Is dryer steam better?

Unknown

JW-

Anna's explanation is right on the money.

I'm just wondering, why are you asking"? Is there a problem?
If it works don't mess with it. You might want to check your boiler's installation instruction manual and see if the job was done to spec. Also insulating the steam piping near the boiler makes a big difference.

As you are a steam system owner, I'd highly advise you to get Dan's books. (See "A Steamy Deal" at the bottom of this page) Start with "We got Steam Heat". They are easy reading, written for the home owner and loaded with facts about steam heating systems. That knowledge has saved me a bundle since I got them and paid for the books many times over.

JW_8

Dry steam

Is dry steam better/more efficient?
I have a situation where a boiler was replaced.
The system works pretty well, and is quiet.
The 2" riser from the header pipes into the old 4" main loop. When the steam expands from the 2" to the 4" is that a problem? Would it be more efficient to bring the 4" right to the header T?

Anna Conda

What we think of as 'steam', for example coming out of a kettle, is actually a mix of true steam and liquid water vapour, known in HVAC parlance as "wet steam." "Wet steam" is water in a change of state. During a change of state, heat energy is used to change from liquid to gas and the temperature remains constant; when the change of state is complete, heat energy will raise the temperature. Thus dry steam can hold more heat energy (higher temperature) than wet steam. Thus the goal of the steam specialist is to ensure that the steam is as dry and as hot as possible and doesn't give up any of its heat energy before it reaches your radiators. Steam leaves the boiler at a fast velocity. When the steam jumps from the 2" pipe to the 4" pipe, it slows down. That allows any water vapour to fall out of the steam back into the header, and not be carried into the mains. Does that help?

Jamie Hall

If it ain't broke...

don't fix it. It is not at all uncommon to take a 2" riser from the boiler and run it into a 4" header -- as has been noted, this will allow any water droplets in there to drop out and go back to the boiler where they belong.

Do not, however, confuse what we here on the Wall call wet steam -- which has water droplets in it -- with what a thermodynamics engineer would call saturated steam, nor dry steam (which we use to mean steam without water droplets) with superheated steam. There are very very very few heating systems which use superheated steam (although almost all steam engines did, and do). You can have dry saturated steam -- which is what we are looking for.

And saturated steam has some really interesting properties which can really ruin the day for the unwary heating person!

JW_8

Thanks for the excellent replies. All helpful.
I see now that the pipe size transition is not the problem I thought. I'll also insulate the near boiler piping. I have Dan's books and they're great. I love the steam system I have but I'm always looking to tweak it for better operation. As an additional question, the boiler was installed with 1-2" tap, whereas the manual shows it pied with 2-2" tappings. Is it worth the upgrade? We have mild water-level bounce during firing, but the system seems to operate fine otherwise.

mel rowe

Just a curious homeowner here. I think I remember being told that it was best to have steam velocity below 18 ft.per second. What is the capacity of the boiler mentioned here and what would be the steam velocity in different areas of the near boiler piping? I am not disagreeing with anything mentioned here, just looking to gain a little knowledge.

Jamie Hall

Well now...

it would have been nice to have used both tappings and brought 2 2" lines up to the 4" line. However... as I said before, if it's quiet and not bouncing that much -- never out of the glass -- I'd leave it alone. There might be a slight gain in efficiency, but the 4" is going to take whatever water was in there out anyway... so... but then I've been accused of being lazy before!

Unknown

JW-

Ideally you use every steam exit port that is available,(The more the merrier) as this slows down the velocity of the steam which means the steam rushing out doesn't carry as much water with it so is therefore dryer.

However quoting Jamie, "If it ain't broke, don't fix it!!!"

Normally I think you would have problems with just the one steam port coming out of your boiler though in this case the 2 inch going to 4 inch main is probably what makes it work. If you are getting good steam to even the most distant radiators I'd just leave things as they are.

mel rowe

Just didn't want this to get lost at the bottom of the list.

Unknown

As the heat source is generally constant,one doesn't have much control on steam velocity coming out of the boiler other than to use all the steam exit ports available. More exits equal slower velocity and slower velocity is better as it picks up less water in its rush to escape the confines of the boiler.

You can further slow the velocity by going to a larger capacity (diameter) piping immediately after exiting the boiler for the risers and drop header. Insulating the risers and headers further limits the amount of condensate formed in the risers/header that could be further carried along by the steam and result in "wet steam".

Note in the attached picture that the pipe sizes increase right after the piping leaves the exit port. Really nice work though I'm afraid I can't remember who did this to give them the credit they deserve.

JW_8

Well then, i'll guess I'll go with the "if it works don't fix it plan"...but then again....
Thanks for all the great help.