New wet underfloor heat strange flow issues.

[Sig_star]

Hi all just done a new Retro wet floor system in new house I am doing up.
scratching my head with the flow of the system.
From my finding and tests its something to do with the mixer not allowing the flow around the system.
I found this out as I thought the pump was one not good enough or 2 broken. Swapped it out no difference.
Removed the mixer stat and spring to clean it out as it did have crap in there from new system install and thought you know what I will try the pump on its own to see and eliminate the mixer as the issue. To my supersize the flow meters now show great flow and I can adjust to suit the flow I need for room and run length.
But as soon as I add the mixer stat holder and spring no mater what I set this too it restricts the flow to nearly 0.
What could be making this happen?
I want the mixer on there to do as its intended not allow to hotter water in to the manifold and system but if i have no flow rooms do not heat up.
Any ideas Thanks

 

[Sig_star]

I have attached a picture of my mixer connected to my manifold. I have highlighted the spring and red round stat if removed will allow the system to flow perfect. As shown on my manifold flow pots but as soon as I add these back in flow almost goes to 0 on the flow pots. Regardless of how many zones I have open 1 or 12 or what temp I set the mixer at 28c to 58c or open fully the posts it just dose not increase or a just the flow.
I need the mixer in the system to make sure I do not send 80 degrees from my boiler to my manifold as the max I need is 55c but I just dont see why its stopping the flow.
Thanks again

 

[Nozzle]

Can you put up a pic of the entire manifold please, including pump, isolation valves etc

Nozzle

 

[Sig_star]

Hi Nozzel.
Thanks for your reply I have one only picture of the manifold and pump/ mixer before it was plumbed up and then close up of the mixer and pump now attached to the flow and return of the boiler. i hope this helps you give me some ideas as i am not stupid on this but am lost on this one.
Thanks

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[Sig_star]

Don’t think my pics worked. Maybe now thanks

 

[Nozzle]

Is there any chance your mixer is piped in back to front - that is to say the flow and return are the wrong way around?

Also, how are you venting the manifold before starting the pump?

Nozzle

 

[Sig_star]

Hi,
I have it plumed in the correct way as attached. Pump flow correct also. I have bleed the system of all air.
what do you mean regarding the venting? thanks

 

[John D v2.0]

I'm not a pro but Is there any flow from the boiler side?
to test the valve I'd just assemble it and blow through the different apertures. You can put it in some warm water to open the thermostat to see how that changes things, although you'll need a suitable mouthpiece to avoid burning

 

[Sig_star]

Hi,
Yes there is flow from the boiler that allows it to get to the mixer. Then the manifold pump will take over. I have had it out mate and mess about with it to see how it works but what ever I try if I do not remove the stat and holder from the mixer I get hardly no flow. When I remove tho it’s fine, flows can be changed maxed out or slowed So something in the mixer is restricting it.
I did give it the old tap with hammer today.
Funny the flow pots move down when doing so but don’t stay there for long.
Thanks

 

[Nozzle]

Also - is that pump one of the smart pumps that changes its speed to generate constant pressure at variable flows?
Once you had the blender open, did the drillings in the housing look complete? (i.e. there is actually an unrestricted flowpath from all ports)

Nozzle

 

[Sig_star]

Hey. Yes the pump is a grundfos upm3 auto L.
I have tried every setting/curve there is on it. For long periods too. I believe I just have it set on max now bec it is a 12 port manifold with approx 700m piping but still nothing.
There is no Restrictions on the plastic drill holes in mixer housing.
You can tell when it’s not flowing good or at all as the boiler just reachers temp and goes in the anti rapid as it’s hit temp But if I tap the mixer I noticed now it will start to work and the boiler temp drops meaning flow but it don’t last for long and there is no way I can get enough flow to set up my flow rates I need per room as there is just no room for adjustment it’s just barely on 0.5 flow maxed open. It only works if this stat and plastic housing is removed.
Grrr it’s a nightmare.

 

[Nozzle]

Bang in a different one!

Nozzle

 

[Sig_star]

Hey, yeah I think I will have too. I have noticed crap still in the system even tho it's been flushed out loads. When I clean it it seems to work better with stat in but still not great flow but better.
I mean with a 12 port manifold is it possible to a just the flow to max if all are open? Max I can get with it in is about 0.5/1 litres a minute. From the chart I need around 2/2.5 for my run length.
I can without the mixer so thought it should be possible but understand this will restrict it little.

Bang in a different one!

Nozzle

Thanks

 

[Nozzle]

Hi,
I have it plumed in the correct way as attached. Pump flow correct also. I have bleed the system of all air.
what do you mean regarding the venting? thanks

How have you primed the manifold so there is no air in it? My manifold has an auto vent on the top and bottom rows which makes venting a doddle. Did you simply run a hose through each leg then isolate and move on to the next?

Nozzle

 

[Ryler]

Removed the mixer stat and spring to clean it out as it did have crap in there from new system install

Should have been a Y strainer fitted before the valve.