Indirect (Boiler Fed) Megaflo Doesn't Stop Heating

[techweb]

Its a possibility but only if scale/limestone is building up in the bottom, the lower stat pocket which is for the immersion? should be even more scaled if this is true so maybe switch this in overnight or today if not on "economy 7" or whatever its called now and measure the actual tap temperature when it cuts out. How far above the bottom of the cylinder coil is the cylinder coil stat located?, if the circulation through the coil is lowish then there could be a dT of 15C or more between the upper yliner temperature and the bottom. My (PT1000) coil probe is located ~ 1/4 way up the coil bottom and there is ~ 10C dT between the tap temp and the probe temp, tap temp is ~ 68/70C with a SP temp of 60C at the end of the reheat period.

The coil(s) are located ~1/4 way up the cyclinder I would say.... Seems that tap temps are ~10c higher than stat temp.

 

[John.g]

Yes, seems fairly typical, how far above the bottom of the coil (where the coil return exits the side of the cylinder) do you reckon the probe is located?.

If this is typical then I wouldn't expect a very big dT but you can live with 10C anyway.

 

[techweb]

Yes, seems fairly typical, how far above the bottom of the coil (where the coil return exits the side of the cylinder) do you reckon the probe is located?.

If this is typical then I wouldn't expect a very big dT but you can live with 10C anyway.

View attachment 94760

Just a few centimeters, it's very similar to the picture above.

 

[techweb]

Thermostat changed... With the new one, it seems to need to be turned up a little higher to get the same result. But ultimately, there was nothing probably wrong with the old.

The pipe with verdigris I was told is just superficial corrosion and not to worry about it.