Mothballing an oil-fired hot-water boiler

DCContrarian

I fired up a boiler today that had been sitting for four years. When it was shut down, the water had been drained out and the fuel tank had been drained. I filled it and purged the air, and put five gallons of fuel in the tank. It started right up. The circulator had stuck in place, I popped the cover and spun the rotor and it started working fine. The house heated up.

My question is, what is the best practice for a situation like this? Is it better to drain the water, or fill the system with antifreeze? Should the tank be left empty, full, or with enough that the pump doesn't need priming? Other thoughts?

Jamie Hall

You ask six different people you will get twelve different answers, and the only common denominator is "it depends".

In my opinion, there are kind of two extremes. One is that the structure is in a location which can freeze, and you are reasonably certain that it will be unoccupied for several years to decades. Then I'd drain the system completely — and go around it with an eagle eye looking for odd bits of pipe which won't drain. I'd probably fill the oil tank as close to the top as I could — but with every expectation that the oil will have to be removed and replaced with clean oil when the system is reactivated.

The other is that the structure may be reoccupied within a few years. In that situation, if freezing is a possibility, I'd fill the system with a suitable glycol/water mix and run it long enough to thoroughly deaerate it. I'd fill the fuel tank as above, using a standard diesel conditioner and stabilizer in the quantity recommended.

Others will have different options!

HVACNUT

What situation, sitting dormant? Is this an unoccupied space? We make machines to work. If they don't work, they stop working. (Is that a Yogi-ism?)

Are you looking to semi permanently winterize?

The more fuel in the tank, the less room for condensation to form. But treat the fuel as well.

Is antifreeze necessary? If its gonna be another 4 years, winterize. What's the design day temperature by you?

Humidity control.

EdTheHeaterMan

I had a customer in Cape May Point New Jersey. The sisters of Saint Joseph operated a retreat house that was only occupied during the summer months. There was no heat in the building. There is a 1000 gallon domestic hot water tank that was heated by a tube in Shell heat exchanger heat exchanger, that was connected to an oil fired boiler. Every September a plumber would drain every pipe in the building and remove the water from the boiler. There was a 1000 gallon fuel tank that was sort of above ground tucked under a porch.

in the 20+ years that I took care of that oil burner, nothing was done to the oil tank. If it had a quarter tank at the end of the season, there was a quarter tank all winter. Eventually, the oil tank failed. The tank was drained of oil and abandoned under the porch. A new 275 gallon tank was installed under a different porch. It’s about 20 years old now and it is still in use.

I can tell you now that the oil fired boiler was not original to the building, so I believe that draining the boiler every winter and refilling it every spring, probably led to an early retirement.

so even though this particular boiler was mothballed annually, I still believe that draining the boiler was a better idea than trying to maintain antifreeze in that small closed loop system between the heat exchanger and the boiler. Since you got to drain the entire building of potable water Might as well remove it out of the boiler also.

EdTheHeaterMan

as far as keeping a fuel tank full of a potential hazardous waste, for several years, in order to reduce condensation: I believe that is not the best idea. This assumes that the vacant or unused building and fuel tank may go unobserved for weeks at a time. And a small leak can grow into a disaster very easily under those conditions.

Part of the recommissioning process should include inspecting the fuel tank and removing any sludge, debris, and inspecting for potential leaks, before refilling the tank. An empty tank cannot leak hazardous waste.

DCContrarian

https://forum.heatinghelp.com/discussion/comment/1802048#Comment_1802048

That's my thinking. This particular house has a sump pump in the basement, if the tank were to leak it would be pumped all over the yard.

EdTheHeaterMan

i just got this great idea. Get a big balloon and put it in one of the tank's top tappings. Then inflate the balloon with dry nitrogen. Every month of so go back and add more nitrogen to keep it inflated. If any moisture does happen, the dry nitrogen will absorb the it before the moisture can condense, When you want to recommission the tank, let the air out of the balloon and withdraw it from the tank. The only thing that will be left in the tank is what was in it when the balloon was introduced.

If you want to avoid the monthly inspection, then set the Nitrogen tank regulator to less than 1/2 PSI and just check the nitrogen tank twice a year. @ethicalpaul loves to experiment, and make videos. This could be a long term production.

ethicalpaul

That video is too boring for even me to make!