UFH pipes not hot enough

[windsortg]

I recently had UFH system installed in a newly constructed orangery. I ran the UFH system today for the first time. The room temperature was 20.5C at the start and I had set the thermostat to reach 22.5C. After 2 hours of the UFH system running, the room stat was showing 21.5C but all the pipes surrounding the manifold were not hot to the touch. The zone valve of the UFH was open. I believe there is something to quite right. No other heating or heating of hot water was running.

Any advice would be greatly appreciated. I have attached a photo of the UFH system.

 

[Madrab]

You can see from the top left dual gauge (bottom reading) that the mix temp is low - around 20 odd degrees - so either the blending valve under the pump is set too low or the system input water isn't warm enough. That and the manifold thermostats both show the same low temps too.

Is the pump running and the flow valves showing flow? If that picture is taken when the system is running then it doesn't seem to be showing any flow.

 

[windsortg]

thanks @Madrab. The photo was NOT taken when the system was running. It was taken when the system was first installed. Shall I attach a photo when the system has been running for 20 mins and then another photo when the system has been running for 2 hours but has not yet reached the set temperature?

 

[Madrab]

Not really, what you need to check for is what temp do the temp gauges reach on the flow side and does that align with the setting on the blending valve, when the the flow from the boiler is up to temp.

The pump and flow rates then need to be looked at.

Basically it seems the system may need setup properly, that should really have been performed when the system was commissioned.

 

[windsortg]

thanks @Madrab. From the photo, can you let me know which gauges I need to check? I have attached a photo of the blending valve (assuming this is the correct one). It appears to be set to 'Max' as I cannot turn it any further anti-clockwise.

Can you point me in the right direction for looking at the pump and flow rates?

The installer is currently away on holiday so ideally I would like to do as much troubleshooting as I can.

 

[Lower]

When the system is on and running, take a photo of the flow valves (the clear plastic tubes with red bases at the top right of the manifold) and tell us if the pipes immediately below them feel hot.

Then tell us if the pipes on the return side feel warm.

 

[windsortg]

thanks @Lower. Attached is a photo of the flow valves I took yesterday when the system had been running for 2 hours. The pipes immediately below these valves were warm to the touch but not hot.

Stupid question but which are the pipes on the return side?

One thing I did notice that after the UFH system was running for 2 hours, I checked the UFH zone valve. This was open. However, the boiler was not firing. This may be because the boiler had internally reached a certain temp and had cut off for a period to allow to cool.

 

[Mr Chibs]

On my UFH, sometimes it does circulate without the boiler firing.

I have my blending valve set to halfway, my boiler water is only set to 55º, the UFH won't come on until 45° temperature has been achieved at the UFH pump. As Madrab has said it probably needs properly tweaking. It's made me think to have a double check at my floor.

 

[windsortg]

thanks @Mr Chibs. What would be the next thing for me to check?

 

[Lower]

The two pipes attached to the flow meters that you've photographed above are the flow pipes. The return pipes are the two pipes on the manifold below the manifold with the flow meters attached. The return side has two grey caps in instead of flow meters.

The mixing valves mixes the underfloor heating water with the main heating system water as the underfloor heating runs at a lower temperature than the central heating system so it's quite possible the underfloor heating will be one without the boiler being on.

 

[Madrab]

Flow runs in through the top of the manifold through the red valve, return through the bottom through the blue valve.

Firstly, the flow rate is way too high, those flow meters should be set at around 2-2.5 L/Min as a starting point, when the pump is running , UFH zone size dependent. That may be the flow meters or the pump setting that needs adjusted, probably both.

The mixing valve should be set to between 40>50deg, floor type dependent. If that blending valve is set to max then how hot is the boiler setting? Is the pipe coming from the system/2 port valve really hot and - really important - which pipe gets hot, the one into the bottom of the blending valve or the one into the side?

Even then though It's not really as simple as that. You need to understand the pipe spacing, heat loss therefore what W/M2 is required, that then drives the flow and pump speed settings, etc.

What controls the room temp, I presume it has it's own stat that is hooked into the 2 port for the UFH manifold and to the boiler for switching?

 

[windsortg]

thanks @Madrab and @Lower. Let me try and answer what I can. I have attached some more photos after running the UFH system for one hour. The flow rate appears to be at 3-3.5

The pipe coming from the 2 port valve (which is in a cupboard in the landing) is hot but I would not say it is very hot.

I spoke with the installer over the phone and he asked me to run the UFH system and check whether the flow pipe (running up to the blending valve) is hotter than the pipe to the left of the blending valve. To confirm, the pipe leading to the blending valve was hotter than the one of the left.

The pipe spacing was mainly laid between 100 - 150mm spacing.

Regarding the room stat. I recently had Heatmiser installed so I have a neoStat v2 thermostat fitted (hardwired) in the orangery which controls the 2 port zone valve for the UFH manifold and running of the boiler. I have another neostat v2 wired thermostat in the hallway for the radiator central heating system, and another neoStat v2 used as a timer for the hot water. When experimenting with the UFH system. I made sure the central heating system and hot water was not running.

Let me know if any further photos are needed or any other checks.

 

[Lower]

You have two flow meters. The one on the left looks like it reads 3-3.5. The one on the right i showing a flow rate of more than 5 which is way to fast. You can adjust the flow down by lifting the red cap and then rotating the whole flow meter.

You appear to have a flow temperature of above 45 degrees and a return of about 35 degrees, so 10 degrees the heat in the water is being transferred to the floor which is correct.

What floor covering do you have? My underfloor heating in our 6m x 6m kitchen is pipes in screed with engineered wood laid on top. When the floor is first turned on at the end of summer it takes approx 4 hours for the slab to heat up and start warming the room. I control it with a nest thermostat so have the room programmed to be warm from 7.30am to 10.30pm. Typically, the underfloor heating will run for about 2-3 hrs in the morning, and the for approx 0.5-1hr at about 7-8pm in the evening.

You shouldn't expect the floor to respond like a radiator. The first time you run it you have to heat the floor slab before any heat starts to transmit to the room.

 

[windsortg]

thanks @Lower. Assuming I am looking at the correct flow meters, I cannot see where the right-hand meter is showing more than 5. I have attached a close up photo of the flow meters.

My internal orangery size where the UFH is installed is 5.4m x 3.7m and I have a fair amount of glass within the orangery that consists of a bi-fold door, large windows, french door and a 4 x 2m roof lantern. The UFH has been laid in screed (with 150mm celotex insulation below the screed) with 12mm floor tiles on top of the screed. I am aware that UFH systems do not perform the same way as radiators but what is concerning is that whilst the temperature in the orangery had not reached the set temperature after 2 hours, the pipework going to the blending valve (and the steel of the manifold) was not hot to the touch.

Should the pipework around the manifold not be hot as it heats up the room?

 

[Madrab]

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.