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how long to pressure?

I've got a new Burnham IN4 gas boiler installed recently, switched over from oil.

The new one matches my radiators better (we have about 200 sqft EDR on the radiators in the house, and the IN4 is rated 271. The old one was close to 500).

I've noticed that with the new boiler it takes longer for the system to reach pressure and cut off on the pressuretrol - almost an hour for pressure to move from 0.

I have one main - about 40 feet long - and it heats up to the end in around 5 minutes. After that it's all the radiators slowly heating up.

The old system got up to pressure in about 30 minutes (didn't time exactly) but this one seems to be taking it's time.

I checked the vents, and they all seem to be working - but a couple had some water in them. I think this is because the boiler still has not been skimmed - the installer promised to come back in 4 weeks (is this too long to wait to skim the boiler after a new install?)

I have three rads downstairs with Hoffman No. 40 valves, and three upstairs with Varivalves, set low.

I also noticed that the upstairs rads now get hot quicker than with the old system, and the downstairs slower - the opposite of how it was before.

The result is that downstairs stays cooler - and that's where the thermostat is, so upstairs gets much hotter than it used to with the same thermostat settings.

Sorry for the rant, but I guess my question really is: is the boiler taking a normal time to fill my rads and get up to pressure, or am I throwing a lot of unused heat up the chimney?


  • Jamie Hall
    Jamie Hall Member Posts: 22,877
    My system...

    which is much bigger, takes about the same.  Probably pretty normal...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • BobC
    BobC Member Posts: 5,470
    edited December 2010

    Your boiler old was over sized and it makes sense it's going to take a a smaller boiler  longer to come up to pressure. Are all the pipes in the basement insulated?

    Once the boiler gets skimmed you will have a better idea of how everything is working. In my opinion 4 weeks is a long time to wait for skimming, if the skim fitting is there you could always try it yourself. Do you know if the installer put any chemicals in the water?

    Your main is 40 ft long and probably a 2 inch ID pipe, maybe more. What kind of main vent do you have now? If it is 2" pipe it contains 0.87 cu ft besides what the header and boilers steam chest have. It's always best to vent the mains fast so a couple of Gorton #1's would do nicely but you can probably get a single Gorton #2 for 30% more than the two #1's and have a lot quicker venting. The #1's are good for 0.5cfm while the #2 is good for 1.7cfm, it's up to you.

    You could also use a variable vent on the downstairs radiators, a Hoffman 1a has a nice wide range and has an internal float, the Heat Timers can be faster but you don't want to vent a radiator too fast, again it's your choice. You might want to wait for the skimming before doing this if you think the water full of crud.
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • AlexR
    AlexR Member Posts: 61
    wanna trade?

    Wanna trade boilers?  Our house has an IN5 for about 200 sqft of radiators.  It cycles after 40 minutes or so.  Ideally you don't want any cycling on pressure- you want the boiler producing as much steam as the radiators condense and no more.  It sounds like your setup is pretty close to ideal so as long as the radiators are heating and the house warms up.
  • Mark N
    Mark N Member Posts: 1,115
    Burnham IN-4


    I also have an IN-4. I have 260sqft of radiators. My system never cycles on pressure. I keep my thermostat set to 70. The boiler kicks on when the tstat calls for heat and will run around 20 to 25 minutes. The better the output of the boiler is matched to your actual amount radiation the better the system runs.

  • conway
    conway Member Posts: 7

    Thanks, that's helpful!

    To answer your questions:

    No, the pipes are not insulated. But I have a finished basement, and I'm afraid if I insulate the pipes it would be cold there.

    The main is indeed 40 ft of 2-inch pipe, but I have no main vent. I looked all over, but it seems it was never there, and there's little place to put one - there are three risers at the very end of the main, right before it turns down to the wet return.

    Is it possible to put the main vent in right before the risers? Or would that cause problems?

    I'll look into getting the Hoffman 1As - the Heat-timer ones seem harder to get the adjustment right - and I already had one fail.

    I don't believe the installer put any chemicals in, but I'm not 100% sure. And I just checked last night, and the skimming connection is not opened. (i.e. on the sheet metal case of the boiler.) So I'm not sure how he's going to do the skim. I'd do it myself if the there was a connector or valve there.

    Is there a wrong way to skim a boiler? (I'm sure there is.) I'd like to know what he might attempt so I can tell him not to do it :)
  • conway
    conway Member Posts: 7

    Thanks guys, that makes sense.

    So I'm not as worried about it now that I know it's normal not to cycle on pressure.

    Now I guess I should re-balance the vents to make them all heat evenly.
  • BobC
    BobC Member Posts: 5,470
    venting, etc

    At the very least insulate all the steam pipes in the near vicinity of the boiler (header, and the attachment to the main.

    From you description your system main starts high above the boiler and gently slopes down to the end where it turns down into a wet return. That main vent wants to be at the end of the main but if there is no tapping there maybe you can drill and tap a hole (or have a contractor do it for you) after the last takeoff. If you can't do that maybe you can get that elbow at the end of the main replaced with a Tee so you will have someplace to mount a main vent.

    If you can't do any of the above try putting the main vent in the available tapping and see if it helps - certaintly not optimal but something is better than nothing. It sounds like you would be able to vent maybe 30 ft of the 40 ft main that way.  What radiators do those last 3 leaders go to?

    The Hoffman 1A's can be bought from Pexsupply.com, they have a good price on a six pack of them.

    Start a log of your gas usage on a day by day basis and see how much your really using. You can use that log to note any system problems and also note any water you have to add to the boiler.

    It sounds like our houses are similar in size, I have 190 sq ft of EDR that feeds 7 radiators. Over the last few cold days my oil burner is running for about 2-1/2 hours a day (I have an elapsed time meter on it and I know it uses 1.1 gal / hr). That is approximately equall to 4.3 therms, all things being roughly the same.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • World Plumber
    World Plumber Member Posts: 389
    Matched / balanced load

    The idea is to match the steam out put of the boiler to the radiation load. If your building pressure faster than the system can use it your over fired. I venture to say you will see a big difference in your fuel consumption. Steam moves faster at lower pressure. You may need to use smaller vents upstairs now. If you have separate mains for up and down stairs check the main vent to the downstairs main add venting if needed. Most likely it's all the same main so you may have to either increase the vent size downstairs or decrease the size upstairs.

        The ideal time to pressure is never!
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