Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

NG conversion - diameter of old raditor pipes

RAndrew Member Posts: 4

My wife and I are about to buy a beautiful 130 yr old Victorian house. Unfortunately I've been informed the oil furnace is the original after replacing a coal one, from 1910. This is a hot water system, not steam.

This is in Long Island, NY and we would prefer to switch to NG as we replace the system (house already has a gas line). Main question-

One of the heating companies I had in (who I liked very much and was a referral) is telling me that since the all the radiator pipes in the walls and ceilings to all the raditors are very old and a very large diameter ( 1 1/2 to 2" ea) we CANNOT convert to NG without changing ALL of these pipes as well (doubling the cost). He is saying a NG heater cannot heat enough water fast enough for such wide pipes and the heater would run constantly, giving no efficiency and voiding manufacturer warranty (and breaking down).

The other company I had in for a quote, whom I also liked, is saying that the above is just not true at all, and a new 200,000 BTU NG heater (and sep hot water heater) will do just fine using the EXISTING, wide diameter pipes throughout the home.

Needless to say I am at a loss as to who is correct here - any opinions would be greatly appreciated.

As a side question, the house has a 1/2 inch gas pipe coming in as gas is only used for the oven right now - will this give us enough gas for NG heat and dryer or will we need a bigger pipe brought in from the street?

thank you,



  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Consider more possibilities than these two contractors.

    I am not a professional, and have direct experience with only one  hot water heating system directly, and indirect experience with one more.

    It sounds to me as though the first contractor is one that I would not trust, and I would want to know a lot more about the second contractor before forming a definite conclusion.

    I think you should especially consider whether using a modulating-condensing boiler with outdoor reset makes sense in your circumstances. This would probably depend to a great extent on what you have for heat emitters in your house, or on whether you might wish to make them larger. If they are large enough already, or you are willing to make them larger, it would increase the chances that changing to a mod-con would make economic sense.

    With my mod-con, that operates cold start, I have an indirect-fired hot water heater. This is basically just a storage tank with a water jacket around it that has circulating hot water from the boiler in it The whole thing is well insulated.. The circulator runs only if the water heater needs heat, and the boiler fires if necessary. For me this is much more economical than my old electric hot water heater.

    It is my impression that a competent contractor would ask you questions on your priorities (initial cost vs. efficiency), survey your house so he can do the heat load calculation, and propose a regular cast iron boiler option and a modulating-condensing option, with approximate prices for each. He should also be able to give you rough guesses as to operating costs for both options.
  • RAndrew
    RAndrew Member Posts: 4
    fyi - the heat dispersals

    for main 2 floors are large, cast iron radiators.

    they have both asked me about budget and our priorities - I'm just trying to find out if a gas system can (or should) be used with large diameter hot water pipes.
  • Unknown
    edited April 2011
    no diff ithinx

    boiler water is separated from combustion chamber?= dont matter what u burn cause it hits the steel/iron be4 conducting to the hot water/steam of the system?
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195
    The large system volume is an asset

    If the current system is hot water using a new boiler with a modulating and condensing design would be ideal. 200Kbtu is a fair size boiler. How many square feet of home are you heating? It may be that neither one is right for the job. I know the first one is wrong. The second may also be wrong.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195
    On the gas supply pipe

    1/2" will not be large enough at normal pressures and you will definitely need a new 1" or larger supply pipe.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • RAndrew
    RAndrew Member Posts: 4
    sq ft-

    the house is 2,650 sq. ft - no insulation (though I will add as much as possible) w/very high ceilings. I imagine very significant heat loss right now.
  • Tim McElwain
    Tim McElwain Member Posts: 4,477
    The large pipes and radiators

    are a plus as you will typically get low return water temperatures back to a Mod/Con which will aid in the condensing process. That coupled with Out Door Reset will give you very good operation. I would have a heat loss done on the house along with a measure of radiation to ensure a good match as far as input to the boiler.

    Add to that some insulation and window replacement and things should work out fine.

    You will need a new gas service (yours is undersized) and also a new meter. Check with the local gas company as to rebates available along with gas availability on your street. Most gas companies in low gas pressure areas are very careful with adding load to the existing system so make sure they will let you convert over and that plenty of gas pressure will be available
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195
    unless you are on the north pole

    or the house is all glass a 150kbtu boiler would be large. You may want to use the find a contractor function at the top of the page.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • icesailor
    icesailor Member Posts: 7,265
    NG Conversion:

    Charlies from MA is right. 150,000 is more like it and probably less.

    There are some really bright guys in your area. I just met a few at 2 days of Veissmann classes.

    Plan whatever you do around adding insulation and weatherstripping to your home which will cut down on your heat loss.

    Here's something to consider if you want to ditch oil. If the Natural Gas is unavailable like Tim McIlwaine suggested, consider LP. A Mod/Con gas boiler can be converted back and forth. 

    Find a contractor that is up to date and knows what is going. One that keeps learning. 
  • rlaggren
    rlaggren Member Posts: 160
    maybe look at a 5-year plan

    If the heating system is functioning now it may well continue to do so (with proper regular maintenance) indefinitely - or at least for a few years needed to allow your other plans to be finished.

    That means that it's not an emergency and you have the option of making changes, upgrades, remodels, etc in an order that allows each change to build efficiently on the prior ones. For example, using your existing heating system for a few years may allow you to replace the roof (assuming that is needed) instead of just patching it temporarily. That would seem to make more sense and be a better use your your resources.

    This becomes more interesting if you plan to insulate, weatherize or replace your windows and doors, add rooms, etc because these changes will affect your heating requirements significantly. Postponing heating system work (if reasonable) until after you make other changes will allow a competent HVAC contractor to spec and install a system that meets your final ACTUAL needs w/out wasting money or redoing previous work. After all your major changes have been completed you can get a final energy audit with will help greatly to pin-point what heat (and cooling) your house needs. Working on the heating system prior to other planned changes makes the heating design much more problematic and you will mostly like waste money either in over capacity or in redoing work to fit your revised circumstances.

    Old houses are really great (IMHO) particularly if you accept the idea that at least _some_ work needs to be done. I hope you get a lot of enjoyment out of yours.

    Cheers, Rufus
    disclaimer - I'm a plumber, not a heating pro.
  • CMadatMe
    CMadatMe Member Posts: 3,084
    The Contractor

    If a heat loss was not done by either contractor then throw both those quotes along with their thoughts into the garbage can. 2,700 sqft house using 75btu's a sqft.. Don't think so unless you keep the windows open for the smell of nice salt air...But bigger is better right? :)
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • RAndrew
    RAndrew Member Posts: 4
    Thank you

    all for your tips and advice. I have read about the importance of not over-sizing and do hope to size appropriately. doing the heat loss it tricky as I'll be replacing all windows and insultaing, so one done now will look different than one done in a year.

    as far as waiting on the new system - this is something to think about. the issue is we'll have most of the walls open just this one time so it seems like now is the time to "do it all" - a/c, heat, electric and plumbing. but, the 100 yr old furmace does work fine so maybe we should wait until next summer, post insulation...

    As the consumer, I can tell you it is extremely frustrating when different licensed professionals tell you completely conflicting information!

    my original post - if wide pipes can use a NG heating system - is still perpexing to me as this guy is swearing on his life my system wont work right w/the house's exisitng pipes -- to the point where he says he wouldnt even do the install because it wouldnt be right.

    I'm going to get a pic of the furnace and post it b/c I'm sure you guys would get a kick out of it. In the meantime attached is the heat exchanger from the Insepction - oh man!
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,195
    Have you taken a look

    In the Find contractor section. There are many good guys near you who will give you answers you can trust. Looks like the old girl needs to see a vacuum and a brush before next heating season. On a side note you have a boiler not a furnace, the more zealot on the board take offense to calling it a furnace.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Steamhead
    Steamhead Member Posts: 14,769
    edited April 2011
    Find out who was "maintaining" that boiler

    and DON'T use them! That much soot is ridiculous- it made the system use way more oil than it should have.

    Is that an old Crane boiler?
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • icesailor
    icesailor Member Posts: 7,265
    Swearing on Life:

    I would swear on my life that it WOULD work with the big pipes.

    I would recommend that a new Mod/Con boiler be at the top of your list A PROPERLY SIZED ONE for the load, now and maybe even a touch undersized. Remember, "MOD" stands for "Modulating". That means that a 150,000 BTU Mod Con will be mostly firing at 100,000 BUT's into a 100,000 BTU load once you cut your heat losses in the future. Start saving immediately for that new roof with the savings in fuel.

    Those look like bricks in the flue ways. That is a trick sometimes used on an old coal conversion to oil to slow down the flue gasses. Coal draft was very slow and a power oil burner was faster. It helped with heat absorption. It doesn't do any good if you don't clean the boiler though. If you have combustion equipment like a Bachrach wet kit, you will probably find that the draft is really high and the flue gas temperature is also. Put in the bricks and the draft will go down to an acceptable limit and the stack temperature will go down too. The CO2 may go up a tad if the boiler is reasonably tight. But no matter what you do to these old gals, they can't dance with the young-un's anymore.

    I drool thinking how nicely a system like this would run with a Mod/Con on outdoor reset. And if it is on two floors, you should be able to split it into two zones. Put two zone valves on the system, leave the zone that stays cooler, always open and let the thermostat and zone valve on the hotter zone, control the system.

    Oh what fun Hydronic Heat can be.

    And IMO, if you want AC, do that separately as a ducted system. I've never seen the two mix. And you can do amazing things with Mini-Splits.
  • unconsidered factor?

    is that the pipes & rads are gonna be rusty & may wear on the pump?
  • Ironman
    Ironman Member Posts: 6,469
    A Btu is a Btu is a Btu

    Btu: "British Thermal Unit"- The amount of heat required to raise the temperature of one pound of water one degree.

    It does not matter what the fuel source is. As long as it is producing the required btu's, and the heat exchanger is transferring the heat to the water, the result is the same: each btu will raise the temp of one pound of water one degree.

    This is learned the first hour of the first class of Heating 101. A contractor who doesn't know this needs to be sent back to Hydronic Kindergarten. He has no business doing a gravity conversion.

    Please pardon the over-sight in not directly answering your question earlier. To the pro's on here, it's something that was easily taken for granted that a contractor should know that the fuel source doesn't matter if sufficiently sized.

    And as others have suggested, a properly sized gas mod/con is ideal for a gravity conversion. Most, if not all of us, are well experienced in doing these.

     You will need to re-do the near boiler piping to primary/secondary, but the risers and mains can remain intact. Insulating them is advised. Your rads need to be checked for orifice plates on the second floor. Remove them if they are present. Flush the system and install a strainer on the return of the new boiler. Also, replace any bad valves, repair any leaks, and you're good to go. Zoning or TRV's are other good options.

    Hope this helps. Please ask further if you need more info. The pro's here are the most knowledgeable in the world of hydronics.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • icesailor
    icesailor Member Posts: 7,265
    Unconsidered Factor:

    I'm still waiting for corculators to fail from rusty water.

    I'm still waiting.
  • meplumber
    meplumber Member Posts: 678
    don't forget hydraulic separation.

    One thing to remember in these high volume systems, is hydraulic separation.  Very important to split the flows to boiler side/system side.
This discussion has been closed.