steam pressure

Jack_6

My house was built in the 30's and I only have convectors under the windows. My question is what should I set my steam pressure to. After initialy reading this site I set my pressure to .5 cut in and a 1 psi differential giving me 1.5psi cut out. This worked ok but my boiler started short cycling because it was firing to hot at 1.35gph. Next I downfired it to .85gph and short cycling stopped but my indirect water heater took priority over the heating so I had to upfire it again back to 1.35gph so I can have hot water and heating at the same time. Next we hit this extreme cold spell and it was around 20deg outside and the house would not get hot enough. Steam was definitely reaching all the convectors and they all got hot but not enough to keep the house at even 68deg "my preference". Now from reading the lost art of steam heating I have learned that all buildings were built to heat a home into the 70's even on the coldest day of the year on 2psi of pressure All of my friends homes were nice and warm and if they turned their thermostats up to 80 deg in about 10 hours the temperature would get there. In my house the boiler ran non-stop and the house would only get to 62deg. In a given month I have consumed 400+ gallons of oil and my house never got warm enough to be comfortable. I know this is long but bear with me. So I cranked the pressure on the pressuretrol to 5 psi with the same .5 cutin. No hammering, no more short cycling, (it fires for two minutes and stays of for around the same time) and best of all the convectors are cranking out more heat then ever. Is this OK? The only alternative is that the house was built with an inadequate amount of radiant area, but that seems unlikely considering nobody has ever done anything about it. Thanks for all your responses.

[Deleted User]

To help understand the high fuel costs at low room temps

I would like to ask you a few questions about your system. How much radiation do you have? How many BTUH is the water heater? Has any of the radiation been removed? Do you have one pipe, or two pipe steam? Is the air vent(s) working, and sized right? Is the piping insulated?

I suspect that you have two pipe, with convectors. Having said that, do your steam traps all work, so that the return piping stays cool? If the return gets steam-hot in places, there is a trap blowing through somewhere.

When you lowered the control setting, did you go so low that the ACTUAL pressure in the pipe was too low to reach the whole system? How did you measure the pressure that you set it to? I like to use a long, clear hose screwed onto the boiler drain. I hold the hose up beside the gage glass, and use the rising water in the hose to set the pressure. When the water in the hose is 14" above the water in the glass, there is a half PSI of pressure on the system. I watch the control cycle the burner on and off a couple times to make sure I have over 7" when it drops down and comes back on. This keeps the steam at the far reaches of the system from falling back too far during the off cycle. Everything stays hot. I set the differential as low as it goes, and the shut off setpoint is whatever it turns out to be.

Yes, it short cycles after the mains are warmed up. It has to, because when we went from coal fired all day long, to thermostats, which built a new fire every twenty minutes, we have to heat the mains up FAST. We add 1/3 to 1/2 of the load to the boiler size so that we can heat those mains FAST. Balance is the reason, short cycles after the mains heat up is the price.

Normally, this isn't an issue, because by heating everything fast, the mains usually heat up at the same time that the room satisfies. Normally, this happens every cycle, except coming out of setback, or when someone turns up the thermostat a few degrees. Then, the normal and expected short cycles will occur after the mains are hot.

If this doesn't happen, fuel costs will be high, and heat will be uneven.

The causes are many. The load sizes and boiler size are the first clues to solving it.

Noel