The Shop > Metal Stuff
Dual Fuel Gingery Type Furnace
DavidA:
On manometers.
Many years ago, when I was working in the maintenance dept of our local chicken processing factory, one of our gas fired boilers developed a problem. It would start ok, but when it tried to switch from start to run it just cut out. The electrician couldn't find any electrical problems. I suspected the gas supply. So I made up a crude manometer using about ten foot of 10mm bore clear plastic pipe. I fixed it to a length of plank so that it formed an elongated 'U', added water until the water level was about half way up the pipe (naturally on both sides of the 'U'), and connected one end of the pipe to a spigot on the side of the gas supply pipe.
A mark was made on the board coinciding with the level of the water.
And the boiler was switched on.
At first the gas pressure showed, as expected, a positive pressure, not much, about 2" of water if I remember correctly. But when the system tried to go to 'run' the pressure dropped back past the original mark. In other words it was, briefly, pulling a slight vacuum. And there was the problem.
A gas boiler system must never have a negative pressure in it as there is the potential to draw in air. This can lead to an explosive gas/air mix. So the electronics detected the negative pressure and shut the system down.
For very low pressure measurement, manometers are simple, rugged and virtually fool proof. There is nothing to go wrong.
Dave.
inthesticks:
Did you determine why your gas was shuting down. Did you connect to the pilot startup line or your main supply line. Sounds to me like your pilot flame was not lighting off, after a set time on your fireye (or other make) flame senser the startup would be shut down. A properly designed system has more than one check valve in adittion to your control valves and unless you loose press. on your supply side (line break) you would not be sucking air into the system.At startup you supply gas to your pilot. After a predetermined time if the fireye does not detect a flame the system shuts down. The valves sudenlly closing and the momentum of the remaining gas in the pilot supply line could momentarily produce a negative press. But you would not be in danger of sucking air into the lines.
Cheers
CB
DavidA:
The problem was handed over to the boiler supplier.
I had nothing else to do with it, but gatherer form later conversations that it was due to the bore of the pipes supplying the gas. It seems they were not really big enough and when the run stage blowers came on the supply briefly dropped below a critical level. A section of bigger bore pipe was fitted leading up to the boiler and the problem went away.
Dave.
inthesticks:
Didn't do a heck of alot of anything today, to hot and sunny not to enjoy it. Did take an hr. out to hang the oil tank. Decided to hang the tank over gravel instead of the high point over the patio in case I spring a leak. Still 9' of head which should be plenty at the burner.
Cheers All
CB
DavidA:
It certainly looks the part.
Edit out the suspension rope it it would make a passable ufo.
Good to see you are making steady progress.
Over here the weather is dull and overcast. Hard to imagine it is well into summer.
Ah well, back into the shed and light the stove.
Dave.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version