Were the thermostats replaced or recommissioned with the boiler? That cycle might take some time even if the heating portion is very short. In that case, your boiler might cycle something like: pre-warm exhaust air or fan startup cycle heat exhaust fan spindown. I've seen older mercury thermostats fail in 'call for heat mode'. I think rather than suspect that boiler oversizing is crushing your efficiency, I would look into improper setup or possibly some defective thermostats. I would think that if your controls were correct, you could make this boiler size (30 - nominal 150) work.
Looking very briefly at your model, it looks like it has a significant turndown capacity to 30 MBH.
Crude calculators typically over estimate so that's more confirmation of Dana's intuition rather than saying you need 95k btus. I used an exceptionally crude (and quick) calculator on for your house size and came up with 95k btus.
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I don't think you should expect anyone to do that for free online as it takes some time to catalog and enter all the components like windows etc. In my area, this service runs $400+ depending on house size etc. Check out:Īlternatively, you could look for a local energy modeler (better IMO than a HVAC guy) who performs Manual J. At the minimum, you'll be better educated about what a load calculation looks like.
As for room to room loads, I don't believe these will help but if you have a good whole house load, that's a start. I have not used the second but it looks like a shorthand J that should give you an idea. I've used the first and compared it to a professional Manual J with satisfactory comparison. Here are two self-help resources that might help you. I think you'll need to do more detailed calculations on your own or hire someone to do a Manual J (which should have been done before the equipment swap out).
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