Polypipe UFH manifold temperature conflicts

[Amarka]

Hi all. Hope all is well and safe.
I need your advice please. I have a Valliant boiler serving the CH and DHW (megaflo). Just recently, we’ve had underfloor heating installed.

Before the UFH was installed, the boiler flow temp was set at 65C (it could be adjusted to 75C) using the -/+ buttons when you pull down the front boiler cover.
The Megflo thermostat is set at 60C.
So if there was ever a call for both at the same time, the CH would fire up and reach 65C warning the house but this would also be sufficient for the megaflo and heat water to 60c. You’d hear the water motorised valve close for water once it it 60c and the CH would continue to warm the house up. Seems like it’s all working fine.

We have had UFH installed and now when there is a call for all three or UFH/CH or UFH/HW - the boiler only seems to reach a temp of 45c (even though the mixer knob at the UFh has been turned to 60c) and the HW/CH only starts to properly fire up when there is no longer a call for UFH. With the UFH taking longer to meet to the room thermostats, it does mean that the CH and HW takes longer to heat up. Hope I’m making sense.

I’ve read the Polypipe manifold instructions and it states the UFh manifold as been factory set to 45C - assuming this is still the same, does this mean the highest the UFH can reach is 45C? And me turning the mixer tempknob at the manifold to 60c is fruitless because the UFH flow is capped at 45c? Could this be why the boiler doesn’t fire up to 65c (like it used to before the UFh was installed)? The boiler is now being restricted to the UFH capped at 45c? Would increasing the flow rate to 60c at the UFh manifold (so it’s the same at the megaflo) resolve this issue? At the moment, it seems UFh is taking priority over the other two. Good if you were in the kitchen (where the UFH tiled floor is) but bad if you’ve getting up in the morning and upstairs is not as warm as it used to get.

Any advice would be greatly appreciated.

Stay safe

 

[exedon2]

Is your ufh a single room pack or a larger manifold set up ?
What type of controls do you have on it?
Picture of underfloor manifold and motorised valves would be useful.

 

[Amarka]

Is your ufh a single room pack or a larger manifold set up ?
What type of controls do you have on it?
Picture of underfloor manifold and motorised valves would be useful.

Hi Exedon2, it’s a multi zone set up with the larger manifold set up. 6 circuits each with the actuator. Pump is set to speed 2. The manifold is in the garage but the motorised valve is closer to the boiler in the airing cupboard upstairs. It’s a Honeywell valve. You’ll see how I’ve got the white dial set to max ie fully anti-clockwise saying its at max of 60c. Hope the pics help.

 

[exedon2]

I take it its a solid floor system?
Assuming worst case scenario with 6 circuits if your attempting to run it with a high floor temperature by turning it up past 45C the heat load on your ufh can easily be 8kw . I take it your installer did check your boiler had enough capacity?

 

[Knappers]

Think you should start by adjusting that valve back down!
45°c is likely the max it should run at.
I really think you should get an engineer in to have a look but basically the lower that valve is set the less UFH will drain from the heating system, and also system balance may need review.
If you have your HW on timed then don't have it come on in the morning at same time as heating, 1-2h before would be better.
Similarly with UFH, response is slow compared to rads and if your heating from cold its going to suck up allot of heat so best keeping warm or timing to come on well before rads.

 

[exedon2]

Following on from what Knappers has said you are operating the ufh with correct back set temperatures?
Polypipe pipe recommended a maximum of 4C different ie if you have a set room temperature of 21C the back set should be no less than 17C.

 

[Amarka]

Following on from what Knappers has said you are operating the ufh with correct back set temperatures?
Polypipe pipe recommended a maximum of 4C different ie if you have a set room temperature of 21C the back set should be no less than 17C.

Thanks to you all. I forgot to mention the boiler is a Valliant ecotec 637 around 5 years old. It’s been set at 37kw so should be able to power the UFH? I’ve set the manifold temperature back down to 45C but maybe I need this even lower. We generally keep our room thermos around 20C but recently the highest they’ve been is 23C for both CH and UFH. So for the manifold, you reckon a lower temp of 16-21C? The flooring is porcelain tiles. Totally agree with the timings of the DHW, CH and UFH. Just recently whilst the kids have been learning from home, all three were changed to coincide with everyone getting up later around 8am-ish (sorry, I know you all are getting up earlier than that!!!). I’ll change the timings back to what they were with the water going on first around 6am and then heating around 8ish. Ufh back to on all day but at 20C. Do you reckon this is a good way to go? I’ll report back. Have a good evening all.

 

[Knappers]

Keep manifold (blending valve) at 40-45.
Set UFH room stat to 20ish in day and not less than 17 at night (set back)