Thermostat and pressure

LANDC

With the thermostat set at 70 degrees,the unit will shut down on pressure.When the thermostat is satisfied the unit will cycle off and on.Replaced Honeywell thermostat model T86A with Honeywell model T87K,the same problem of cycling after the thermostat is satisfied continues.Any pointers would be appreciated.

BobC

Your steam boiler probably creates a lot more steam than your system needs. As the air vents close the pressure builds until the pressuretrol trips.

You may be able to eliminate some of this cycling by increasing the venting on the steam mains so you don't build pressure while the steam is trying to squeeze out all the air. How long does it take the steam to reach your main vents? Does the pressuretrol trip before the main vents are hot?

Bob

Fred

Have you programed the thermostat for 1 cycle per hour (for steam)? Also, most thermostats have a fractional degree swing so the thermostat may say 70 degrees but it may be 69.5 and still calling for heat.
As Bobc says, it may be cycling on pressure because the system needs more Main venting or the boiler may be somewhat oversized for the amount of radiator EDR.

Mark N

Did you set the Cycle Rate switch to 1CPH? It most likely came preconfigured to 6CPH. 1CPH is the correct setting for steam. How have you determined that you're cycling on pressure?

JUGHNE

If I read your question correctly, the boiler continues to run after the T-stat is satisfied? If so then if you removed T-stat from wall and separated the wires, power up boiler, then will it continue to run cycling on pressure?

LANDC

Thanks for all the input,it is greatly appreciated.

nicholas bonham-carter

I don't know how the system determines that this question has been answered, as there are now more questions from us about the symptoms related to the original question. How do Vanilla determine this?--NBC

JUGHNE

Exactly what I wanted to know. If the OP answers that "I have NG", that gets the "answer" pop-up. Then what determines "answer" with check mark.

Fred

LOL, I think (my guess) when the OP clicks on "Like" that triggers "Answered"

JUGHNE

Fred, if you go down the page to "Dunkirk Quantam 90-200..." (Jan 1) the first post is OP, then someone asks what gas do you have? Then the OP answers NG and that reply/posting was immediately marked as "answered". That does not make sense. However this morning there was the e-mail " that LANDC accepted the reply posted". All the replies for that posting were suggestions or more questions for the OP; not a definite answer.

LANDC

The suggestion on the setting the thermostat for steam only,which I over looked when installing was my mistake and thus the input from the forum was spot on.The system is operating correctly now.

Fred

JUGHNE said:

Fred, if you go down the page to "Dunkirk Quantam 90-200..." (Jan 1) the first post is OP, then someone asks what gas do you have? Then the OP answers NG and that reply/posting was immediately marked as "answered". That does not make sense.

If that's the case, then my theory is wrong. I said it was just my guess. What can I say? As to LANDC'S post, I assummed he got the answer he needed, even though we provided it in the form of a question. But again, I made that assumption because the posting said "Answered" so maybe I'm wrong again to make that kind of assumption. maybe the site admin will answer your question.

Mark N

Glad to hear it was as simple as setting the thermostat to the proper setting. Enjoy.