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-   -   central home oil heater, pump cavitating, what to do? (http://www.houserepairtalk.com/f8/central-home-oil-heater-pump-cavitating-what-do-15579/)

 paulmars 02-18-2013 10:46 PM

central home oil heater, pump cavitating, what to do?

I had to move the tank 3 feet further down towards ground. So, now the heater pump needs to pull fuel up 3 more feet. There was already a long distance from tank to pump. About 40 feet. The tank was at the same height as the pump. fuel got pulled up about 5 feet, over about 30, then down about 5 feet. Its been working like this for 26 years. However, I had to move tank down 3 feet. So, its now pulling up 8 feet, then over 30 feet, then down 5 feet. However, now it keeps cavitating. What to do? Last resort is to move the tank back up. Someone said a small low pressure automotive fuel pump mounted at the tank to push the fuel. This work?

tks,
pa

 Fireguy5674 02-19-2013 10:55 AM

It is always easier to push fluid than pull it. The other thing you might check for is any leaks in your delivery piping. If you have even a small leak and are sucking any air at all you will get cavitation.

I found a sight on the web for heating oil pumps. The first thing it said was that the maximum lift height was 8'. It also gave this formula for figuring your line length and size.

Where
L= Line length in feet
H= Head in feet (amount of lift)
Q= Firing rate in Gallons per hour or GPH

Then for a 3/8" line L=6-.75H
.0086Q

For a 1/2" line L=6-.75H
.0218Q

They also note that any fittings, valves and filters will reduce the maximum line length you can have.

Using these formulas you can see 6-.75(8)=6-6=0 so it does not matter what you GPH burn rate is you won't get it to work.

I looked at:
http://www.wardheating.com/pages/oil-heating/oil-heating-pumps

They talk about booster pumps under technical resources area on the lower left of the page. Read that before trying to rig up anything on your own.

 paulmars 02-19-2013 02:33 PM

maybe a tigerloop will help? I looked and cant find any leaks.

 Fireguy5674 02-19-2013 03:12 PM

I read the Tigerloop info very quickly but I think your problem is you are trying to lift above the maximum 8' of head and the pump won't do it. It is like trying to pump water from a depth of over approximately 20'. There is not enough atmospheric weight to push it that high even under perfect conditions. All suction does is allow the weight of the atmosphere to push a liquid into an area from which the pressure has been removed. Evidently 8' is all the higher it will go under perfect conditions without considering plumbing losses.

 paulmars 02-19-2013 03:32 PM

pump maker just replied and recommended tigerloop. I need to be sure there is no leak or blockage before I buy a tigerloop though.

pa

 Fireguy5674 02-20-2013 08:05 AM

They would be the experts. I read a couple of articles about tigerloop. Of course the seller says it is the best thing since sliced bread. But the points they make sound plausible. Hope it works for you. Let us know how it does.

 paulmars 03-07-2013 10:59 AM

I cant get any advice on which tigerloop to use. I cant afford a contractor.

 nealtw 03-07-2013 11:43 AM

It seems the TN would be the model, if all the numbers work. But they do make it clear, they do not want you to install it and that might be the reason you can't get any good suggestions.