boiler vs furnaces ?

Discussion in 'Off-Topic' started by Mathematics!, Aug 3, 2013.

  1. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    I am curious why one would uses a boiler over a furnaces?

    Is there any benefit or case where you have to uses one over the other?

    Seems to me boilers work on heating up water to create steam which then is used to heat.
    Where as furnace to me is the more natural way of doing heating the air with fire to produces heat. Why waste water but I am probably missing something.

    Or on a large scale it is some how better to uses one over the other?
     
  2. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,675
    2,723
    I am far from an expert on this but I would imagine that, with a latent heat of vaporization of 2,260 kJ/kg, steam can carry far more heat energy than air (specific heat = 1 kJ/kg/C). It's probably easier to plumb it around a building so as to provide distributed heating from a centralized source.

    And, I would think that the water is not wasted, but reclaimed back into the boiler.
     
  3. LDC3

    Active Member

    Apr 27, 2013
    920
    160
    1. I am curious why one would uses a boiler over a furnaces?
    The requirements for a boiler are different than for a furnace.

    2. Is there any benefit or case where you have to uses one over the other?
    Yes.

    3. Or on a large scale it is some how better to uses one over the other?
    Yes, it is better to use a boiler.
     
  4. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    I see so then my next question is does most big buildings , or places use boilers over furnaces when it comes to non-residential places (like homes).

    It seems like for efficiency they normally would but in most houses I just see furnaces.

    Separate some what related questions I am confused about is

    1) if a thermocouple in a furnace wasn't working properly i.e not producing electricity when heated then would this prevent the gas from flowing to the burner and ultimately preventing the whole furnace from working/coming on.

    And if so is there a way to bypass the thermocouple by running a small current down it in some way?

    2) There is an on off and pilot option on most gas powered furnaces and hot water tanks...etc I never understood what the pilot was for I only put it do that position pushed down on it and lighted the furnace then put it to on position. Though I am curious why I couldn't just put it to on position and then light the furnaces why the extra pilot option ? To me it is either on or off what is this pilot crap and why did they make it separate from just on.
     
  5. Metalmann

    Active Member

    Dec 8, 2012
    700
    223


    I've lived in a couple houses with boilers, and the steam heat worked pretty well with my chronic sinusitis. Some claim, that steam is an overall better heat, for your health.....:confused:
     
  6. #12

    Expert

    Nov 30, 2010
    16,259
    6,766
    If you tried to open the gas flow to "run" volume, and then light it, it would burn your eyebrows off when the gas cloud lit.

    While I am a State Certified Air Conditioner guy, I have never done, "heat only". (That would be a stupid thing to do in Florida.) That requires less air flow than cooling, so my numbers are probably off a bit.
     
  7. joeyd999

    AAC Fanatic!

    Jun 6, 2011
    2,675
    2,723
    #12, long ago when I was a young boy (< 5y.o.), we lived in an apartment with one of those cast iron radiators. I've got the scar of 4 stitches on my face from when I fell into one.

    Those were steam powered, right?

    That is one tall, very skinny building! :D
     
  8. #12

    Expert

    Nov 30, 2010
    16,259
    6,766
    1)Yes, those old, cast iron radiators are powered with steam.
    2) it makes the math easier:rolleyes:
     
  9. LDC3

    Active Member

    Apr 27, 2013
    920
    160
    First, the main gas will not flow if the control senses that there is no pilot flame. If the pilot goes out (due to a drop in gas pressure), there will be no gas flowing when the pressure is re-established. Second, there is no gas for the pilot unless you press down on the switch.
     
  10. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    So my question is then why do we need both the thermocoupler and the thermostat. Isn't the thermostat responsible for regulating the temperature hot / cold , on / off , blower motor on/off , ...etc. Why the need for the thermocoupler. I know I am being stupid with this but I don't get it even when I installed a digital thermostat for a house it was pretty simple but never got the thermocoupler part.. why cann't we have one unit do everything.
    I know the thermocoupler looks very easy to install even easier then the actual digital thermostat.

    Question 1)
    I have lighted the pilot jets on a gas oven when power was out to cook on. That was pretty easy but I never could find the way to light the oven when the power was out. It looks as if there is a box similar to the one on a furnace or gas water heater. Though I haven't figured out yet where to light the oven manual where to hold the flame. And if it is some pilot button ,or thermocoupler that is not allowing me to turn on the oven.

    Looking at a thermocoupler it seems as it is just a long metal stick that screws into the gas box so I am kind of wondering how this is even holding gas back or doing anything for that matter to regulate gas flow. Don't look like a car thermostat so it is hard to see how it functions to regulate gas thru?

    As for the ON OFF PILOT button settings on the gas box. I am still unclear with these... since on should open a gas valve (allow the gas to flow just like in a water pipes on valve position) , OFF is the opposite of ON . So logically putting the setting to ON and then trying to light the pilot should be all that is needed ... since gas will flow ...I would imagine when the button is in ON position "THIS IS JUST LOGICAL THINKING UNDER THE CURRENT KNOWLEDGE"

    So if one could explain better what the need/what the thermocouplers uses is for and how it works interms of the inner gas box. As well as the 3 settings ON OFF PILOT / the difference between the ON or PILOT setting. I would greatly appreciate that.


    Because by the looks of it it is the thermostat , relay (allows the turning on of different devices like fan , blower , air conditioning ,...etc) , transformer (120 to 24 volt conversion) and the electrical connections on the gas box (from the transformer/terminal screw downs) that make/ regulate the opening of the gas valve... sort of like I am thinking some electrical mechanic valve opener for the gas. So really don't understand about the thermocoupler and looking at the honey wire diagram which is understandable how it is rigged up I see no indication that the thermocoupler plays any role in opening the gas valve in the gas box.

    Also checking the oven I see when I turn it on there is like 4 small mini florescent light bulbs that start to glow bright just before the whoose/fire start coming out of the oven jet. So I am wondering where the electrical component of this comes into play... like if the power was out I still won't start ? I understand the jets on top stove need the electric to create the spark but one can manually do it with a sparker/match. I know I am probably missing what some inner component function is doing with electricity for the oven. But if all it is is just heating/making the bulb area hot enough then one should easily beable to do it manual. (provided he takes safety precautions.

    Anybody out there HVAC or appliance installation people that are more experienced in this area and care to answer.
     
    Last edited: Aug 3, 2013
  11. LDC3

    Active Member

    Apr 27, 2013
    920
    160
    A thermocouple is 2 wires of different material connected (fused) together. This junction generates a potential that varies with temperature. So when you place the thermocouple in a flame, the potential change is substantial. This potential is monitored in the control box and if there is no flame, a solenoid closes the gas flow (you need power to open the gas flow).

    So in the OFF position, both the solenoid valve and the manual valve are shut. In the pilot position (before the flame is lit), the solenoid is cut and the manual valve is partially open. You push down on the switch to open the solenoid valve and light the pilot. In the pilot position, the main burner will not light, so you need to move it to ON.
     
  12. #12

    Expert

    Nov 30, 2010
    16,259
    6,766
    As he said, pilot and on are two different circuits. One is a very low flow so you can light it safely and the other is a high volume flow, so you can't safely light it. From real world experience, a delay of 2 1/2 seconds from "on" to lighting accumulates enough gas to blow the front cover off the furnace.

    I'm really getting worried that you are going to try some of this stuff. You'll shoot your eye out, kid!
     
  13. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,004
    1,525
    The pilot thermocouple/safety is not electrical. It uses a capillary tube full of a wax substance. When the pilot is lit/working the wax expands putting pressure on a internal valve allowing the main gas to flow when the thermostat calls for heat. With out the thermocouple/safety, the appliance would fill with gas and a spark could cause an explosion.

    Most modern single family boiler systems don't make steam. They use only hot water in the system. And a circulating pump to move it to what ever area is calling for heat. Safer for modern people to use.

    Multi-story apartment buildings an some office buildings use steam. Because steam doesn't need to be pumped. But they have a "fireman" or boiler attendant, to watch the pressures and water levels in the boilers.
     
    #12 likes this.
  14. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    Ok , so there is like 2 valves in the gas box one controlled by the theromcoupler and the other controlled by the ON/OFF/PILOT Light button. Correct me if I am wrong?

    Questions

    1)And if the theromocoupler was taken out would gas not beable to flow even if the main gas line to the furnace was open ?

    2) If the theromocoupler was working properly and and the OFF light button was turned on then correct me if I am wrong gas wouldn't beable to flow even if one heated the theromocoupler manually because the second valve would be shut off.

    3) So what you posted above if I am understanding you correctly there is 2 valves in the gas box and both have to be open for gas to flow to the furnace. The pilot setting is to regulate the gas so you don't get to much coming out to soon when you manually light the furnace ... so that you are safe and won't blow up. Though once its lite you have to turn it to ON position for the furnace to keep operating.

    4)
    Ok for a furnace and a gas hot water tank lighting it manually and setting the heat settings is pretty straight forward now that I understand the more detailed advice from you guys. But for the one other gas appliance in the home i.e the(gas oven/ranger ). How would one light this oven manually if the power was out ? Does it still work like the gas furnace , gas hot water tank ... interms of a gas box that functions internally the same way thermocoupler , ON/OFF/PILOT button because from where I see it ... it is hard to reach and doesn't really look the same as the other gas units.


    Please correct me if I am wrong in any of my understanding of what you said.
    Basically though the thermocoupler is just a safety precaution is if the furnace got to hot or started melting the thermocoupler would fail and the valve would be shut. On could have created a gas box with out a thermocoupler and just the ON/OFF/PILOT light one valve but then it wouldn't be as safe. Or maybe my understanding is still a little off. Please correct it if I am. Then again I would think the thermostat would control when to shut off the furnace / won't let it get to high to melt/burn the house so why the 2 thermostat to regulate the temperature and the thermocoupler ?

    For example the center air unit is controlled by the thermostat and I don't see any thermocoupler in it just for the heat/gas unit. The evaporator , condenser, copper lines , electrical circuit 240 / 24volt circuits , and refrigerant , fans are all that is need in the central air unit system. The to systems are married by the thermostat and wire screw down panel near the transformer in the furnace normally but doesn't have to be. The circuitry is ok to understand for both systems, and most of the components are ok to under stand it is basically the interior of some components that need to be understood that is giving me a little trouble... mostly just the gas box with it comes to gas powered systems.

    One last odd question is other then electric or natural gas appliances for homes. Is there still any propane , coal , or other types of fuel appliance systems being installed in homes. I know propane though not sure on any other options that are currently in uses for residential areas? As such is propane systems work similar to the gas ones i.e do they have a thermocoupler/propane box with a pilot button...etc Or are they rigged up completely different?
     
    Last edited: Aug 3, 2013
  15. LDC3

    Active Member

    Apr 27, 2013
    920
    160
    http://www.ehow.com/how-does_5541560_furnace-gas-valve-works.html
     
  16. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    So if there was no thermocouple then what would the ON/OFF/PILOT button position to ON do. I would assume that open the valve? Based on the pilot setting opening the valve great enough to safely light so the thermocouple does not completely keep the valve closed in the ON or Pilot position???

    I understand it it is like a saftey kill switch for gas even if the button is on Pilot or ON position provided it gets hot enough... if it never gets hot or not installed properly this could be a major safety hazard I would imagine. Say somebody cuts the tip .... that could be an issue for safety.

    So my understanding is the thermocoupler only can close the valve if it get to hot other then that the ON /OFF/PILOT switch or main gas line shut of valve is responsible for blocking the gas/ shutting the valve.

    I understand this for the oven top part one can bypass it be the spark/electric self ignition by using a match or sparkier. My question is not for the top of the oven (oven top) but for the oven/broiler unit themselves provided you are out of electricity. And don't have a generator or UPS devices and want to start it manually.
     
    Last edited: Aug 3, 2013
  17. #12

    Expert

    Nov 30, 2010
    16,259
    6,766
    If the thermocouple is damaged or missing NOTHING can get gas to flow except maybe smashing the valve with a hammer or running a drill through the gas valve. A missing thermocouple is not a safety hazard because NOTHING will flow if it is missing.

    As for how to light an oven without electricity, I suggest you look up the model number and read the instructions. This is not allaboutgasappliances.com. It would be a rare stroke of luck if somebody here guessed which brand of oven you have and knew how to light it under unusual conditions.
     
    shortbus likes this.
  18. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    O never mind found the manual to this model gas oven I have it was behind the oven in a plastic envelope.

    Apparently for the gas come out of the valve for the oven 2.9amps of current is needed for 30 to 60 seconds. So this part of the oven makes it impossible to start thru non-electric methods. aka bake ignitor, control valve ,glowbar ...etc
    The glowbar is what I was seeing now I saw and observed /understand the circuit from the diagram.... Although one would have to be careful handling the spark module I would discharge it after unpluging the power to be safe.... similar to discharing capacitor ...

    Though the iginition system module for the top of the unit can be by passed by moving the dial to open (this opens the valve) (and if electricity was being supplied activites the spark module and the 2 electrode get a spark which starts the flame ) But one could skip and light manually with a pilot lighter or match.

    To get at alot of the part you need a special hex alan wrench and a screw driver . ( mostly everything is put together with just these tools except for the spring for oven door which can be manual adjusted ...etc)
    Though I learned that one can turn up the flame on the burner with a screw drive as the instructions say. But for me I tried this and then just set them back... not really necessary in my configuration.

    Also squirted some soapy water on the gas connection to check if I loosened anything in the process of moving the oven out a foot (no bubbles so I don't have any gas leaks )

    The gas oven is now installed back where it is and works great.
    Now I finally understand you cann't really use this gas oven with out electric for the broiler/oven part. Makes sinces ...sense the thermostat and other internal components of the devices would have to regulate the temperature of the oven in some way ... or is built that way .. the top burners are only regulated by how much gas you let thru.

    Question
    curious is there any oven/ranger models that allow self iginition of the oven/broiler when electricity is not available or are they pretty much all just oven top workable?

    The other question had to do with the furnace and gas water heater can these unit run with out electricity. I know to start the pilot on these you can but what would happen once you start it... since I would imagine they would just keep doing the same thing it was doing once you light it. remain in its same state... could you regulate the temperature or anything else without the electricity. And how would it know when to shut off or turn on would there be any safety issues for these devices if the electricity is out.... ??? (since there would be no thermostat available though the thermocoupler would be available)

    Thanks for any help.
    Obviously one could manually heat his water with an out door fire or out fire pit, or fire places ,...etc but lets not go into these primitive means.. (however the appliances are just modern versions of these primitive ways :)

    Technical data sheet for my oven was 183D8077G077
    Pub. No. 31-21211
    Part of the model number is worn off but it is a GE oven. I think its 2003 if I am reading the sticker right.
     
    Last edited: Aug 3, 2013
  19. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    And for the heat pumps , central air units they all have to run on electricity to work for the inner components like compressors , fans ,...etc so curious what a gas furnace or hot water tank without electricity would function like?


    Also curious when central air or just plain air conditioners installed in windows are more economically efficient ? Like when would the small area get to be over kill for central air . When would a large area get to be not enough for plain air conditioning.

    And normally what is the difference in price in using an air conditioning unit installed in windows or central air installed in furnace vent.
    What I know is on average people pay half there electric bill on heating and air conditioning. So was kind of wondering what air conditioning method is better.
    Is there like a way you can punch in your location , approx sq ft of your living quarters , rooms ,..etc and it tells you how much for central air or using plain air conditioning units / how many...etc, quality of method used,...etc
     
  20. K3CFC

    New Member

    Dec 4, 2012
    29
    0
    Without getting into a very long explanation forced hot air furnaces not very efficient because they cool down too fast after it shuts down. it takes a lot longer to heat back up before it will turn the blower on. on the other hand a boiler forced hot water be it base board or radiator stays hot a lot longer so it takes less time to bring the water back up to temperature to turn the circulator on. base board is better than hot air but then radiator is the best because they stay hot way longer then all other. about the thermostat. it controls the furnace to regulate how warm it gets in your house. digital are far more better than the old mechanical ones having a bi metal spring and a mercury bottle. about the thermocouple. be it a water heater or a gas furnace/boiler they produce 400 micro volts to the gas control when heated to 212 degrees by the pilot light. if the pilot light goes out for any reason the thermocouple cools and the gas valve shuts off preventing a gas build up and resulting in BOOM!! bypassing it if you could is a fools trick and if you did some how you would be responsible for all damage death ect. they are pretty cheap and you can get them at any hardware store get a couple hang them by the furnace/water heater along with a wrench to change it. now if you need to run the appliance you can just push the red button down and have a match and it will light but when it shuts down you will have to restart it. but the pilot light will not work without the thermocouple period.

    Hope this helps.

    K3CFC
     
Loading...