steam radiators under the floor?

Question for all the steam experts out there. Do they make a certain type of steam radiator for under the floor (between the joists) in some type of of sheet metal box, with say a cast iron grille on top? Would the grille get too hot? I’ve seen the “in the wall” types of steam radiators and so I was wondering if there’s a model that can be concealed in the floor too. Maybe the convection properties don’t make sense. This would be in front of a window well. There’s already a branch of my steam piping going through this area serving a regular bulky radiator, so the logistics wouldn’t be too bad. I should mention its a 1-pipe system. I’m somewhat aware of all the challenges to keep the system balanced, sizing, etc, but I just wanted check if this was even possible. Thanks for all your insights!

fkeels1973

in Heating 10 years and 10 months ago

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Master Plvmber | 10 years and 10 months ago

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Yes. And so I said “put whatever appropriate radiator in the enclosure”. I guess I was thinking “pipe appropriately for your system” was implied.

ellenlourie | 10 years and 10 months ago

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Regio in the link refers to hot water system and will not work on 1 pipe steam system. Question was about 1 pipe steam system.

Master Plvmber | 10 years and 10 months ago

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We do it all the time in townhouses AND we’re plumbers. Go figure. You can buy a pre-made product like this https://www.reggioregister.com/prod_detail_list/recessed-radiation and put whatever appropriate radiator in the enclosure, or you can just have a contractor make a custom enclosure. You don’t need a separate grill for air intake. You just need to create a fixed louvre (factory supplied with the Reggio product) to provide a thermal barrier within the enclosure. That’s enough to influence convection. This is me: http://brownstoner.staging.wpengine.com/gatewayplumbing

ellenlourie | 10 years and 10 months ago

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If you find radiators designed for this purpose you can do it. You will need to build insulated enclosure for radiator. To get better result you will need to make second grill to supply return air to radiator. Original piping for stand alone radiator will not work, because gravity condensate return. You will have to re-do steam pipe to radiator and connect it to riser at the point below radiator with 2 elbow swing connection. Grill will not get too hot. Size radiator to the room or get oversized radiator with TRV valve and remote sensor actuator. Do not hire regular plumber for this job. Get heating contractor with proven track record and good references.

williamsburgguys | 10 years and 10 months ago

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You know I just read that yours is a 1-pipe steam system, so not sure what the neighbors did would work for you. Theirs and ours are both old circulating water radiator systems. I’m not a steam expert at all. I guess as long as the drainback feed was at the correct level and you had the correct coil and valve it could work. Maybe a steam person on here can tell you for sure.

williamsburgguys | 10 years and 10 months ago

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The people who just redid the house next door to ours did this, but used a modern aluminum finned coil similar to what you see in a baseboard system then topped the floor with a decorative old-style iron floor grille about 6-8 feet wide. It looks cool and authentic but down inside it’s a modern aluminum fin coil plumbed into the old hydronic radiator loop. In their remodeling of the 1895 house, they added an entire back wall of floor to ceiling windows and there was nowhere to reinstall the radiator that wouldn’t look odd, so they did the in-floor model instead. It looks good. I suppose winter will tell whether it works efficiently or not.

fkeels1973 | 10 years and 10 months ago

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I’m referring to something like what’s on page 100 here: http://www.heatinghelp.com/files/articles/1256/205.pdf “Excelsior Indirect Steam Radiator. Showing method of introducing hot air into a room through a register in floor.”