Posted by Clifford Weir on November 13, 2001 at 23:30:09:
In Reply to: Instant Highfire! posted by Robert on October 24, 2001 at 10:06:35:
: I have a Cleaver Brooks 125 hp firetube boiler generating 100psi steam. This morning I discovered that after blowing down boiler and after prepurge boiler came on line as normal but went to 100% fire even though it was set to only go to 50%. In automatic mode it is bypassing the preset setting (ignoring it) and continuing to 100% fire. When I switch to manual mode it will stop at the preset mode of 50% fire. Where should I start looking for the problem? Modulator motor?
I have ran the Cleaver Brookes boilers, both the 150 and 200 horsepower boiler. It sound to me that your banking the boiler during off loads and low steam demand and starting the boiler and running it during high demands. If this is correct the pressure has reduced and needs to be made up due to the lack of heat and by putting the boiler on automatic you are asking the boiler to meet the preset pressure on the pressure regulator.
If you are watching the water level in the low water cut-off element site glass you should see a reduced level due to the high steaming rate and firing rate and the pressure increases and comes closer to the prescribed pressure setting the boiler should start to settle down.
There are though some things that you should be aware of though.
1)If the pressure of the unit is low and you go from no fire to full fire, you are putting a great deal of stress on the unit and it may cause some serious troubles for you down the road in maintenance cost due to the boiler setting being unevenly stessed due to raped a start up.
2)Another thing to look at is the time the unit is down. If the unit is off for some time the burner panel should be place on hand and the amount of fuel allowed to enter greatly restricted, may-be three pins on the modulator and slowly increased.
Eg. Once the main flame has been established start on the lowest setting for 5 minutes allowing the burner and surrounding area to heat up. After turn your fuel valve so the burner valve opens to 2 pins for another 5 minutes. Once your past 75 P.S.I. on the steam space gauge the boiler can be put on automatic and the normal course of operation will take place and the start up stresses can be greatly reduced.
Have fun, and remember, it's only equipment, so if you take care of it, it will give you years of good service. If you don't it won't.
Cliff..