Hello all, I am new to this forum and I hope I can get some help. I have an old Burnham Holiday gas hot water boiler in my house. It is original to the house, circa 1961. It has 3 zones and has an awful air hammer going on. I read some info on bleeding the thing. I understand I have to close the return valve to the boiler right under the spicket where my drain hose goes, drain water in 5 gallon pail until no more air bubbles, but how do I know how the thing refills to the proper level? Is it auto fill? Should I turn off any electrical controls? There is 12-16 psi of pressure on gauge, it is a ranch home so the hot water doesn't have to climb more than 1 story. This has happened since we moved in 1 1/2 years ago, the furnace works fine, just very loud. Any help would be appreciated, thanks, Jeff
Burnham Holiday gas hot water boiler air hammer
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In general it's better to bleed air at the highest point in the system, since that's where the air tends to collect. See if there aren't any bleeder valves on radiators/baseboards elsewhere on the system.
Banging and hammering is often symptom of having too low a system pressure- don't drain any more water out of the system until you're sure you have at least 10psi (12-psi is better) at the boiler. When the pressure is too low the micro-boil at the water side of the heat exchanger plates first starts out with an audible sizzle when the thing is firing, but if you're leaking water somewhere an the system continues to lose pressure that micro-boil turns into fairy substantial bubbles on the heat exchanger plate, that then collapse with a BANG as it collapses when the flow moves it away from the heat exchanger.
If the existing pressure gauge has seized up and isn't working properly, you can put a pressure gauge with a hose fitting on the drain-spigot where you've been purging, open the valve and get a quick read. It doesn't have to be super accurate, just be sure it's between 10-20 psi, and closer to the 10 than the 20. If it agrees pretty much with the original gauge, move on.
If it turns out to have been a low-pressure condition, it could be running low pressure due to leaks and stuck auto-fill valve/close fill valve. Or if the fillvalves are closed and the expansion tank fails it might lower the pressure sufficiently to cause the banging/clanging if the original fill pressure was marginal.
If it turns out the pressure is really fine, systems don't just magically take on air, but leaks that draw in fresh water via an autofill valve can bring in some dissolved air that later become problematic, and sometimes finding those leaks is difficult. If you see a lot of air in the water coming out your system drain spigot, you might have some sleuthing to do.
Banging and hammering is often symptom of having too low a system pressure- don't drain any more water out of the system until you're sure you have at least 10psi (12-psi is better) at the boiler. When the pressure is too low the micro-boil at the water side of the heat exchanger plates first starts out with an audible sizzle when the thing is firing, but if you're leaking water somewhere an the system continues to lose pressure that micro-boil turns into fairy substantial bubbles on the heat exchanger plate, that then collapse with a BANG as it collapses when the flow moves it away from the heat exchanger.
If the existing pressure gauge has seized up and isn't working properly, you can put a pressure gauge with a hose fitting on the drain-spigot where you've been purging, open the valve and get a quick read. It doesn't have to be super accurate, just be sure it's between 10-20 psi, and closer to the 10 than the 20. If it agrees pretty much with the original gauge, move on.
If it turns out to have been a low-pressure condition, it could be running low pressure due to leaks and stuck auto-fill valve/close fill valve. Or if the fillvalves are closed and the expansion tank fails it might lower the pressure sufficiently to cause the banging/clanging if the original fill pressure was marginal.
If it turns out the pressure is really fine, systems don't just magically take on air, but leaks that draw in fresh water via an autofill valve can bring in some dissolved air that later become problematic, and sometimes finding those leaks is difficult. If you see a lot of air in the water coming out your system drain spigot, you might have some sleuthing to do.
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Hi, thanks for the reply, it is greatly appreciated. I thought about opening up the bleeder furthest from the furnace while its running and see what happens, but will the furnace auto fill back up with any water that was lost? How would I identify an auto fill furnace? I am not sure about this. The furnace had a new expansion tank on it when we moved in 2 springs ago (spring 2012) and has been banging since day one, so maybe they didn't bleed the system right all the way back then? I don't see any puddles of water anywhere?
First, it's a boiler not a furnace- the nomenclature gets confusing when you call a boiler a furnace. 
The boiler & circulator don't need to be running to bleed air at the radiators.
It's entirely possible that they didn't properly air-purge the system on day 1 after breaking it open to install the expansion tank. It's also possible they didn't properly charge the expansion tank. Most systems will have a vent or air-scoop to slowly purge air from the system while it's running, yours may or may not. Air scoops typically have the expansion tank attached directly to the under-side, with a vent installed on the top:
If that's what you have, it SHOULD purge the air on it's own over time, if the vent is working properly.
Standalone vents are usually attached on a riser-stub somewhere, often on a fatter section of pipe (preferably, but not always near the high point of the system), or at a radiator, some point on the system where the water velocity is lower, which makes it easier to catch the bubbles rising as they pass the stub.
If you have manual bleeder valves under the end caps of the baseboards, with the system OFF and cooled to not-scalding temps, go bleed each one. If you get air out of any of them keep going until it's clear & fizz-free. You may have to do this multiple times when there is a lot of air moving around in the system, since bleeders don't trap big volumes at the valve.
The boiler & circulator don't need to be running to bleed air at the radiators.
It's entirely possible that they didn't properly air-purge the system on day 1 after breaking it open to install the expansion tank. It's also possible they didn't properly charge the expansion tank. Most systems will have a vent or air-scoop to slowly purge air from the system while it's running, yours may or may not. Air scoops typically have the expansion tank attached directly to the under-side, with a vent installed on the top:
If that's what you have, it SHOULD purge the air on it's own over time, if the vent is working properly.
Standalone vents are usually attached on a riser-stub somewhere, often on a fatter section of pipe (preferably, but not always near the high point of the system), or at a radiator, some point on the system where the water velocity is lower, which makes it easier to catch the bubbles rising as they pass the stub.
If you have manual bleeder valves under the end caps of the baseboards, with the system OFF and cooled to not-scalding temps, go bleed each one. If you get air out of any of them keep going until it's clear & fizz-free. You may have to do this multiple times when there is a lot of air moving around in the system, since bleeders don't trap big volumes at the valve.
FWIW: (Warning, unsolicited advice ahead... ) That 52 year old beastie-boiler probably had a steady-state combustion efficiency of no better than 80% on day-1, and that was BEFORE all of the rust, scale and corrosion on the heat exchanger plates of a half-century of use. If experience in my neighborhood means anything, odds are pretty good that it's 3-4x oversized for the actual loads, which means that even on day-1 it's as-used AFUE was probably something around 70%. Today it's steady-state efficiency might be as high as 75%, but it's probably lower, and with cycling & standby losses you're probably only getting 60% out of it.
Even though the price of natural gas is currently near record lows, at any fuel price it's probably time to retire the thing and put in something that is
A: Sized for the actual heat load at the 99% outside design temp. This maxes out both efficiency AND comfort.
B: Higher efficiency (even if it's an 85% cast-iron thing, rather than a modulating condensing boiler.)
Even newer-better cast iron boilers sized to your load would cut your fuel use by about 30%. Depending on how much radiation you have relative to your peak load, a mod-con boiler would probably cut it by about 40%, maybe more.
Since the thing is still able to heat the house you have time to carefully consider your options and save up for it, make a plan, maybe even dig up subsidy money for it, if there is any available from the utilty or state. (It's a moving target, I don't keep track.) With a couple of heating season's fuel use behind you, it's possible to put an upper bound on the size requirements of any new boiler by the ratio of fuel use per heating degree-day, using boiler as a measuring instrument. It's most-accurate if you have gas bills from mid or late winter, on periods where the house was occupied the entire period between meter-reading dates (not the month you spent 2 weeks surfing in Belize with the thermostat set to 50F.)
It's much better to have a pretty good idea of what you need BEFORE the thing bangs & clangs for the last time, cracking a heat exchanger plate and dribbling a steaming load onto the basement floor. That way you won't have to make hasty decisions under pressure and end up installing another wrong-sized boiler that'll be there for the next 20-50 years. The typical boiler installer in an emergency-hurry situation would come in and just replace it with something of equal (sometimes slightly greater) output and call it a day. While that method of boiler sizing would still keep you warm, it would be a mistake on both efficiency & comfort grounds, and would cost a bit more up front to boot.
As long as the existing boiler keeps chugging away there is little immediate incentive to change it out unless the price of gas skyrockets. But I've retired functional boilers less than 1/3 it's age when 4x oversized (and I'm not in the biz), without regrets. The cash to do these things may not always be readily available, and you may have to prioritize differently, but a boiler that old isn't worth fixing once it starts to go- it's realistic service life was already up by the end of the Reagan administration, but since it hasn't failed catastrophically, it has been left to the "next owner" of the house to deal with. There are much older and even more decrepit boilers than yours still in service, I'm sure. But if you intend to live there for awhile, it's worth having systems that you're not always picking away at and worrying about.
) That 52 year old beastie-boiler probably had a steady-state combustion efficiency of no better than 80% on day-1, and that was BEFORE all of the rust, scale and corrosion on the heat exchanger plates of a half-century of use. If experience in my neighborhood means anything, odds are pretty good that it's 3-4x oversized for the actual loads, which means that even on day-1 it's as-used AFUE was probably something around 70%. Today it's steady-state efficiency might be as high as 75%, but it's probably lower, and with cycling & standby losses you're probably only getting 60% out of it.Even though the price of natural gas is currently near record lows, at any fuel price it's probably time to retire the thing and put in something that is
A: Sized for the actual heat load at the 99% outside design temp. This maxes out both efficiency AND comfort.
B: Higher efficiency (even if it's an 85% cast-iron thing, rather than a modulating condensing boiler.)
Even newer-better cast iron boilers sized to your load would cut your fuel use by about 30%. Depending on how much radiation you have relative to your peak load, a mod-con boiler would probably cut it by about 40%, maybe more.
Since the thing is still able to heat the house you have time to carefully consider your options and save up for it, make a plan, maybe even dig up subsidy money for it, if there is any available from the utilty or state. (It's a moving target, I don't keep track.) With a couple of heating season's fuel use behind you, it's possible to put an upper bound on the size requirements of any new boiler by the ratio of fuel use per heating degree-day, using boiler as a measuring instrument. It's most-accurate if you have gas bills from mid or late winter, on periods where the house was occupied the entire period between meter-reading dates (not the month you spent 2 weeks surfing in Belize with the thermostat set to 50F.)
It's much better to have a pretty good idea of what you need BEFORE the thing bangs & clangs for the last time, cracking a heat exchanger plate and dribbling a steaming load onto the basement floor. That way you won't have to make hasty decisions under pressure and end up installing another wrong-sized boiler that'll be there for the next 20-50 years. The typical boiler installer in an emergency-hurry situation would come in and just replace it with something of equal (sometimes slightly greater) output and call it a day. While that method of boiler sizing would still keep you warm, it would be a mistake on both efficiency & comfort grounds, and would cost a bit more up front to boot.
As long as the existing boiler keeps chugging away there is little immediate incentive to change it out unless the price of gas skyrockets. But I've retired functional boilers less than 1/3 it's age when 4x oversized (and I'm not in the biz), without regrets. The cash to do these things may not always be readily available, and you may have to prioritize differently, but a boiler that old isn't worth fixing once it starts to go- it's realistic service life was already up by the end of the Reagan administration, but since it hasn't failed catastrophically, it has been left to the "next owner" of the house to deal with. There are much older and even more decrepit boilers than yours still in service, I'm sure. But if you intend to live there for awhile, it's worth having systems that you're not always picking away at and worrying about.
Here's the monster. I agree with you on the antiquity of the furnace, it was our "muscle" on negotiating a price for the house, we definitely need a few quotes on a new one to have an idea of price. For now, I am a civil servant-government employee recovering from a furlough, with big budget cuts coming. When we ultimately work for congress, God help us. Thanks, Jeff
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Jadnashua
Retired Defense Industry Engineer xxx
Local labor rates can vary quite a bit, but figure a ballpark of $8-12K for a boiler replacement including an indirect WH. A new one would likely be about 1/4 the volume, and many hang on the wall. How it gets vented will likely be different so you may no longer need the flue you have. At its age, that may need to be replaced or resized to be safe and some vent through a sidewall rather than up.
Without being there and seeing it in total, or doing some analysis to determine the size and type that would best fit your needs, anything is just a guess.
Without being there and seeing it in total, or doing some analysis to determine the size and type that would best fit your needs, anything is just a guess.
Size also affects price, so doing the analysis ahead of time to not over or under size the thing matters. There is usually a plate with the model number and BTU in/out figures somewhere on the boiler, or inside an easily removable panel on most cast iron boilers. If you can find those numbers, it's useful for the analysis. It looks like it's about a 4-plate design, but it's hard to even take a WAG at what it's output & efficiency is. It should look something like this:
Within the past 5 years I've seen local quotes for 3-plate mid-efficiency cast-iron between ~$6K (simple swap-out) and ~$8K (complete new system, including new baseboards, broken into 2-zones, plus indirect-fired hot water heater as a priority-zone.) Add at least a couple grand for a reasonably designed modulating-condensing system, with efficiency tweaks.
If you have a mid or late winter gas bill with the meter-reading dates, with a zip code you can look up and sum the day-by-day base-65 heating degree days for the days between meter readings on degreedays.net, then with simple arithmetic convert the ccf or therms per degree day to BTU/ per degree-hour. The zip code would also let you look up the 99% outside design temp. The difference between your design temp and 65F, multiplied by BTU/degree-hour will be very close to your actual whole-house heat load, provided the place was occupied and heated during the billing period.
With that load number in hand you can look at possible boilers with sufficient output, but not too much output as possible replacements, and solicit bids. As previously stated, leaving it up to the contractor to size it for you is an iffy proposition. The tendency is to oversize (no contractor wants the 5AM call from the irate client on the coldest night of the year that it isn't keeping up), but it's in YOUR interest to not oversize from the actual load by more than 25% if possible, since that would deliver the longest most efficient burns and the most stable room temperatures. AFUE testing is done at a presume 60% oversizing (1.6x the actual load), but at temperatures below what most cast-iron boiler can tolerate long-term (too much corrosive condensation on the heat exchanger plates.) Sizing it at 25% over the peak load the average efficiency will hit pretty close to the steady-state efficiency, and it'll really meet the AFUE figures. At 2x oversizing, it won't quite, and at 3-4x oversizing it's a substantial hit, running well below the AFUE test efficiency. (With mod-cons it's sometimes possible to beat the AFUE test numbers, but that is not likely with fin-tube baseboard as the heat emitters.)
Within the past 5 years I've seen local quotes for 3-plate mid-efficiency cast-iron between ~$6K (simple swap-out) and ~$8K (complete new system, including new baseboards, broken into 2-zones, plus indirect-fired hot water heater as a priority-zone.) Add at least a couple grand for a reasonably designed modulating-condensing system, with efficiency tweaks.
If you have a mid or late winter gas bill with the meter-reading dates, with a zip code you can look up and sum the day-by-day base-65 heating degree days for the days between meter readings on degreedays.net, then with simple arithmetic convert the ccf or therms per degree day to BTU/ per degree-hour. The zip code would also let you look up the 99% outside design temp. The difference between your design temp and 65F, multiplied by BTU/degree-hour will be very close to your actual whole-house heat load, provided the place was occupied and heated during the billing period.
With that load number in hand you can look at possible boilers with sufficient output, but not too much output as possible replacements, and solicit bids. As previously stated, leaving it up to the contractor to size it for you is an iffy proposition. The tendency is to oversize (no contractor wants the 5AM call from the irate client on the coldest night of the year that it isn't keeping up), but it's in YOUR interest to not oversize from the actual load by more than 25% if possible, since that would deliver the longest most efficient burns and the most stable room temperatures. AFUE testing is done at a presume 60% oversizing (1.6x the actual load), but at temperatures below what most cast-iron boiler can tolerate long-term (too much corrosive condensation on the heat exchanger plates.) Sizing it at 25% over the peak load the average efficiency will hit pretty close to the steady-state efficiency, and it'll really meet the AFUE figures. At 2x oversizing, it won't quite, and at 3-4x oversizing it's a substantial hit, running well below the AFUE test efficiency. (With mod-cons it's sometimes possible to beat the AFUE test numbers, but that is not likely with fin-tube baseboard as the heat emitters.)
hj
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There should be NOTHING in a hot water system to cause "air hammer", unless the flow is so restricted that the boiler is overheating and creating steam but that usually only occurs in boilers with a copper heat exchanger, such as Raypak.
Steam-bubble bang can happen with either very low pressure or VERY low-flow. But it's true that it's more common in water-tube boilers (like RayPak or Laars glorified pool-heater boilers.)
If it was primarily or purely a low-flow situation from eroded impeller or corroded iron pipe (looks like it's plumbed in copper, though we don't have a great picture) it probably would have failed the point of not being able to heat the house over the past two heating seasons he has lived there. (cood b rong, offen am.)
It's unlikely that air in the system is causing the bang, but it's worth purging in any event. If the symptom goes away, great. If not, it needs to be chased a bit further. It doesn't hurt to try to zero in on exactly where in the system the noise is coming from
If it was primarily or purely a low-flow situation from eroded impeller or corroded iron pipe (looks like it's plumbed in copper, though we don't have a great picture) it probably would have failed the point of not being able to heat the house over the past two heating seasons he has lived there. (cood b rong, offen am.)
It's unlikely that air in the system is causing the bang, but it's worth purging in any event. If the symptom goes away, great. If not, it needs to be chased a bit further. It doesn't hurt to try to zero in on exactly where in the system the noise is coming from
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