Underfloor heating system explanation

[stmartinsdiver]

Hi – Well done, it looks like you finally cracked it. I've just replaced all the actuators on our old 4-port UF system. I too had been puzzled that our set up was the opposite way round to what I saw everywhere else, with the hot input pipes above the cold return pipes on the manifolds. After isolating and depressurising the manifolds, I removed all the flow meters hoping I could clean the sight glasses as it was impossible to see the flow indicators, and wondered that if they are the same on your system, as mine are not bi-directional, as when the actuator is closed, the flow meter closes off the neck of the return pipe. When the actuator opens the flow of cooler water pushes the flow meter upwards, opening the circuit again.
The flow rate is then controlled depending on the adjustment of the spring-loaded flow indicator. The more the indicator is turned clockwise, the greater the pressure (flow) required to overcome the spring. Unscrewing the flow meter indicator reduces the pressure (flow) required to increase the flow rate. I've attached a couple of pics of my flow meters open and closed - needless to say, this are no longer the type commonly used now.
As my existing flow meters are still difficult to read, and two of them are weeping slightly, I'll be replacing the manifolds with modern flow meters as the total costs are about the same as buying these expensive ones which it turns out, Uponor are about to discontinue.