Converting central boiler to furnaces (75 unit property)

7 Replies

I am evaluating a 75 unit apartment complex (2 buildings) with 2 boilers that heat the units. The owners currently pays gas bills and the expenses are very high. I am considering converting the units to individual furnaces to reduce the expenses and remove the boiler. That said, I am trying to determine how much to assume per unit going from a central boiler to furnaces, including the duct work, for +/-75 units. Thank you 

now that's a loaded question a lot has to do with how the units are constructed, is there room for new furnaces in each unit etc... the furnaces themselves are the easy part to figure out the cost the hard part is figuring out where they fit and to give you a dollar figure without seeing it would be just a total guestimate. we have done plenty of conversions in the Chicagoland area and never had the price been the same some have been $5500 a unit some a little higher

Jerry    

HI Brad,

As Jerry mentioned this is a loaded question and pretty difficult to estimate, but I would like to add a few comments for you to consider.

When replacing a central boiler system with new individual units there could be other substantial cost impacts to consider outside of just the furnace units themselves.  To name a few:

  1. Wall modification and drywall patching for new ductwork locations
  2. Floor plan modification - You will need to build-out of mechanical closets to house the furnaces for each unit which will alter the floor plan
  3. A/C - Not sure what the existing cooling system is, but the new heating system could effect the cooling system
  4. Electrical - May need new electrical panels to accommodate the furnace load, & wiring to power the new furnace units

With that said, I think this could easily cost over $5,500 a unit when you consider these additional scopes of work.

I would highly recommend getting in touch with a local HVAC contractor who can provide some insight on the construction considerations & costs as apart of your due diligence.

It may be worth it to look into boiler replacement.  There are such things as 90%+ efficient boilers.  Some even rate at 98%.  If the boilers in your units are older, say pre-90s, the payback on the replacement could be relatively quick.

Quick, dirty math here, but $5-10k per unit wouldn't be unreasonable.  You would have to do all of the units that are fed by the same boiler, or you will still need to run your boiler.  So assume 40 are fed by one boiler, you'd be looking at $200-400k.  I would think you'd not only need to add ductwork to a space that presumably doesn't have any, but also run electrical circuits the new unit.  A boiler replacement could be had for a fraction of that.  Payback could be as quick as ten years with a service life far greater than that.

With that being said and knowing nothing of your system, you could do different things as well.  You could convert your boiler system to solar hot water which would pay back incredibly fast.  You might also look into variable refrigerant flow (VRF) if you want to add individual heat and cooling to the units as well.  VRF would likely require electrical upgrades.

More details (steam or hot water boiler, mechanical space in units, etc...) would give us a better idea of how to offer guidance.

My suggestion, talk to a reputable commercial mechanical contractor (or three) and have them propose to you options that list payback durations.  I don't think if I were in your shoes, that I could make a case for adding a ducted system.  I'd be happy to look things over for you as well.  That is the world I live in.

Brad, 

As is mentioned above there's alot of other variables to consider to give you a good answer. What is the existing heating system, what is the existing cooling system in place. If you have steam radiators and you want to put a new combination hot water heater/boiler in every unit, you also need to remove the steam radiators and put in hot water radiators. with the combo unit now you need to remove the hot water heaters from each space or is it fed from a centralized plant. If you're putting in new furnaces in every unit now you need to install a meter for every unit plus gas piping, plus intake/exhaust flue. 

Why not just replace the existing boilers with high efficiency units and split up the gas utility between all your tenants. 

How about mini-split systems for each unit? That would lessen the ductwork requirement; but then each unit would not be gas fired (at least I have not seen any mini-split where gas is the fuel for the backup heat).

check on the VRF systems that are high efficient and gives you the ability to charge tenants through submeters as well.more expensive than traditional HVAC but for that many units i thing would be worth looking in to it.http://news.mehvac.com/WhitePapers/Multifamily+White+Paper.pdf