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?

 

[Chalked]

That's all correct. But no flow through any of the zones!
Two initial things to try.
1. Take off one of the White heads ( unscrew from manifold) make sure system us calling for heat. Then see if the flow starts. ( look at flow meter on the top)
2. Take off the red clip below the flow meter ( pull straight up) then unscrew ( anticlockwise) the flow restrictor. Again see if any flow.

After that look on you tube on how to bleed air from underfloor heating.

If this does not work and the pump on the manifold is operating.You would be best calling out an engineer to sort.

 

[Chalked]

Another quick question. When was it installed and has it ever worked?

 

[Ricky85]

Thanks Chalked. Ill give those things a try tomorrow. It was only installed recently and has not worked. The system was filled with a hose pipe, each loop run through until air had been cleared.

Anyways I'll check those again and if still no luck will call in engineer.

Cheers.

 

[Worcester]

It was only installed recently and has not worked.

In which case whoever installed the controls and piped it up to the boiler should come and sort it out...

With such a small ufh system and that fact that it should run (flow) at 35 - 40° max, then you are in danger of short cycling the boiler anyway.

 

[Ricky85]

In which case whoever installed the controls and piped it up to the boiler should come and sort it out...

With such a small ufh system and that fact that it should run (flow) at 35 - 40° max, then you are in danger of short cycling the boiler anyway.

OK, thanks. Looks like short cycling is what it is doing. Are there solutions to such problems?

 

[ShaunCorbs]

OK, thanks. Looks like short cycling is what it is doing. Are there solutions to such problems?

get the installer back

 

[Worcester]

On a new system #1 get your installer back

An emmeti system and heatmiser controls is a good set up, the only reason it's not working is something wrong with the installation.

Noise is usually caused by three items:
Air
Unclipped pipes
Excessive pressure form multiple circulators (pumps)

Low or no flow is caused by:
Incorrectly set up flow regulators (they should ONLY be set up after they have been left fully open for a while to allow the system to stabilise - we usually do it 1 - 2 weeks after we've started to put heat into the system.
Blocked Pipes
Air Lock / air in the system - it can take up to 20 mins per loop to get all the air out.
Actuators not opening
Actuators connected to the wrong zone controller
TMV incorrectly set.

The solution for short cycling is a buffer tank. If you have enough radiators, then the water in that circuit can act as the buffer, in conjunction with the radiator circuit, sometimes an auto bypass is all that's needed.

The problem is that the return from an ufh heating system to the boiler can be:
a) lower temperature than radiators
b) lower flow rate than the boiler wants
Hence any system with ufh needs designing and installing correctly.

Done properly they are the best heating system you can have.

You may also need an auto bypass installing for the boiler circulator (pump), it may be that with no call for heat elsewhere, when only the ufh is calling for heat the main boiler circulator is over pressurising the ufh pump and that will make it noisy. An auto bypass will also help solve a) and b) above.

Don't do any of this yourself - Your installer should have sorted all this, get them back, don't stand for any truck about it being christmass

 

[Sharp Point]

You have a flow fault between the boiler and ufh manifold , not the ufh loops. Suggested problems are.....

Physical Blockage in flow/ return pipes, valve turned off or debris.
Zone valve not opening gate
isolation valve on manifold not truly open, although inline handle says so. ( it can happen)
Pipe work seriously undersized in screed

System needs draining down and physically testing for clearance/ flow

 

[Ricky85]

Thanks a lot guys. Appreciated.

Bit more clued up now for when I get the installer back.