Relationship between factors

[Pocster]

😁 - titles not helpful !

So with wet ufh ; what’s the relationship between the pumps speed , the ufh water temperature and the actual air temperature ( I.e the bit SWMBO complains about ) .

We were running at a ufh temp of 30 degrees which Google implies is bitchingly low . Just set to 34 . Need hours to see how it affects air temp . But pump speed relevance ???

 

Essentially how do I balance these parameters to get the air temp I want ?

Edited January 22, 2023 by pocster

[jayc89]

3 minutes ago, pocster said:

😁 - titles not helpful !

So with wet ufh ; what’s the relationship between the pumps speed , the ufh water temperature and the actual air temperature ( I.e the bit SWMBO complains about ) .

We were running at a ufh temp of 30 degrees which Google implies is bitchingly low . Just set to 34 . Need hours to see how it affects air temp . But pump speed relevance ???

 

Essentially how do I balance these parameters to get the air temp I want ?

 

Pump speed should really depend on how many loops you have and how fast you need to pump the water around them to achieve your target delta T (generally 7c with a flow below 35c). I keep my pump speed as low as possible providing my delta-t looks good. 

 

As far flow temp, really depends on your heat loss, which will dictate the air temp. Keep the flow as low as SWMBO can tolerate. 

[Pocster]

1 minute ago, jayc89 said:

 

Pump speed should really depend on how many loops you have and how fast you need to pump the water around them to achieve your target delta T (generally 7c with a flow below 35c). I keep my pump speed as low as possible providing my delta-t looks good. 

 

As far flow temp, really depends on your heat loss, which will dictate the air temp. Keep the flow as low as SWMBO can tolerate. 

Pump speed is low .

Have the self regulating actuators so flow and return don’t deviate much .

I guess it’s the SWMBO factor - which is hard ( impossible ) to define ….

[jayc89]

1 minute ago, pocster said:

Pump speed is low .

Have the self regulating actuators so flow and return don’t deviate much .

I guess it’s the SWMBO factor - which is hard ( impossible ) to define ….

 

Do your rooms reach temp without overshooting? If the UFH flow was too high you should see overshooting too. 

[ProDave]

It's all one big experiment.  And the golden rule of experimenting is change ONE thing at a time.

 

I would start increasing the water flow temperature.  Start with say 35 degrees.  Let that settle for a couple of days.

 

If your return temperature is not much lower than the flow temperature then you don't have a problem with flow rate.

 

Is the UFH on 24/7 or on a timer?  Is it a case of taking too long to get warm, or never getting warm enough?

[JohnMo]

Pump speed is just a tool to get your required flow rate. Speed is adjusted to over the system resistance, if you have the flow rates you want and speed is to high you are just wasting electric. Nothing to do heat transfer, except providing the motive force to move the water at your set flow rate 

 

Temp, on its own isn't the whole story, it's the combined outcome of flow temp and return temp, so the mean flow temp that sets the kW output.  Flow rate alters the mean flow temp. You also have floor covering u value to add to the mix.  The more resistant the higher the mean temp needs to be for a give kW output.

[Pocster]

Have changed the ufh temp ; nothing else . Will report back after a few days . Overshooting desired temp is rare . Floor coverings are non existent … 

[Adsibob]

How much overshoot is acceptable? We have a room which overshoots by 0.4C and another that overshoots by 1.9C. I need to do something about the 1.9C room. I guess just reduce the flow rate OR the temperature?

[Pocster]

20 hours ago, Adsibob said:

How much overshoot is acceptable?

Now there’s a question ! 🙄

[ToughButterCup]

20 hours ago, Adsibob said:

... We have a room which overshoots by 0.4C and another that overshoots by 1.9C. I need to do something about the 1.9C room...

 

What would happen if you changed the position of the thermometer? 

I ask because  1.9 seems to me to be well within the range at which a SignificantOther would not notice the difference.

 

Actual temperature and perceived temperature differ in this household.....🙊

[Adsibob]

4 minutes ago, ToughButterCup said:

 

What would happen if you changed the position of the thermometer? 

I ask because  1.9 seems to me to be well within the range at which a SignificantOther would not notice the difference.

 

Actual temperature and perceived temperature differ in this household.....🙊

It's not possible to move the thermometer, as the thermostats are wired in already. Unless by "thermometer" you mean SWMBO, in which case she is even more difficult to move.

[Adsibob]

On 22/01/2023 at 18:27, jayc89 said:

I keep my pump speed as low as possible providing my delta-t looks good. 

How do you measure (or “see”) the delta? My temp is set to 38C; I rather not go much higher as one of the loops from this manifold run under a wooden floor.

[jayc89]

20 minutes ago, Adsibob said:

How do you measure (or “see”) the delta? My temp is set to 38C; I rather not go much higher as one of the loops from this manifold run under a wooden floor.

 

I use an IR thermometer to measure the difference between flow and return temp. Given you have auto balancing actuators, this should be done for you (assuming they're working correctly!). 

[Adsibob]

44 minutes ago, jayc89 said:

 

I use an IR thermometer to measure the difference between flow and return temp.

I have an IR thermometer, but not sure what emissivity setting I would set it to. The pipes are Pex -Al -Pex pipes, I think. They are described on the website as "Combines the benefits of both metal and plastic pipes". So do I set the emissivity setting on the IR thermometer to plastic or metal?

46 minutes ago, jayc89 said:

Given you have auto balancing actuators, this should be done for you (assuming they're working correctly!). 

I don't have auto balancing actuators. I have a very basic manifold system made by a company called Warma. My actuators look a bit like this: https://www.amazon.co.uk/dp/B0819Z6LPV?tag=picclick02-21&linkCode=osi&th=1&psc=1

[jayc89]

39 minutes ago, Adsibob said:

I have an IR thermometer, but not sure what emissivity setting I would set it to. The pipes are Pex -Al -Pex pipes, I think. They are described on the website as "Combines the benefits of both metal and plastic pipes". So do I set the emissivity setting on the IR thermometer to plastic or metal?

I don't have auto balancing actuators. I have a very basic manifold system made by a company called Warma. My actuators look a bit like this: https://www.amazon.co.uk/dp/B0819Z6LPV?tag=picclick02-21&linkCode=osi&th=1&psc=1

 

My bad, I thought when you mentioned self-regulating actuators earlier you were meaning something like the Salus ones. In that case, you should check your flow rates too. As a starting point take your loop lengths and divide them by 40. (i.e. a 100m loop should be running at around 2.5 l/m). Once your loops are balanced (defined as achieving approx. 7c delta-t), you can focus on your mixing temp to ensure your rooms aren't overshooting too much (I generally want to see mine not overshoot by more than 0.5c) and then the only other variable is the room stat temp (we still have draughts and find 21c never feels like 21c...)

[Adsibob]

59 minutes ago, Adsibob said:

I have an IR thermometer, but not sure what emissivity setting I would set it to. The pipes are Pex -Al -Pex pipes, I think. They are described on the website as "Combines the benefits of both metal and plastic pipes". So do I set the emissivity setting on the IR thermometer to plastic or metal?

Just to clarify the above further, here is the guidance from my IR thermometer manual for emissivity settings:

 

 

So the choice appears to be:

• plastic 0.85 to 0.95
• copper oxide 0.78
• iron oxide 0.78 to 0.82

Maybe I should go with 0.85 which is more or less in the middle of these? 

[JohnMo]

You don't need to do anything complex.

 

For the rooms that overshoot 0.4 - do nothing for now.  For the 1.9 overshoot you are putting too much energy in the floor.  Reduce that loops flow rate by 0.5L/min.  Monitor and adjust as required. Less flow less energy, more flow more energy, adjust at the loop flow meters.  Auto balance actuators will not help with this.

 

Once your room over shoots are all roughly the same, reduce flow temp a degree at a time.  If you hot water and CH are set at different flow temps you can reduce the flow temp to CH at the boiler.

[jayc89]

1 hour ago, JohnMo said:

You don't need to do anything complex.

 

For the rooms that overshoot 0.4 - do nothing for now.  For the 1.9 overshoot you are putting too much energy in the floor.  Reduce that loops flow rate by 0.5L/min.  Monitor and adjust as required. Less flow less energy, more flow more energy, adjust at the loop flow meters.  Auto balance actuators will not help with this.

 

Once your room over shoots are all roughly the same, reduce flow temp a degree at a time.  If you hot water and CH are set at different flow temps you can reduce the flow temp to CH at the boiler.

 

Why wouldn't auto-balancing actuators help with this? Wouldn't they effectively drop the flow rate for you, until the return is the correct temp and therefore not dumping too much energy into the floor?

[JohnMo]

 

6 minutes ago, jayc89 said:

Why wouldn't auto-balancing actuators help with this?

Because they give a set delta T, they auto balance the system as and when actuators open and close, so a loop always has a set delta T.  In this situation @Adsibob is supplying too much energy in to a loop and the way to balance this, is to increase delta T over the loop, so the mean flow temperature reduces

[Temp]

Lots of suggestions but what actually is SWMBO unhappy about?

 

If she's cold it can only be one of a few things ..

 

System is working but room stats set too low?

 

System isn't working properly and  rooms aren't reaching set temperature or are taking too long?

 

It's that time of life or they have a medical issue.

 

Our system keeps our living room bang on the set temperature which is 21 at evenings and weekends. Despite that various members of the family feel either too hot or too cold. I get complaints it's too hot then a few hours later same person says it's cold or fine despite no change in temperature. I sometimes ask them to guess the room temperature without looking at the stat and they always get it wrong. Sometimes I pretend to turn it up/down 🙂

 

Making them a cup of Tea is sometimes effective. Ten mins later they are too hot.

 

 

[Pocster]

38 minutes ago, Temp said:

I sometimes ask them to guess the room temperature without looking at the stat and they always get it wrong. Sometimes I pretend to turn it up/down 🙂

I agree - perception is the key . A tenant will moan their room isn’t 21 degrees . It’s actually 20.5 . They request I turn it up to 22 . I do nothing . Hour later ask them if that’s better - they say yes .

[Bramco]

19 hours ago, jayc89 said:

Why wouldn't auto-balancing actuators help with this? Wouldn't they effectively drop the flow rate for you, until the return is the correct temp and therefore not dumping too much energy into the floor?

 

Would auto balancing actuators work with an insulated slab?  Or conversely, do they only work with radiators and UFH in screed, both of which lose heat quickly.

 

With our system with an insulated slab, the feed and return temperatures from the manifold are only about 3deg apart. The slab stays warm, which is the whole idea and gets topped up at scheduled times during the day.  The thermostats are turned up higher than the real target, so that they call for heat all the time and don't cycle which means the ASHP runs continuously and doesn't cycle.  At the moment while it's cold outside, the schedule is twice a day for 4 hours each time. When it's warmer, it's only once a day.

 

Simon  

[JohnMo]

Auto balancing actuator is there to do one thing.

 

Maintain a set delta T on the loop it is attached too. If flow temp is below 30 degs, it maintains 4 degs over 30 it maintains 7 deg delta T.  As zones open and close, this delta is sometimes lost, the actuator open or close to ensure the delta T doesn't change.

 

They don't care or know what they are attached too.

[Bramco]

53 minutes ago, JohnMo said:

They don't care or know what they are attached too.

 

But do they?  Our flow temperature at the moment is 29deg and the return temperature is 26deg - what would an auto balancing actuator do?  Turn off?   If so, then we'd stop trickling heat into our insulated slab which wouldn't be great.   

 

Which was why the original question - are they intended for applications where the emitters lose heat rapidly, i.e. radiators or UFH in screed.  Maybe being thick but I can't see how they would work with an insulated slab where heat is lost very slowly to the house and basically you want to keep it at or around the same temperature most of the time. 

 

Simon

 

 

[JohnMo]

1 hour ago, Bramco said:

what would an auto balancing actuator do?  Turn off?

They are just the same as any other actuator, if powered the allow flow if you remove the power they switch it off.  They only added function is auto balancing to maintain a fixed delta T.

 

1 hour ago, Bramco said:

are they intended for applications where the emitters lose heat rapidly, i.e. radiators or UFH in screed

They don't care

1 hour ago, Bramco said:

I can't see how they would work with an insulated slab

They have a probe on the loop supply and return pipe and monitor/measure the flow temp and temperature change as heat is transferred to floor.  As said any system will do, they open or close the flow rate to get a fixed delta T.