Question for the Steam Guys, re: vaporstat

Bob W._3

We are installing a new Burnham boiler for our simple single pipe steam system. The mains are well vented. Is there a benefit in installing a vaporstat instead of a pressuretrol, and running the system in ounces? Or, is that device only for vapor systems? Thanks.

Steamhead (in transit)

Yes there is

since you've vented the mains, you only need a few ounces to circulate your steam. So why build more pressure then needed? It only wastes fuel.

Steam Bunny

Steamhead, I'm confused. I thought you needed a bigger main/steam supply to run in ounces as a vapor system.

What criteria would force a home into a pressuretrol?

Dean_7

vaporstat

Listen to steamhead. I followed his advice two years ago and installed a vaporstat on my one pipe steam system when I restored it. it does save fuel and has long since paid for itself.

Steamhead (in transit)

Most steam mains

had extra capacity. They weren't sized to the absolute minimum. So the resistance is low enough that steam will move thru them at a few ounces.

Besides, if this is the system I think it is, the gentleman has removed some radiation. So the mains are now even bigger than needed.

That's why I suggest the Vaporstat.

wentworth

wentworth

wentworth

wentworth

wentworth

Hey Steamhead -

If a one pipe system currently has a presuretrol set to cut out at 1.5 pounds and on really cold days it cuts out and cuts in and cuts out and cuts in until the thermostat is satisfied, wouldn't changing to a vaporstat make that happen even more? i.e. wouldn't it promote short cycling?

Unknown

Short cycling

I've been wondering about that too! But what exactly IS the "short cycling" that wastes fuel? Can somebody help us out? What is short cycling:

A) Many BURNER on-off "cycles" during a single thermostat call for heat, where the boiler and piping stay hot, or

Many THERMOSTAST on-off cycles, between which the system cools down and pressure drops.

Bob W._3

Good question, Geoff. I vote for B. My oversized boiler comes on for 4 minutes or so. I don't believe it ever goes off on high pressure. We are hoping the replacement boiler will burn a little longer and cycle a little less often.

Lets see what Steamhead has to say on your question.

Bob W.
North Mankato, MN

Steamhead (in transit)

And the right answer is......

C- "Both A and B"

Either situation can be described as short-cycling.

Try for about 3 cycles per hour. This is a good figure for gravity hot-water too, and converted gravity systems that now have circulators.

Gene_2

Cycle time

You mean 3 THERMOSTAT cycles per hour? Because my Pressuretrol usually cycles the burner several times before the thermostat is satisfied.

Patrick Linhardt, \"Linhardt's Field Guide to Stea

short cycling

Hi Geoff,

Have you checked the vent capacity? Steam pressure can build up against the air not vented, cycling the boiler on the pressure control, vaporstat or pressuretrol.

Best regards, Pat