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Not enough hot water

Larry C_20
Larry C_20 Member Posts: 4

I am having issue of not enough and non consistant temperature DHW. We have a Peerless EC-05 with a Becket RWB burner with the pressure set to 140 psi and a 1.5 gpm 60 degree B pattern nozzle. The boiler has an indirect coil with a Watts 70A tempering valve on the output. The Honeywell Triple aquastat L8124L settings are as follows. Hi is 180, Lo is 140, and Diff is 20.

I have disassembled the tempering valve and cleaned out some debris. I can not guarantee I assembled it back together correctly. I believe I did, but I have been wrong before, and I will be wrong again.

Any help is always appreciated.


Larry C


  • When you say

    you have an indirect coil , do you mean an internal coil ?

    If it is an internal coil , you might need to bump up the low limit setting . With no call for heat , 140 with a diff of 20 can give you hot water problems . It can also be a gunked up coil or the 70A . What did you set the tempering valve at ?
  • Larry C_13
    Larry C_13 Member Posts: 94
    Low limit of 140 with a diff of 20 means what.

    Does the LO limit of 140 means that the boiler will turn on at 140 or it will turn off at 140? And is the DIFF additive or subtractive from the setpoint(s).

  • scrook_3
    scrook_3 Member Posts: 66
    Honeywell L8124 aquastat?

    If it's an L8124 it's tricky: Low set for 140° boiler turns on at 140°-10°=130° that 10° is fixed. If differential is set for 10° it turns off at 140° (+10° from LOW-10°), if diff is at 15 then it turns off at 145°, at 20° then 150°, at 25° then 155°.

    Your case: ON at 130°, OFF at 150° The High limit should be AT LEAST 20° higher than Low limit (at least 160° in your case, so you're good) so they do not interfere with each other.

    If you're a visual person see page 7 of install instructions: http://customer.honeywell.com/techlit/pdf/PackedLit/95-6571.pdf

    High limit is fixed 10° subtractive diff, so if set at 180° than burner shuts off at 180° and back on at 170° (if a thermostat's calling for heat). With no call for heat you'd cycle between about 130° and 150°

    Do you have hard water? If so, the coil could be scaled up w/ calcium deposits on the domestic hot water side, limiting heat transfer.
  • bruce_21
    bruce_21 Member Posts: 241
    Do you have hard water?

    Water hardness above 5 or 6 grains will load up a tankless coil quicker than you might think. You will know it because the hot water flow goes way down, then there is no flow. The coil can be cleaned with acid if there is still some flow. But that process is not for an inexperienced person.

    Another thing to check is if the 70A is mounted below the output of the tankless coil per Watts' install instructions. If not the element inside gets cooked.
  • Buster
    Buster Member Posts: 36

    To check the element AND coil output pull the element out of the tempering valve and just put the head back on. Now it uses ALL hot water so you can tell if the coil is producing and if the element is bad.
  • Larry C_13
    Larry C_13 Member Posts: 94
    Thanks for the assistance.

    To Scrook and Ron Jr.

    Thanks for the assistance. I bumped the Lo setting up to 150 and showers are alot nicer.

    Now I am noticing that the boiler cycles more often. I am assumming that is partially due to the aquastat change and some sort of ghost flow thru another loop. I finally realized that the kitchen has been warmer because the radiator was warm, even though the thermostat has been off for the last week.

    Last night I shut the kitchen loop isolation valve to stop the thermal circulation. I also disabled the kitchen loop circulator to prevent damage to the circulator pump. I'll see if that cuts down on the short cycling.

    Larry C
  • billtwocase
    billtwocase Member Posts: 2,385

    Larry, keep in mind that all tankless coils are rated at 200 degrees F. Generally you need to maintain atleast 160-180 degrees to get any kind of output. Also the nozzle rating is gallons per hour, not per min. It will cycle on more often to maintain that higher temp. peace
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