Question on 2 pipe oil system

MikeC555

I agreed to help a friend by teaching him how to clean his boiler; a Weil Mclain Gold with top breech and swing door for oil burner (Beckett). I have always had single line, gravity feed in my homes and this was the first time I'd encountered a 2 pipe system. First thing I notice is the burner is plumbed with copper lines, which must be disconnected to allow door to open. No sign of a shut off valve anywhere (except the fireomatic just before burner mounted filter). We tried disconnecting each line from burner with my hope that only what was in the line would drain and instead it appeared that siphoning was ocurring. The tank is outside, a short distance and is above the basement floor level (so gravity feed would work). I read a couple of threads where others have experienced this problem of no shut off and it seems there is no easy solution. The easiest would appear to be disconnecting the union present in each copper line that is about a foot or so from top of tank outside (the tank is 3/4 full). The lines come out of top of tank through a duplex bushing.

At this point, I think shut off valves are in order. Are they needed for both lines? The one connecting to top of burner oil pump is, I assume, the supply line and the lower connection is the return. I assume the shut offs can be anywhere on the line (I would prefer to have them inside, near the boiler). This is also the time to install flex lines, so future servicing would be easier. Looking at oil flex lines, I see some that say 'for return line only', but I don't find any that specifically say 'can be used for supply line'. I'm confused… neither line is going to see much pressure. Do I need a special line for supply side?

One other question on the unions. The system uses what appears to be 1/2" OD copper pipe (I have yet to measure it). He will need to splice a shut off valve into the line and add a union for the flex hose. It's not clear to me what type/size fittings should be used. The splices in line up near the top of tank appear to be flare, though I haven't yet taken one apart yet.

It seems incredible to me that a system was installed with no means to easily shut off oil supply. Just to save a few bucks on shut off valves?

clammy

Flex oil supply lines are not really required to open a swing door ,when faces w that in the past i would usually just unbolt the fuel pump and pull it to the side . Personally when unable to to get the burner to operate as a single pipe due to hi vacuum or pump cavitation i would install a tiger loop no sense filter oil your not burning . All shutoffs should be a firematic type and as for shot off on returns thats a personal preference mainly because that if return line becomes clogged or restricted you have a better chance to damaging the pump seal and have it leak .The other issue as i see it is flame retention burner need a steady fuel supply that does not make the oil pump run in vacuum or cavitation due to air bubbles being formed which will result in flame variation and possible lock out of the burner ie flame sensor /cad cell . my other reason for my dislike of 2 pipe oil lines is a breakage or leak in the return line where as instead of returning to the tank it is leaking some where and possibly causing a environmental issue which shall be costly to get clean up ,also the fact that even a small a pump will flow close to 18 gallons a hours so if your burning 1gph your filter 17 that your not burning . also the fact that every above ground 275 on a 2 pipe always seems to water in the tank i gather from the rise in the fuel temp over time as it runs through the lines and back to the causing the inside of the tank to condensate . All oil line connections should be made if using copper is flare other wise steel or brass threaded using the proper oil rated pipe dope . As for oil filters spin on are the easiest to change and do have a higher micron filtration then a old style canister type but do not enable you to see if the evidence of moisture and how dirty the filter is the dirtier the filter the worse either the fuel is or the tank . a side note is when using a tiger loop ultra there been more then one call back due to vacuum leaks at there vacuum gauge connection i stop using them due to this issue .I just order a standard and add a vacuum gauge and a spin on filter . With a oil tank that has a history of being dirty i add a standard canister and spin on w a vacuum gauge prior to . A 2 pipe oil line system with a outdoor or non conditioned space tank which see below 20 temps in the winter will always be a single pipe tiger loop and may still depending on the oil quality need a anti gel or in very cold condition possibly burn kero which on some very low gpm burners may be the only way to prevent lock outs . I ve found this on mobile home oil fired hot air (miller )

peace and good luck clammy

MikeC555

Thanks, Clammy,

His 2 pipe system works fine and so he is reluctant to change that aspect (if it ain’t broke…). The shut off vavle(s) would not replace the existing fireomatioc shut off (just prior to oil filter), but be added upstream from the burner/filter. Since there are already unions on each line near the top of tank, this might be the most convenient place to install ball valves (is any particular type/brand ball valve recommended, they will be outside.).
as for the flex lines, since his boiler is in a rather confined space, it is important to make servicing as easy as possible. Members, can you recommend flex lines suitable for supply and return?

EBEBRATT-Ed

You can use flex lines. I personally would put a firomatic valve in the supply to shut the suction line and put a check valve in the return line. You should not put shut off valves in the return. If you use a ball valve use one with a WOG rating (water oil gas)

in most areas firomatics are required at the tank and at the burner in the supply.

SuperTech

I was taught that you can't put any firomatic valves on the return. I've run into the problem you described a few times. I pull the oil filter, and with the filter removed I run the burner for 30 seconds or a minute. I'll disconnect the solenoid valve so the burner can't fire up and in the process the oil pump will send any oil in the return line back to the tank. Then when I open the oil pump there will be no siphon because the return line is empty.

A check valve is the best solution, but this process works for me without having to alter the customers setup

MikeC555

Thanks for the comments. With the tank outdoors and lines coming out the top, I didn’t think a firomatic would be required or the best choice of shut off valve. A check valve in return line makes sense. Would you put this closer to burner or tank?