Stealing Steam Boiler Water for Hydronic Baseboard?

Harry_6 · April 17

Greetings. Recently I saw a video in which a steam boiler had a pump attached below the waterline which was apparently taking boiler water and running it through a nearby basement hydronic baseboard. There was no Hartford loop on the boiler, either. It wasn't the subject of the video and it was never mentioned, but is this kosher? I can think of several reasons it seems really problematic, but I'd never seen this before. The boiler had a wet return running at about the same elevation as the baseboard, but not connected to it. I couldn't tell, but I suspect the pump was both taking water and returning it below the boiler waterline at or near the main condensate return connection. Thoughts?

delcrossv · April 17

Probably not picking up much heat if the baseboard supply and return are near each other, but they do need to be below the waterline.

Jamie Hall · April 17

Depends a lot on whether the system was pulling from the boiler or the wet return. If it's pulling from the boiler such a system can work very well, although ideally the return will be to a tapping some distance from the supply.

EBEBRATT-Ed · April 17

Yes it can work. If all the piping is below the boiler water line and never rises above it that is best although it can be done if the piping does rise up. Best to use a bronze circulator. @DanHolohan tells how to install this in his books available on this site. They call it condenste hot water heating.

Long Beach Ed · April 17

We specify these all the time with small residential systems needing a baseboard loop to heat a finished basement below the boiler's waterline. Sometimes the loop is overhead, as in an attic.

There are several ways to make this work, and there are some limitations and control considerations.

A Hartford loop should still be present, and all the steam trim and piping is unchanged.

The baseboard loop is best piped through the boiler, entering and leaving from different sections at different levels to insure mixing. A bypass should be made on the loop to temper the baseboard water eliminating the chance for cavitation of the pump due to high temperatures when steam is produced.

An improved way of adding baseboard would use an internal hot water coil in the steam boiler with the subsequent hot water heating trim.

Harry_6 · April 17

Fascinating. Doesn't having the pump suction directly from the boiler kinda defeat the purpose of the Hartford loop? A leaking pump seal could theoretically empty the boiler. Of course the Hartford loop, itself, is kinda pointless, since we don't burn coal and have LWCo's. And certainly it's silly to have one on a system with a dry return. But I've seen it. What about feeding a first floor hot water radiator/baseboard from the pump discharge?

Jamie Hall · April 17

Well, technically you are correct on a leaking pump seal — or for that matter any leak on the pumped loop — emptying the boiler. That's one of the reasons, among many, for having a LWCO. The Hartford Loop, however, still protects the boiler against a leaking wet return, and since that is by far the most common sources of leaks in a steam system, why not have it?

You could, in principle, have a hot water radiator fed that way on the first floor. There are several ways to do it — the simplest being to have it up there and make sure it has no leaks, so that once it is purged a standard circulator can circulate it. However, a standard circulator likely will not be able to fill it if is allowed to empty for any reason. A higher head pump would work — provided there is enough head to avoid cavitation at the inlet. Another approach would be to use a heat exchanger and run a normal closed hydronic loop… more complicated.

ethicalpaul · April 17

The Hartford Loop, however, still protects the boiler against a leaking wet return

For a few minutes anyway. Don't worry about the hartford loop, it's orthogonal to this issue.

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

And here's my video of the one I made

https://youtu.be/IzIO-IAIoOM

Harry_6 · April 18

Well, that's fascinating. In the couple hundred boiler installations I've seen in my area I have never seen it done this way. I have seen a domestic hot water heater used to power a baseboard loop, but that's it. Good to know there are other options available.

EBEBRATT-Ed · April 18

@Harry_6

Its not that common but commonly done.😊

Mad Dog_2 · April 18

On Long Island, we have many old Villages (95% Steam heated) with a Zone of Baseboard for the finished basement or even a 1st floor den. This is super common here. Mad Dog

Big Ed_4 · April 18

If you pick up the suction from the wet return , and return it carefully back to the boiler , it will not delete the safety of the Hartford loop ?

Jamie Hall · April 19

If you want any useful heat, you have to pick up your suction from the boiler — and then the best place to return it is the wet return. @Big Ed_4 's suggestion would reduce the possibility of the circulating pump on the hot water loop pumping the system dry, true — but the wet return water is likely to be much cooler than the boiler water, unless the circulating loop flow is a large fraction of the boiler output.

ethicalpaul · April 20

https://forum.heatinghelp.com/discussion/comment/1852827#Comment_1852827

This is not a concern for 2 reasons.

At least in my Peerless, the output port from the boiler (for indirects and for this) is not at the bottom, it's higher up, so it's impossible for the pump to empty the boiler regardless.
The Hartford loop doesn't protect the boiler from dry firing, it only delays it for a short time, like an hour or so. The LWCO protects the boiler from dry firing.

4Johnpipe · May 29

We've done this with a shell and tube heat exchanger creating a boiler and system loop. All below the Hartford water line.

Jackmartin · May 29

All excellent ideas. I would not do this because I have had jobs where the boiler dry fired and opps, the condensate pumped. The last one blew a 20 inch chimney liner and the cap 300 feet( the cap). Theoretically a wet return cannot do this, I am too old to believe in theoretically. The chap that said set up an heat exchanger that is part of the steam system and supplying hot water as the emitters heat source seems to an old guy like me much safer. I know this works and if Dan says it works it works, but I am still very hesitant to introduce variables in a steam system. Which brings me to my next comment, I am getting very fed up with older guys who should know better employing ," magical thinking ". The term means I don't know how this works so I will just make it into something I do understand. These aren't apprentices they have been around much longer. We have some truly excellent people here but they seem to be outnumbered. My question is have you had the same experience? I would like to know what book tells you to put a pumped return on a single pipe system or the boiler control is 1/2 on 2 psi off, you at the pressuretrol the idiot has the vutin and cutout mashed together magical thinking. Cheers Jack

Jamie Hall · May 29

I rather agree with you, @Jackmartin — though I might refer to it as incomplete thinking.

Of which that one job you mentioned at the beginning there may have been an example. There is a risk of running the boiler dry, OK… but if you are going to install such a system, shouldn't you have two LWCO devices, one manual, and either of which shut off power to the entire operation? Or at least the manual one would? Perhaps it is due to some early and rather unpleasant experiences involving jungles, but I've always had a tendency to think to myself "what could go wrong here?" … and plan accordingly…

jumper · May 30

How about using return hot water to inject condensate in case Dimension is insufficient? How about filtering or straining hot water to help keep boiler clean?

Stealing Steam Boiler Water for Hydronic Baseboard?

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