UFH pipes not hot enough

thanks @Johntheo5. Unfortunately, by the time I remembered to check the d.40 & d.41 temps, the heating had already been running for 30 mins from cold this morning. I guess I will need to wait until later in the day when the rads heating starts again to immediately check what d.40 & d.41 are showing. We have the heating set to run for a few hours in the morning.

I have not changed d.05 so this is still set at 65C. I have noticed that the boiler has been happily running for 30 mins and is showing s.04 which is presumably expected. The rads nearest to the pump are piping hot but the rads away from the pump are luke warm at best. Since an s.53 has not kicked in yet, if the rads that are away from the pump are luke warm, does this point towards a possible issue with the pump? I am thinking that if there is a blockage somewhere in the rads heating, the delta between the boiler flow & return (d.40 & d.41) would shoot up and trigger the s.53 or am I completely off track? :(.

I have just now gone to see what the boiler is doing in the garage after running for 35 mins from cold. The boiler is showing s.04, d.40 is 65-66 and d.41 is 46. The house is still being heated and the rads away from the pump are very, very slighly getting warmer but no where near as hot as those rads near the pump.

I had forgotten to change the UPS2 25-80-180 pump setting from III to I. I have just felt the pump and it is very hot. I have now changed the setting to I. I will wait to see what this does as the hallway where the room stat is located is warm and therefore the temp in the hallway has reached 22C which is what the room stat is set to. What should I look out for, now that the pump setting has been set to I ?

@Johntheo5 - thanks for all the graphs and data in the spreadheet but TBH, I am lost in what this is telling me :oops:.

Later this afternoon, I will test the UFH system on its own. The orangery where the UFH system is installed consists of a concrete screed floor and porcelain tiles for the floor finish. I assume that if I increase the mixed flow temperature in the UFH, this will not damage the floor covering I have?

If I have to resort to changing the boiler (which I am happy to do if it solves the problems and especially as the boiler is 13 years old), is there a particular boiler you would recommend?
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Reducing the pump speed to I, 8M to 6M should only result in the flow rate falling to 87% of the flow rate at 8M, so I would let it at 8M while on the rad circuit and 6M on UFH.

You might persevere a bit more with the rads and we can determine the flow rate fairly accurately.
At the moment d.00 is 18kw and the boiler dT is 19C, (65-46), now if the rad demand was exactly 18kw then the flowrate would be exactly 13.6LPM (0.82m3/hr) which is seriously low with a 8M pump circulating through 20 rads and assuming all the lockshield valves fully open.
Its probably lower than this and we can determine it (the flowrate) by getting the flow temperature to fall a few degrees, so suggest reducing d.00 to 12kw, if the rad demand is higher than this then d.40 will start falling, when it has reached a steady reading, wait say 10 minutes, then note d40&d41 and the flowrate can be accurately arrived at. I wouldn't do any UFH tests until this is established accurately.

Either wait until the roomstat calls for heat again or increase its SP to get the boiler to fire up again.
thanks @Johntheo5 but I only have the one Grundfos pump that is located in the landing cupboard by the zone valves so to manually change the pump speed depending on whether I have the rad system running or the UFH running will be impossible, unless I have misunderstood your point?

I have had a look at the boiler and unless I remove the front panel, I cannot tell if there is an internal pump. I have cycled through the d settings and there is no d.19 so I am assuming an internal pump does not exist.

On the rads, I know that not all the lockshield valves are fully open. I have partially closed the ones closest to the pump that get hot the quickest so as I can get more flow to the rads furthest from the pump. Should I not be doing this? Not sure if this is an added problem but some of the TRVs on the rads are on the 'flow' path and others are on the 'return' path.

So, am I right to think that for next steps, it is:
1) set d.00 to 12
2) fire the boiler
3) change the UPS2 pump setting back to III
4) wait 10 mins and note the values for d.40 & d41
Yes, steps 1 to 4 above, but you may have to increase the roomstat setting to get the boiler to fire up?
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thanks @Johntheo5. I carried out the above steps. After about 10 mins, d.40 is 57, s.41 is 33

Boiler is showing s.04 but is firing at low output. Nearby rads are luke warm, rads further away are cold
after 25 mins, d.40 = 63, d.41 = 40. Boiler still showing s.4

Nearby rads are getting warmer
This isn,t looking good, above gives a flowrate of only 7.8LPM
Can you leave the boiler firing and knock d.00 back to 10kw and watch it for another while, I'd like to see d.40 at ~ 60C, is the UPS on speed III, if not, just leave it as is and continue with above test, thanks.
@Johntheo5 - I've knocked back d.00 to 10kw and after:

10 mins, d.40 = 63-65, d.41 = 45
20 mins, d.40 = 63-65, d.41 = 45
30 mins, d.40 = 63-64, d.41 = 45

UPS speed is on III, and boiler is continuing to show s.4

The fact that d.40 is not getting ~ 60C, what indication is this giving?
It can only mean that the range rating isnt limiting the boiler output , try knocking it back to 5kw but only wait 10 minutes before posting back, do you have a link to your exact boiler model??.
@Johntheo5 - the minimum I can knock it back to is 7kw. After 10 mins, readings were d.40 = 62, d.41 = 45

Attached are some photos of the labels shown on the boiler; one of them shows that it is a Vaillant ecoTEC plus 438 along with its serial number.

The furthest rads are still struggling to get hot but I guess that is partly down to the d.00 settings.

The fact that the range rating is not limiting thr boiler output, what does this mean? - boiler issue? pump issue? (btw - pump is very hot to the touch but running quieter than before when d.00 was on 18), blockage somewhere?


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Looks as if the rad(s) demand might only actually be 7kw as the flow temp has dropped & the return decreased, if so, then the flowrate is only a virtually unbelievable 5.9LPM. (7x860/60/17).
OK then leave everything as is and now switch in your UFH. (leave pump at setting III).
oh, @Johntheo5, I turned everything off as the house was getting too hot . Shall I turn back on the heating with d.00 at 7kW and then also turn on the UFH?

Do you want me to note down d40 & d.41 after a period of time?
Yes do that ASAP, and after 10/15 minutes also take UFH flowrates and flow/return temps and that will do.
You may have to turn on the CH & the UFH together to get the boiler away without cycling.

You might care to leave the UFH on alone afterwards for awhile if not too uncomfortable.
These ones, just add the two together or post a photo. take the temperatures from the flow&return from the thermometers.

This a better one, taken after you had adjusted them.



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