Gas burners on oil boilers

Glen

I have cast my eyeballs on it - not yet available. And would prefer to tune a few before I move away from the standard vitola. It is intriguing ...

Rocky_3

Trying to decide which way to go...

Have a customer who appoached me today regarding swapping out some old oil boilers with new gas boilers. This is a medical/dental building with 4 separate boiler rooms with two boilers in each room, for a total of 8 boilers. Each set of boilers feed an air handling system. No baseboard or rads, nada, zip, zilch, only fan coil units. Am trying to decide whether to use a Vitola Biferal so that I may fuel swap in the future by replacing the burners, or, go with a mod/con gas boiler like the Ultra or Lochinvar or something along those lines. The reason is we do not have a main gas line feeding Fairbanks. The local gas company trucks the gas up in tanker trucks from Anchorage and then re-gassifies it and injects it into the gas infrastructure feeding the town. The gas company had some difficulty recently in obtaining a long-term contract with a gas supplier and is now basically having to buy it from whomever will sell it to them, at whatever rate they quote. Needless to say, has is starting to get a bit expensive now at $2.13/therm, the equivalent of about $2.94 cents-per-gallon heating oil. Now, eventually, we will have a gas line from Prudhoe Bay oil fields, but Lord knows how long that will be. Gas company swears they are in the process of obtaining better contracts which should drop prices down to previous rates of about 1.65/therm, but I think behind the scenes they are really scrambling to find another supplier. I am trying to make the best decision for my customer. If I put in VB boilers with oil burners now (because oil is about $2.35/gallon), I could swap the burners out for gas later in life if gas truly does come down to a reasonable rate. Or, I could install some mod/cons now and hopefully take advantage of some operational efficiency gains from modulation to offset the higher gas prices. With this being strictly fan coil heat, where the boiler temps will be relatively high all the time, what way would you guys suggest I go? Any help or suggestions would be really appreciated as I could see it "six one way, and half-a-dozen" another. Bear in mind, Fairbanks has on the order of 14,000 degree days per year, so these boilers tend to run rather hard and often.

Warm regards from not-so-chilly Fairbanks,
Rocky

Steamhead (in transit)

With such high-temp water

the mod-con has less of an advantage. I'd opt for fuel flexibility, especially in a medical facility like that one. That way they can burn whatever is cheaper per BTU, or whatever is available.

Not sure what size these boilers have to be, but you can get the same fuel flexibility from other boiler brands too, even down to the small residential sizes. The Solaia and the Smith 8 series are two of the latter, though on these one has to change the complete burner assembly to switch fuels. .

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Glen

Dual fuel - ???

then the Vitola is probably the most well adapted boiler you can use. In my travels in the Canadian artic - the vitola is king - with the Riello burner - both oil and gas. I do not think a mod/con will fit your needs with any sort of efficiency that you would expect - your heating needs and temps would place a strain on their capabilities. Also consider the vitorond - with a dual fuel Weishaupt burner.

Weezbo

say Glen...

do you have any thoughts or crystal ball visions on the Vitola add on for condensing oil?

any murmur of that idea in Canada?

The Wire Nut

Hmmm...

I guess I have a couple of questions...

For one, is there a reason that all these boilers are on different loops? In other words, is tenant metering going on or was the hydro-air arrangement the simplest way to do it? The reason I ask is that you could potentially bump fuel efficiency nicely by tying all those boilers into a loop and stage-firing them.

That way, you get most of the benefits of modulation without having to resort to using gas exclusively. BTU metering by office is still an option even using this approach, there are some dedicated devices for that (measuring flow, and ΔT to derive BTU's "consumed" by unit).

If they have to remain separate and you want to consider mod-cons, I'd clock the system on a design day and see what the lowest possible return water temperature can be. That is, would super-hot water be required for the fan coils or can the return temperature drop to the point (even on a design day) where the mod con not only reaches its effciency potential but also manages to heat the building?

Anyway, I'd investigate the staged system first, since it would give you the widest range of boiler possibilities. Besides the upside re: efficiency, the client might be sold on the concept based on reliability. Chances are, 8 boilers working in parallel will have a better time ensuring that all parts of the building are warm than 1 boiler per fan coil.

Plus, you can run hybrid fuel systems with this kind of rig also... some oil, some NG, and give the owner the possibility of switching the controller back and forth re: what fuel to favor (based on local prices). A hybrid system would also bump reliability since you now have multiple fuels to rely on.

Lastly, a boiler like the Vitola that is rated/approved for either type of fuel is the way I would go. It CYA in case something goes wrong and is an efficient solution to boot. With the low return water temperatures that Ms. Vitola gets to play with here, we achieve 89.7% AFUE (allegedly). Your rigs will probably run a bit hotter, but considering the location, that may not be such a bad thing!

Rocky_3

There are 4 separate air handlers

Building has been added on to in the past and it is not really integrated. Each quadrant of the building is served by its own air handling system/fan coil. There are four mechanical rooms, each having two boilers and a fan/coil unit. These rooms are pretty spread out and I think it would be difficult to tie all of them together. Also, there is no where to place 8 boilers in a single room due to space constraints. I am leaning more towards the VB as I think it will deliver more of what I am looking for in efficiency, ease of fuel swapping, serviceablility, longevity.

regards,
Rocky