Commercial Boiler replacement

More than $10K, but less than $250K. That doesn't help you at all, does it. No pricing means just that.

We would need to know more about the job in order to tell you what to watch out for. Take plenty of pictures of the old boiler, piping and any zone valves; expansion tank, indirect water heater?, etc. And ask lots of questions, like what's wrong with the existing boiler.

Radiators or radiant? You may need boiler protection if it's radiant. Plenty of make-up air? Is the exhaust in good shape? Correct size gas pipe? Do you have to drain the whole system to replace the boiler. Purging air problems?

Scaling up for a big job if you're used to smaller work means new tools to handle bigger pipe. Lots of things to consider, no?

I can imagine the owner and the tenants not wanting you rummaging through the apartments to do a heat loss.

A radiation survey would get you close. I agree with @Steamhead the boiler should be the right size but in an apartment building is difficult without cooperation.

Wouldn't it be nice if there was an easy formula for pricing boilers, Like $1.23 per BTU, but it doesn't work out that way as I recall. Where are you located and what does does the competition bid on a job like this? You should be able to just call them and ask, right? That doesn't usually work either. Have you asked AI for that info? I just asked Alexa and she said "it depends". She is smarter that you think. She doesn't want to get in trouble for giving you bad info.

Hope this helps!

And one more thought! how do you know that the 40 year old boiler was the correct size for the building. back then a lot of mechanical engineers went with the Bigger is Better sizing guide so they didn't get a law suit for undersizing the boiler. Besides they didn't have to pay the fuel bill of being inefficient, and they DID get paid for making the system oversized.

I remember that pricing system @EBEBRATT-Ed when I started to price jobs. That was a ballpark price not one that I would bank on though. I got burnt on a job pricing that way.

I was told ions ago all equipment and materials x 3 and you will be able to do the job properly and possibly pay yourself a little . On a side note being a low baller will help no one when you did not make any money you usually do not return being you have a bitter taste like working for nothing . Which none of us like to do . As of lately that x 3 rules means nothing being the public utilities are charging way more but got to remember zero financing which leaves little guy like me outta the picture .

In these times x3 really isn't being greedy if your doing everything on the up an up unless ya skip a couple of steps you should be able to eat and lets not forget your business expenses and all the cost that your customers pay ya just ta get ya there . All that being said maybe ya like to make no money and work for free it certainly ain t me thats for sure .

clammy

I'm sure the leases for those apartments specify that management has to have access for maintenance and repair work. Normally they have to give a certain amount of notice for this. Check with management and local laws.

You can probably do a block HL from outside the building and get close enough.

Speaking as home owner that has had a steel compression tank for the last eleven years that has performed flawlessly to maintain the point of no pressure change on a single loop heating system they work very well.

If the each of the 18 apartments are 300 square feet they must be single rooms?

Is the boiler leaking? when was the boiler serviced last and the burners cleaned?

Does the single circulator have isolation flanges to prevent water loss in the event of a circulator failure. If it has isolation flanges do these isolation flanges have gauge ports for pressure and vacuum gauges?

Does the existing boiler have an immersed low water cut switch or pair of immersed low water cut off switches to comply with plumbing code?

Do not remove the steel compression tanks, the steel compression tanks have been sized for your both boilers volume and the heating systems total volume and they have been doing their job silently for 40 years.

If anything adding one or two more of these identical or larger steel compression tanks will only help the building owner as the amount of thermal mass will increase and aid in heating the building more efficiently in my opinion. Bell & Gossett describes how 4 or more steel compression tanks can be plumbed successfully if there is less head room above the boiler.

Replacing the existing boiler with three boilers will only complicate matters for the owner and you and require more plumbing to complete the installation.

If the steel compression tanks have been properly plumbed there is a single Internal Air separator that is feeding an upward sloped feeder pipe to the two steel compression tanks which have a Tee connected to the first steel compression tank that is either connected to the base of the first tank with an airtrol fitting an elbow that allows the system to be vented while it is being filled with a drain-o-tank valve and also allows any air bubbles in the system to be trapped in the air blanket in the upper third of the compression tank.

The second steel compression tank will terminate in an elbow and a riser to the rear of the tank where it has an airtrol fitting or an elbow and a drain-o-tank fitting in the base of the tank to drain excess water out of the steel compression tank to create the correct amount of pressure change for the system to operate properly.

If there is more room in the mechanical room adding a buffer tank would be even more advantageous as it would add much more thermal mass to the system and would allow the boiler to tun less as the cool water would return to the buffer tank and the boiler would run less often as the feed water to the boiler sump would be warmer and require less heat energy to bring it up to temperature.

Speaking again as a homeowner adding a smaller second boiler and a buffer tank as a backup boiler with additional hot water storage and 2 or more steel compression tanks would be the better option as it would allow the small boiler to work by the larger boiler with separate valving and piping if the other boiler is leaking and must be replaced.

OK, so an older apartment building in Pittsburgh area, maybe 14,000 sq ft with hallways/lobbies added in? Could be under 20 BTU/hr/sq ft if not terribly leaky. So 280MBH total?

Still doable with 2 x 150MBH output boilers, or 3 x 100MBH output. You will get somewhat better overall efficiency with 3 smaller boilers vs 2 larger. If the owner is willing to pay for 3 smaller, that may be the way to go.

If you go with a cast iron boiler you'll also need return water temp protection/bypass with that high water volume system to prevent flue gas condensation. The single zone for a large building means you will be flooding a relatively small boiler with a massive volume of cold water on cold starts.

Does the existing boiler also provide domestic hot water?

Do you have any idea how much gas the boiler burns per season?

That diagram makes more sense to me than the ones I remember from the seventies.