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Lochinvar Noble Combi nkc-110 cold sandwich problems

EliNY Member Posts: 1
Hi all,
Just got brand new Lochinvar Noble Combi nkc-110 installed and having cold water sandwich issue when running ANY hot water, shower or faucet.The hot water comes in waves and if I look at the unit when the water are running I can see it heat up to around 130 and going down to around 97 and over again. My DHW temp is set up 120. and I have the pre heat enabled and DHW RESPOND TIME set for 2:00 . called tech support the told me to try and replace shower head to lower gpm but this didn't pull the trick as the unit does not provide a constant temp flow of hot water .

Any ideas??

Thank you very much


  • hot_rod
    hot_rod Member Posts: 19,924
    Maybe measure the gpm coming out of the shower heads. You may be flowing more that the unit can keep up with. That may be why tech support suggested lower flow heads?

    Are the shower valves single handle type with scald guard or a thermostatic cartridge?

    I have had a Nobel combi for a few years it tracks well with a small lav flow or a outdoor full flow hose bib running.

    It could have a defective sensor in the mix block?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • bob eck
    bob eck Member Posts: 930
    Is there a domestic hot water mixing valve installed on the hot water supply coming out of the boiler? This boiler with the mixing valve will deliver 2.6 gpm at a 70 degree temp rise.
  • cosmo123
    cosmo123 Member Posts: 1
    ok iam having a prompblem with my shower its not holding any hot water i have a nkc110 .ok here it goes i changed my symmons valve twice and put in a direct line still not holding hot water but my sink kitchen sink washing machine is all getting hot i have a bout 70 lbs of pressure comming in does this matter nobody can figure this out is their something with the flow going to shower need help is it the mixing valve, on symmons is it the unit shower head is rated for 2.6 my email is rcapp58476@aol .com
  • DZoro
    DZoro Member Posts: 1,048
    You are at max flow with that shower head. Try a 1.5 gpm head.