I recently had a new heater installed. It is an upflow gas furnace. 75000 BTUs. The top of the heater has an opening that’s 20×20. The contractor put a self-contained A-coil which measures 14×20. He closed off the rest of the 20in. opening with sheet metal and screws, which meant he closed off an area of 6×20. Does this affect my airflow across the heating tubes? Also, the return air duct was reduced where it hooks to the side of the heater. From 15×18 to 8×24, thereby reducing it some 90 square inches. Does this affect my return airflow?
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Freddy,
The answer to both of you questions is: "Yes". The manner in which a furnace is ducted will affect the air flow though it. It depends on the rest of the system, and the capacity of the AC side on whether or not the affects are necessarily bad.
Did you hire this guy because he came highly recommended or was the cheapest you could find? If you hire the cheapest guy you could find, you probably got what you paid for. Sounds like a hack to me.
Tim
thanx tim for typing back and you are right. i did use the cheaper guy of all three estimates i got. but he has like fifteen trucks and i see him all around so i figured he should be good . but in talking to other high quality HVAC men I know now that I did get what I paid for. the guy I used sent two men out and did a complete R&R of the HVAC systems in 5 hours . these others men said a good quality install should take 14 to 18 hours. by the way ,Iam sorry I switched to gas. It doesn't seem to heat the air as much as oil did. I went with gas to use a direct vent type so I could tear down my chimney . It was ready to fall down and i was adding three bedrooms on upstairs. now I find out there are direct vent oil fired furnaces . but i hear they are really pricey Oh well ,live and learn
"it doesnt seem to heat the air as much as oil did" Its not the type of fuel you are using. Gas is just as effective as oil, some would say more so. The problems can be two fold. 1. You have to have a furnace that is properly sized/rated for your app. 2. The heating system needs to be properly installed.
Get one of those 'high quality HVAC men" to come out to take a look and see what can be done to rectify the problem. Hopefully the furnace you have is the correct size and you just need the duct work redone. Yes its gona be extra $ but the sooner you get it fixed the sooner you start feeling warmer and start saving money on your heating bill. BTW it sound like he may have put in a furnace that is to big for your home; duct work reduced, cycling on and off to quickly.
I'm no expert here, but I think oil burners are usually a good bit bigger than 75000 BTU. I have the smallest one I could get for my house and its still over 100,000. If they restricted the airflow, you may not even be getting the 75000 BTU and it would not heat as well as what you had before. I'd get a second opinion. I've used cheap HVAC guys and expensive ones. Doesn't seem to be all that much correlation between price and quality. I've used expensive guys who didn't do great and vice versa.
Bob,
75,000 BTU oil furnaces are easy to come by around here. Don't know what the problem night be where your are though.
And....almost without exception......an oil furnace with a 100,000 BTU output rating can be reduced by installing a smaller nozzle and adjusting the combustion air.
Example: Our oil furnace carries a 100,000 BTU rating with a 1 gpm nozzle installed. Change that to a .75 gpm nozzle and you've got 75,000 BTU output. That's what we run here. Better sizing to our maximum needs and so much better efficiency.
There is a limit as to the smallest nozzle and largest nozzle that can be used with any particular burner assembly, fuel pump and firebox, but usually there's a pretty wide range of operating choices that are allowed.
Knowledge is power, but only if applied in a timely fashion.
Yep, mine has a 1.0 gph nozzle. I don't know exactly why they wanted that. Its a very small house. But, this is a hot water system. A lot more stored heat than a hot air system. It doesn't cycle too often. Once an hour maybe. I like the hot water systems a lot better for heat. Need a separate cooling system, but I'll worry about that some other decade.
Yeah...I meant to type gph, but obviously input was gpm from the fingers. You got the gist of it anyway.
Most folks don't realize how much efficiency is lost by running an unnecessarily large nozzle in a forced-air oil furnace. Losses are huge really. That coupled with too slow of a blower speed to capture heat, improper settings of the blower controls regarding on and off, improper adjustment of combustion air and over-fire draft....and then, well you might as well shovel $5 dollar bills instead of fuel oil into the firebox.
Most HVAC outfits around here are lackadaisical at best about fine tuning the system. Hit and run sorta deal. In and out as fast as possible and then on to the next crime scene. Is it makin' heat? Okay then, we're outta here. Makes me grind my teeth sometimes.
Knowledge is power, but only if applied in a timely fashion.
I have not found an outfit that does a good job on my home system. I've also had some pretty bad jobs done for me by contractors on new homes. It takes a lot of attention and also a willingness to come back after the house is complete to fine tune everything. Had a lot of problems about that recently. The system is installed and they don't want to come back and tune it. A big system, 3 heat pumps, multiple zones.
I'm glad I have a woodstove. My most recent repair at home took them 3 weeks to get the parts and install. It works, but not like it did before. The burner sounds louder, the flame is less stable and there's a weighted damper on a "T" into the chimney that now flaps and makes a lot of noise. Have not decided whether to call them back and get it partly fixed again. I figure if I call them it will take 2 or 3 more trips to adjust it right. Or, I can figure it out and fix it myself. Can't be all that hard.
Around our area too, it's become increasingly difficult to find service technicians that are knowledgeable and schooled in the art of tuning an oil-fired unit. Don't feel alone in that regard. Since the vast majority of homes are located within easy grasp of natural gas, that's what they sell the most of and as for those of us who are out in the hinterlands, they push LP units. They push LP units to those customers primarily because they don't like working on oil-fired units and have willingly admitted so over and over again.
The proper adjustment of an oil-fired unit requires special equipment if you're going to be certain that things are truly right. While a very experienced guy can hit it pretty darn close (maybe even within say 5 - 10% of the ideal of each particular adjustment) without the expensive special combustion gas analyzer and such, you can't get the assured maximum efficiency. And only one of the HVAC outfits around here has this equipment. Even their techs are grumpy about having to get it out and use it in a residential setting, but they'll happily loan it to me to use on my own furnace or even a client's unit……..just for the asking! At $100 for the service call and an additional $57 an hour for the field time they could make some coin while tuning the furnace themselves, but just don't want to. Go figure. Nonetheless, they do use it routinely in commercial and institutional installations because of the strict regulations regarding these venues. Because of that, I have to call ahead and make sure it's available the day I'd like to use it. Again…..go figure.
The flapping weighted thingy that you refer to is a barometric draft control. Adjustment of this is critical to overall efficiency, not to mention the safety of the inhabitants. It assists in control of the over-fire draft on the combustion chamber. Properly adjusted and the maximum amount of generated heat is left lingering in the heat exchanger where it is available to your blower to heat your house. Improperly adjusted and more of the heat and your dollars go up the chimney. If it's really out of whack, you may have potentially serious and eventually costly problems. I doubt this is the case in your situation because although it may not be adjusted for maximum performance, I like to think the service folks would know enough to get it fairly close. It's currently bobbing around in response to chimney draft, which is influenced not only by the draft of the hot air rising while the furnace is operating but also in response to the velocity of the wind outside and how tight your house is.
Anytime the wind is blowing outside, it is pulling on this device causing it to open against the counterweight. When it does this during the non-operation of the furnace (which it is supposed to) there is heated air from the interior of your house being drawn up the chimney. This represents dollars. Most people don't bother doing anything about it except noticing and complaining. I install Oil Saver units between this barometric control and the chimney. These are spring-loaded and motorized damper units which close off the flue when the furnace isn't running. They're wired into the furnace controls in such a manner that the furnace itself cannot fire unless the unit proves first that it is open for draft handling. You might consider installing such a unit sometime in the future. It's no substitute for a properly tuned furnace though, just an adjunct to dollar-saving and fuel efficiency.
The fact that they installed "parts" and then your equipment is louder leads me to think that perhaps they changed out the nozzle for a different size. If the nozzle is smaller than the previous it could roar more if they didn't also reduce the combustion air and it's getting too much. This also makes for too hot of a fire. If they changed out the nozzle for one that's bigger AND also adjusted the combustion air to a proper setting……….that's to be expected because the larger the nozzle, the louder the fire in the box. If that nozzle is larger than necessary for your heating needs, it could be costing you some dollars from inefficiency. Can't say for sure from here.
As far as this adjustment of the unit being "not that hard"……..it is…….. if you don't have any previous experience or knowledge. I wouldn't recommend that you go it without some qualified help who's good at teaching also, at least the first few times anyway. If you, for example, set the combustion air too low, your heat exchanger and/or flue will start clogging with the soot from unspent fuel. This eventually leads to complete choking and CO invasion into your home is likely. Not good at all if you like waking up in the morning or would rather not suffer from headaches and flu-like symptoms for days or weeks on end until you either succumb or realize what's happening and resolve the problem.
A good CO detector is one of your best friends all year round, but especially so during the heating season. It won't lie to you about the truth and it'll tell you if there's a problem you need to know about. Buy one today……don't delay. <G>
I hope you can find someone qualified and willing in your area to get things running well and safely. If not, look further. You'd be better off paying someone good to drive some more miles to get to you than fighting with the locals ad infinitum, I think.
Knowledge is power, but only if applied in a timely fashion.
I don't like to have people fixing stuff for me unless I have some reasonable clue how how to do it myself. They can probably do it better, but I like to know they are doing it better. Can't judge whether they do a good job unless you know how its supposed to work. I'm not too worried about CO, although I do have a CO detector near the woodstove. Maybe I should stick one in the crawlspace too. The boiler is in a crawlspace with no connection to the house. A separate bulkhead outside. If the damper isn't adjusted right, its only drawing unconditioned air out of the crawlspace. Still probably not a good thing. The wind here blows most of the time. I'd say 15 mph gusts are typical. Anyway, the damper did not make anywhere near as much noise before it was serviced.
The burner does need to be adjusted right. The boiler is a little Burnham V1. The burner is an old Becket. The new nozzle is exactly the same size as the old one. (1 GPH 80 degree B) Now it seems to go out every day or two. Maybe some crud in the line. At last service, all filters, nozzle, electrodes and chamber liner were replaced, plus a cleaning. The service guy had only a smoke tester and a thermometer. No high-tech analyzer. As far as I know, the company only has the one tech out here. I'm not sure that I'm in the service area for any other contractors. You're right, they are trying to switch everybody to propane. I'm not interested. Less maintenance, but a lot more expensive fuel. I see virtually no new oil systems getting installed around here.
I'll keep looking for a decent service company. In the meanwhile, I'm learning a bit more and hopefully won't burn anything down if I tinker with it slightly. If I need a couple $150 service calls to adjust the thing, that wipes out all of the cost savings from using oil. I'd rather not do that. I'll purge the lines and see if it will stay running for more than a day. If not, don't know what I'll do yet.
Judging from all the stuff that was done, I'd suspect the draft control would probably need readjusting. This and the setting of the electrodes and the combustion air can all effect the stability of the flame and cause or contribute to intermittant flame failure. And of course, a piece of gunk in the nozzle could shut things down in a hurry.
Those electrodes have to be "just so" or you'll have trouble or no ignition. The tips of them have to be a prescribed distance apart, a prescribed distance in front of the nozzle and a prescribed distance above the center point of the nozzle if ignition is to be reliable and constant.
You'd first need the specs for all of that on your particular unit and then if you go in there in an attempt to adjust things, there's dissassembly involved to get at those electrodes and the nozzle. The slightest slip of the wrench while you try to loosen nozzle or the brackets that secure the electrodes and you can easily crack the porcelins. Then the show is over until you have a new set in hand. (Never replace one electrode. Always as a pair.)
Maladjustment of the combustion air can also lead to or contribute to an unstable flame.
I may have some material here that would be helpful to you in understanding how all this works. If you're interested, drop me an e-mail thru the board and I'll see if I can find it and send you a copy.
Edit: Another note of interest is that it's always best to keep a spare set of electrodes and a spare nozzle on hand for your burner. Those electrodes need to be the exact ones prescribed for your unit for the best and longest lasting life. While substitute electrodes can be installed in an emergency situation, they frequently won't last as long as the right ones and sometimes can cause a constant buzzing while the unit is fired. They may look the same to the eye or so close that one would suspect it doesn't make any difference, but it usually does. The wrong electrode set can be "eaten up" during operation causing the gap between them to widen little by little, which happens to all electrodes eventually but much faster when the wrong set is installed. The result is that sooner than usual, the gap is too large to supply reliable ignition and the unit will act erratically or refuse to fire at all. Since there doesn't seem to be many oil-fired units in your area, I'll suspect the HVAC joints don't usually stock a wide array of parts and then when you have problems requiring those parts, long wait times can occur. A couple of weeks wouldn't be unheard of these days around here. That $12-$15 invested in an extra set of electrodes and $5 for a spare nozzle can be worth a few hundred if things go sour unexpectedly.......whether you're installing them or someone else is.
I'll tag on one more bit of info here since you seem bound and determined to get a handle on all this. The correct combustion air setting is one thing; maintaining it is another. Numerous times I've found faltering units running too rich because the ports of the combustion air blower are partially blocked over with lint, animal hair, etc. Make sure all of the ports are clear before anyone adjusts the combustion air setting and look to see if this problem exists if things seem out of whack. A person should just get in the habit of taking a look every couple weeks or so. It only takes about 15 seconds of your time. Check more often if the unit resides in a dirty environment where this type of occurrance is even more likely.
Well.....since I've already butchered this sucker with edits...what's one more?
I realized that I didn't address one of the things you mentioned as being different after the last service and that's the current noise level as it concerns the liner that was installed. Since a larger nozzle size will result in a bit more noise from any unit, so will shrinking the size of the firebox with a liner and leaving the same nozzle size that was previously installed. This may exlain all of the rise in noise level, but not necessarily. The combustion air may need to be adjusted also because they may not have not that or done it well. However, let me caution you against turning down the combustion air just to lower the noise level. It's really easy to turn that combustion air too low and end up with unspent fuel and sooting problems. The ratio of air to fuel has to be sufficient, no matter what or problems will result. Same general thing as in your car engine. A stuck choke or clogged air cleaner results in black smoke pouring from your tailpipe.
Knowledge is power, but only if applied in a timely fashion.
Edited 1/30/2004 8:52:19 AM ET by GOLDHILLER
Edited 1/30/2004 8:54:16 AM ET by GOLDHILLER
Edited 1/30/2004 9:18:18 AM ET by GOLDHILLER
Edited 1/30/2004 11:15:31 AM ET by GOLDHILLER
Thanks, that's a considerable help. When the unit first started getting flakey, I ordered a couple items off the internet. A couple nozzles, some spare filters, and a Beckett electrode kit. There's a setting gage in the kit, so I could probably get them about right. When the unit first stopped working, I pulled the burner off and saw that the liner had disintegrated and a big hunk was blocking the burner. I couldn't locate a liner kit on the internet, not that I knew what I was doing, so I called the service guys. As ever, they did about 80% of a good job. When he had it all apart, I showed him the electrode kit and asked him if he'd put it in. He said it didn't need it. I didn't argue, but the set installed has to be at least 15 years old. I think it wouldn't hurt to put them in. That could be part of the unreliable starting problem. I think they may have left a few things undone so they'd get another service call out of the deal. I think they should have spent the extra 10 minutes and done it right the first shot.
The service company had to order the liner, which took them about 2 weeks. Nobody around here stocked the nozzles or electrode kit. If I want to keep this thing running, I'll have to learn enough to do the routine stuff and keep some spares around. I'd certainly be willing to buy a textbook and service manual if I knew what and where to get it. Its not real convenient to have no central heat for 2 weeks in this weather.
best of luck with your burner - we have an oil boiler that is close to a hundred yrs old - probably began its life as a sawdust burner
my first reaction after reading original post was it could be as simple as your thermostat not being compatible to your boiler - an issue we have experienced
sounds like you are on track Goldhiller would a tiger loop be something to consider when burner problem is solved?
So how does the heating tech figure out if the nozzle is too big, and what size it ought to be?
We have an oil-fired hot-water furnace, Burnham I believe, that is tied to baqseboard radiators. When our thermostat calls for heat, our furnace fires up for only a couple of minutes, then shuts down for a bit longer than it was on. That cycle continues.
I believe that the furnace was oversized, in anticipation of an addition of about 900 SF, so I'm assuming that's why it short-cycles?
For the size of the house, we don't seem to use all that much oil, but if we could use less, that'd be great!
You ask some big questions.
How big of a nozzle do you need? The smallest that meets your heating needs in the most extreme of conditions your home will be exposed to will be the most efficient size. This can be determined/calculated from the size and running characteristics of a previous unit's BTU output…… or it is done according to the calculated heat loss of your home. The most efficient size of a heating unit would be a unit that runs 100% of the time in the very most extreme of conditions and is able to just keep up at that pace with your desired heating comfort. This is rarely achieved in reality. Usually calculations are made and a certain percentage of extra buffer is added in to allow for error or more extreme conditions. As concerns achieving this all in reality, you can reduce nozzle size incrementally until you find a size that barely meets your needs or find the size that can't quite keep up during the worst conditions and then you return to the next larger nozzle. Trial and error sorta deal. If doing this oneself, all you're out is the cost of the nozzles and the time to adjust everything. If hiring it done, you'll reach a point of diminishing return. You'll have to decide when that point has arrived. Maybe you're there already. The cost of heating a home is not only in efficiency of fuel consumption, but in the total cost of service to the equipment……….be that the furnace, the windows, the insulation, etc.
Whether your unit is "short-cycling" because it's currently oversized in anticipation of the addition is hard to say from here. That just might be. Might depend on what the HVAC contractor was aware of or told to anticipate and address. Or it may be only a part of the issue of the "short-cycling". There are other factors that can come into play and/or interplay.
I'm presuming you mean boiler when you say "hot water furnace". A boiler can be configured to constantly maintain a reservoir of water heated to X degrees, or it can be configured to only heat the water when the thermostat calls for heat. In the latter instance, temperature recovery times in the living area will be a bit longer. In the former, recovery times will be shorter but you'll hear the boiler fire more often for shorter periods of time as it maintains the reservoir "at the ready". Can't say for sure how yours is configured.
One of the other factors that come into play is the aqua-stat. If the kick-in and kick-out are set too closely together in either of the above scenarios, it can cause "short-cycling". Typical settings for this would be 160F and 190F. If set closer, shorter fire times would result.
The relationship of size of supply pipes and the size and number of radiators come into play, as well as the potential of a failing circulation pump.
Flue exhaust draft can't be totally ruled out which could result in kicking a high-limit switch.
I'm afraid I can't provide any real answers or tests from here as too many inter-related variables are involved. A good HVAC tech should be able to answer these questions and discover any "issues" on site.
Knowledge is power, but only if applied in a timely fashion.
Thanks for the detailed reply. I didn't expect an exact answer to our situaiton, of course, but was interested in the general theory at work. You provided that.
We have a hot-water boiler, as you suggested. There is no hot water storage for heat, but there is a "Superstor" indirect water heater/storage tank for domestic hot water, which is also heated by the boiler.
When the thermostat calls for heat, the boiler starts, unless the hot water tank is calling for heat, in which case all of the other heating zones are shut off until the hot water tank is satisfied.
I do recall that we had contacted the hot water tank manufacturer, they recommended a boiler size that actually exceeded what was required by the entire house. I guess they really wanted us to have hot water...
Good advice about the kick-in and kick-out limit switches. I'll have to see what they're set to.
When the furnace was installed, we did have a tech, separate from the guys that did the install, come to fire it up and do an efficiency test. But they didn't do much beyond that - didn't make any adjustments that I can recall.
I guess we need to have somebody who's very knowledgeable, and who has the right equipment, take a good long look at it all. I mean, somebody who can do more than replace the oil filter and run a vacuum over everything. :)
By heating the air, do you mean that the air leaving the registers is not as hot as the old furnace?If yes, then you are right. Most new gas furnaces have a lower temperature rise.The total btu output is the same, it just doesn't feel as hot.
Myself, I'd be looking at the installation and operating Manual, that somebody ought to have, perferably the HO. Best of luck in your travels,,, Jim J