UFH pipes not hot enough

[Lower]

You've got temperature gauges in the flow and return manifolds. I'd trust those more than how the manifolds feel.

I think the flow plunger in your right hand flow meter is so high its gone off the scale and is hidden below the red plastic lock shield.

 

[windsortg]

Thanks. @Madrab - you say "the blending valve certainly should be up at max". Just to be certain, do you actually mean "be up at max" or did you mean to say "not be up at max"? If it should not be up at max, what setting should it be at?

I think I will discuss with the installer about setting the pump to auto and both the flow metres to 2.5 L/min - stupid question but what will that achieve if the flow metres are set to the same value?

Over the past few days, the temperature (according to the room stat in the orangery) has not dropped below 20C. What would you suggest I have the UFH system set at during the day and at night time so that it is at the most cost effective way of running UFH?

 

[windsortg]

There's a mis-match, the output from the blending valve is almost 60Deg - but the water through the manifold is around 48Deg - so one stat isn't reading correctly. Needs to understand what the flow temp actually is, may need a IR thermostat to check. If it's 454 then the manifold won't be that hot to touch, if it's 60 then it should be but the blending valve certainly should be up at max.

As suggested, if both those flows are feeding one room then you need to balance the flows and set them both @ 2.5L/min to start with. What length are the pipe runs, do you know? I would suggest the pump may also be too high, you want that set to constant pressure - which it looks like it may be - and set it to auto, then set the flow meters to 2.5 L/min.

Your temp drop is within range whereby the floor should be outputting as per design.

The issue I see here is that UFH in screed can't just be turned on and and then expecting the slab to heat up quickly, the slab takes at least 2-3 hours to become thermally efficient, then the CH system is left to maintain the temp in the slab, controlling the heat via the stats. This is the most efficient way to use UFH in screed. The more you switch it off and the mass cools down, the more energy it needs to warm it back up again and that's all cost.

@Madrab - I will check with the installer but from what I recall, each of the 2 pipe runs around 60-70m in length

 

[SpecialK]

Does the input flow temp stay constant (ish) or does it cycle hot and cold fairly quickly?
My Vaillant internally bypassed. I had to put the bathroom rad on the same circuit as the UFH to stop it. Depending on your boiler you can check the flow and return temps. If the return temp shoots up without the return pipework getting hot you know its bypassing internally,

 

[windsortg]

Thanks @SpecialK. I have a Vailant ecoTEC Plus 637 boiler. Not sure what you mean by “the input flow temp stay constant (ish) or does it cycle hot and cold fairly quickly?” - is this the input pipe into the blending valve? How can I check for this?

What do you mean by “internally bypassed”? There is no way I can put a radiator on the same cools the UFH system.

 

[SpecialK]

Sorry - the input to the blender valve or the output under the boiler. Either use a thermometer or judge it with your hand. Does the temp swing from hot to cold pretty quickly after the boiler fires?

Listen to the boiler. Does it fire up, modulate down and then go in to anti cycle? I think it's an egg timer on the display on mine for anti cycle.

To check the values at the boiler....

D.040 Flow temperature actual value in °C

D.041 Return temperature value in °C

If the return temp shoots up it's bypassing internally. You may need a buffer tank or a rad somewhere on that circuit....

 

[windsortg]

thanks @SpecialK , @Madrab and @Lower for your help so far. I have lowered the flow metres so that they are now at around 2.5/3 L/Min. I have also reduced the temperature on the Blending valve to 45C. Attached are photos showing reading on the various dials.

The problem I have now (which has occured on ad-hoc basis before) is that my boiler (a Vaillant ecoTEC Plus 438 installed around 9 years ago) goes into a S.53 state after running for a period of time. When the boiler goes into this state, all the pipes going to the zone valves of the central heating system and UFH system are luke warm, and the boiler does not fire. I have attached a photo showing this S.53 code being displayed on the boiler.

From my earlier research of the S.53 code, I believe it means that the flow-return temperature difference is too great OR Boiler is in waiting period of modulation f block function (or operation block function) due to water shortage (VL-RL spread too big). Can anyone please advise what can be done to avoid the boiler going into this S.53 state?

For background, I have:
- Vaillant ecoTEC Plus 438 boiler
- 20 radiators
- Grundfos UPS2 25-80 pump
- UFH system on separate zone
- Heatmiser NeoStat thermostats for controlling radiator heating system, hot water, and UFH system

 

[Johntheo5]

What is the boiler flow temperature SP (setpoint), is this problem occurring with UFH only required?

 

[windsortg]

Thanks @Johntheo5. How can I find out what the boiler flow temperature SP is?

It is happening with central heating only, with UFH only, and when both heating types are requested

 

[Johntheo5]

I would just try the system on CH only first but change setting d.00 first.

Suggest setting d.00, the maximum boiler heating output to say 10kw (from Auto)
d.05 is the boiler flow SP (target) temperature.
d.40 is the actual flow temperature.
d.41 is the actual return temperature.
Monitor d.40 & d.41 while the boiler is running.

Also ensure that the UFH manifold pump is not running when on CH only.

Not sure how you access these codes/settings but will look it up, you may know yourself??. Utube will show you anyway?.

 

[windsortg]

Thanks @Johntheo5. I will do this tomorrow.

Isn’t setting d.00 to 10kW too low? I believe the maximum for this boiler is 38kW.

How often should I monitor the d,40 & d.41 readings?

What is the overall intention of this? I was recently closing slightly some of the lockshields on radiators that were heating up the quickest so that other radiators furthest from the boiler could heat up sooner. I’m not sure by doing this, I may have encouraged the S.53 happening to my boiler

 

[Johntheo5]

Its to give it a longer warm up time and, hopefully limit the dT (which brings up the S.53) and hopefully wll get the bioiler to stay on continuously for at least awhile, by noting d.40 & d.41we can then calculate the flowrate through the boiler as it should then be running at a max output of 10kw. You should monitor these very closely for the first two minutes or so after fire up. and then once/twice after say 5 minutes. You can always up the output depending on findings.

Did you have any problems before installing the UFH???

You say you have a Grundfos UPS2 25-80 pump installed on the boiler primary circuit?, can you also note when next running, its mode/setting or just post a photo of the LEDs when running.

Is your system sealed with a expansion vessel or is it open vented with a feed and expansion tank in the attic?

Edit: Another unwelcome feature of Vaillants is that they hold the firing at ignition setting (65/70%) for 60 secs before allowing modulation, in which time the flow temp can overshoot the flowtemp by 5C and shut the burner down and cycle, so relatively high flowrates are required to prevent this, as you say, balancing your system may have contributed to this.

 

[windsortg]

many thanks @Johntheo5. By the time I got to the boiler, it was already in a S.53 state . I did try to look up on the internet on how to display the d.40 and d.41 values but unfortunately I could not come across any instructions. I did watch this video but the control panel is slightly different to what I have on my boiler. If you are able to let me know how I can get to displaying the d.40 & d.41 values, that will be great. I am able to display and adjust the d.00 value. I have attached a photo of what my boiler control panel looks like. The d.00 value was on 27 and I have changed it to 25. I have not reduced it down to 10 yet as I thought I would wait until I know how to display the flow & return temps.

The UFH system was only installed this summer but due to the hot weather in the summer, the installer could not really test it by turning it ON as the temperature in the newly built orangery (where the UFH is installed) was already over 30 degrees. I did have the S.53 problem many years ago and I believe I got round it by adjusting the d.00 value. I have a maintenance on my boiler with British Gas and when I mentioned to their engineer as part of the annual service, some years ago, that I was adjusting this d.00 temp to combat this S.53 problem, he said I should not be tinkering with this as it affects the gas supply and efficiency of the boiler. During the summer, we also changed the majority of our radiators to new radiators, as well as adding an additional radiator, so I am not sure whether this (and my attempt in recently balancing the rads further) has contribted to the S.53 problem.

I have attached a photo of the Grundfos pump when it was running. It appears to be running at the highest speed, i.e. 3.

My system is sealed with an expansion vessel. The expansion vessel shows a reading of around 1.5 bar when the CH system is not running. Both, the boiler and expansion vessel are located in the garage whereas my megaflo, pump and zone valves are located in a cupboard in the 1st floor landing. I am 99.9% certain that 28mm copper pipes run from the boiler.

 

[Johntheo5]

This may enable you to view the D parameteres, if you had d.00 up before then you should have been able to scroll up/down to see all the d values?, I think if you press the button above the + button then you should be able to scroll through the parameters, it certainly won't do any harm to reduce d.00 to 10kw, you can always changs back, I will have another look but the only utube video I have is probably the one you lookesd at, slightly different display.
Have you any link to your exact model installation manual?

 

[windsortg]

thanks @Johntheo5. I think the situation has got worse . I managed to find out how to display the d.40 & d.41 temps. I turned down d.00 to 10. After starting the CH, the boiler fired for about 20 seconds and then immediately went into a S.53

After 2 minutes, I took readings, i.e. d40 = 35, d.41 = 22. After 5 mins, it was d40 = 38, d.41 = 24, and after 6 mins, d40 = 38, d41 = 25. During this time, the boiler did not fire and it remained at S.53