ᐅ Underfloor Heating – Flow Meters Show Zero Despite Flow

Hello everyone,

maybe this question is too basic, but:

Do you need to do anything special with the flow meters (the small glass tubes with a scale up to about 3 liters per minute) to make them show the flow? In our distribution boxes, all except four of them do not show any flow, even though there is definitely water running through the heating circuits (warm supply and return).

Unfortunately, my builder (or rather the builder of my general contractor) is no help and a complete disaster, so I trust the collective intelligence here in the forum much more than any of his statements... 🙄

Thanks in advance!

BananaJoe schrieb:

Do you need to do anything else with the flow meters (the small glass tubes with a scale up to about 3L/min (0.8 US gallons/min)) to make them show the flow? In our distribution boxes, all except four do not show any flow, even though water is definitely running through the heating circuits (warm supply and return).

Take some photos. That will make it easier for us.

Depending on the set flow rate, it can be so low that nothing is displayed.

Benutzer200 schrieb:

Take some photos. That will make it easier for us.

Good point, I will do that this evening.

Mycraft schrieb:

Depending on the set flow rate, it can be so low that nothing is displayed.

Even when the flow is set to maximum (the builder once tried that because he said, "That can’t be, it always shows something" 🙄 :rolleyes 🙂, it still shows zero...

By the way, the builder thinks it’s not a big deal and that he can do the hydraulic balancing this way. I do wonder how he plans to manage that if he doesn’t even know whether 0.3 or 3.0 liters (0.08 or 0.79 gallons) are flowing through the circuit...

BananaJoe schrieb:

I do wonder how he plans to manage if he doesn’t know whether 0.3 or 3.0 liters (0.08 or 0.79 gallons) are flowing through the pipe...

That’s not a problem at all. The flow indicators are just for display. You can do the calibration without those parts completely.

Mycraft schrieb:

That’s not a problem at all. The flow indicators are just for display anyway. You can balance the system without using those parts.

OK, then I suppose it’s actually possible. But my general contractor probably can’t manage that. He can’t even figure out that the reason the underfloor heating isn’t working is because he didn’t open the shut-off valves in the distribution manifolds, and he often connects the heating circuit return sensor to the heat pump supply line (just to name some of the recent mistakes he’s made)…