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How to cold start my furnace to avoid cracks? Oil, forced hot water.

LeonardLeonard Member Posts: 240
edited March 13 in Oil Heating
To avoid boiler cracks Is there a special way I need to start my house oil furnace from cold start, about 60 deg F. It's operating fine now , but I'm thinking if loose power from ice storm and it cools to 60 deg.
I'm thinking thermal shock/stress to it's cast iron during heat up.
In past I just turned it on, but now I'm wondering.

Forced hot water
60 year old National Sunray IV , boiler # 5-19A/O/OP , rated 128k BTU/hr 1.6 gal/hr
Has original burner, National -US model NB2-K2, firing rate .85-2.0 gal/hr, 1.1 gal/hr nozzle

Chimney is most 4 stories from cellar floor to top of it
Tankless coil in water jacket
Cast iron baseboards, 1ft tall .


  • newagedawnnewagedawn Member Posts: 406
    that boiler is a tank, it can handle it
  • lchmblchmb Member Posts: 2,682
    im sure after 60 years it's been cold a time or two.. I'd worry less on the old and start thinking down the road to new...
  • DennisDennis Member Posts: 84
    Boilers crack because either they are not installed correctly, they freeze up, or are fired with out water. On a few occasions burner techs who need a little extra money, might over fire the boiler to hasten its demise. Oil boilers are easy to crack by stepping the nozzle size above the rated firing rate. I will admit I did so on a boiler the customer refused to pay for. That was in my impetus youth now days I just foreclose on your house.
    Just do it, right.
  • HVACNUTHVACNUT Member Posts: 1,027
  • newagedawnnewagedawn Member Posts: 406
    beware of wolves in sheep clothing, dennis sounds like a real great guy,...not!!!! those of us that care about our reputations dont do anal things to our customers, thats why our businesses grow and people are happy to use us
  • LeonardLeonard Member Posts: 240
    edited March 15
    Was just that I remember dad saying to not add water to system unless circulator was running, to avoid thermal shock to boiler cast iron.

    Have run out of oil ~ 5 times in last 4-5 years and boiler cooled to ~ 70 deg F till I discovered it. Never froze, nozzle is 1.1GPH --- boiler rated at 0.8-2.0. Fire does not touch cast iron. Firebox hard ceramic insulation box is intact.

    LEAK.....Well that comes to next part of the story, think I've got a very small crack in boiler water jacket. ~3-5 years ago after I ran out of oil and boiler cooled to room temp ~ 75 degs. I heard a small water leak from fire box. Did not see any water, but had to be boiler water since there's nothing else pressurized in there. Got oil, fired it up, and no more squirt sound when it was hot.

    Had to add a little water now and then, Past few months seems to need water more often, maybe once a week. If I filled it to ~ 10-15 psi then it would bleed down and stabilize to ~ 3-5 psi.
    Top of tallest baseboard is only ~ 5.5 ft above gauge, so that pressure is enough to be sure it's always full of water. (Circulator is on outlet of boiler. )

    30 psi pressure only relief valve is OLD and leaks sometimes, plan on replacement in summer. I put a 5 gal bucket under it and water doesn't seem to be going there. Although some times it will fill with 4 gal water. But I'm loosing pressure even when it doesn't fill

    Ideas , comments. Can I just keep topping off the water? Or am I running into problems. Maybe oxygen in water rusting issues of baseboards? Copper piping to 1ft steel pipe into cast iron baseboards.
  • SuperTechSuperTech Member Posts: 251
    edited March 15
    Time to budget for a new boiler. You got your money's worth out of the old beast. A properly sized and installed boiler will provide you with significant energy savings and superior reliability.

    Oxygen from fresh fill water is the enemy of the hydronic system.
  • Big EdBig Ed Member Posts: 1,031
    If you have a brick chamber , you should candle it to dry out the moisture ... If not the moisture turning to steam will break the brick into crumbs .. The older National original came with a metal chamber , we changed them out years back ...The Sunray , I am not too sure ..It may be brick .... To candle a chamber , slowly fire the unit up on temperture by turning it on or off
    I have enough experience to know , that I dont know it all
  • DZoroDZoro Member Posts: 249
    FYI didn't know the site could have two of the same user names.
    I do not agree with the above Dennis. @Erin Holohan Haskell
  • Erin Holohan HaskellErin Holohan Haskell Member, Moderator, Administrator Posts: 544
    Dennis said:

    FYI didn't know the site could have two of the same user names.
    I do not agree with the above Dennis. @Erin Holohan Haskell

    I'm sorting out the multiple usernames situation. Dennis, please send me a private message via your Inbox here. Thanks!
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