UFH running too hot

[johnrhug]

Thanks everyone for your suggestions. Lots for ne to try, plus a replacement blender valve has arrived. She who must be obeyed has decreed no more UFH work until Monday. I'll provide an update on progress next week

Despite saying I wouldn't do any further work until Monday, curiosity got the better of me.

From the responses received I did the following.
Setting the blender to minimum I could hear the blender doing its work. Set midway the flow rates on the loops were correct. Set to minimum they dropped.
With the blender set midway when I switched on the radiator zone the flow rates on the loops dropped.
It seemed that if the pressure dropped i.e blender working or the radiator zone operating, then the flow rate on the loops dropped.
I looked at the pump Wilo-para ma nual but to be honest I don't really understand it. It was set as in picture 2(2 leds diag) . I think this variable differential pressure. I cycled through the settings until the pressures didn't drop see picture 2 (3 leds in row) I think this is constant speed. Everything seemed to be working OK. Blender set to minimum water temperature not going above 35 loop pressures maintained. You can hear the pump so not sure I have got the correct settings.
I'll contact Wunda on Monday and see what the pump should be set to.

 

[johnrhug]

Thanks everyone for your suggestions. Lots for ne to try, plus a replacement blender valve has arrived. She who must be obeyed has decreed no more UFH work until Monday. I'll provide an update on progress next week

Despite saying I wouldn't do any further work until Monday,

From the responses receive I did the following.
Setting the blender to minimum I could hear the blender doing its work. Set midway the flow rates on the loops were correct. Set to minimum they dropped.
With the blender set midway when I switched on the radiator zone the flow rates on the loops dropped.
It seemed that if the pressure dropped i.e blender working or the radiator zone operating, then the flow rate on the loops dropped.
I looked at the pump manual but to be honest I don't really understand it. It was set as in picture 1. I cycled through the settings until the pressures didn't drop see picture 2. Everything seemed to be working OK. Blender set to minimum water temperature not going above 30. You can hear the pump so not sure I have got the correct settings.

 

[Johntheo5]

Photo1 shows the pump off, not running, IMO.
Photo2 shows the pump running in constant pressure (CP) mode on setting 1 (minimum) which may be a little low, suggest changing to setting 2, still on in CP mode, CP mode should work quite well with a mixture of CH&UFH and is certainly recommended if running on UFH only.
That pump may (like my Wilo Yonos Pico) show the power in watts W and even the head in M, post the readings if it does (+settings).
I will try and poke out the relevent pump curves later.

If 30C mixed temp is still too high you can remove the adjusting TMV setting knob and turn the spindle with a pliers or whatever, CLOCKWISE, a little to see does it further reduce the mixed flow temperature, you can then replace the knob.

If it does, try it on UFH only.

 

[Johntheo5]

Setting1 on CP mode will give a constant 2.0M head which should be sufficient to circulate 2.0LPM/loop
Setting2 on CP mode will give a constant 4.2M head which should be more than adequate to circulate 2.5LPM/loop or greater if required.

 

[johnrhug]

Setting 1 the loop flow rates dropped slightly
Setting 2 maintained the loop flow rates

However the minimum temperature was 40c. I changed the blender and it started to control the temperature of the water. Changed the pump setting to the original and the flow rates dropped. Set it on continuous and setting 2 for the
When I took the cap off the blender the cap was stopping the knob from touching the stop. The new blender has a washer between the cap and spindle so the cap touches the stops.
I'll leave it on that. Glad I didn't replace the 22mm with 15mm.

I can't test the UFH fully as the outside temperature is 27c but the floor is not getting to hot now.

Thank you for your time and advice really appreciate your help, and everyone else who contributed.

 

[Bperry86]

@johnrhug @Johntheo5 hi chaps - apologies for jumping in on this but this is the same issue I am having with the Wunda system. I have also had Wunda suggest the 22mm pipes are too ‘big’ for the system but I’m now not able to swap these out (it’ll mean ripping out plastered walls etc). I was really interested to see if you had any details re changing the ‘default’ position of your blending valve, as I note you were able to reduce it further.
Wunda have suggested a new blending valve but I’d prefer to check the current valve before getting a tradesman to swap out. Do you have any instructions for how you did this or is it simply just unscrew and re position with pliers?

The only difference between my set up
And yours is tiled floor finish and it is an ufh only system (no rads on the same circuit).

My temps will sometimes stay fixed on 40 but more often on 45-46 but if the boiler isn’t on and warming the house rads (on a separate circuit) it can rise to 55 and beyond (nb I normally switch off at this point in fear of damaging floor).

Any help would be really appreciated as no one seems to be able to help me
Thanks in advance

 

[Johntheo5]

When the UFH is only on, (no rads) are the loop flowrates the same as when both UFH & rads are both on?
How many UFH loops and total flowrate and what is the dT.
What is the boiler target flowtemp and does it reach this temp when both UFH&rads on?
Does the boiler run continuously without cycling with UFH only on?
What boiler (gas/oil) and make/model.

As a temporary measure, UFH only on, and to give some indication of whether the blending valve is actually moving can you set the boiler target flowtemp to the required UFH flowtemp of 35/40C? and see what happens.

Can't assist with blending valve adjustment, but from post #20

"When I took the cap off the blender the cap was stopping the knob from touching the stop. The new blender has a washer between the cap and spindle so the cap touches the stops."

Give that a shot.

 

[Bperry86]

Thanks very much for your reply. I’ll try to answer as best I can (some of this is new to me).
Flow rates remain consistent regardless of whether ufh and/or central heating to rads is on/off.
There are three loops, one is 74meters and is 1.8lts flow rate, second is 84meters and is 1.9lts flow rate, the third is 81meters and is also 1.9lts flow rate. This is what Wunda gave me as the ideal setting. My actual flow rate is holding at nearer 2lts in reality.

The Gas boiler is a Worcester green star 24 ri

I’ll try adjusting flow temp on boiler later and see what that shows

I’ll also have to check on whether boiler runs continuously when only ufh is on. I haven’t tested this as I normally only have it on at same time as CH because temperature is lower to ufh and less of an issue for flooring

Thanks again and will report back

 

[Johntheo5]

Any idea of the manifold flow and return temps?, can then calculate exactly the UFH/boiler output.

Total lool(s) flowrate, (1.8+1.9+1.9), 5.6LPM.
Manifold dT of 4C = UFH output of, 5.6*60*4/860, 1.56kW, a dT of 6C, 2.34kW, a dT of 8C, 3.13kW and a dT of 10C, 3.91kW. so, even if you are running at a dT of 10C/3.91kW, more than likely that the boiler is cycling on/off on UFH only, except there is a buffer.

 

[Bperry86]

Thanks again. Excuse my ignorance but is dT the temp differential between flow and return temps?
Is it right for the boiler to be running in that way with just the ufh on?

 

[Johntheo5]

The dT is the difference between the UFH flow and return manifolds, normally temperature gauges on both manifilds,

 

[Bperry86]

Yes ok, this can be very random and in most cases is 10c or slightly more

 

[Johntheo5]

Yes, but you said the flow temperature can be as high as 55C at times, the average loop temperature then with a dT of 10C, is (55+45)/2, 50C which might result in floor surface damage.

 

[Bperry86]

Ah OK. The return temp is never quite as high as 45, max is about 35, so 55+35 / 2 =45c.
Not entirely sure if that’s too hot for tiled natural stone tiled flooring or not?

 

[Johntheo5]

Don't know re tiled flooring temperature limits but the TMV should control the manifold (mixed) flow temperature to whatever you set it to.