WTGO-3 Options?

A new coil would have cost far less than your new water heater.

Heat your whole house to 70 degrees evenly with wood pellets and compare the cost.

I did it years ago with coal. All I got for the effort was a PO'ed wife because of all the coal dust/ash, parts of the house like a sweat box, and other areas good for cold storage of vegetables, and a lot for "cheap" bags of coal. That far outweighed the cost of comfort with oil.

My wife still remarks about "That Nasty Coal".

How many BTU's in a 40# bag of wood pellets/horse stall pellets?

139,000 BTU's in a 8+# gallon bucket of oil at $2.32 #2 oil.

I have no idea. Kitty Litter doesn't burn. Stall/wood pellets do. I don't burn them. My issue is humidity and cooling. Stall pellets don't keep me cool. If I need heat, I have 9 KW worth of heat strips Last year, I never used them. Its 81 degrees outside now and the humidity is 45%. If the humidity goes up much more, I'll shut the front door and turn on the AC.

Fresh Water: 8.33 # Per Gallon
#2 Fuel Oil: 7.2 # Per Gallon.

Anything below 140 degrees increases the chances of condensation exponentially.

120 degrees is less so than 100 degrees.

And makes the boiler get dirty much faster and harder to clean properly.

@rick in Alaska:
@mpking:

You make my brain hurt from thinking so hard.

The difference is a small volume water system on cold start and a large volume water system. A system with a WGO-4 and less than 10 gallons of series looped baseboard will heat up quickly and go above 140 degrees. The same boiler connected to a system full of large cast iron radiators that holds 50 gallons of water, will run below 140 degrees for far longer and condense.

How do I know. Well, I had a lot of customers that kept their heat on all winter set to 40 or 50 degrees (to "save" something). They had drive by caretakers. I knew that flowing water in a system won't freeze, so I set the "LO" as low as it would go and if the boiler went off, the circulator would run. Much like a cold start boiler. But with the thermostat set that low, the system temperature gets low, and when the burner comes on and starts pumping cold water into the return, the pumps never stop until the call is satisfied, and the boiler condenses until the return water gets to 140 degrees. That means that not until the water leaving the boiler is 160 degrees, the incoming return water is still below 140 degrees. You should have seen the filth in them.

ODR was even worse. Anytime the OAT only needed system temps below 140 degrees, they condense constantly.

The OP has a system with two floors of old cast iron radiators. That's the kiss of death on a cast iron boiler. And the building will be all uneven with the heat.

Some get all twisted by my avocation of 4 way Mixers with boiler protection control like the Taco "I" series mixer. Let that system run at whatever temperature at whatever it wants. Keep that boiler warm and toasty. No sweat. WTGO/WGO's are bomb proof. An "I" Series valve is a lot cheaper than a rotted out boiler because no one could be bothered to clean it properly every year.

I don't/didn't have to think of every reason when I saw something better when I saw it. Just that it was better.

Like Columbus sailing over the Horizon. Neither one of us fell off the edge of the earth.

Cold start a WTGO 3 boiler you will have gaskets leaking and also it a 3 section boiler that means it only has 2 flue passages. The front flue passage is very tight that only leave one other.
What's going to happen once the boiler goes cold for a while there will be any soot or scale that has formed on the cast iron to fall off blocking the flue passage sections.
Wait till next season when you call for heat you'll have back pressure from the boiler. Smoke, exhaust fumes etc.
Your better leaving the boiler at a warm temperature until it calls for heat. If you have a L8124A aqua stat I would go 120/180.
The boiler will stay at the lower temperature of 120 until it calls for heat. Then go up to the higher temperature of 180.
If its a L4081B you'll have to lower it yourself when you don't need the heat anymore. It might seem like a waste of oil but its better then wrecking your boiler or filling your house with smoke.

Two door American Standard Boiler with a Beckett.
Life was so much simpler then..............

Since the OP is not even using it, I would suggest leaving it as a warm start and just flipping the breaker until he needs to use it. I would not keep a boiler warm that I didn't use.

Ice, were you agreeing with me or disagreeing? I couldn't quite understand.

What's the difference cold start or off at the switch for the summer. No respectable Oil Burner Tech would ever tell a customer to shut the boiler off for the summer. That's a sure way for a smoke call in the fall.

You know the saying I can't see it from my house.
Like you said you can advise them but they will do what they want to do anyway. Every body has a different opinion.
The roof only leaks when it rains same thing applies to the boiler in the summer.

Unless you work for Petro than you are not permitted to work on equipment in the rain.

So you had two service technicians from two companies come out on Christmas day and you're worried about money?

You're screwed either way you go...my wife can freeze but, my cat and dog like the heat. I would do whatever it takes to keep them happy and warm.
9 degrees on Wednesday in New Jersey...
If you aren't going to run your boiler, your oil tank may start to condenses, water will accumulate at the bottom of the tank. Water will cause rust. Rust will cause problems...

What are these people doing?

"If they call you on the phone, they want to spend money".

If they had called me, there is no way that I wouldn't have left there without giving someone hot water, by some way or how. Who are these people working for? Their competition? Someone suggested a "Hybrid Water Heater" and hooked them up with someone to do it? This is what happens when you do all your shopping on with the Internet Supply Houses. I'd have trotted right down to my local wholesaler who I trade with. If he didn't have a coil on the shelf, he would have had one at a different store or picked up one for me. Or taken one out of a Weil-McLain boiler in the building. Or I picked up a electric and installed it. Unless the person is a PITA. In which case, I wish them Health, Happiness & Long Distance. And happy to be gone.

Too many variables here.