Heat Going In Unexpected Places: Ghost flow, convection high pump rate, normal, unavoidable??

[velvetfoot]

I'm running my system on oil for the moment. It is a parallel arrangement. I'll put in a diagram, but I haven't updated it-the buffer tank supply is now on the top.

I have the oil boiler's B&G Ecocirc Vario pump set at it's max setting. When the boiler comes on to charge the tank, the two heating zones heat up to some degree, without their circ pumps running. When the boiler return temperaure is low, ie, below 130F, I can feel the Caleffi thermomix working since I can put my hand on the return. I think the buffer tank top is also getting some heat. There might continue to be a little heat coming up after the pump turns off, but not muh. What causes this?

I am thinking it's convection, and unavoidable. There are flow check valves on the supplies to the zones and check valves after each boiler and before each supply hits the supply header. This flow is in the right direction though.

Could the pump's high setting be a factor? It's not like it's huge.

Bottom line, I don't think this is going to be a big issue, but still would like to know if this is a common phenomenon.

 

[maple1]

I'd try turning the vario down & see what happens.

You might not be able to totally avoid ghosting through the zones though without zone valves.

 

[velvetfoot]

I'd try turning the vario down & see what happens.

You might not be able to totally avoid ghosting through the zones though without zone valves.

Thanks. There's no or just a tiny effect when the boiler pump is off, so it might not what the typical ghosting usually refers to.
I really don't know what speed to set the boiler pump at. The zone circs are identical, and you would think the boiler pump should be able to supply both pumps when they are running at the same time, which leads me to want to set the pump on high (60 watts!) and charge the tank with the excess. I still might fool around with turning it down, but I think it'll be hard to get qualitative results.

On the other hand, maybe it's a good thing. More natural convection in a power outage. But yeah, zone valves would've stopped it.

 

[velvetfoot]

This might have contributed a little to the long warmup: I extended a 1/2" makeup water line to the supply side of the ThermoMix valve to facilitate filling. I suppose it was flowing water to the tank, since it got pretty darn hot, and not just from conduction. I haven't been noticing it with the pellet boiler.

 

[jebatty]

U-shaped heat traps are very effective in reducing/eliminating ghost flows. Need a rise of about 18" and then a drop of the same. The down-side is some added pump head.