Oil fired water heater

[TPro]

Another water heater question.

I am looking at a house with an oil fired hot water heater. I have never had one of these before and it may need replacement. The flue is rusted away and the top of the water heater may be rusted enough as well that there may not be enough to attach the new flue.

Does anyone have any experience with these or have any suggestions?

I have not tried to price one yet. I suppose the pump attached to the side is still good as the water heater does work even though it appears to be allowing CO to escape into the house.

Replacing with gas is not an option.

Thanks,

Thomas

[LazyPup]

Oil fired water heaters are not commonly used in residential construction due to thier initial cost and the necessity to install an oil storage tank, however for structures that have oil heat or presently have an approved oil storage tank oil fired water heaters offer some very distinct advantages.

Water heaters have two recovery rate figures, the first hour rating and the second hour rating. The first hour rating determines how many gallons of hot water the unit can provide during the first hour of demand when considering the volume of hot water stored as well as the water ebing heated during the demand. The second hour rating defines how much hot water the unit can continually produce once the stored water has been consumed and it must heat all the water as it is required.

Understanding that tankless water heaters have no stored energy it then stands that they are by necessity all rated by the "2nd hour rating."

Typically a gas fired water heater should be able to produce a second hour rating equal to about 70% of the tank volume. This means a 50gal gas fired water heater can provide 35gal/hr under continous load.

Electric water heaters typically have a 2nd hour rating of approximately 60% of the tank volume thus a 50 gal electric should produce about 30Gal/hr under continuous load.

By contrast an oil fired water heater is capable of producing approximately 3 times its tank volume per hour thus a 30gal oil fired water heater has a 2nd hour rating of 102gal/hr.

AS you can see, while we are commonly installing one or sometimes two 50 or 60 gal gas or electric fired water heaters in new construction one 30 gal oil fired water heater would take up much less space and actually provide much more usable hot water per hour.

Due to there output capability Oil fired water heaters are commonly installed in larger multi-family (apartment) dwellings or in light commercial applications.

Because oil fired water heaters are primarily only used in commercial applications they are built to an extremely rugged standard and will normally provide a much longer service life if properly maintained.

The down side is that oil burners are much more complex than gas burners and they do require periodic maintenance by trained technicians.

[LazyPup]

Oil fired water heaters are not commonly used in residential construction due to thier initial cost and the necessity to install an oil storage tank, however for structures that have oil heat or presently have an approved oil storage tank oil fired water heaters offer some very distinct advantages.

Water heaters have two recovery rate figures, the first hour rating and the second hour rating. The first hour rating determines how many gallons of hot water the unit can provide during the first hour of demand when considering the volume of hot water stored as well as the water ebing heated during the demand. The second hour rating defines how much hot water the unit can continually produce once the stored water has been consumed and it must heat all the water as it is required.

Understanding that tankless water heaters have no stored energy it then stands that they are by necessity all rated by the "2nd hour rating."

Typically a gas fired water heater should be able to produce a second hour rating equal to about 70% of the tank volume. This means a 50gal gas fired water heater can provide 35gal/hr under continous load.

Electric water heaters typically have a 2nd hour rating of approximately 60% of the tank volume thus a 50 gal electric should produce about 30Gal/hr under continuous load.

By contrast an oil fired water heater is capable of producing approximately 3 times its tank volume per hour thus a 30gal oil fired water heater has a 2nd hour rating of 102gal/hr.

AS you can see, while we are commonly installing one or sometimes two 50 or 60 gal gas or electric fired water heaters in new construction one 30 gal oil fired water heater would take up much less space and actually provide much more usable hot water per hour.

Due to there output capability Oil fired water heaters are commonly installed in larger multi-family (apartment) dwellings or in light commercial applications.

Because oil fired water heaters are primarily only used in commercial applications they are built to an extremely rugged standard and will normally provide a much longer service life if properly maintained.

The down side is that oil burners are much more complex than gas burners and they do require periodic maintenance by trained technicians.

[TPro]

Thanks. After reading this and doing some pricing, I think in my case it will be worth it to keep the oil system even if the tank needs replacement.

The burner appears to be much newer than the tank and hasn't had a chance to be neglected.

[LazyPup]

Good Mornig Thomas;

After looking at your photo I would agree that the problem looks very unsightly but I doubt if it is nearly as bad as what you might think.

Normally whenever we see rust on the exterior of a water heater the first thing that comes to mind is the tank is leaking, but in the case of an oil fired burner such is not the case.

An electric water heater has no internal combustion so there is no associated flue gasses and Natural Gas is very closely regulated to insure the sulphur content of the fuel is absolutely minimal. Typically less than 0.3 grains of hydrogen sulfide per 100 cubic feet therefore the presence of sulphur-dioxide in the flue gasses is almost non-existant. Oil on the other hand has a much higher content of sulphur and one of the primary problems with oil combustion is the production of sulphur-dioxide (S02). There is also water vapor both present in the combustion gasses and in the air surrounding the flue piping which will condensate on the flue pipe as it cools. The water vapor, H20 will then combine with the sulphur-dioxide SO2 and form sulphuric acid H2SO4. While the actual percentage of suphuric acid in the flue gasses remains quite small, none-the-less in time it has a very corrosive effect on flue piping and in this case the light guage sheet metal external skin of the water heater.

I would definitely recommend you have the burner and flue piping inspected by a certified burner technician to insure the flue gassess are within the allowable parameters but I would not be overly concerned about the remaining service life of this water heater in general. I have seen many an oil fired water heater where the top skin is completely corroded away, yet the internal pressure vessel is fine and the tank continues to operate with no adverse problems for many years.

[TPro]

Thanks again. The inspector checked, I believe with a meter and wrote “Carbon Monoxide backdrafting into the living area”. He also noted Faulty TPRV and recommended replacement.

I will have another tech look at the situation. I was concerned that after removing the rusted out flue there would be nothing to fasten the new parts to but after seeing the construction of the water heater I see that while the flue is light sheet metal, where it attaches to the water heater is quite substantial.

The person that showed me the construction also recommended changing the anode rods as we agreed that this along with periodic draining has probably never been done. I’m not sure if I would try and remove the anode rods from this tank or not but it does sound like something to put on a schedule if and when the tank is replaced.

Would a small expansion tank be a worthwhile addition to this system?

Thanks,

Thomas