boiler system with cast iron radiators

MaryCharles

Hello everyone,

I have recently purchased a home built around 1850 in Vermont with a hot water boiler system most likely installed between 1930-1945 based on the design of the radiators. The first boiler was oil the current boiler is cord wood and we are looking to replace that with an oil boiler

I met with an HVAC contractor who suggested I replace everything including the radiators and pipes with slant fin baseboards and a high efficiency condensing boiler. His reason behind this is that I would have too much iron in the system to run a high efficiency ECM circulator.

I do not want to replace the radiators or the pipes if I don't need to. I also like to set back my thermostat to have a cooler house at night. He then suggested a PurePro Advantage oil fired boiler.

I would also like to know if it is advantageous to have a water tank to store thermal mass.

The house is getting new windows and will be completely insulated after which we will be get a heat loss calculation.

All advice and suggestions are appreciated.

Mary

STEVEusaPA

Get a new contractor if he wants you to rip out all the radiators.
Not a lot of acceptable choices for condensing oil boilers.
But a properly sized triple pass with outdoor reset, with near boiler piping to prevent condensing, or an Energy Kinetics boiler would be most efficient.
If you don't zone the system, you probably don't need storage. Unless you need an indirect for domestic hot water.
Properly sized boilers don't recovery quickly from deep set backs, so maybe TRV's to keep the bedrooms cooler might do the trick.

Jamie Hall

What @STEVEusaPA said. Just a matter of designing the piping and pumps right and sizing the new boiler properly, but that is absolutely critical. Whoever does your work do a heat loss calculation on the house!

ECM pumps on the old iron aren't a problem, though you should have filters and a magnetic separator. And a larger than normal expansion tank. But a good man will know all about that.

Permit me to say a word about windows. It is likely that windows from that era aren't worth saving, although replacement windows aren't going to be cheap. Again, do your homework and get good ones. Those have lasted well; you want the new ones to last, too.

GroundUp

Lack of being able to use a certain circulator was grounds to charge tens of thousands of dollars for a whole new system huh? I'd be for losing that guy's number like yesterday.

psb75

Permit me to say that windows from that era are very likely to be worth saving. They made windows very well back then. They can be thoroughly reconditioned by someone who knows what they are doing, and made to function and LOOK like they did originally. Will the next windows you are putting in last 170 years?
Why are we talking about windows here? Well it IS a heating forum after all.

Jamie Hall

psb75 said:

Permit me to say that windows from that era are very likely to be worth saving. They made windows very well back then. They can be thoroughly reconditioned by someone who knows what they are doing, and made to function and LOOK like they did originally. Will the next windows you are putting in last 170 years?
Why are we talking about windows here? Well it IS a heating forum after all.

I think the OP said 1930 to 1945 -- not 1830 to 1845! And I quite agree -- if it's 1830 to 1845, hang onto the original windows. Easy to recondition, and there are superb storm window arrangements to upgrade the thermal performance without fuss or damage or visual distraction. Which are a good deal cheaper than new windows...

psb75

Respectfully, the OP said "house built around 1850". The math says: 2020-1850 = 170 years for the windows... perhaps. Not the heating system.

Jamie Hall

psb75 said:

Respectfully, the OP said "house built around 1850". The math says: 2020-1850 = 170 years for the windows... perhaps. Not the heating system.

So they did. I misread. So -- if those windows are original, as we have both said, much better to refurbish them (it's not hard) and use storm windows built for the purpose (I use windows from https://stormwindows.com/ in my restoration work, but there are other similar products). The end result will be as good or better than even the best modern replacement windows.

MaryCharles

Thank you for the comments. I mentioned windows and insulation as in all my research that seems to be a question I get when asking about replacing the boiler.

MaryCharles

The house is from around 1850 the boiler/radiator system is from around 1940.

Jamie Hall

There is a point here about windows and insulation. Unlike steam heat, hot water heat boilers (which is what we are talking about) need to be sized closely to the actual heat loss of the structure, rather than to the installed radiation. Something which a lot of contractors miss.

Therefore, since you are talking hot water heat, you need to determine (or have a useful contractor determine!) the actual heat loss of the house. This, of course, is strongly affected by how much insulation and storm windows (the ones I mentioned above are equivalent to a modern double pane, high end window for calculation) -- so the windows and insulation and boiler size interact with each other.

My experience with insulation in a house from 1850 is, to put it mildly, mixed. If your work involves gutting the house -- tearing out all the interior material on the outside walls -- you can usually do a moderately decent job of insulating, although you may find that the walls are thinner than you might like. This depends very much on exactly how the house was built -- post and beam is likely to have thin walls and be rather difficult to get good insulation numbers on. If you intend to retain the interior finish of the exterior walls -- if, for instance, it is high quality plaster on lathe -- it may be very difficult or nearly impossible to effectively insulate the exterior walls, depending on exactly how it was framed -- which may be, in turn, very difficult to impossible to determine! All is not lost, however. While you won't get up to modern R values, a high quality plaster on lathe wall on studs, with sheathing (typically true one inch) and siding, has a usable R value of around 5 or 6. Since the wall is likely thin (4 inch true would be relatively thick!) you might get it up to R 10 with blown in -- but your might not, too. Is the lack of insulation a catastrophe? No. Granted, it will cost more to heat -- but often not enough more to warrant the other hassles. It's a tough call.

Roof or attic is a different story. Usually you can get at it fairly easily, and it's worth insulating the dickens out of it. Just make sure that there is some ventilation to prevent moisture problems.

It's very much worth sealing up all the possible draught locations -- particularly in the basement! Expanding foam and a windy day... !

For what it's worth, here's a handy table of R values...
https://inspectapedia.com/insulation/Insulation-Values-Table.php
(minor note: the value for storm windows is obsolete -- modern ones are much better)

JohnNY

High efficiency boilers don't run efficiently when used with baseboard radiators because they need hotter water than big cast iron radiators to create convection. The demand for hotter water negates any efficiency gains.
Definitely need a new contractor.

Erin Holohan Haskell

@MaryCharles, can you please share photos of your system and radiators? Thanks!

MaryCharles

@Erin Holohan Haskell Sorry I am unable to post pictures currently as I am away from the area.