Adding a radiator to a riser

Bio

I have a 11/4" riser that feeds a small radiator 11.65 sqft edr and I'm looking to extend that riser to the attic and attach a 27 sqft edr radiator, according to burnham heating helper page 3 a 11/4" riser has a capacity of feeding 55 sqft, but is this as big to only feed one radiator? or I can combine the two as long as I don't go over the capacity of 11/4" (55sqft) and be able to heat both?



Attic is small and is finished and insulated with new windows and boiler is big enough to cover it, rad Edr will match the room, thoughts?



<a href="http://hvac.amickracing.com/Hydronics/STEAM%20&%20Hot%20Water%20.pdf">http://hvac.amickracing.com/Hydronics/STEAM%20&%20Hot%20Water%20.pdf</a>

MDNLansing

Yes and Then No

This exact scenario come up on a ride along I did with a pro 2 weeks ago. His answer was yes, it will technically work. But no if you want to ensure its quiet. He explained to me that in a case where steam is in the riser and condensate drains from the third floor, you can get water hammer at the second floor radiator. If the steam is leaving the pipe into the radiator on floor 2, and water falls into its flow from floor 3, you will hear it.



He told the customer a new pipe was needed to ensure it didn't hammer, and that's exactly what they installed. I don't know what it would have sounded like on the same riser, but I know its quiet with a dedicate one.

Dave in QCA

multifloor risers

I have several risers in my building that feed both the 2nd floor and the 3rd floor radiators. It have never caused any kind of a problem for us

MDNLansing

Size Matters

Are they 1 1/4" risers Dave? I'd think they are bigger if originally designed for multiple floors.

Dave in QCA

no, but....

They're 1 1/2", but much more radiation, but within the maximum allowable for 1 1/2.

mcsteamy

I plant to do the same thing, eventually, and ...

My research says this is fine so long as the piping is right and adequately sized (and properly pitched).  Where you need to pay attention (as it also says in the Lost Art of Steam Heating) is in any horizontal runouts or in the valves.  Do not just use 1-1/4" and assume it will work.  If you have a long horizontal runout, you may need to upsize it. 



Feeding attic radiators from a second floor riser was a common practice in many old Victorians I have been through.  They would not have installed things this way 100 years ago if it resulted in noisy and poor heating systems. 

MDNLansing

Done all the time...

Feeding multiple floors off the same riser is in fact done all the done. However, there is a deference between designing for it, and retrofitting it. I doubt you'll find many 100 year old installations with 1 1/4" risers feeding multiple floors with a T at the second floor. At least in this neck of the woods, it wasn't done. If it's designed properly, sure it can be done. But one pipe isn't always like another.

mcsteamy

Huh?

There is no difference between designing it and retrofitting it--so long as you design the retrofit, which the original poster is doing. All you would need to do is pull off the existing valve, add the tee for the existing radiator on floor two, install a straight instead of angle shut off valve, and reattach the radiator.  If a 1-1/4" pipe will service 55 sq ft EDR it does not matter if it takes one radiators or five, so long as the piping is correct.  There's no magic in the fact that it goes another 10 feet up and services another radiator. 



Inch and a quarter is the right size to service the connected load.  Why would you install a larger one in the first place, or install another one all the way to the basement? That's why the tables for one pipe and two pipe steam risers differ--to account for the condensate on one-pipe. 



Speaking of which, even if you install too much radiation, you might still get away with it if you vent slowly to slow down the return condensate flow, or get creative.  I've got a situation I might have like this in my house, and have been trying to come up with a creative way to use the existing single pipe to service way, way more EDR than I should.  Looking at the tables, I just arrived at a brilliant idea.  In two pipe, that 1-1/4" riser services at least three times the EDR of single pipe.   That gives all sorts of opportunities.   In theory, you should be able to install the radiator as two pipe but with the return line running back into a tee fitting below the riser valve, then installing a straight pattern trap backwards and upside down so that when the steam is up, the trap is always shut (hopefully).  Condensate will then accumulate in the radiator or the return pipe, and finally dump when the steam goes down.  Might work like a charm when you've got to figure out a way to heat a 1000 square foot attic on existing risers.  Then again, it might be a real mess--particularly if the boiler doesn't cycle coming out of a set-back, or the trap doesn't stay shut. 

MDNLansing

Page 4

Take a look at page 4 -Up Feed



http://www.gogeisel.com/geiselonline/support/Hoffman/Steam_Vents/Basic_Steam_Heating_Systems_1_2_Pipe.pdf



Note that risers heading to a single floor have a 90 to the top and head to the radiator take off. Then look at how the risers feeding two floors are piped. If you have the ability and room to feed the radiator with a Y and then continue to the third floor it will work fine. However, replacing the 90 with a T and continuing up has the potential of banging. The take off to the second floor radiator has to pitch immediately coming out of the riser. A horizontal take off from the riser COULD make noise.



This is what I meant by proper design. Typically, a riser dead ending at a radiator, isn't piped properly to continue up another floor. But, if you can repipe it to use the 45 take off to the radiator, it should work fine.



In the end, who knows. I'm sure there are plenty of systems that people have extended with a T and had no problems at all. And then again, there are probably lots that don't work. What is known though is that piping like this is pretty much a sure bet to stay nice and quiet. If designed properly, no issues. If not, roll the dice.

Bio

Decisions, decisions

On page 8 of the Hoffman booklet shows a diagram for " double radiator branch for riser " which may work if I only use a single branch at top and bottom, seems the extra elbow may help slow down condensate



http://www.gogeisel.com/geiselonline/support/Hoffman/Steam_Vents/Basic_Steam_Heating_Systems_1_2_Pipe.pdf



On a different HVAC blog steam guru Noel Murdough talks about it, so it seems to be doable? (Old post)



http://hvac-talk.com/vbb/showthread.php?75962-Adding-Steam-Radiator

MDNLansing

Currently

How's it piped right now? does it come through the floor with a 90 degree valve, from the side with a straight valve, or from the wall with a 90 degree valve? Do you know what the top of the riser looks like? Posting a picture of the valve might help.



There's no question it's doable, you just have to pick the correct configuration. I don't think I emphasized the word "ensure" enough in my original post. No matter how you do it, getting steam in and air out will make it work. The guy I'm shadowing right now is an old timer. He has a standard with this business practice that probably goes above and beyond what most people would use. However, in the install I was referring to, the only way he could guarantee it didn't hammer was to run a new pipe. To him, even a small tick in the pipe is too much. He never chances a configuration, even if it means losing the work. I discussed this in depth with him today and he feels that 1 1/2 pipe can handle vertical T's just fine, but 1 1/4 needs a pitch no matter what. It's a general rule he never breaks. Post a pic so we can get more accurate to your specific situation.

Bio

Currently

It's currently pipe coming from the floor to 90 degree valve, I'm going to try to do it this weekend, the plan is to tee off the riser to the attic and use two elbows before the horizontal 4" pipe that will connect to the radiator

mcsteamy

.

Horizontal 4" pipe that will connect to the radiator?  I hope that's a typo!



Think about what's happening here--those Hoffman charts are nice to look at, but they aren't telling you that this is how it must be done.  As long as we're proving points without resorting to critical analysis, here's a really, really old drawing that says you'll be fine:  http://chestofbooks.com/home-improvement/repairs/Mechanics-Household/images/Fig-3-A-gravity-system-steam-heating-plant-of-two-radiat.jpg

Bio

Just an Update

It works great, fully heats both radiators at the same time as the rest of the radiators in the house, the tables were correct, 1 1/4" has a capacity of 55sq ft edr and I'm only using 41 sq ft edr

MDNLansing

Great

Good job. Thanks for the update!

mcsteamy

Fantastic!

I always like to see an update, particularly when it works out. 



We should clarify one thing, though, for future reference:  The 1-1/4" vertical riser will actually handle substantially MORE than 55sqft EDR.  The chart referred to earlier notes an 8' maximum run-out, which is key.  The RUN-OUT limits the capacity to 55.  I don't have the table in front of me at the minute, but I think the vertical riser itself will actually carry about 98 EDR.  Again, the limitation is using an 1-1/4" runout from that riser.  If you upsize the run-outs, you can use the full capacity of the riser, limited by any pickup factor from the piping. 



Based on a comment in Lost Art, taking a riser directly off the top of a horizontal main reduces the capacity of that main by about 5%.  So, given the way that gravity and surface tension work, a run out at 90 from a horizontal riser would probably cause even less loss.  Most of the condensate should stick to the side of the pipe even without a 45 in there.  The issue here is probably forcing the steam to make a 90 degree bend, which can result in poor steam travel when done from a massively vented main into a riser.  From a small riser to a radiator, however, the problem is likely very minor, unless the top radiator has such a large vent that it acts as a main vent.



Long story short, since you have basically no run-out from your description, you still have probably half the capacity that the riser itself is capable of carrying.  You've got plenty of safety margin to add on even more radiation, provided the run-outs can take it.