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Noritz Combi CB199DV issues with domestic side "filling"

Afternoon folks
Wanting to get off a completely electric heat and heated water system, we recently installed a CB199 LP fired (yes converted over) for both underfloor hydronic heat and flash domestic hot water. Every so often we're are getting a glitchy bit where no domestic hot water! Cold as ice
Checking the boiler screen getting a flashing "fill" as if not getting any water - yet there is plenty of water flowing just none of it hot!
Leaves us to wait it out 30 minutes or so
Some details might be pertinent
We are on a well, we do have a 2500 gal above ground storage tank well pumps into.
We do have a pressure tank - was replace just before we bought the place.
The type we have is one with the float as opposed to diaphragm
The Husband wonders if the float type is not maintaining exacting enough pressure to make this unit happy? Possibly needing an Amtrol diaphragm style tank
Otherwise in last 3 months, since install, the whole unit seems to be performing admirably.
Thank you for any help or suggestions in advance


  • Smyth
    Smyth Member Posts: 2
    The unit will go into "fill" mode when the internal pressure drops below a threshold. When filling it will not fire. For the DHW 29psi is the recommended minimum pressure, 12psi is the minimum heating pressure.

    Do you have a pressure gauge on the space heating loop? A leak on the space heating side could cause it to lose pressure over time, then fill during which time any calls for hot water will not be satisfied. This could be occurring without any noticing unless they want hot water.