GFI for boiler in an outbuilding?

If it's a dedicated outlet, then no. Gfi's are to protect people , not equipment. If you needed it for an inspection, just swap it out for a receptacle that only one plug can be plugged into. This would meet the code requirement.
I would definitely get ri of the GFI in that application.

Sorry to hear you had a GFI caused problem. Another good example is that the outlet for the kitchen refrigerator is not to be a GFI. To many times folks have lost the frig's content due to a trip.

I've seen a lot of GFIs in recent years that are prone to false trips; I don't recall seeing this with earlier GFIs; my only explanation is that with more and more of these things being assembled wherever is cheapest, the QC has seemingly gone to heck.

i had the ome in my animal barn stop working. idid replace it with an other gfi. my green wood is hard wired to the the fuse panel. dedicated circut.

Heck yes take out that GFI , the other thing is look for a UPS that can handle the load of the GW ,pump, blower , and whatever else it needs to run. Size the ups so it can keep the whole deal going for a couple of hours and you will be much safer in a power outage.

I would not recommend using a GFI on a dedicated outlet with anything that has a motor. I used one for my whirlpool tub, and it kept tripping when the pump was on for a few minutes.

When I hooked up my Econoburn 150 in Minnesota I asked the electrician to install a plug in so if there was an outage I could just plug into a generator. He said he would be required by code to install a GFI. He said if it was his he would wire it direct on own circuit which I did.

GFI's outlets, GFI breakers and regular breakers in your panel can wear out after repeated tripping. GFI's can be a pain around motors. They are good for protecting current to ground, generally required within 6 feet of wet areas, sinks, tubs, showers, garage areas where you could have standing water from a wet vehicle, decks, greenhouses etc.
For power outages, make a short extension cord that has 2 male plugs on it. Plug one end into outlet on wood stove and the other into generator. Just remember to shut off the breaker in the panel that the stove is on so you don't have a back feed situation.

I think the double male idea is very dangerous situation for a lineman working on the same line as your house. It can back feed back into the utility line. Chances of that happening are slim, but I wouldnt do it.

My Dad just failed his electrical inspection for his boiler- similar situation, dedicated outlet for a condensate pump. He was told it had to be GFI. I disagree, I don't think this is the intention of the electrical code, especially when the outlet is dedicated for equipment usage. I am going to go change it though & get him through the inspection. The inspector did not quote the section of code that he failed him on, now I have look into this.

Dedicated equipment outlet (for a refrigerator, sump pump, etc) does not need to be a GFCI but does need to be a single outlet (only one place to plug in a cord in the receptacle). But if your local inspector wants it otherwise, get past the inspection and then make it work.

That was the premise I had in mind when I installed the single outlet for his condensate pump, and there are GFI protected receptacles in the vicinity, but I will make the change. I'm guessing the inspectors logic is that someone could unplug the pump, and use the receptacle for something else and not be protected. I'm more concerned about what happened to Jimbo.