So the electric boiler was in addition to the fuel oil boiler you had? Did the new boiler work when it was warmer outside?

The new boiler could be faulty, I've installed a lot of boilers without issue but the one for my own garage doesn't work as it should. It's plenty big enough but it will never modulate down, always runs at 100% and can't get the water temp over 120, which works for in floor. It keeps the space at temp but runs more than it should, but gas is free so it doesn't matter. I can get it to modulate by slowing pumps down but that throws my delta T way out of whack. I've had the rep there running diagnostics, replaced gas valve, talked to factory, no resolution, it just doesn't do what it should. They hooked my up with there newer model but it's still sitting in the crate. I'm glad it was mine & not a customers but average person wouldn't know since space temp is satisfied.

The installers are back working on it. The exhaust pipe is to small according to the manufacturer. They are also moving the pump from the return side to the supply side. Will see if any of it helps.

So they got it running on all cylinders?

What was wrong?

Is your house well insulated?

With a high of 8 degrees today and 30 mph S wind and all thermostat set at 72 and the highest the house got was 67 degrees.

They know there's a problem, they just don't know what to do.

The house was built in 1974. We put new windows in 10 yrs ago and they put in blow in insulation. The Fuel oil boiler had no problem keeping up on the coldest days. It could be 20 below zero, with a 30 mph wind and it still kept the house at 70 degrees. They know there's a problem, they just dont know what to do to fix it.