practicality of start delay timer for 2 pipe home system

Gary Segal

Hi all,

I have been pondering ways to further reduce energy consumption in my 2 pipe steam system (single home, oil fired0, Thanks to firsthand help from Steamhead and advice from others, the system is running pretty well. It makes steam in about 21 minutes from a cold start on a typical winter day.

I am running a vaporstat and have the cutout pressure set slightly below 2 PSI (supported by calculations and observation). So here is my question:

In normal operation, from a cold start, the boiler will cycle on and off every 1.5 minutes (takes 1-2 minutes to come back up to pressure) after the first cycle of 21 minutes. The cycling appears to be due to the relatively low cutout pressure and the fact that it takes very little time to dissipate this pressure.

I've observed that the convectors stay very hot for a good 30 minutes or more after the first cycle, even if it turn the boiler off. Making fresh steam as soon as the room temperatures begins to drop only takes 10-11 minutes. The I'm good for another 30 minutes of slightly increasing or stable room temperatures.

Thus, I feel that much of the cycling that the boiler does until the thermostat set point is reached is just wasted, primarily just repressurizing the pipes. So, I was thinking of implementing some sort of restart delay timer on the system to see if i could reduce the duty cycle a little.

Any thoughts to the practicality of this suggestion and (if practical) the best way to implement it? I see that there are a lot of start delay thermostats on the market for heat pump systems - I was not sure if they are suitable for the purpose as most seem to have a keep running delay that can not be set independently.

Thanks,

Gary

Mike T., Swampeast MO

Is this the "normal" operation or mainly when recovering from setback?

Is your weather currently rather mild?

Gary Segal

normal conditions

Mike, It has actually been quite cold and windy here todat when I made these mose recent observations. However, I observed the same behavior through the cold of last winter, too, so I believe the behavior is typical.

Regarding setback, the heating system is usually off at night and often throughout the middle of the day. So my 21 minute estimate to make steam is from a cold start.

Even when maintaining constant temperature, the system does not have that many periods of operation - although the house is old, it has been insulated and had new windows installed after the original heating system was installed. Further, we keep the house pretty cool - 65-66 when we are awake, 59 when we are sleeping.

What bothers me is that after the initial steam cycle (21 minutes), the boiler is running approximately 50% of the time until the thermostat set point is reached. My feeling is it could make steam far less frequently and with a lower duty cycle if I had a timer in the circuit, while not compromising the time to reach set point.

Thanks for any suggestions,

Gary