Have a gas fired indirect system. Was working fine until about 1month ago. Hotwater temperature is not being maintained when heating goes down for night or long periods where heat is not required. Have to run water for several showers or baths to heat up to temperature. Priority switch is on! Circulator is good. technician turned up the low limit temp on the aquastat to no avail(gave a good tip too!). 4 zones each with its own circulator pump. Is there something I am missing? Thank you.

What temperature does the oiler get down to before it fires ?
Does the indirect heater have it's own circulator pump or does it use a zone valve ?

it has its own circulator pump

water is luke warm. Well below the low setting on aquastat.



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Either the pump is not running or the boiler temp is too low.

Thank you I will check it right away!Boiler is firing at 180 degrees.



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pull the sensing bulb out of the thermometer well. stick it in cold wter to see of it is calling the control to heat?

Replaced thermostat on Weil McClain Gold plus30 storage tank.Drywell for sensor was dry when removing old sensor. Removal was smooth no buildup of corrosion in tube, No change to problem, Water still cools down during overnight. Taco control box priority switch is on and confirmed wiring to water tank thermostat. Has anyone experienced trouble with controls? Control box is working fine for three heating zones.