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Rinnai E75CN Heatting Issues

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erinlem77
erinlem77 Member Posts: 3
I have a Rinnail E75CN combo unit. I've had it for 2 years now and it has never worked properly. Sometimes the heat shuts off in the middle of the night and I wake up at 2 in the morning and it's 50 degrees in my house! Then sometimes it's 85 degrees in the middle of the night! It's crazy! No one can figure out what's wrong with this thing. I have no error codes either. Does anyone know what the problem could be? Any advice would be great!

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  • Tom_133
    Tom_133 Member Posts: 893
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    Lots of Pictures, we ned to see what you have for piping. Then you will get plenty of help. Try to get pics from a little ways back so we can see all of it.
    Tom
    Montpelier Vt
  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,255
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    Did you install? Contractor? All these great energy-efficient products are very finicky in regards to pipe size supplying them and venting. .....and that missing link....... LACK of ANNUAL MAINTENANCE!!!!!! Mad Dog
  • erinlem77
    erinlem77 Member Posts: 3
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    Ok Tom will get some pics up tonight! Thanks for all of your responses!
  • erinlem77
    erinlem77 Member Posts: 3
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    Mad Dog, my father is a licensed pipe fitter and did the piping. We had a licensed contractor oversee the install. I also did some research on my own and while I was reading the manual, I noticed that the PSI should be at 16 to 18 and its reading at a 23 PSI. When I shut the hot water off the water pressure goes to 30. Do you think that has anything to do with the heat not working properly? Thank you!
  • 143friend
    143friend Member Posts: 4
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    I have a Rinnai E75CN combo boiler which is 5 years old. I've performed yearly descaling myself. As of now the heat works, but very little, and although there are no error codes, the temp in my house (while set to 68) is in the low 50's. The radiators are warm but not hot. I have someone coming down on Friday, but it's pretty cold right now. Are there any screens or filter which may need to be cleaned that may be causing this problem? thx for your input.
  • 143friend
    143friend Member Posts: 4
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    Just an update.......my display constantly shows the number 6 (with a temp of 166 showing after that, and the unit says that this means that the zones are calling for heat, but the pump is not operating.
  • DZoro
    DZoro Member Posts: 1,048
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    Have to find out why the pump isn't operating, pictures of the system would help.
    D
  • 143friend
    143friend Member Posts: 4
    edited January 2019
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    Here's a pic of the unit.
  • Brewbeer
    Brewbeer Member Posts: 616
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    Step back 5 feet and take another photo, we would like to see all the near boiler piping.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
    System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg
    DZoro
  • Grallert
    Grallert Member Posts: 671
    edited January 2019
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    erinlem77 said:

    I have a Rinnail E75CN combo unit. I've had it for 2 years now and it has never worked properly. Sometimes the heat shuts off in the middle of the night and I wake up at 2 in the morning and it's 50 degrees in my house! Then sometimes it's 85 degrees in the middle of the night! It's crazy! No one can figure out what's wrong with this thing. I have no error codes either. Does anyone know what the problem could be? Any advice would be great!

    I'd be interested to know which lights on the display are illuminated. In other words is the hot water (domestic hot water) light illuminated when you find the house at 85? and by chance is the hot water extra hot when you find house cold? Just guessing here but I've had some issues the internal bypass valve getting stuck in the wrong position.
    OOOPS I didn't read the date of the original post. Sorry
    Miss Hall's School service mechanic, greenhouse manager,teacher and dog walker
  • Alan (California Radiant) Forbes
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    Usually when there's no error message, the boiler is operating as it's supposed to. If these boilers are operating with the on-board outdoor reset feature, check to make sure the outdoor sensor is reading the outdoor temperature properly. You will have to have an ohm meter and the troubleshooting manual for the boiler which will give you the ohm reading at different temperatures.

    It also could be the way the boiler was set up. Check the programming to make sure target water temperatures are realistic for design conditions. You may need to bump up the water temperature.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • DZoro
    DZoro Member Posts: 1,048
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    Post a picture of the entire system pumps and piping, we can zoom in if we need
    D