Underfloor Heating issues

[Maxwell_Montes]

Firstly, I'm new to the forum, so hi!

 

I have been battling my UFH for a few years - I think the original owner did it wrong, annoyingly he has a habit of getting it wrong at both ends so sometimes stuff works.

 

After a few months we started on the kitchen, the plumber got the lay of the land and pointed out a few bits he'd like to fix on it - fast forward, it still doesn't work well.

 

• the bit with the actuators on gets got first, making me think the flow is reversed
• the bit with the flow meters on is very cool - I thought this could be a blockage, but I noticed they warm up when the system stops calling and the pump turns off - not sure if this is a pump thing or a thermostatic valve thing
• whilst the floor isn't cold cold, its just warm enough when the system runs but I'm doing it for hours to get to 24c, but as I said when it turns off, that temp creeps up for a bit.

 

I looked at the data sheet for the valve and sensor, this seems to suggest that the valve should be mounted on the return and the sensor on the flow side, this isn't what's going on in my system but I'm not sure if this would stop anything getting hot as I can feel both sides of the manifold are hot.

 

I've included a diagram of what I almost certain is going on. Any suggestions about the return warming up once it turns off would be ace. TIA

 

 

[ProDave]

the pump is in the right place.  That type works by the pump circulating water around the UFH pipes and the thermal valve opening when it needs to to let more hot water into the loops when needed, and when the water in the loops reaches the right temperature it shuts off and the water just circulates until it cools down and then it opens to let more hot water in.

 

The sensor for it that looks to be currently on the bottom manifold, I would move it to the top manifold and to the right between the flow meters and the pump.

 

Are the actuators opening properly when required? and is the motorised valve opening?

[Maxwell_Montes]

39 minutes ago, ProDave said:

the pump is in the right place.  That type works by the pump circulating water around the UFH pipes and the thermal valve opening when it needs to to let more hot water into the loops when needed, and when the water in the loops reaches the right temperature it shuts off and the water just circulates until it cools down and then it opens to let more hot water in.

 

The sensor for it that looks to be currently on the bottom manifold, I would move it to the top manifold and to the right between the flow meters and the pump.

 

Are the actuators opening properly when required? and is the motorised valve opening?

 

Brilliant news, thank you for shedding light on this - lots of setups have the pump at the start but I also noticed they looked different elsewhere.

 

It's interesting you mention the sensor. I took it off to see if that held any answers and interestingly the return started to heat up, so could it be the sensor overheating and closing off as it's so early in the chain?

[JohnMo]

Another thread on this same subject about a month ago in the UFH section I think.

[JohnMo]

4 hours ago, Maxwell_Montes said:

• whilst the floor isn't cold cold, its just warm enough when the system runs but I'm doing it for hours to get to 24c, but as I said when it turns off, that temp creeps up for a bit.

 

The thing with UFH is you are generally heating many tonnes of concrete, it takes ages. The longer you leave it off to cool down and the colder it is outside, the longer it takes to heat up.

 

Boilers and heat pumps don't let you rush either. They generally run to maintain a return temperature to flow temperature differential, set point is a secondary set point. So if the water coming out the floor cold, the boiler or heat pump doesn't get to target flow temp for ages (I let my floor completely cool when it was -7 outside, it took 20 hrs before the heat pump hit target flow temp). Slowing things down more.

 

You possibly need to look at how you operate the heating of the floor, overshooting room temp indicates you have the flow temp set too high. Would guess you try to heat for a couple of hours, off most the time. Long and slow or loads of heat in managed chunks if the screed is thick enough and use as a storage heater.

[jack]

5 hours ago, Maxwell_Montes said:

• whilst the floor isn't cold cold, its just warm enough when the system runs but I'm doing it for hours to get to 24c, but as I said when it turns off, that temp creeps up for a bit.

 

How thick is your screed (or slab, if the UFH pipes are in that)?

 

Ours are in the slab underneath about 70 mm of polished concrete overlay, and it takes 3 hours for a change of 0.1 °C to be apparent at the floor surface. The floor surface takes about 12 hours to increase by 0.3-0.4 °C once it starts rising.

 

Here's the slab temperature under the kitchen island over the last few days, with the ASHP running 12 hours a day. Lowest temp was 19.8 °C, highest was 20.2 °C:

 

 

Admittedly this is an extreme case given we run our flows temps quite low (25-28 °C depending on outside temps), but UFH does react very differently to radiators.

[Maxwell_Montes]

37 minutes ago, JohnMo said:

Another thread on this same subject about a month ago in the UFH section I think.

 

Is that the Pump Orientation thread? Looking at it, their supply and return pipes are on the same side as the boiler, whereas mine isn't, which is more the question of it affection the fuctionality.

 

21 minutes ago, JohnMo said:

The thing with UFH is you are generally heating many tonnes of concrete, it takes ages. The longer you leave it off to cool down and the colder it is outside, the longer it takes to heat up.

 

Boilers and heat pumps don't let you rush either. They generally run to maintain a return temperature to flow temperature differential, set point is a secondary set point. So if the water coming out the floor cold, the boiler or heat pump doesn't get to target flow temp for ages (I let my floor completely cool when it was -7 outside, it took 20 hrs before the heat pump hit target flow temp). Slowing things down more.

 

You possibly need to look at how you operate the heating of the floor, overshooting room temp indicates you have the flow temp set too high. Would guess you try to heat for a couple of hours, off most the time. Long and slow or loads of heat in managed chunks if the screed is thick enough and use as a storage heater.

 

I understand this concepts, its more of a case that the heating up of the floor, once it stops, is very sudden. If it was hours later, then sure but its less than 10 minutes and it's up by 5 degrees or more. The sudden change in the return pipe temp also suggests something odd happening

[Maxwell_Montes]

2 minutes ago, jack said:

 

How thick is your screed (or slab, if the UFH pipes are in that)?

 

Ours are in the slab underneath about 70 mm of polished concrete overlay, and it takes 3 hours for a change of 0.1 °C to be apparent at the floor surface. The floor surface takes about 12 hours to increase by 0.3-0.4 °C once it starts rising.

 

Here's the slab temperature under the kitchen island over the last few days, with the ASHP running 12 hours a day. Lowest temp was 19.8 °C, highest was 20.2 °C:

 

 

Admittedly this is an extreme case given we run our flows temps quite low (25-28 °C depending on outside temps), but UFH does react very differently to radiators.

I'm not sure, as it was installed by the previous owners. I guess it's not that thick as the temperature on it changes under 10 minutes. I was brought up in a house with UFH, so I understand the principles of it working differently to radiators, and that it will heat up slower BUT I also understand enough to know something is amiss with the way something in the manifold is behaving. Annoyingly,  keep getting similar responses from plumbers, assuming I don't know how it works and they don't even want to look at it. I wondered if this forum might be able to give me some suggestions that I can pass on

[jack]

1 hour ago, Maxwell_Montes said:

I wondered if this forum might be able to give me some suggestions that I can pass on

We're trying, honest! 😄

[JohnMo]

1 hour ago, Maxwell_Montes said:

that the Pump Orientation thread? Looking at it, their supply and return pipes are on the same side as the boiler

All the drawings and the functionality is there (in the thread), yours is either correct or not. Side things on this side or the other of the manifold has little to do with functionality.

[Super_Paulie]

6 hours ago, JohnMo said:

All the drawings and the functionality is there (in the thread), yours is either correct or not. Side things on this side or the other of the manifold has little to do with functionality.

Do you regret your ufh setup John?

I'm yet to commission mine but it's happening imminently and I'm dubious myself. Too late now, but if I could go back I'd just fill the gaff with quad rads and be done with it.

[JohnMo]

7 hours ago, Super_Paulie said:

Do you regret your ufh setup John?

I'm yet to commission mine but it's happening imminently and I'm dubious myself. Too late now, but if I could go back I'd just fill the gaff with quad rads and be done with it.

In the house no, but adding it the garden room yes, a fan coil or a couple of radiators would have been better suited to use pattern.

[Maxwell_Montes]

15 hours ago, JohnMo said:

All the drawings and the functionality is there (in the thread), yours is either correct or not. Side things on this side or the other of the manifold has little to do with functionality.

Fair enough, I wondered if it was pulling it across the flow meters, rather than forcing it down the correct pipes, creating a reverse flow (if that makes sense)?

[JohnMo]

26 minutes ago, Maxwell_Montes said:

Fair enough, I wondered if it was pulling it across the flow meters, rather than forcing it down the correct pipes, creating a reverse flow (if that makes sense)?

 

Take you are looking at this thread

 

 

So a few issues that jump out

 

Top manifold is flow to floor, this should have the flow regulators, so top and bottom manifolds need to swopped over. The pump and thermostatic valve are in the correct position and flow direction.

 

The other issue is your thermostatic valve needs some feedback from the top manifold and I do not see the sensor wire or probe. The sensor operates as a simple set point controller if the return water is too cool the thermostatic valve opens and let's warm water in, if the floor is hot enough the thermostatic valve closes.

 

Improvements you can make.

 

Swop the top and bottom manifold.

Leave all other components in original positions.

 

Get the correct thermostatic valve. Would check you have a sensor pocket at the outlet piece from the pump, should be a deep 10 to 14mm hole.

 

 

[Maxwell_Montes]

24 minutes ago, JohnMo said:

 

Take you are looking at this thread

 

 

So a few issues that jump out

 

Top manifold is flow to floor, this should have the flow regulators, so top and bottom manifolds need to swopped over. The pump and thermostatic valve are in the correct position and flow direction.

 

The other issue is your thermostatic valve needs some feedback from the top manifold and I do not see the sensor wire or probe. The sensor operates as a simple set point controller if the return water is too cool the thermostatic valve opens and let's warm water in, if the floor is hot enough the thermostatic valve closes.

 

Improvements you can make.

 

Swop the top and bottom manifold.

Leave all other components in original positions.

 

Get the correct thermostatic valve. Would check you have a sensor pocket at the outlet piece from the pump, should be a deep 10 to 14mm hole.

 

 

Yes, the first response mentioned this. It might be a little while before I can get someone to swap them around. I have moved the sensor to the position just after the pump connects to the top manifold for now. Do you think this will help until they are inverted? 

 

Is it a case of taking the manifold off, or could the flow metres and valves just be switched over?

 

From a technical perspective, does having the flow from top to bottom, or bottom to top make any odds? (my guess is yes, as I imagine the flow meters are unidirectional)

[JohnMo]

1 minute ago, Maxwell_Montes said:

as I imagine the flow meters are unidirectional)

Not sure. If they are you could leave as is.

 

4 minutes ago, Maxwell_Montes said:

have moved the sensor to the position just after the pump connects to the top manifold

Where was it connected too?

[Maxwell_Montes]

4 minutes ago, JohnMo said:

Not sure. If they are you could leave as is.

 

Where was it connected too?

I've moved it from the area pre-flow meters to the area circled in green. That manifold seems to be about the same temperature as the bottom half, so I'm not sure how much impact this has.

 

Would the area circled in pink (return to the boiler), be too far over for it to mix effectively?

[JohnMo]

Green circle area is where you need it.

 

The lockshield valve before the pink circle is used to balance the flows I believe. Limits the amount of hot water escaping and being allowed in, so after the lockshield is the wong place.