Setback Temps For Steam?

jmob77

Hello, All.

I'm wondering what a reasonable setback temperature is for a one-pipe steam system. My understanding is that going too low risks wasting fuel, as the system stays too cool for too long and that this can also lead to excess condensation and water hammer.

This seems to be more a question for the dead of winter, as opposed to my current chilly nights in NYC, where my thermostat is pretty much pinned to 68 degrees all the time and therefore never kicks on, except in the middle of the night.

So, what is the magic number for maximum fuel efficiency as well as taking advantage of my programmable thermostat's functionality?

John
Brooklyn, NY

Fred

This is a topic of much discussion around here. Many of us believe there is very little fuel savings with set backs on a steam system because it takes a good amount of time for recovery. Those that do use a set back suggest 3 degrees as a reasonable setback. Setbacks don't really cause excess condensation that will cause a problem or hammer unless you have other issues like radiators that are sloped the wrong way or pipes that have lost their pitch or have sags in them.
The one thing that can happen, if the boiler is over-sized for the amount of radiation connected to it, after running up to an hour or more to recover, the system can build enough pressure that it causes the Pressuretol to shut the boiler down. Once that happens, pressure will build and drop, build and drop every couple minutes, shutting the burners down each time until the thermostat is satisfied. Won't do any damage to the equipment but it is hard on the boiler controls.

hboogz

Recently, I've had luck in my own home keeping the tstat at a constant temp (oversized boiler here) However, I think in NYC (I'm in Queens) the tstat location can determine the settings. Sometimes in multi-families its on the highest floor, which you may not contol too often, or you or the tenant may cook a lot, or you may have a varied schedule, or you may prefer more heating while you sleep, in those cases setbacks of more than 3 degrees could work to your benefit.

The pros have and can talk about, as Fred has mentioned, issues with pressure and short-cycling, in addition to collapsed steam that forms into condensate quickly on cold pipes ( the reason why insulation on the mains helps) and a myriad of other concerns.

I believe you could find a setting on the tstat that provides comfort for you in your space then work from there. In my experience, some Tstat's can be programmed for 72 while others at 66 and provide comfort depending on the person and space and type of radiation.

Harry

jmob77

Just out of curiosity, is there a simple formula for sizing your boiler to the amount of radiation? I have a feeling mine is oversized, as the previous owners redid the first floor (it's a two family) with two-zone hot water. I imagine the whole house was served by steam previously.

jmob77

Haven't gotten to look yet, is the output spec usually indicated somewhere on the boiler?

Jamie Hall

jmob77 said:

Haven't gotten to look yet, is the output spec usually indicated somewhere on the boiler?

Unless it's a real antique, there will be a nameplate on the boiler for all that information.

ChrisJ

It's really easy to see what your system can tolerate.

On a fairly cold night make the system raise the temperature a few degrees. Let it drop 5 degrees or so, and then raise it.

Watch what it does.

If it starts hissing and cycling on pressure after 1 degree, don't do any setback. If it goes up 3 or 4 degrees fine, it'll tolerate that.

Make sure it's fairly cold out though as this has a huge effect on the performance. For my area in New Jersey I'd try it on a night when it's in the teens or 20s out.

KC_Jones

I can do setback about 95% of the time, but when I am at design (or below) I typically have to suspend it. My system is radiation limited, which is unusual.

RomanGK_26986764589

@KC_Jones Do you plan on increasing radiation?

KC_Jones

lol I have a lot of ideas, but not sure which one will be implemented. Due to previous remodels the floor plan of the house was changed. Rooms that were connected no longer are which left some rooms with no heat, primarily my 2 bathrooms. When I remodel I am adding heat.

ChrisJ

KC_Jones said:

lol I have a lot of ideas, but not sure which one will be implemented. Due to previous remodels the floor plan of the house was changed. Rooms that were connected no longer are which left some rooms with no heat, primarily my 2 bathrooms. When I remodel I am adding heat.

I've heard rumor that steam radiant under ceramic tile yields a self drying floor in bathrooms.

Gordy

ChrisJ said:

KC_Jones said:

lol I have a lot of ideas, but not sure which one will be implemented. Due to previous remodels the floor plan of the house was changed. Rooms that were connected no longer are which left some rooms with no heat, primarily my 2 bathrooms. When I remodel I am adding heat.

I've heard rumor that steam radiant under ceramic tile yields a self drying floor in bathrooms.

Unless you can't hit the toilet, plug up the toilet, or dry off after getting out of the tub/shower not seeing a big plus factor.....
Dry your bath towels on the floor.

ChrisJ

Gordy said:

ChrisJ said:

KC_Jones said:

lol I have a lot of ideas, but not sure which one will be implemented. Due to previous remodels the floor plan of the house was changed. Rooms that were connected no longer are which left some rooms with no heat, primarily my 2 bathrooms. When I remodel I am adding heat.

I've heard rumor that steam radiant under ceramic tile yields a self drying floor in bathrooms.

Unless you can't hit the toilet, plug up the toilet, or dry off after getting out of the tub/shower not seeing a big plus factor.....
Dry your bath towels on the floor.

For some odd reason it seems I'm the only one in my house that dries off in the shower before getting out.

Haven't figured that out yet. This includes guests.

KC_Jones

People get out of the shower before drying off? That's weird.

ChrisJ

KC_Jones said:

People get out of the shower before drying off? That's weird.

I know right?

But that's not why I said you should do steam radiant.

I was more interested in seeing you master this to use the John.

KC_Jones

After you add it to your house I will put it in mine.

Gordy

ChrisJ said:

KC_Jones said:

People get out of the shower before drying off? That's weird.

I know right?

But that's not why I said you should do steam radiant.

I was more interested in seeing you master this to use the John.

I suppose you could paint the walls with Redgard, and make it a sauna........