Question about Mr. Heater MHU45LP

2 Answers

Heater will not ignite

Hi I have a MHU45LP and it worked fine. But now it will not ignite I changed the igniter, flame sensor and even swaped the board out. The gas comes on and still no heat unless I lite it myself. Gives 2 flashes which means no flame detected, and I already know that. Q: How much volts should I have at the igniters?
Any help in this matter would surely save my hairline.
Thanks

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  • 2 more comments 
  • Anonymous Mar 10, 2008

    I have identical issue. I have troubleshot it back to the board as well. I ordered on online today as I have not yet located my original invoice (unit is 8 months old). I will pursue reimbursement for board.

  • Anonymous Mar 18, 2008

    same exact problem.

  • Pnatrick Apr 11, 2008

    same problem but i have the 75 unit

  • shaun35 Dec 06, 2008

    did changing the board work mine is doing the same thing and they are sending me a board

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2 Answers

Thanks, I called the manufacurer and they told me it was most likely the board which was not igniting flame. They are sending me a new one. I will see if that does the trick. Thanks for your help.

Posted on Mar 04, 2008

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The igniter should have 120v if it is Hot Surface Igniter (HSI). You may be having a problem with gas pressures. Possible transformer problem also if you changed that with other parts.

Posted on Mar 04, 2008

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Being as how you changed the gas valve, make sure the arrow on the bottom of the gas valve is pointed towards the burner. Check for 24 volts at the common and main valve terminals on the gas valve when the thermostat is calling for heat...terminals MV and C. You will only have 24v there if the flame sensor senses flame... either pilot flame or main gas. You coud have 24v there without gas flowing or flame if is is a thermocouple standing pilot system and the gas valve is not in the 'on' position. But standing pilot systems usually do not have flame sensors.

With a flame sensor in the system, you have to have either spark ignition or glow coil ignition. If its spark ignition check for 24 volts at the pilot valve and common terminals on the gas valve WHILE the ignitor is sparking. That would be PV and C. The ignitor should spark and 24v should be on PV and C for 30 seconds to a full minute without ignition if it is a spark-to-pilot system.

If you have a glow coil, it will energize and burn bright orange for a minimum of 30 seconds BEFORE the main valve is energized. Then MV and C is only receiving 24v for approximately 5 to 6 seconds. This gives the flame sensor the time to prove the flame....if it does not prove flame, the system shuts down.

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I have a Big Maxx MHU45LP....1 1/2 yrs old....used maybe 5 times. 10 hrs running time at most...... The furnace was hard starting right from installation.....the burner was hard to ignite.....try 3...


There are several things that could be causing this problem. Low gas pressure comes to mind, first. Followed by an electronic ignition problem. Which may simply be caused by poor line voltage or a dirty sensor. Amazingly, not using the heater regularly, can do more harm than good. Because, in the long down times, spiders like to go into these heaters and build nests. These nests can really clog things u

As far as the lots of flame on ignition, this is probably a result of delayed ignition, which causes a gas build up.

In addition, if you live in an area that is more than 2000 feet above sea level, the pressure regulator should be adjusted to provide more gas.

Juts in case you have misplaced your Owners Manual, I have included a link to it, that you can download and print for future reference.

http://www.mrheater.com/upload/newsletter/MHU_HSU_CUH_60016_BL.pdf

If you continue to have problems and are dissatisfied, contact ENRICO (the manufacturer of Mr Heater Products), Technical Service Dept at 800-251-0001

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On a call for heat, the 24 volt thermostat sends a signal to the control module. The control module will indicate a call for heat with a light on the control either blinking or remain solid depending upon model. The inducer (exhaust) blower will purge all gasses from the furnace and pressurize a pressure switch. Once the pressure switch tells the module to continue, the electronic ignition will energize and send 120 volts to the igniter. The igniter will glow and you will be able to see it if viewed thru the small inspection port. Once the igniter gets hot enough, it sends a signal to the module opening up the gas valve (24 volts). Either a pilot will come on or the burner tube will ignite then spread the flame to all burners. Lastly a safety sensor will be looking for a certain temperature within a few seconds and the furnace will continue to operate and the room air blower will turn on in a minute or two.

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Intalled an overhead 130K BTU Mr. Heater last


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1 Answer

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