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www.fueloilnews.com | FUEL OIL NEWS | JULY 2015 43 HVAC/ HYDRONICS BY GEORGE LANTHIER* E ver hear the following; "Gauges, smauges, real burn- ermen (sic) don't use gauges. If ya know what ya doing, ya don't need gauges." Well, I have heard that as I'm sure you have and hope you're not one of the people saying it. That statement is just not right whether it's about pressures of any kind (air, gas, oil, refrigerant, steam or water) and it sure is really stupid to say it about vacuum. Vacuum, when you think about it, is "reverse pressure" and you must know what it is to diagnose a problem. "If an oil pump isn't getting any oil, and everything's clean, it's the pump pure and simple." That's another one for the books. Really? How do you determine that "everything's clean" without using a gauge or opening everything up? Opening everything up isn't a bad thing, but on Christmas Eve in a blizzard at 2 a.m. its not any fun, either. The focus of this article will be on fuel oil pumps and the use of gauges, and maybe we will come back and show you why using gauges on gas is important too, because it may even be more so. Let's start with a service call. You arrive on a brand new installation and can't get the pump to prime. For the record neither could the guys who put it in—sound familiar? After installing gauges (pressure and vacuum) the vacuum gauge on the oil pump tells you that you have 14 inches of vacuum on the pump. This is a one-pipe system, with gravity feed to the burner from an inside tank that has just been filled, Figure 1. But, it turns out that when they put the oil line down, one of the workmen pouring the floor pinched the tubing and that has caused the high vacuum. Gravity jobs should have zero vacuum, nada, zip, nothing! Since the line is only about ten feet long, you run a temporary line. With the temporary line in place the job now pulls zero vacuum, primes right up and runs. Zero vacuum would be typical for a new job with a couple of thermal valves, and two spin on filters. The following procedure for testing oil burner pumps is taken from our book, "Advanced Residential Oilburners." VACUUM TESTS: Two vacuum tests should be performed to verify pump and system performance; 1. Pump test. Isolate the pump from the system by removing all supply and return lines. Make sure that the pump is full of oil and install a vacuum gauge in the inlet port of the pump, Figure 2. Turn the pump on and wait for a vacuum reading of 15" hg. Turn the burner off and wait at least five minutes. If the pump will not reach 15" hg., or will not hold the vacuum it should be replaced. Operating Vacuum Test Install a vacuum gauge in an unused inlet port or a tee installed in the suction line, Figure 3. Operate the pump and make sure it is full of oil. Read the gauge and ensure that the pump is operating within its design limits. A chart supplied by the pump manufacturer should be checked for acceptable performance levels. Gauges Always Work Best! Figure 1 Figure 2