old house with oil/steam heat - help

Discussion in 'Boiler Forum' started by elizabeth40, Aug 5, 2013.

  1. elizabeth40

    elizabeth40 New Member

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    Location:
    Massachusetts
    3 story 100+ year old colonial with 3000 ft3 living space. New England area. We now have oil fired steam. Boiler and steam infrastructure is 100+ years old. Someone told me that to replace the old boiler with a new gas furnace (82% efficiency) would save a lot money. Someone else said not exactly as much as you think. Due to the nature of the fuel having less bang for the buck. This some one also said it was not a good idea to put in a new boiler due to the potential impact on the steam infrastructure. In other words, it's been there 100+ years, eventually it will fail and, I don't want that to happen after I install your new boiler. Then you can have a repair nightmare. Good point, yes?
    So the recommendation is to put in a gas fired furnace with forced hot air duct work install. With 2 phase air conditioning unit/heat pump. This will bring AC to the second and 3rd floor. 2 furnaces will be installed actually. The first floor serviced by one and the second and third floor serviced by the heat pump system.
    Thoughts? foreseeable problems?
  2. BadgerBoilerMN

    BadgerBoilerMN Master Hot Water Mpls,MN

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    Location:
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    We consult on and install many steam to hot water boiler jobs here in St.Paul/Minneapolis and around the country. 100 years in more the average in our neighborhood, than a number to worry about.

    First, the cost of available fuel in your area.
    Second, measure the radiation to see if there is enough to replace the heat lost using a lower operating temperature than steam.
    Third, forget about low-efficiency cast iron boilers.

    A condensing boiler will thrive on the average water temperatures needed by most steam to hot water steam conversion systems.

    There can be quite a bit of re-piping to do, experienced experts need only apply, but the outcome will be an improvement in comfort and likely a very considerable fuel cost savings.

    Talk only to those who are installing condensing boilers. They will likely also install steam, and low efficiency boilers but not the other way around. These are the smart guys.
  3. Tom Sawyer

    Tom Sawyer In the Trades

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    Where are ou in mass?
  4. Dana

    Dana In the trades

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    Oil has been running ~$3.5-4+ in MA for a few years now. In the same period NStar's gas grid gas has been running under $1.25/therm, but it might hit $1.50/therm again before the end of the decade (or even the end of the year.) And if gas did hit $1.50 it would still be half the cost of heating with $4 oil, even if you were using the same crappy antique boiler.

    A typical steam boiler in a house this old started out as a coal-burner with little or no controls, later retrofitted with an oil-burner and only slightly better controls. As-operated most are only running 45-60% efficiency. A replacement gas boiler properly sized for the radiation really will run 82% if the system is sized properly for the house, but since most of these antiques are 2-3x oversized it's realistically more like 70-75%. If we generously assumed the oil-burner in the existing system is getting 72% efficiency (NO WAY, but just figgrin' ) and replacement boiler's gas-burner delivered only 72%, at $4/gallon oil you'd be getting ~100,000 BTU heat into the system or $40/MMBTU, whereas with $1.50 gas you'd be getting 72,000 BTU, or ~$20.80/MMBTU. But in fact the antique with the retrofit oil burner isn't doing nearly that well, and is probably costing you ~$60/MMBTU.

    Steam piping & radiators don't fall apart very easily- the repair nightmare argument is really not very valid at ALL! That has the ring of a scare tactic for making the sale, but has very little basis in reality.

    A steam heating system is simplicity itself, with very few moving parts, and while it does need to be maintained, deferred maintenance doesn't particularly degrade the system, (only the comfort.) Steam systems do need to be re-tuned occasionally, maybe once every decade or so when the system vents & radiator vents start to stick or clog. It's possible to micro-zone 1-pipe steam using thermostatic vent valves, to better balance the heat distribution or run some rooms colder than others as-desired, with significant fuel savings. It's not the worst thing in the world to "recommission" a functioning steam system, fix any missing or failing pipe insulation, etc., which would almost certainly cost less than cutting up a century old house for a duct-retrofit. A well tuned steam system is very quiet and quite comfortable, and only slightly piggy on the fuel use. And since it doesn't use any power for heat distribution, it's comparable in operating cost to heating with mid-efficiency gas boilers, and can be cheaper than heating with mid-efficiency gas furnaces (steam has no air handlers or pumps load sucking power off the grid.)

    Many 2-pipe systems can be reasonably restructured & fitted as a pumped hot water system, in which case it's likely that you could get the efficiency of condensing gas along with improved comfort, and a right-sized boiler capable of hitting it's AFUE numbers (or better), deliver stabler room temperatures, and use only ~2/3 of the gas that a pretty-good steam boiler would on a fully tuned-up steam system. (This is where BadgerBoilerMN is steering you.)

    If you are on one of the municipal power companies (not NStar or National Grid) you electricity is pretty cheap, and you COULD heat & cool the place with ductless air source heat pumps (mini-splits) for about the same operating cost as condensing gas, without running ducts everywhere, using the steam system only as backup.

    All condensing gas furnaces are going to be oversized for your actual heat loads, and having it only serving the first floor only compounds the issue- it'll be efficient enough, but it won't be doing anything for comfort, since it'll be cycling on/off a lot. The ducted air source heat pump would cost a somewhat more to operate than condensing gas and you're more likely to find a right-sized solution, but it will not as efficient as ductless mini-splits.

    A good heating solution typically starts with a room-by-room load calculation (Manual-J or similar), and sizing the equipment correctly. But before spending money on a new heating system it's also important to seek out and rectify all of the low-hanging fruit on the building envelope, and in most century-plus homes those are many. It starts with air-sealing, followed by retrofit insulation, rebuilding or replacing any ancient windows and adding low-E storms, etc. And don't neglect foundation air-sealing & insulation- even if you're not heating the basement directly an uninsulated air-leaky basement is a large heat load, and insulating the foundation reduces moisture/mold issues while improving first-floor comfort. All of these retrofits affect the heat load calculations and the system sizing (and cost).

    Which is all leading up to the point that increasing the efficiency of the BUILDING increases the comfort levels far more than anything you can get out of the heating system (barring radiant floors, which would be a huge cost-adder as a retrofit.) Accept no HVAC proposals that don't come with room-by-room load calculations based on the building construction and the true 99% and 1% outdoor design temperatures, but running those numbers ahead of time on building before & after any envelope upgrades can be eye-opening. (My house just turned 90 this year, but since I've lived here I've brought the heat load down by ~35-40%, while increasing comfort and decreasing heating/cooling costs, even while adding onto the conditioned space.) In NStar & National Grid territory there is a great deal of subsidy available for building envelope improvements, even though you're heating with oil.

    In many 3000' homes in MA a 3/4-ton mini-split per floor is more than sufficient cooling, but would probably come up shy on the heating end at the 99% outdoor design temp, but is often reasonably sized for the January average temp, in which case it would cut the fuel use of the boiler by more than 3/4, at an installed cost under $10K. With oil as the fuel this is a huge payback, with gas, not so much. But if installing air conditioning (ducted or not) sized for the cooling load it's probably going to be worth the upcharge for making it a heat pump rather than cooling only, whether you swap out the boiler for a mod-con or not.
  5. gennady

    gennady New Member

    Steam system done 100 years ago is much better quality than anything you will get today. people knew how to do quality job 100 years ago. as per efficiency, install properly sized steam gas boiler, line chimney, install TRVs on radiator, insulate existing piping and you will have all you need. Hot air system is the worst , and regarding heat pump systems i think in poorly insulated house it is not a best idea. but I might be wrong on heat pump systems.
  6. Dana

    Dana In the trades

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    On ductless heat pumps, it's really cost per BTU of operation against low efficiency (or even highest efficiency) oil, not so much the heat load of a poorly insulated house.

    The exit air temps of ductless air source heat pumps are more comfortable than that of ducted ground source heat pumps, and the velocity (wind chill) & noise of that air is usually favorable to that of fossil-fired ducted air systems. They deliver very stable room temps- about as good as it gets with air-delivery. When it's 0F outside it's not a comfortable as the steam radiators, but when it's 30F outside it can be- especially in when the wallet-nerves are part of the deal. If you're in the position of having to run the place a lot cooler and with deep setbacks to avoid spending $5K+ in heating costs and you can keep the place at a comfortable temp 24/7 for under $2K, that's a real comfort upgrade!

    A 4 ton multi-split can typically deliver ~60,000BTU/hr @ +5F, which is a typical MA style 99% outside design temp. The average heat load of all single family homes in MA is a bit under 50,000BTU/hr. (And you get air-conditioning...)

    Not all homes are well laid out for ductless heat pumps, but sometimes it's the cheapest way to go from an up-front cost point of view, and on lifecycle cost point of view it'll surely beat gas-fired steam at MA electricity & gas prices (maybe not always at NYC electricity & gas prices.)

    But it's always worth attacking the load first, getting the load down where ever it's can be done reasonably cheaply, THEN deciding what mechanicals make sense for supporting the load. The mechanicals are need to keep the house at a temperature, but it's the lower-loss home that's providing most of the comfort, not the heating system.
  7. BadgerBoilerMN

    BadgerBoilerMN Master Hot Water Mpls,MN

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    Some were, some were not. You can only do so much with steam and a 4 to 5 hundred degree stack. If you have a one-pipe steam you have few choices, if you have two pipes you have one good choice and one old choice. Conversion to condensing technology could reduce the fuel bill by 2/3. Naturally follow Dana's advice on the envelope first and don't be steered toward new windows since payback may be a couple of lifetimes.
  8. Dana

    Dana In the trades

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    New windows are a total dog of an investment from a purely financial point of view for sure, but high-performance windows are a real comfort boost.

    If the existing windows are in pretty good shape, storm windows are an EXCELLENT upgrade from a financial perspective, particularly low-E storms, which despite being more expensive than clear-glass will pay back quicker than clear glass storms (and they'll add more comfort too!) Harvey has the tightest storm windows in the biz, and have a hard-coat low-E option, but the Gold or Silver series low-E Larsons sold through box stores really aren't bad either (worth the upcharge from their low-end Bronze series.) From a comfort upgrade point of view it's not bad at all, though not the same as a U0.18 window when it's -10F outside (which happens once every couple of decades in MA.)

    (I wonder if elizabeth40 has even checked back on this thread...)
  9. BadgerBoilerMN

    BadgerBoilerMN Master Hot Water Mpls,MN

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    I actually have specified several good exterior storms for the old house around here, as it is easier to trim the exterior without degrading the historic significance of those dandy old double-hungs. Good to know about Harvey.

    Thanks again.
  10. gennady

    gennady New Member

    Steam

    I had a chance to install steam boiler with modifications of steam heating system and condensing boiler on 2 identical brownstones within couple blocks from each other. The gas bills were within 20 dollars difference on winter month. Taking into account electrical charges to drive 2 pumps I would say it was very close call. Good steam system can compete with hot water system. And definitely not worth to convert steam system to hot water. On steam systems oil to gas conversions our average results are 70-75% fuel reduction, depending on how screwed up steam system was.
  11. Dana

    Dana In the trades

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    Yer welcome!

    Be sure to specify the hard-coat low-E option when ordering up those super-tight Harveys- it makes a real difference in performance. Indium tin oxide is fused with the surface of the glass making it harder and more scratch resistant than standard clear glass types, doesn't reduce the visible light very much at all, and still passes reasonable amounts of solar gain, but it's sufficiently low-E to produce easily measurable improvement in heat retention when the low-E surface is facing the interior (the standard method orientation). In cooling dominated climates it would be slightly better to flip the glass to put the low-E surface on the exterior, but even on the interior it cuts in to solar gains enough to make it worthwhile.

    gennady's observations about tuned-up steam vs. condensing boiler are not unique, but probably more the exception than the rule. Pumping power costs make a much bigger difference in NYC's retail electricity price than in the vast majority of US markets. Micro-zoning single-pipe steam with thermostatic vents, insulating all of the distribution piping, and fixing any design issues or stuck system vents etc. are all critical to getting there though. Retrofitting ultra-low temp radiation into a steam-heated Brownstone to max out the condensing efficiency is usually cost-prohibitive, and I'd expect most mod-con retrofits in these mostly-uninsulated buildings spend most of their burn time running in the high 80s or at best low 90s rather than high-90s for combustion efficiency.

    It can be a heluva lot cheaper up front to fully recommission the steam system and do it right, and spending the difference in cost between conversion to mod-con on reducing the load can often make a bigger hit in fuel consumption and a bigger bump in comfort than chasing the highest combustion efficiency. Whether that would be the case in this 3-story antique depends on a lot of particulars not in evidence, but don't rule it out.

    The ducted mid-efficiency gas furnace + heat pump scenario seems brain dead though- the likely additional air-handler-driven infiltration and air handler power would likely end up costing more to run than a tuned-up steam system with an 82% AFUE boiler. In most of MA a ducted heat pump would average a seasonal COP of 2 (best case), and would be more expensive to run in heating mode than even 70% AFUE gas-fired steam. But heating with ductless would be cheaper, and like radiators, do not incur an infiltration-penalty the way ducted-air does. When it's 40F+ outside heating with ductless is cheaper to heat with than condensing gas at average MA gas & power rates, due to extremely high efficiency at part load & moderate outdoor temp. The upcharge for going heating & cooling on ductless vs. cooling only is quite modest, and almost always worth it.

    Finding contractors who really understand how to get the most out of steam is probably harder in MA than in NYC though (not that finding contractors who do mod-cons right is a cake-walk here either...), and most people have a hard time investing real money in optimizing their steam systems, presuming (against all reason) that it's present condition is about as good as it's going to get. I'm no steam expert but I've managed to reduce fuel use in a friend's house by more than 15% with a few hundred bucks of venting tweaks/repairs and pipe insulation, not touching the boiler or thermostat.
  12. BadgerBoilerMN

    BadgerBoilerMN Master Hot Water Mpls,MN

    Messages:
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    Location:
    Minneapolis
    Poppycock

    This defies the laws of physics and no one who knows steam and hot water heat could believe it.

    Let's start and end with the latent heat of vaporization.

    "Good steam system can compete with hot water system."

    I had to break this unbelievable statement out from the rest, as there are know logical arguments to defend it.

    NO ONE wants steam heat. They suffer with it because it is often too expensive to convert, more often people get bad advice from horse-and-buggy days "professionals", or they have a one-pipe steam that can't be converted.

    If your new condensing boiler costs as much to feed as your old steam boiler, someone has made a very serious mistake; over-sizing comes to mind.

    As for electrical charges; we install many condensing boilers and find few systems that actually require two pumps. Certainly an ancient steam system in a Brownstone with one thermostat, oversize radiators, huge iron pipe distribution and essentially no pressure drop, would require but one pump. The cost to operate said pump would amount to less than $50 dollars per year, and certainly cost less to operate that building a head of steam with a 400°F stack. In fact, while you let the latent heat fly up the chimney, to land on your neighbors to the east as acid rain, I'll be happily recovering the energy of the condensate at 970 btu's per pound. Not to mention making all more comfortable with outdoor reset.

    It is always a good idea to insulate and make weather-tight any living space but ROI is another matter. We often cut fuel bills in half just upgrading from an atmospheric to a condensing boiler. We can do this in a house that is simply impossible to insulate, a recent turn-of-the-century mansion built of block, with stucco outside and plaster inside was is a good example.

    http://portal.hud.gov/hudportal/HUD...lic_indian_housing/programs/ph/phecc/strat_h8
    Last edited: Aug 27, 2013
  13. Tom Sawyer

    Tom Sawyer In the Trades

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    I love steam. Been around it my entire career. Spent some time with Dan Holohan the undisputed master of the vapor but evn though I'm fond of steam there is no way in hell to approach the efficiencies possible with forced hot water. The big drawback to steam is that you hafta gt the water up to 212 before you get anything at all and, you need to keep the boiler near steam temperature for most of the winter months. Adding new cold water constantly also drives the efficiency numbers down. Steam is nice. Scalding radiators are great for drying winter gloves and boots and keeping the cats happy but its days are numbered. Now, if you want to talk about high pressure process boilers for industrial use.........
  14. gennady

    gennady New Member

    Why would you add cold water constantly to steam system?

    High pressure, low pressure boilers, What it has to do with efficiency? What you do is burn fuel, generate heat and transfer it to where it is needed.
    How you do it and what you lose in the process depends on system design, not a media. And I stand behind my statement. It is a fact. Steam system I restore work with no knocks, very quiet and extremely efficient. It might not beat radiant system, but on conventional high and medium temperature systems it is on par with forced hot water system.BTW I do a lot of condensing systems with excellent results. I track performance of systems I build. I can compare and I can see for myself. image.jpg
    Last edited: Aug 24, 2013
  15. gennady

    gennady New Member

    You do a lot of forced hot water systems and do not utilize primary secondary piping? That is strange. How you decouple boiler from the heating system?
    In my steam systems people set the temperature in each room independently. And over sizing of the radiators are things of the past. System accommodates to internal and external heat gains automatically in each room. And please differentiate between boiler efficiency and system efficiency. These are 2 different things.
    And last thing I need is the government teach me heating stuff.
    Last edited: Aug 24, 2013
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The higher the temperature of the heating medium, the more likely it is to waste energy in a typical residential heating situation. The delta between heat on/heat off means you have to put in a lot more to restore the operating temp, and the higher the delta, the more likely it is to waste energy. The bigger the differential, the faster it can disperse the heat to the outside, too. Things are more efficient when the delta is lower. Steam takes a lot of energy to go from liquid at 212 to steam at 212 - it does have LOTS of potential energy which is both a benefit and a problem. Keeping things liquid is lots better for the typical home verses using steam.
  17. gennady

    gennady New Member

    In injection loops for radiant heat you might find 70F delta t with delivery temperature of water 180F. It is done to reduce GPM , pumping costs and installation costs. In hydronic applications the larger delta T supply return ( non radiant ) desired, to reduce pumping costs, installation costs and so on. In Europe in hydronic non radiant applications installers are shooting for 60F Della T. If you are talking about indoor outdoor temperatures difference, who said that on steam indoor temperature is higher than on forced hot water system? Indoor temperature stays set by customer
  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    By it's nature, steam is at least 212-degrees, often higher. While the room temp may be the same, there are MUCH bigger deltas involved. More of the room is comfortable when the radiant input matches the losses, and that is only done reasonably with lower temperatures MOST of the year. 180-degree supply temps are not required for most residential heating situations except maybe on the coldest day of the decade. And, even then, probably not if there's enough radiation surface area. Pumping in a typical residential situation is not a big load...it is potentially in a larger commercial/industrial situation where you need to move large amounts of heat long distances - steam can be a great and maybe the only solution if you want a central heating plant. Mostly irrelevant in a typical residential situation.
  19. gennady

    gennady New Member

    Btu is btu. What gets lost trough envelope of building gets replenished by radiator output. When balance loss/gain is reached temperature in the room gets stable. Your reference to lower radiator temperature on forced hot water system probably is outdoor reset, on steam I use indoor reset. High and medium temperature radiators use mostly convection heat rejection, radiant heat rejection is less of the factor. Also even steam has 212 F at atmospheric pressure, it does not mean whole radiator is 212F all the time. Maybe first section will be 212F the rest of sections might be much less.
    Last edited: Aug 24, 2013
  20. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    And, if you had children around, would you prefer a radiator that had a section that was 212+ degrees, or something that was maybe 120-degrees. Which one would you like to sit next to? Water verses steam also likely means you can actually use more of the room, and not get boiled. If you're putting in 212+ steam, and your load is low, like most of the season, how often does it need to cycle verses running more constantly at a much lower temperature. Commercial steam? Maybe a good solution, residential, not.
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