Simple UFH Query

[Noz85]

Thanks for having a look at this .. 

 

We have lived in our house for 5 years now and it has UFH heating throughout installed to the developers spec. The ground floor is screed and upstairs is installed between floor joists. Due to the ever-rising cost of our energy bills, I have looked into the potential saving that can be achieved by lowering the flow temperature that leaves the boiler. It has always been set to 55degrees and I have lowered it to 45degrees as suggested by a couple of articles I read online.

 

Unsurprisingly, the house is colder. I anticipated that the system would get the house to the safe comfort level but take a little longer. However, it is a little colder than I expected, and depending on what is going on outside, not quite comfortable enough. The mixer valves on the downstairs and upstairs manifolds are set to 55degrees, as they have always been. I have not yet altered this setting, and this is why I am writing this query on the board. I assume that the mixer valve temp should match the flow temp? Could this 10degree discrepancy between boiler flow temp and mixer valve setting be contributing to the house being particularly cold? Or not really? Do I just need to increase my flow rate back to 55degrees and forget this experiment?

 

Unfortunately, the manifolds do not have temperate gauges for feed and return. So I have no idea what the temperature difference is. My concern is that a lot of the rooms are calling for heat, even though I am only trying to achieve 17/18degrees in most rooms, 19degrees in two. (These temperatures may appear to be low, but when the flow rate was 55degrees the house was a nice temperature). Constant calling means that the boiler is running a lot and therefore I assume this is probably using more gas than having a 55degree flow temp.

Edited November 29, 2022 by Noz85

[JohnMo]

We had a normal reliance mixer on our UFH and it was really hit or miss what temp it gave to floor.  Leave the dial where is alter the flow temp going to it, was anyone guess the flow temp to the floor.  They generally like a 10 degree hotter difference in water temp in and water temp setting.  I've just installed an Ivar mixer, which mush stable and has adjustable internal bypasses, to make it really adjustable.

 

A lot of this internet articles are written with a good theory in mind, but often not tried in a real world situation.  I turned my combi flow hot water temp down, monitored gas consumption it went up, turn it back to original setting +5 degrees gas consumption went down.  Go figure. 

 

I would set everything back how it was, measure the temp of one of the pipes coming from the hot side of the manifold or manifold temp, see what temp it actually is.  That will give you a reference, then lower boiler temp a couple of degrees, adjust floor flow temp to match previous temp, ignore the dial markings.  Do that step by step trying to keep manifold temp stable.

[Conor]

Get yourself an IR thermometer and start pointing it at stuff. Brilliant for figuring out flow temps in different pipes quickly.

[Noz85]

Thanks, both. I have an IR thermometer for the pizza oven. My dad also has a temperature sensor which is accurate to 1degree so he claims so could try that also. 
I think you are right, JohnMo. Dropping the flow temp 10degrees was a little bit hasty. Careful trial and error is a more suitable approach. I have taken a meter reading the other week after reducing the flow temp. So I will see what it has used and put it back for comparison, then maybe starting making finer adjustments.

 

So we don't think that the mixer setting matching the flow temp out at the boiler is important?

[Fly100]

I keep beating this drum. Make sure the temp on the dial matches the actual flow temp. I have to remove the plastic knob part and alter it a good few splines to set the corect reading. Mine showed 40C and was only reaching 25C. Simple fix but can throw your data way out. As above, you need boiler flow  10/15c ahead of the mainifold set temp.I can also recomend the Salus Auto Balancing Actuators. Solved a few issues for me.

[Noz85]

6 hours ago, Fly100 said:

I keep beating this drum. Make sure the temp on the dial matches the actual flow temp. I have to remove the plastic knob part and alter it a good few splines to set the corect reading. Mine showed 40C and was only reaching 25C. Simple fix but can throw your data way out. As above, you need boiler flow  10/15c ahead of the mainifold set temp.I can also recomend the Salus Auto Balancing Actuators. Solved a few issues for me.

So you are suggesting that my boiler is set at 55C and the mixer 45C?

Edited November 30, 2022 by Noz85

[Fly100]

7 minutes ago, Noz85 said:

So you are suggesting that my boiler is set at 55C and the mixer 45C?

I run mine at 15c as we have Rads upstairs so its a happy medium. Just check flow into UF Manifold is what it says on the dial.

[V1ks]

On 29/11/2022 at 14:36, Noz85 said:

Thanks for having a look at this .. 

 

We have lived in our house for 5 years now and it has UFH heating throughout installed to the developers spec. The ground floor is screed and upstairs is installed between floor joists. Due to the ever-rising cost of our energy bills, I have looked into the potential saving that can be achieved by lowering the flow temperature that leaves the boiler. It has always been set to 55degrees and I have lowered it to 45degrees as suggested by a couple of articles I read online.

 

Unsurprisingly, the house is colder. I anticipated that the system would get the house to the safe comfort level but take a little longer. However, it is a little colder than I expected, and depending on what is going on outside, not quite comfortable enough. The mixer valves on the downstairs and upstairs manifolds are set to 55degrees, as they have always been. I have not yet altered this setting, and this is why I am writing this query on the board. I assume that the mixer valve temp should match the flow temp? Could this 10degree discrepancy between boiler flow temp and mixer valve setting be contributing to the house being particularly cold? Or not really? Do I just need to increase my flow rate back to 55degrees and forget this experiment?

 

Unfortunately, the manifolds do not have temperate gauges for feed and return. So I have no idea what the temperature difference is. My concern is that a lot of the rooms are calling for heat, even though I am only trying to achieve 17/18degrees in most rooms, 19degrees in two. (These temperatures may appear to be low, but when the flow rate was 55degrees the house was a nice temperature). Constant calling means that the boiler is running a lot and therefore I assume this is probably using more gas than having a 55degree flow temp.

 

Like you i had a similar setup with the Manifold Temp set to 55C and the boiler set to 70c (15c difference) and pump speed to 2, this setup worked well with my kitchen and living room heating up in good time. However as i have LVT in my living room i think at 55c on the manifold the floor was getting too hot so recently i have reduced the temp down to 45c and the flow on the boiler 65, changed the pump speed from 2 to 3 so i get better flow in the loops. I have been using this for the past week and seems to be stable. I think once the temp drop to 0c or lower the time it takes to heat may take longer if you are running the UFH all day....

 

i would say keep 10/15c difference between the temp on the manifold and boiler... or as someone pointed out above the Salus actuators could be a option too...im thinking to get them so the flow and return temp are controlled automatically. 

[JohnMo]

All I would say about Salus Auto balance actuators, is they keep a supply and return DT stable.  They do not control or limit the flow temperature.

 

So if you set your flow temp to 50, then return will be 7 degrees lower, at 43.  If you set it 40, same again return will be 33.

 

What they are designed to do, is keep the DT constant on each loop they are installed, irrespective of loops being switched on/off on the same manifold and a fixed pump speed.