What size boiler

I did 2 heat loss cal's and came up with 17,000 (tenant),38,000 (main apt).What size hot water boilers would be best size.Want conventional,cast iron will use with BB hot water heat. Where can I get a small boiler for the 17,000.

Some of the higher tech jobs use a modulating burner, but I've not see any cast iron ones that small.

If you use the boiler to fire an indirect water heater, you might want a bigger boiler to get the recovery rate, but that means keeping the boiler on all summer. Not a huge deal if it is one of the newest designs that only has a very small internal capacity, though.

First off: what fuel are you planning to use?

If it's gas then lots of folks appear to be going to the high efficiency unit with modulating burners and stainless steel heat exchangers. Of course you may be making a very sound economic decision to go with a cast iron boiler for the small heat load. In other words, if you aren't using much heat it is tough to save enough money to pay for a higher efficiency boiler.

It looks like New Yorker has some small output units. You'll want to look at boiler output rating and not input requirements.

If your looking at oil, I have no clue.

For the small unit, maybe just a water heater would do? Sounds like an opportunity for radiant rather than BB heat.

To make a long story short, what ever you buy will eventually need service. Make sure that someone local is familar with the brand. Maybe get bids from a few HVAC guys to see what the locals think and do?

I would be using Gas as the fuel.I have thought of using a domestic water heater but the temp output is way to low.I need temp of around 180 not 130-140.Any ideas of a water heater that has a high temp output.

While some people use WH for domestic heating, I don't like the idea. Unless you have a heat exchanger, you've got a long pipe of potentially stagnent water sitting in the pipes, especially in the summer when you bypass the heating circuit. That, and the fact that WH aren't really designed for continuous operation make it a poor choice for household heating.

I've heard both good and bad about the latest version of the Munchkin and the Munchpak. I put in a Buderous this winter and like it. Weil-Mclain and many others make modulating HE boilers, but none, at least in the small output category, yet qualify for the federal tax credits because they set the threshold quite high. I did qualify from the utility company for $1100 rebate for the boiler and indirect WH I installed, though, which helped. You may want to check your local utility company and see if they are offering any, and what brands and types qualify...this could save you some money.

Baseboards can be sized for lower temperature. As an alternative, in-floor or in-wall radiant heat uses lower water temperatures.