How long is the steam on (per day) in your 2 pipe system?

Sailah · April 2016

Forgive the open question but here's what I am looking for.

I am trying to replicate typical "thermostat calling for steam" times in a controlled environment to test a new product. I have 2 regular cast iron radiators hooked up to our 50 psi steam system, with a PRV reducing pressure to 3 psi to the radiators. I don't have any way to thermostatically control these radiators so I am using a computer controlled steam solenoid to put steam to the radiators.

I would like to replicate a normal situation in a house or apt.

How long does "steam on" last in your house per event?

How long is it off?

How long does it take for the radiators to cool down from temp to say 80 degrees?

Right now I have the steam "on" for 15 minutes (but it's instant since the solenoid is 3' from the radiators) and off for the same with a 85 minute random either way. So the steam could run for 15 minutes + 0-85 minutes, and be off for the same. I think that's too much so I'm asking for opinions.

It's been a long time since I was a kid growing up in Maine with steam heat so I forget what is normal.

Thanks!!

Abracadabra · April 2016

Systems that I've worked on will have a on time of about 45-55 minutes, unless it's the first call of the day coming back from setback. Coming back from setback, could be as long as 1.5 hours depending on outside temps. Off time depends on outside temps. Anywhere from 1 hour on up. 90% of these systems are on a space thermostat type control, not an outdoor reset.

Sailah · April 2016

Thanks that's helpful

The Steam Whisperer · April 2016

I typically tell customers that they should see their boiler run about 20 to 25 minutes minutes per cycle on a typical winter day with maybe 45 minutes off. This is with a properly vented system, properly sized boiler with standing radiation. I have seen many system that run over an hour at a time, but typically they suffer from poor venting and/or see very large internal temperature swings. Also, most of the boilers are about 60% or more oversized, so to maintain even temperatures in the space, shorter cycles are required.
Probably related to your interest, systems that are properly vented and provide stable air temps, also rarely see the steam getting to the trap, so the trap just sits there most of the heating season. Convectors will give the trap a much greater work out, as do setbacks.

PMJ · April 2016

The Steam Whisperer said:
I typically tell customers that they should see their boiler run about 20 to 25 minutes minutes per cycle on a typical winter day with maybe 45 minutes off. This is with a properly vented system, properly sized boiler with standing radiation. I have seen many system that run over an hour at a time, but typically they suffer from poor venting and/or see very large internal temperature swings. Also, most of the boilers are about 60% or more oversized, so to maintain even temperatures in the space, shorter cycles are required.
Probably related to your interest, systems that are properly vented and provide stable air temps, also rarely see the steam getting to the trap, so the trap just sits there most of the heating season. Convectors will give the trap a much greater work out, as do setbacks.

If I use 25 on and 45 off from this example I get a burn of 36% of the total elapsed time which is about where I am on medium heating days say 15-25F outside. My boiler is significantly oversized(which I like) and runs approximately this same percentage. My difference is that in these conditions I spread the 25min burn into 3 evenly spaced 8 minute burns on purpose over each hour to even things out. I watched a recent call for heat which took 4 hours to satisfy - a time I try to make as long as possible with the temp moving up as slowly as possible from Tstat cut in to cut out. The result as stated above is very even heat and traps that are never used as the rads are never full(and never empty either). The max steam pressure might be an ounce or two and way too low to be part of the control. It is a two pipe system and operated this way venting is a non-issue also. One single vent in the garage on the dry return for the whole system.

Fizz · April 2016

Using 1CPH my cycle time ranged from 16-28min depending on ambient temps. Two mo ago switched to 3CPH and put system in vacuum. Results are 5-8 min cycles, so 15-24 min/hr. This change per advice of PMJ.

Sailah · April 2016

Thanks, I've adjusted my run time accordingly based on the feedback

How long is the steam on (per day) in your 2 pipe system?

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