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Wind blows out pilot in mobile home water heater

Luv'nsteam Member Posts: 277
Hello all,

My mom lives in a mobile home in Vermont.  She has a new, gas-fired water heater (brand? model? size?) that is accessible from an outside door.  She describes it as being in a closet.  I have never seen it and she lives 400 miles from me (she moved in last year).

Each time the wind gusts hard, it blows out the pilot or that is what she thinks is blowing it out.  I have no idea.  There is no vent on the access door and I have no idea how the combustion air is provided.  She had someone silicone the cracks around the walls, etc, but the problem still exists.  She did say the door does not fit tightly but neither of us know if it is supposed to.

I know nothing of gas water heaters or how they are supposed to be installed in a mobile home.  If I can figure this out, she can get someone to do whatever is suggested.

If anybody can help me help my mom, I would be truly grateful.

Thank you,



  • Mark Eatherton
    Mark Eatherton Member Posts: 5,839
    edited December 2010
    May not be wind induced pilot outage...

    Water heaters, and gas consuming appliances in general don't care whether they are in a mobile home or in the Taj Mahal. They MUST have adequate air to fully complete the combustion process, or there can be serious consequences (CO production).

    AT a minimum, there should be 1square inch of free air available for each 4,000 btuH of fire capacity in the closet, and half of that should be within 1' of the ceiling, and the other half within 1' of the floor. If not, when running, the appliance will attempt to pull combustion air down the same pipe that the products of combustion are exiting through. It is a well known fact that you can't sustain combustion in the presence of CO2, and the flame will begin generating copious amounts of CO. If the occupants are fortunate, the heater will self snuff. If they are un-fortunate, they can get CO poisoning.

    Make certain she has a good working CO detector in the home, preferably near where she sleeps, and near the location of the heater.

    If in fact it is a wind induced pilot outage problem, there are some after market pilot re-lighters which could be installed that would relight the pilot if the window blows it out, before the thermocouple has a chance to cool off and drop the safety valve out, shutting the heater down. You will have to provide some electricity in order for the re-lighter to work.


    What part of the state is she in? Some frequent readers here may be near her and capable of providing good service.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Luv'nsteam
    Luv'nsteam Member Posts: 277
    edited December 2010
    Mom's location

    Is Compton, VT.

    I will find out if she has a CO detector.  Thanks for the link to the Robert -Shaw re-lighter.  I will look into this. 

    I have been reading other forums in an effort to learn a cure for her outing pilot.  One of the things I have read several times is about the flue either not being high enough (I read the flue should be two feet higher than the closest roof line within eight feet?) to prevent back-draft into the flue and/or a rotted or MIA flue cap that allows the wind to blow down into the flue.  What are the chances one of these is the cause?  As I said, the water heater is new (about a year old) and I did not install it nor do I know the qualifications of the person that did the install or the requirements of the installation.

    Your statement about the free-air space - I presume you mean the air around the unit, between walls, ceiling & floor?  Please correct me if I am wrong.  But, what about the supply air?  Is there supposed to be a vent or something in or near the bottom of the unit to supply combustion oxygen?  If so, how is this sized and where might it be located?  And, should the access door be sealed tight, preventing wind from blowing inside the closet and extinguishing the pilot?

    Thank you,

  • rlaggren
    rlaggren Member Posts: 160
    free air

    I believe Mark was referring to the square inch area of ventilation holes or ducts to the outside from the room/space where the appliance is located. Visiting a website for the maker of that water heater or another similar (capacity, fuel, etc) you should find installation manuals which will explain the basic requirements.  The flue cap can be eyeballed from outside. The combustion air is sometimes supplied partly from a hole in the floor of the WH closet so if she has changed the skirting around the trailer that may have some affect - but it seems doubtful; however, if she has insulated the floor of the trailer and the combustion air hole was covered, that  _could_ be a problem. If the combustion air vents exist at or greater than the required size, it should be fine to seal other openings in the closet. However, if she is running propane I believe there does need to be a vent a the bottom of the closet to "drain" the gas. A lower vent 6" above the floor (as required for combustion air for natural gas) in a sealed space would not work for this - it would accumulate 6" of propane gas before it started overflowing out the vent because  propane gas is heavier than air and does not naturally rise and disipate out openings like NG. Somebody w/propane experience needs to confirm on this because my work has all been with NG. There does need to be fresh air going through that WH closet and if she sealed things because of drafts coming through the walls to the interior from the WH closet just sealing the _outside_ of the  closet isn't going to fix the problem; in that case she needs to seal the _inside_ if the closet to keep the fresh air in the closet out of the interior of her home. That would help reduce (but not eliminate) danger from gases in the WH closet as well.

    If she moved in last year then the WH must have been working for some time, including some possibly windy days (maybe even last winter?). So something may have changed in her set up that is causing the problem and it might be good to consider any changes made recently. Or possibly the thermal couple is getting weak and dropping out at the cooler temperatures or possibly the fellow who "sealed" the closet dislodged the cover plates over the WH combustion chamber and didn't put them back properly or at all.

    Best luck.  Rufus
    disclaimer - I'm a plumber, not a heating pro.
  • Tim McElwain
    Tim McElwain Member Posts: 4,506
    I am assuming this unit is using LP

    gas is that correct?

    If so it could perhaps be serviced by the local propane company who would be able to tell what is wrong. There are a number of things that thermocouple operated appliances must have checked including the remote possibility of wind blowing out the pilot. If need be I can post the things that need to be addressed here for you to pass on to her.
  • Luv'nsteam
    Luv'nsteam Member Posts: 277
    The water heater is one year old

    Rufus, and she has not had this problem before (a new WH was required for the loan).  The weather up there has been very nasty the last week. 

    Thanks for the clarification of the free air and the explanation for the need of a floor vent.  I do think she has LP, so I will let her know the importance of the floor vent. 

    I do not know what brand the WH is, but if I can find out, I will certainly investigate the manufacture requirements for a proper installation.

    Is it possible or maybe a better question is, is it probable, the thermocouple is going south so soon?

    Thank you,

  • Luv'nsteam
    Luv'nsteam Member Posts: 277
    edited December 2010
    Hello Tim, I do think

    the WH is fueled with LP.  Any troubleshooting you can offer, I will certainly pass on to her.

    Thank you,

  • Tim McElwain
    Tim McElwain Member Posts: 4,506
    Here you go Mike



    I am often asked about troubleshooting a thermocouple on gas systems. This will be a permanent reference that will give a step-by-step procedure.


    A thermocouple is a device used to satisfy pilot safety on many 24-volt gas systems. The thermocouple is a device made up of two dissimilar metals. They are joined together at the tip (Hot Junction). When heat is applied to that hot junction a small millivoltage is created. This develops because of temperature difference between the hot junction and what is called the cold junction. The flame has to envelop the upper 1/2" to 3/8" of the thermocouple and the tip should glow a "dull red". If the flame is adjusted to a sharp flame it will glow "cherry red" this will cause the tip to be welded and eventually the thermocouple will fail. The flame should be adjusted to a soft blue flame, not roaring or lifting. The normal millivolt output is 25 to 35 millivolts, on some you may even get up to 35.


    The other part of this safety pilot system is the electromagnet (power unit). It is if you will the LOAD and we can say the thermocouple is the SOURCE. The electromagnet is made up of a coil of wire and "U" shaped iron core. When the thermocouple is heated and the millivolts generated the coil will be energized and create a magnetic field. The magnetic field will cause the "U" shaped iron core to be magnetized; it in turn will hold open a seat allowing gas to pass through.


    When this system malfunctions it typically causes the pilot to go out and the gas will not flow. The first thing that should be done when arriving at a pilot outage situation is to do some visual checks.









    Once those things are addressed it is a good idea to take some millivolt readings. It should also be mentioned that many times it is the policy of some to replace the thermocouple on a call and clean the pilot. It is not a bad thing to do, however it is statistically about 85% of the time it is the thermocouple giving the problem. It is the other 15% of the time that taking readings can solve other problems.


    You need a multimeter with a DC volt scale, as the millivolts generated are DC volts. There are four readings we are going to take they are


    OPEN CIRCUIT - this is taken with the thermocouple disconnected and the meter leads attached to the outside of the thermocouple and the other meter lead attached to the tip of thermocouple. The pilot-on-off knob will have to be held manually to take this reading. This measures the output of T'couple the readings must be above 17 to 18 millivolts.


     * CLOSED CIRCUIT - This measures the millivolts used by the coil in the electromagnet. A rule-of-thumb is this reading should be roughly half of the open circuit. It is taken using an adapter screwed into the magnet and the thermocouple screwed into the adapter.


    CLOSED CIRCUIT LOAD - This reading is taken the same as the previous reading except the burner is now on. With a proper flame this reading should be about the same as the previous reading. With a lifting main burner flame or excessive drafts or chimney pull, this reading may reduce from previous reading (flame being pulled away from the thermocouple). With the cold junction being heated this reading may increase. If the "cold junction" is heated excessively it will break down.


    DROP OUT - This is the final reading. It requires the pilot to be blown out. It measures the ability of the magnet to hold under reduced MV input. A good unit should drop out below 6 MV's - normal is 1 to 2 MV's. The allowable "drop out" time is 180 seconds yes three minutes. It is more likely to be a minute and half to two minutes. There will be an audible "click" when the magnet shuts down.




    A normal set of readings


    OC- 30 millivolts

    CC- 15 millivolts

    CC(load) -15 millivolts

    DO- 1 millivolt


    The best way to be able to diagnose these readings is to use MILLIVOLT CHARTS these can not be displayed here but I can provide them if you e-mail me.


    Thermocouples from different manufacturers vary as to their dependability. The only thermocouples I recommend are made by Johnson Controls. The K15 and K16 series are the best. If you are having durability problems then use the K16RA, which is a nickel-plated high ambient or corrosive environment thermocouple. The Husky (K16) will fit most applications and for those that it does not the Slim Jim (K15) will fit.


    To repeat the adjustment of the pilot flame to envelope the upper 1/2 to 3/8 of the thermocouple is important, the flame should be a soft blue flame not roaring which will cause the tip to glow a "dull red" versus "cherry red".


    The combustion condition (excessive temperatures) in the chamber is also an issue and this will require a combustion test and draft measurement to insure that excessive temperatures are not being applied to the pilot. In some cases on water heaters it may be necessary to alter the pilot adaptation to get better quality performance. This however should not be done unless you have had proper training.


    The possibility of the equipment operating in a depressurization environment will certainly lead to thermocouple failure. In addition if the equipment is flued together with a "fan assisted" furnace or boiler this can lead to problems. There are solutions to this also but training is required.


    The thing that I find is often a problem is the environment in which the equipment is operating. Many times corrosive chemicals and airborne contaminants are being drawn into the air gas mix and a chemical reaction takes place. This again requires attendance at a training session by a professional combustion person to help you to see the various affects this will have.


    Last of all the failure to put all the doors and covers back in place on equipment. The failure to do this will cause an alteration in combustion air and the flame stability is affected.


    The design of some equipment is also a problem. When there is high demand for heat (very cold weather) the temperatures that are created in the chamber have an adverse affect on the pilot and thermocouple system. The addition of the K16RA thermocouple can offer some assistance toward extending the life of the thermocouple in this situation.


    Insufficient air for combustion and dryers operating in close proximity to equipment also lead to problems.


    Last of all and this is not directed at any one in particular but just plain lack of service personnel and installers knowing what they are doing.


    My book "Circuitry and Troubleshooting" Volume II addresses many of the things in question here.


  • Luv'nsteam
    Luv'nsteam Member Posts: 277
    Tim, that is an excellent

    Troubleshooting guide.  I will not only share it with Mom, but I will keep a copy for myself.

    Thank you!

  • rlaggren
    rlaggren Member Posts: 160
    Service from a qualified tech a good idea

    Tim gave you the best possible advice in suggesting a service call from the company. He has been in the biz a long time and has helped many people, but really and truly:  When dealing with a combustion appliance a visit by an experienced qualified tech on site is worth a million words of guesses. While WH's are relatively simple creatures they should be treated with good and proper respect (recall the CO warning) and it's impossible to relay the myriad of little details that might matter by messaging back and forth.

    It's also a very good idea to get acquainted and establish an ongoing relationship with a service company; starting with something like this is a good way to find one the she feels comfortable with. Nobody likes to pay out $$ to auto mechanics, plumbers (me) or various other tradesman (lawyers?), but it's better to find the people you need  and can trust in relatively non-emergency circumstances such as this. The propane company has a bit of a built-in interested in her situation and they may well be the best place to start.

    Best luck.  Rufus
    disclaimer - I'm a plumber, not a heating pro.
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