How accurate is an oil Watchman?

[Kes]

We had a new 2500 ltr oil tank fitted last December, and the oil from the old tank pumped into the new. The Watchman (wonderful gadget) showed 4 on installation, going to 3 on Christmas Day. Then to 2 on 10th Jan (16 days). I thought that this would be a heavy use period. Today the sensor has fallen to 1 after only 12 days. I'm sure we aren't using nearly 30% more oil than over the Christmas period.

How accurate are Watchmans? As the tank is cylindrical, does the Watchman measure depth of oil so that low and high readings pass quickly (as there is less oil at the top and bottom of the tank), and middle readings pass slowly, or is there some compensation for the shape of the tank?

I'm just miffed that my precious oil is going up in smoke.

 

[collegeboy]

Which model Watchman do you have???

 

[oilman]

Would depend on the size of your tank, shape of your tank, size of your house, how hot you have it. It should be calibrated for a cylindrical tank.

Use a dipstick. They are reliable. Nothing else is.

 

[Kes]

Thanks chaps,

The Watchman is a Watchman Plus, in an 2500 ltr Atlas bunded. It's difficult to see the inner tank but I think it's a horizontal cylinder - the outer tank shape is cylindrical with buttresses to enable it to sit squarely on the floor.

Over the Christmas period it was frosty and the heating was on all day most days. It took 16 days to fall from level 3 to 2. Now the weather is better, the boiler and room stat are unchanged, one bedroom rad is off, and the heating is rarely on all day. It took 12 days to fall from 2 to 1.

According to Sensor Systems the Watchman is suitable for all shaped tanks. The Watchman Niveau has a converter for cylindrical tanks, I can only think that this compensates for the tank shape. There's no such mention of a converter for the Watchman Plus, but as it was supplied with the tank it should be suitable, non? I dunno.

 

[snb]

the watchmans are usually very accurate. they register 9 on full down to 0 when there is still about 150mm of oil in the tank.

This is to allow for the fact that the outlet is usually 30mm above the bottom so debris doesn't get drawn into the feed pipe and to give you time to order your next delivery.

 

[Kes]

The blooming thing flicked back to 2 when the heating came on yesterday afternoon, then went to 1 quite quickly, and now it's back at 2 this morning! I think I might reboot the sensor if I can do that without dropping the bits into the bund.

 

[vanmanm1]

Would depend on the size of your tank, shape of your tank, size of your house, how hot you have it. It should be calibrated for a cylindrical tank.

Use a dipstick. They are reliable. Nothing else is.

 

[Nige F]

I`ve heard that " travelling" oil theives have a little device they bung in the bund that wirelessly fools the Watchman into giving a false reading - costs a few pence from China

 

[oilhead]

Wqatchmans monitor the oil level, so on a cylindrical tank, the top and bottom will move faster than the middle. On a rectangular tank movement should be fairly constant, unless it is one of those with holes in the middle, when the middle will fall fasrer than top and bottom. After a month or two, you should be able to compensate for this.