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Oil boiler piping rebuild

mrtmills Member Posts: 3
I am converting an old large house in Canada into 2 apartments and want to use the existing CI radiators and boiler. I have a plumbing and heating guy that helps me but I wanted to seek some advice from this great forum.

1) Oil boiler firebox looks in rough shape. Previous owners had no boiler protection and the old 2" black iron pipes along with CI radiators and 2 years vacancy on min temp probably did not help.

2) I want to add outdoor reset with boiler protection, manifold home run piping to every rad (one per room, all piped directly to accessible basement) and have each room individually zoned (not TRVs, I lock the thermostats out from tenant access). Preferably I would have some type of constant circulation with variable speed pump and wire the thermostats to the valves only.

3) Figuring out all the details on sizing pipes and pumps.

1) Attached is a picture of the inside of the firebox. From the sketch it appears as though there is only refractory liner on the target wall. The actual cylindrical firebox looks like it's wrapped in sheet steel and there are clearly holes right through the ceiling of it. The heat exchanger works fine and we ran the system multiple times before pulling the thing apart so the holes are only superficial - but what are they and what can be done to salvage this boiler? It is from 2002.

2) What procedure can I start to begin calculating the needed sizes of pipes and pumps? I assume I need to calculate heat loss per room as well as the BTU/hr output of the boiler? Also, calculating the power rating for the old CI rads.

That should be a good start. I don't have much experience with this but am eager to learn.

Thanks for your time today,
Nova Scotia, Canada


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,132
    There's not enough info in the pictures to really give you an idea if everything is ok, or will be ok with a proper cleaning, new gaskets, etc. I think a video would be better for reference.
    The inside of the chamber (pic 1) looks ok but dirty. I don't know what is going on in front on left side. Is that the front door panel or just more crud.
    The last pic, where are the holes in relation to the cleaning diagram in the other pic?
    The target wall (back) looks fine, even with the crack.
    I think home runs to every radiator is a bad idea. How is it piped now? I guess you could, but even with bypass protection you are going to have some short cycling. At best I would use trv's, break the system into 2 zones, and use thermostats in the basement with remote sensors in each apartment. Then the tenants can control heat in each room, but can't turn the heat on/off.
    You're probably going to need a buffer tank.
  • mrtmills
    mrtmills Member Posts: 3
    Hi Steve,
    Thanks for your suggestions, I appreciate it. The holes in the picture are on the ceiling of the firebox and my heating guy had a look yesterday and wasn't sure why there is a sheet metal liner on the walls and ceiling of the cylindrical firebox. It's hard to tell what is behind this thin layer of metal but we're assuming it's fine. Other than those holes everything else is just dirty.
    After your suggestion of a buffer tank I started researching and found many people are using them and I am now planning exactly that. I already pinned down a number of pressure vessels in a town nearby and will incorporate that into the system. I do plan to do micro zoning and constant circulation. The current piping was not something that would have been salvageable. Likely it never worked well. There was lots of evidence of pipe replacement due to freezing and I just don't like old stuff. A good landlord has to offer exceptional temperature control in every bedroom (electric heat makes this easy but is expensive) and my experience with another building running on traditional zones is that tenants are always messing with the radiators. On top of that I don't want them having any control of the temperature. I set it to 21-22C and that's it. On one of my electric buildings I put lock out thermostats on all the heaters and my yearly energy bill went from $10k down to $8k just like that. If they had control of the heat it would be set to 28C at all times with the windows open.
    The current plan is to use a tekmar 256 to control the buffer with outdoor reset. Constant circulation with variable speed and zone valves on every room. Anything less than fine control of each room and I would have to go to electric - most landlords seem to be doing this around here.
    Thanks a lot,
  • Scott M_2
    Scott M_2 Member Posts: 26
    Pictures aren't great but looks to me to be a dry based boiler that burned through.if so not a safe situation and forget a new chamber replace the boiler.If your going to dump that amount of money into th system an upgrade on the boiler should be included.
  • mrtmills
    mrtmills Member Posts: 3
    Thanks for the advice Scott. I just double checked and it is a wet base boiler. There is for some reason a sheet metal liner before you get to the heavy steel and this is what has a hole in it. The metal is maybe 24gauge, not sure why it's there. I am picking up the buffer tank in a few days and will post pictures to see what everybody thinks.