New boiler and indirect HW heater options

milkman

I'm in the process of getting estimates on replacing our 30 yr old oil boiler oil fired hot water heater with a new boiler and indirect WH system. Live in VT. House is 30 yr old, 2 story colonial 2,600 sq/ft. Two zones upstairs (1,300 sq/ft) and down stairs (1300 sq/ft). Current boiler is 175,000 BTU Peerless. My problem - I have 3 estimates that are all over the place w/ regard to what size boiler is recommended. One estimate is for 100,000 MBH 4 section Trio w/ Riello burner w/ 41 gal purepro IDWH ($); next estimate is for a Buderus G115 5-section 136 MBH w/ F5 Riello burner and 55 gal IBC BTI IDWH ($) and a New Yorker 3-pass 167 MBH w/ Beckett burner and 55 gal IBC BTI IDWH ($).

Never purchased a new boiler or HW heater before; all new to me. So,...couple questions. First - I'm assuming the MBHs quoted are the net IBR specs? Second - what is a reasonable size boiler for this size house? Third - do I need to consider any add'l MBH for the IDWH? I've asked a couple friends who have had boiler/ID system replacements and their general gouge for boiler size was 50% of your square footage (in my case, 130,000 MBH). Fourth question - do I need to consider a larger boiler for heating the IDWS? I'm assuming it will be zoned as part of the install and set up as priority zone. I like the Trio - there is a 5 stage P5 Trio with 133,000 net IBR. Thoughts on the Trio system? Is 130,000 MBH about the right size for the house? Do I need to consider additional MBH w/ the IDWH? Thanks.

Docfletcher

I'm not a pro... I'm a homeowner like you. But I'd like you to know here on the board the pros will not discuss pricing at all. They are sure to tell you to get a proper heat loss calculation for your home to help determine proper boiler size. Go to main site and use the find a contractor listed in your area. A heat loss calc is very important and the 1st thing to do. Welcome to the site, you can learn a lot here.

Erin Holohan Haskell

Thanks, @Docfletcher. And welcome, @milkman! Here are some tips for using the forum: https://heatinghelp.com/forum-user-manual

Jamie Hall

As the good @Docfletcher says -- the very first step is to get an accurate heat loss for the house. There is a nice on-line calculator for that provided by Slant/fin which you can use, but your contractor(s) should do their own and you can compare the two for giggles if nothing else.

Your friends' rule of thumb is quite useless -- no offence to them, but it is.

They don't do a heat loss? Forget them and find someone who will.

Once you have the heat loss you can -- or your contractor can -- determine what size boiler to use; you are comparing net BTUh output to your heat loss. Try to get reasonably close.

And getting a good contractor is essential -- the best boiler in the world won't perform well if the installation is botched.

milkman

Thanks. Good resource.