Underfloor heating system explanation

[vrb03kt]

Hi there,

I was hoping to get some insight into my underfloor heating system. I am having a problem with one of the zones not coming on at all, and another zone radiating full blast and not being controlled by the thermostat. It then occurred to me that I have very little idea of how the system actually works. If anyone could explain my system to me from the pictures, in fairly simple terms assuming I know very little, that would be very helpful!

I seem to have 8 zones, there are only 6 wall mounted thermostats so I’m guessing two rooms have 2 zones. The labelled pipes aren’t completely useful as they don’t match what is written on the zone actuators above them.

Three things I particularly don’t know are;

1) the blue mixer on the far left appears to mix the flow and return water, it is set to 10 but I don’t know why
2) the black unit on top of the red pump has a grey switch with 3 settings I II and III. It’s set to II.
3) there are little blue tabs on top of the zone actuators. These sometimes seem to pop up, as can be seen in the picture. When that happens the zone actuator feels ‘loose’ on the valve. They then seem to retract again later on. I have been unable to locate any manufacturer docs or instructions.

I would be interested to hear thoughts on how to work out which zone is which, and how to regain control of the zones that I can’t seem to control using the thermostats.

Thanks for your thoughts!

 

[Madrab]

If you only have 6 stats then 2 rooms will be large enough to have 2 loops.

The blue mixer is the blending valve and yes it's regulates the flow temp by mixing some of the UFH return water with the HW from the boiler flow. Flow and return temps are read on the manifold stats and should be set, along with pump speed and flow meter adjustment, to ensure that heat output of the UFH in each zone is optimal.

The black unit is the pump speed controller - leave that where it is for now.

The blue tabs are the thermals actuator stems, when the NC actuator is activated by the controller after a signal from the stat, the actuator heats up and melts the wax internals, that then open the valve - the stem coming out the top is just an indicator that the actuator is open/active. These don't open straight away, they take a bit of time to open/close fully.

The zones are easy as the actuators/flow pipes are marked.

Loads of documentation online covering the nuts and bolts of UFH.

 

[Murdochcat]

Are the room stats hard wired ?

 

[vrb03kt]

Thanks for your replies and the explanations. Yes the stats are hard wired.

The zone actuators seem to be able to turn, similar to a TRV. Is this significant or are they just open or closed based on the position of the stem?

Looking at this zone in particular, the thermostat is turned off, the stem is showing fully flush with the actuator yet in the flow meter it is showing 4L/min flow..i don't understand why there is the maximum flow rate if that zone is meant to be off. Also the floor feels warm in that zone.

 

[Madrab]

Does the pipework from the valve feel hot? Could be a problem actuator then, I'd remove it and use one of the manual caps you can see in your pic and wind it down and see if it stops the flow.

That being said, looking at that pic again the meter in the red box doesn't seem to be registering any flow, the red tab is at the top of the meter, can't see the one to the left of it that is marked the other lounge loop on the return but hall on the return but they both look off. The one to the right though, marked utility but lounge on the return looks like it is flowing 4L/min with the actuator off. I think someone has been in swapping heads about, are any of the actuators actually loose?

I think you need someone well versed in UFH in to check all that out.

 

[Johntheo5]

If, which I think it is, the pump is pumping into the top of the manifold, are the flow meters bi directional as the flow is upwards through them on the bottom (cold) manifold.

 

[Madrab]

are the flow meters bi directional

Good spot, usually the flow meters would be on the flow (hot) side of the manifold. Are they directional, good question and TBH it's never come up. If they were directional then would the meters flow, these obviously do.

Given the design of the meters it does look like the flow can enter from any direction and the flow will still be metered, correctly is another thing though I guess.

 

[vrb03kt]

The flow meter on the right is actually showing 0L/min, the red tab is at the bottom. The one I've highlighted is showing 4L/min with the red tab nearer the top. Perhaps this answers the bi-directional question? 0 flow is at the bottom and max (4L/min) is at the top.

I have noticed that my system is the opposite way around to anything I've seen online so far, they all seem to have the flow meters on the hot side, and the zone actuators on the return side. This doesn't make sense to me though, why would the zone actuators be placed at the end of the loop after the hot water has been pumped around the floor? Surely I want to turn off the zone before it has been pumped through the floor.

 

[Johntheo5]

It doesn't really matter where the actuators are placed, once they shut then there is no flow through the loop(s)?, re the flowmeters, with no flow these are spring loaded to be up reading 0LPM, when installed on the hot side then the flow will be downwards pushing them open, on the return one would think the flow being upwards would keep them closed.

 

[Madrab]

The flow meter on the right is actually showing 0L/min, the red tab is at the bottom.

Is there any name on the flow meters, usually if the indicator is at the top then it's 0L p/m at the bottom it's under full flow. Not typical to have it the other way around but can see it is in the pic with the spring above the meter indicator rather than below. Does that mean they work differently, possibly but if they do actually flow just now that would suggest that flow direction may not be critical.

 

[Johntheo5]

If the spring is on top and 0LPM on the bottom of those flowmeters then they are correct IMO for installation with upward flow.

 

[vrb03kt]

The flowmeters and several other bits are branded "tn", which I can't find anything about online. But they do seem to work as described above. Upward flow on the cold side.

With a bit of swapping around of actuators I've worked out that the problem seems to be with 2 of those actuators - one doesn't open at all and one doesn't fully close once it has been opened. I'm now having trouble locating replacement actuators. GLO as far as I can tell no longer exists, these are 24V NC actuators with the connector shown in the picture. Any suggestions of a suitable replacement?

 

[Madrab]

You will get 24V actuators, not sure about the connection though, nor the throw on the actuator itself

TN - John Guest flow meters use that mark too but haven't ever seen that configuration of flow meter.

I hate to say it but you may be finding yourself in the position whereby you have obsolete bits of kit and any repair required may not be possible. There is a thought process whereby if affordable, it might be time to change over to something more standard.

 

[vrb03kt]

I managed to locate 2 new actuators, went to a local plumbers merchant and they had the exact model, but branded tn rather than glo.

Thanks for all the help!

tn = taconova

 

[Madrab]

Well done you - persistence is a wonderful thing

They also do return flow meters too - they call them balancing valves - so that's a positive.