staging steam boiler

Steve Whitbeck

We are getting WAY off track - will he save $ by running only half of the boiler untill it gets cold out and the other half needs to fire???
I know that a two stage furnace will save $ on gas and increase comfort level do to the fact that the cycles will be longer.
You will get cycles that are a lot longer with this boiler if it is firing only half rather than the whole thing.

Steve Whitbeck

staging steam boiler

I have a customer that has a very large old house that has a 800,000 BTU steam boiler. This is a UTICA boiler that has TWO gas controlls. It is like two boilers caravaned togeather.
The question is will it help lower gas usage and increase comfort by installing a two stage thermostat on this boiler so that only half of it fires up on a call for heat?
My thoughts are that with the boiler running longer to satisfy the thermostat this should help heat the wings of the house on mild days. And since it would be burning half the gas he should save some on his gas bill.
Could this possibly damage the boiler from uneven heating.
I have one of the gas control valves turned to pilot right now to se if it will help.
Thanks Steve Whitbeck

Steamhead

I'd stage it by pressure

rather than with a thermostat. This would involve an extra pressure control (preferably a Vaporstat) that would stop one burner when the steam pressure reached the setpoint, say 10 ounces or so. I think Slant/Fin's Caravan modular steamers work like that- check with Noel for further.

However, if the wings don't heat like they should in mild weather, I think you have an air-venting problem. The mains should fill with steam before it enters the radiator runouts. The solution here depends on the type of system- tell us more about it!

If you haven't done so already, you might want to count up the radiation to see if the boiler is oversized.

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Steve Whitbeck

Staging

it has a pressure trol on each half but they are the mechanical type and are not that accurate. Wouldn't adjusting one of the pressure limits to cut out at a lower setting be backwards of what we want. We want only one to run untill the other half is needed. The whole idea here is to get the boiler to run as long as possible.
The system is a two pipe system and the main vents work great. this is a big - spread out house and in mild weather the boiler doesn't run long enough to get enough heat to the wings. running half the boiler should make it run far longer so maybe the steam would have a chance to fill the system.

Boilerpro_3

You may want to do a little balancing..

using the hand valves at the rads, too. Throttle those rads down that are getting hot too soon so steam will move out further in the system. Also, how many cylces per hour are you getting. Your thermostat heat anticipator setting may be way off, causing the boileto short cycle. This is real common for hot water and steam... at best they get set at the gas valve current draw, which is often not even the circuit that is powered by the thermostat. I'd start out with as long a cycle as possible and see if you have too much swing on each cycle, and then shorten it as necessary.

Boilerpro

Mike F

I think not. On mild days the system shuts off from the t-stat not the pressuretrol. If you shut off one boiler the other will definetly run longer, but you will have the same result of no heat out in the wing. In order to get heat to the wing you need to balance the system properly. In a properly balanced system steam gets to all the radiators at about the same time. You also need to fill that iron balloon as quickly as possible, which is why I like steamheads idea of a vaporstat that shuts off one boiler at a lower pressure (once the iron ballon is full) than the other. This will allow longer run times and still fill that balloon as soon as possible. On a mild day all the pipes and radiators are cold because the system has not run before, and need to be heated up enough that the steam does not just turn to condensate in the mains. That is your pick-up factor. Once that happens you can start to deliver btu's upstairs to the radiators. Which is why it is so important to have properly insulated mains and run outs, especialy in a large house.

Mike F

I think not. On mild days the system shuts off from the t-stat not the pressuretrol. If you shut off one boiler the other will definetly run longer, but you will have the same result of no heat out in the wing. In order to get heat to the wing you need to balance the system properly. In a properly balanced system steam gets to all the radiators at about the same time. You also need to fill that iron balloon as quickly as possible, which is why I like steamheads idea of a vaporstat that shuts off one boiler at a lower pressure (once the iron ballon is full) than the other. This will allow longer run times and still fill that balloon as soon as possible. On a mild day all the pipes and radiators are cold because the system has not run before, and need to be heated up enough that the steam does not just turn to condensate in the mains. That is your pick-up factor. Once that happens you can start to deliver btu's upstairs to the radiators. Which is why it is so important to have properly insulated mains and run outs, especialy in a large house. Check for proper insulation and balance to relieve the no heat in the wing problem. And install a staged vaporstat for longer run times. For more details check out Dan's book the lost art of steam heat.

Unknown

Exactly.

Heat timer makes a control that stages steam boilers on pressure, and is pretty sensetive.

Noel