its simple so, i'm considering it.

4. Running a conventional, circulated hot water loop to some water baseboards from the wet return. Issue here is I don't know the first thing about how to install this.

I think that's it. Let me know what you guys think.

Jamie Hall

In your place I'd consider your options 2 and 4, and not the other two. Both will work, and work well. Whether you'd want both 2 and 4, or just one or the other, depends on how the space works out.

Option 4 for a basement is actually very simple (it's more complex if you want to go upstairs!). What you do is find a convenient port on the boiler, near or slightly below the low water cutoff, and tap into the boiler there. Pump away from that, run your baseboard loop, and return into the wet return anywhere convenient. Two controls: an aquastat on the boiler, to keep the water temperature in the heating season above 140 (not that crazy an idea anyway...) so that the heating loop will actually heat, and a thermostat to control the circulating pump. You won't need much of a pump.

Simple. Quick. Done.

Option 2 is a little trickier, but not much. You do, as you note, want the bottoms of the wall hung radiators above the boiler water line. There are a number of decent wall hung radiators. They would need air vents in the usual single pipe way. I'd probably pitch them in the single pipe way, too -- back towards the inlet, with the inlet low -- and take the inlet from a T. upper end of the crossbar up to a convenient steam main, bottom end down to a convenient wet return. Done.

stormbytes

Jamie Hall said:

In your place I'd consider your options 2 and 4, and not the other two.

What's the problem with running hot condensate through 2 baseboard radiators? Understand this isn't optimal. When we got the house (some 20+ years back) there was an old tall radiator sitting on the basement floor, connected in series with the condensate return. It gave off a good amount of heat and worked for decades until I had to replace the return line and pretty much tore it out. Seems like two 4' baseboard cast iron rads in series with the return line would be cheap and simple.

Jamie Hall said:

Option 4 for a basement is actually very simple (it's more complex if you want to go upstairs!). What you do is find a convenient port on the boiler, near or slightly below the low water cutoff, and tap into the boiler there. Pump away from that, run your baseboard loop, and return into the wet return anywhere convenient. Two controls: an aquastat on the boiler, to keep the water temperature in the heating season above 140 (not that crazy an idea anyway...) so that the heating loop will actually heat, and a thermostat to control the circulating pump. You won't need much of a pump.

Simple. Quick. Done.

I did a bit of research and quickly found myself more confused. Read this article on HeatingHelp and that didn't help at all.

https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/

I'm looking at buying a SteamMAX which already has a 1-1/4" tapping for running a hot water loop.

1) How does an Aquastat work with the thermostat/pressuretrol in this configuration?

2) Do I need any heat exchanger or expansion tank? (I have exactly no idea how any of that works!)

3) How does a circulator pump running hot water into the radiators (which then drain back into the return) not cause that water to back up into the steam trunk?

4) I assume the hot water loop can use ordinary heating PEX lines to feed the radiators?

Jamie Hall said:

Option 2 is a little trickier, but not much. You do, as you note, want the bottoms of the wall hung radiators above the boiler water line. There are a number of decent wall hung radiators. They would need air vents in the usual single pipe way. I'd probably pitch them in the single pipe way, too -- back towards the inlet, with the inlet low -- and take the inlet from a T. upper end of the crossbar up to a convenient steam main, bottom end down to a convenient wet return. Done.

This is my least favorite option as it requires additional steam piping. Also the cost of wall hung radiators (from the bit I researched) seems exorbitant. One of my favorite things about steam heat is the thermal mass of cast iron which I'd likely have to give up with stamped metal being common for raised units, from what I've seen.

Jamie Hall

Ok. You ask near the beginning "what's the problem with running hot condensate through 2 baseboard radiators". Nothing -- if you don't want much heat. Suppose we consider a fairly typical 100,000 BTUh steam installation. Running at full song, it produces some 100 pounds of steam (and therefore condensate) every hour. That's right around 0.2 gallons per minute. If the steam system is operating properly, by the time that reaches the wet return the temperature shouldn't be much over 120, if that. If we further assume that you have a lot of baseboard -- baseboard doesn't radiate much at those temperatures =- and can manage to get a 10 degree drop, that's all of 1,000 BTUh. Or the same as about 3 100 watt bulbs...

Now to go on to the other questions.

1. The aquastat works in parallel with the regular house thermostat. The regular thermostat will request heat in the house and the boiler will raise steam. If the pressure gets too high, the pressuretrol will shut it off. The aquastat, on the other hand, will simply maintain the boiler water at whatever temperature the baseboard was designed for -- typically 180 -- and when the basement thermostat calls for heat, that thermostat will turn on the circulator to provide it.

2. If the baseboards are below the water level in the boiler, you don't need either a heat exchanger or an expansion thank.

3. The water being pumped into the wet return will flow back into the boiler -- where it came from. In any event, it can't rise higher in the drips than the pressure in the boiler will cause it to.

4. Yes, you could use PEX rated for heating use.

leonz

stormbytes said:

In the early stages of a soup-to-nuts redo of a 100 year old steam system in a NYC 2-fam. I'm trying to work through some heating options for the basement/garage and would love some input. I'm already set on installing a steam system so please address my question in that context. I'm not an HVAC professional. I'm a DiY'er with years of experience as a technician, tooled and comfortable working with pipe, water and gas. I'm looking at this **practically** so please criticize constructively, understanding that I'm just doing the best I know how.

System consists of a steam boiler, two main trunks (north and south) and a fully exposed (brand new) wet return that runs along the exposed basement walls. I'm considering the following options:

1. Running the wet return through some baseboard water radiators

2. Mounting steam radiators on the wall, above NWL. Steam would feed through one side and the condensate would come out the other (rad would be pitched accordingly) and piped to the wet return directly below.

3. Running several 2-1/2" horizontal branches (vented) off the main trunk, that would 'act' like radiators. Think: Old rooftop TV antenna. I realize this is sub-optimal, but its simple so, i'm considering it.

4. Running a conventional, circulated hot water loop to some water baseboards from the wet return. Issue here is I don't know the first thing about how to install this.

I think that's it. Let me know what you guys think.

================================================================

Is?, or will the steam boiler be somewhere other than the garage?????????? It has to be installed per NYC plumbing code.

Installing a 2+ steam chest tapping boiler would be ideal for this employing a dual drop header to dry the steam even faster and increase the speed of the dry steam delivery reaching both home spaces.
If you install a dual drop header you may be able to have a smaller boiler but that is dependent on a heat loss study exactly as Dan has done in the past and the final math for determining what size boiler you need.

You need the correct size vents for the trunks and steam rated TRV's for each radiator to make them so much more efficient.

If you have a good boiler already and if it has two tapping's in the steam chest that can easily be unplugged you could use it to make a dual drop header or if it has one tapping it could also be used for a dual drop header to make very dry steam that will dry that much faster and that is good for your steam heating system as the radiators will heat that much faster

To paraphrase Dan Holohan; the more tappings in a steam chest you have the more steam will be created faster and the steam boiler will run less as the radiators will become hotter faster and hold the heat longer.

Using wall hung steam radiators would also be ideal for this using a boiler with a dual drop header.
Using a dual drop header would also heat the garage faster with dry steam using less gas and heating wall hung steam radiators hung above the water line of the steam boiler. Using TRV's for the basement radiators will save you fuel too.

By using one pipe dry steam for the garage you avoid having to plumb for a wet baseboard heating method requiring a circulator, separate thermostat to control the circulator a return line and bleeding slugs of air out of your system with a boiler drain.

JUGHNE

A few month ago someone posted a discussion concerning a basement radiator sitting on the floor with the end of main piped thru it.

Stormbytes, was that your posting?

It included pictures and a fair amount of discussion.

EBEBRATT-Ed

If you put steam to a wall mounted radiators the bottom of the rads would have to be 28" minimum above the water line.

In most of the old houses they used ceiling mounted radiators

stormbytes

Jamie Hall said:

You ask near the beginning "what's the problem with running hot condensate through 2 baseboard radiators". Nothing -- if you don't want much heat.

That answers my question.

Jamie Hall said:

The aquastat works in parallel with the regular house thermostat. The regular thermostat will request heat in the house and the boiler will raise steam. If the pressure gets too high, the pressuretrol will shut it off. The aquastat, on the other hand, will simply maintain the boiler water at whatever temperature the baseboard was designed for -- typically 180 -- and when the basement thermostat calls for heat, that thermostat will turn on the circulator to provide it.

So, if I understand correctly, the aquastat [switch] is fed from the same input wire as the boiler thermostat and closes the same circuit. Presumably the aquastat thermal range is well below that of the pressuretrol so no real conflict there.

What's the math on burning fuel to maintain the boiler's water temp over an extended period?

Is there generally a switch to turn the aquastat on/off ?

Jamie Hall said:

The water being pumped into the wet return will flow back into the boiler -- where it came from. In any event, it can't rise higher in the drips than the pressure in the boiler will cause it to.

I still don't understand how this does not result in water backing up through the A dimension and into the main trunk. What am I missing? Does the circulator pump not pressurize the water? If so, the water is effectively 'pumped' through the radiators. Once in the wet return, why does the water necessarily flow back into the boiler? If its pressurized by the circulator pump, what's keeping the water from backing up as I described?

Jamie Hall said:

Yes, you could use PEX rated for heating use.

That sounds cheap and easy!

Jamie Hall

Water, as I've noted before, is terminally lazy. So when you pump the water back from your baseboards into a wet return, it can go either one way and try to back up into a steam main (which is your concern) or it can go the other way and over the Hartford loop into the boiler. Which is less resistance (lower elevation) -- so that's the way it will go.

JUGHNE

I believe for added BB heat in the basement you use the returned condensate water that is already in the bottom of the boiler.
Your pump simply moves the water thru the BB's. The BB loop would always be full.
There are several gallons of water in the boiler, you are not connected at all above the water line.
If you need basement heat, you are probably needing heat upstairs anyway.
That water would already be heated and waiting to be moved thru the BB.
Almost a bonus.
IMO....IIUC.

stormbytes

Jamie Hall said:

Water, as I've noted before, is terminally lazy. So when you pump the water back from your baseboards into a wet return, it can go either one way and try to back up into a steam main (which is your concern) or it can go the other way and over the Hartford loop into the boiler. Which is less resistance (lower elevation) -- so that's the way it will go.

That makes more sense. Thank you!

Any thoughts on my other points?

stormbytes

EBEBRATT-Ed said:

If you put steam to a wall mounted radiators the bottom of the rads would have to be 28" minimum above the water line.

In most of the old houses they used ceiling mounted radiators

Well, then I guess that's that

stormbytes

JUGHNE said:

A few month ago someone posted a discussion concerning a basement radiator sitting on the floor with the end of main piped thru it.

Stormbytes, was that your posting?

It included pictures and a fair amount of discussion.

Nope.

Jamie Hall

No other thoughts, really. You certainly could have a switch in series with the aquastat to keep the boiler from firing to keep the water hot when you didn't need it. Might not be a bad idea.

The aquastat -- based on temperature and shutting off well below boiling -- and the pressuretrol, based on pressure and only active when the boiler is making steam -- won't interfere with each other at all, nor will the low water cutoff or any other safeties you may have.

ethicalpaul

This is the article with all the information. I chose to pump my boiler water directly through my hot water radiant floor loop and it's been fine (that's one of the options in the article: no heat exchanger and only one pump necessary). Don't tell anyone but I am even running a cast iron pump because I wanted to try one before I sunk the $$$ into bronze. It's been fine so far (one heating season and counting), but I also keep my boiler water PH around 11 which minimizes corrosion.

https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/

stormbytes

ethicalpaul said:

This is the article with all the information. I chose to pump my boiler water directly through my hot water radiant floor loop and it's been fine (that's one of the options in the article: no heat exchanger and only one pump necessary). Don't tell anyone but I am even running a cast iron pump because I wanted to try one before I sunk the $$$ into bronze. It's been fine so far (one heating season and counting), but I also keep my boiler water PH around 11 which minimizes corrosion.

https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/

Skimmed through that. Actually did more to confuse me than anything else. There's virtually no information out there on this seemingly simple approach to heating a basement!

Have been posting back and forth on this thread with Jamie Hall who has been super about sharing his knowledge. I'm still unclear about how pressurized water coming out of the radiators and into the wet return wouldn't back up into the main. Is the circulator pump just really slow?

Which model pump do you have?

What are the considerations there?

How do you maintain a PH of your boiler? (I'm assuming you've got an access port plumbed into the NBP)

Do you have any zone valves?

Jamie Hall

The main thing on that water coming out of the radiators is that at the point where it joins with the wet return it will have exactly the same pressure as the water already in the wet return at that point. No more, no less. And that pressure will be determined by how much flow is in the pipe from that location to the boiler. Unless the wet return is really badly clogged or is very small or very long, that pressure will be remarkably small -- a few ounces per square inch, most likely.

But what about the pump on the hot water loop? Well, centrifugal pumps -- such as what we will be using here -- have the characteristic of adjusting the flow and the pressure which they had in relation to each other, in a fixed way determined by the mechanical design of the pump and the power supplied to it. If there is less pressure added, there will be more flow. Or if you are asking for more pressure, there will less flow. In either direction there will be a maximum pressure -- or in the other direction a maximum flow.

Which of the many pumps available one would use would depend on the flow you wanted to have and the pressure required to get that flow through the pipes and the radiation -- which is remarkably little. There are several very good makes of pups out there -- Taco and Grundfoss are pretty common -- and a number of models in each line. There are also different materials used, and for this application I'd want bronze, as boiler water isn't really friendly to cast iron.

How does one maintain boiler pH? That depends a lot on the quality of your feedwater -- and how much you have to add. If the feedwater has a low pH, there are boiler chemicals which can be added -- very cautiously -- to adjust that pH. If the feedwater is neutral to slightly basic, though, no chemicals need be added at all.

Zone valves on steam systems are rare, particularly on smaller ones. They introduce a host of complications to control and piping and are best avoided.

stormbytes

Jamie Hall said:

You certainly could have a switch in series with the aquastat to keep the boiler from firing to keep the water hot when you didn't need it.

How is the aquastat installed? Is it something that screws into one of the tappings on the boiler?

Jamie Hall said:

The aquastat -- based on temperature and shutting off well below boiling -- and the pressuretrol, based on pressure and only active when the boiler is making steam -- won't interfere with each other at all, nor will the low water cutoff or any other safeties you may have.

I'm inclined to go this route as it seems simple and relatively cheap. I am concerned about having a single point of failure (aquastat). Are there any available safety devices or redundancies for situations where the aquastat fails to cut out?

Jamie Hall

"Are there any available safety devices or redundancies for situations where the aquastat fails to cut out?"

You could always use two, in series... but if it does fail to cutout, the boiler will make steam -- and the pressure switch will shut it off.

stormbytes

Jamie Hall said:

You could always use two, in series... but if it does fail to cutout, the boiler will make steam -- and the pressure switch will shut it off.

If I understood the wiring schema correctly, the pressuretrol is entirely out of the picture. The call for heat is coming from the aquastat, not the pressuretrol. If the aquastat fails to cut out, I don't see what would stop the boiler from building pressure until the T&P blows.

bburd

If it’s wired correctly, the aquastat is connected to the TT (thermostat) terminals on the primary control. The pressuretrol is wired in series either with these or with the 120 V burner power circuit. Either way, the pressuretrol will stop the burner if its cutout setting is exceeded, whether the space thermostat or the aquastat is calling.

The pressure relief (safety) valve is the backup if the pressuretrol fails to open, which they can do for various reasons.

stormbytes

Jamie Hall said:

The main thing on that water coming out of the radiators is that at the point where it joins with the wet return it will have exactly the same pressure as the water already in the wet return at that point. No more, no less. And that pressure will be determined by how much flow is in the pipe from that location to the boiler. Unless the wet return is really badly clogged or is very small or very long, that pressure will be remarkably small -- a few ounces per square inch, most likely.

I keep forgetting the radiator is flooded at this point. As long as it works, that's all that matters.

How many radiators could I hook up to this loop? I need about 4-5 in total.

Is there any sort of calculation I need to make? I'm assuming these are all connected in series, is that correct?

Would you recommend any particular style or type of baseboard radiator? (eg. older cast iron v. modern, metal finned)

Jamie Hall said:

Which of the many pumps available one would use would depend on the flow you wanted to have and the pressure required to get that flow through the pipes and the radiation -- which is remarkably little. There are several very good makes of pups out there -- Taco and Grundfoss are pretty common -- and a number of models in each line. There are also different materials used, and for this application I'd want bronze, as boiler water isn't really friendly to cast iron.

Very helpful information. Thank you!

Could you also say if the aquastat in installed on the boiler itself, or nearby plumbing?

The Steam Whisperer

If you have one pipe steam, the water coming down to the wet returns is pretty hot, but it flows very slowly. The flow rate for a steam system is about 1/80 that of the same btu output hot water system. A radiator with return condensate running through it can generate a good amount of heat because the temperature drop of the condensate through the radiator is huge. We have a number of one pipe systems where we installed condensate heated radiators at the lower level and they work quite well.
Now if you have two pipe steam, the return water off the main is almost 0 volume and the return water off the radiators should be quite cool most of the season, hopefully never above around 120F on the coldest days. If you have an orificed 2 pipe system, like many vapor/vacuum systems from the 1930's, the return water will likely be only slightly above room temperature even on very cold days.
The condensate heated radiator technique generally would work best with one pipe systems rather than two pipe.