UFH on S plan plus not getting up to temperature

[Ricky85]

Hi all,

New here to the forum.

Got a slight problem with my UFH. Have 3 valves, DHW, Rads and UFH.

Rads and DHW work fine using the programmers, switch on and off and heat up no problem.

However whenever the UFH is calling for heat, the flow pipe at the manifold barely gets warm. Its a 4 zone system, actuators open up circuit when fired, boiler fires up. Zone value is open for UFH. The flow pipe at the boiler gets hot, but it seems by the time it gets to the UFH manifold, barely any heat is getting to the UFH flow pipe.

The run is quite a bit, but have left on the whole day, and still no heat.

Boiler is a vaillant 630 ecotec plus. I noticed that unlike when DHW or the rads are calling for heat, the boiler does not stay on constantly, as in fired up. Keeps displaying the eggtimer and on live monitor, shows pump overrun sometimes.

Assuming the reason the UFH flow pipe at manifold is not heating up is that boiler for some reason is turning itself off even though constant demand for heat is there. Wiring center at manifold shows Boiler, Value and Pump lights on. At the megaflo wiring centre, when UFH is calling for heat, switch live active and so telling boiler to come on. So I don't believe it is a wiring problem.

No air at UFH manifold, rads and HW aired too. Pump at UFH manifold is on and pulling, can be heard.

Any ideas why boiler is not staying on for long enough to get the temperature up?

 

[Worcester]

New / Old System?
Worked until this heating season?
Never Worked?
Does the UFH system have a blending / mixing valve and it's own circulation pump?
Circulation pump built into boiler or seperate?
Have you tried turning rads and dhw off, and only calling for heat on the ufh?
as above, manually opening the valve?
Need more info...

 

[Chalked]

Is it in a screed floor.?

Don't expect it to warm the room that fast. May take two days to get the room up to temp

 

[SimonG]

Sounds like poor circulation, is the underfloor heating pump running?

 

[kris]

It sounds like the ufh circuit when calling is very short do not taking long to heat, either that or valve isn't opening allowing the water through and just going round the bypass, this would explain the short burst if boiler operation, is there a separate pump on the ufh manifold along with mixing valve and is the pump coming on??

 

[Ricky85]

Thanks for the replies lads.

Some answers to the questions.

It's a new system.
UFH system has its own mixing valve and pump.
System boiler, so pump built in boiler.
Rads and dhw off, call for UFH heat and boiler comes on.
Have tried manually opening value, still no difference.
Is a screeded floor.
UFH pump comes on, can hear it humming away, and pump light on heatmeiser UH3 wiring comes on.

If I try with rads on and UFH on, the flow pipe after the rads zone valve is piping hot. Cannot touch for more than a few seconds.
Try the same on the UFH flow pipe and its only warm, I can confortably keep my hand on there without having to pull off unlike the rads.

The UFH pump at the manifold light is illuminated, so defo is on and can hear it humming, plus have it set to max.
Turned all 4 zones on to call for heatt, Emmetti acctuators open up. Confirmed via the little black plastic that slowly rises up when open.

Have just tried again and seems the flow pipe just doesnt seem to heat up enough so no chance of heat reaching the manifold at this rate..?

 

[ShaunCorbs]

have you tried turning all zones on to heat and see?

 

[Ricky85]

Hey Shaun,

Just tried that now. And seems now the heat is coming through. 35 degree on temp gauge up from 20 before. Although UFH pump is no longer making a low humming sound and is quite loud. Maybe air was trap in the system? Hopefully should quieten down and its pretty loud at the moment, can hear from upstairs landing.

 

[ShaunCorbs]

Hey Shaun,

Just tried that now. And seems now the heat is coming through. 35 degree on temp gauge up from 20 before. Although UFH pump is no longer making a low humming sound and is quite loud. Maybe air was trap in the system? Hopefully should quieten down and its pretty loud at the moment, can hear from upstairs landing.

either that or wired wrong, turn one zone off until the pump turns off note the pump may over run for 10 - 15 mins so after you turn one zone off wait a good 30 mins before turning another one off

repeat until pump turns off and if doesnt turn off when you turn your ufh control/stat off then its wired to the wrong zone

hope you understand if not please ask

 

[Ricky85]

OK got you. I'll give that a try tomorrow. In the mean time I'll leave the system running.

Although still not sure it's functioning correctly. Gauge on manifold was showing up to 40 degrees at one point, but has since dropped back to 25 degree. The flow pipe at the manifold is warm only now.

I've been up to the boiler and monitoring the live info, and it seems like its only igniting for a really short time, sometimes only a minute or so, then it goes to "Pump Overrun" then "Anti cycling" then "Pre pump run" etc. I'm expecting it to be on ignition and pump hot water to the manifold for a lot longer time.

Especially considering everything is still stone cold. Non of the individual pipe for each heating circuit are anything close to hot. Got slightly warm at one point, but not anymore, has lost heat. Shall I leave running overnight and see how it's looking in the morning? Or is there anything else I can try?