UFH zones not heating

[rhymecheat]

Hi there,

 

I’ve had UFH installed about a year ago but this is the first proper winter that it’s going through. Long story short, I can’t get it to go anywhere above 18C (-2 outside). 
 

the manifold is being supplied with 55C (actual value oscillates between 48/55) flow temperature. And the return is around 40/45C targeted by Salus auto balancing actuators.

 

I’ve used a thermal camera and can see the loops actually heating up under the floor so I know the water is flowing to the zones, but still it remains cold. It’s been running like this for about 48h straight and the temperature doesn’t go up (or down for that matter). Any suggestions of what to check or try?

 

 

[Radian]

-2 shouldn't be a big challenge but it sounds like it's reached thermal equilibrium. What's your floor build-up?

[rhymecheat]

16 minutes ago, Radian said:

-2 shouldn't be a big challenge but it sounds like it's reached thermal equilibrium. What's your floor build-up?

Floor is suspended with thick insulation between the joists and boarded with amtico glued on top. 

I thought equilibrium would be when the air temp and the floor temp matched. Mind you the gauges rarely meet

 

One thing I was thinking could be the issue would be air in the tubes. But I don’t know how to be sure of it without bleeding the whole thing. 

 

[Radian]

2 minutes ago, rhymecheat said:

I thought equilibrium would be when the air temp and the floor temp matched.

No, what I mean is you're putting X Watts in and nature is taking X Watts out, and it's all happening with a mean inside/outside delta of 20^oC

If it the outside temperature dropped another degree and so did your inside temperature, that would be the biggest hint. It's unlikely to be this but you meet all sorts in this game.

[ProDave]

What are the details of the building?  Insulation levels, calculated worst case heat loss etc?

 

As a trial, remove the actuator heads for a while, this will let all loops run at maximum flow rate uncontrolled, if that can;t put enough heat into the house then it never will.

 

 

[rhymecheat]

16 minutes ago, Radian said:

No, what I mean is you're putting X Watts in and nature is taking X Watts out, and it's all happening with a mean inside/outside delta of 20^oC

If it the outside temperature dropped another degree and so did your inside temperature, that would be the biggest hint. It's unlikely to be this but you meet all sorts in this game.

Yeah I feel like it can’t be this because temperatures have varied over the last 24h but the inside temp has always remained the same

[rhymecheat]

13 minutes ago, ProDave said:

What are the details of the building?  Insulation levels, calculated worst case heat loss etc?

 

As a trial, remove the actuator heads for a while, this will let all loops run at maximum flow rate uncontrolled, if that can;t put enough heat into the house then it never will.

 

 

I don’t know the technicals apart from knowing that since it’s been recently extended all external walls are new and therefore insulated. 
 

I’ll try removing the actuator heads over night and see what’s what in the morning. 

[rhymecheat]

9 hours ago, ProDave said:

What are the details of the building?  Insulation levels, calculated worst case heat loss etc?

 

As a trial, remove the actuator heads for a while, this will let all loops run at maximum flow rate uncontrolled, if that can;t put enough heat into the house then it never will.

 

 

So I’d been running all night and believe it or not… temperature inside has dropped .5C

 

the return temperature is now close to 50C with flow at 55C

 

One thing I noticed when opening the actuators is the red pins don’t fully go down no matter how much I turn them. Don’t know if relevant. 

[ProDave]

So you are putting as much heat in as you can constantly, and the temperature in the room has dropped as the outside temperature has dropped.

 

So as @Radian said above you have reached thermal equilibrium and this is as hot as the room is ever going to get with this outside temperature and the UFH system you have.

 

All you can really do is supplement it with some other heat source in the very cold weather.

[Radian]

1 hour ago, rhymecheat said:

One thing I noticed when opening the actuators is the red pins don’t fully go down no matter how much I turn them. Don’t know if relevant. 

 

Are you sure the acuator pins are returning to their fully open position when you remove the actuators? (I'm assuming these are like radiator TRV's where sometimes the pins get stuck down in the closed position)

 

11 hours ago, rhymecheat said:

Floor is suspended with thick insulation between the joists and boarded with amtico glued on top. 

 

Also you didn't mention spreader plates in your buildup - there has to be a way for the UFH pipes to conduct their heat to the floor surface. The way you describe it there's nothing around the pipes to do that.

[rhymecheat]

3 hours ago, ProDave said:

So you are putting as much heat in as you can constantly, and the temperature in the room has dropped as the outside temperature has dropped.

 

So as @Radian said above you have reached thermal equilibrium and this is as hot as the room is ever going to get with this outside temperature and the UFH system you have.

 

All you can really do is supplement it with some other heat source in the very cold weather.

Well that’s no good!

 

Im calling the installer tomorrow morning for him to come and have a look. 
 

im secretly hoping there’s air on those loops because even the floor isn’t warm enough for this temperature imo…

[rhymecheat]

2 hours ago, Radian said:

 

Are you sure the acuator pins are returning to their fully open position when you remove the actuators? (I'm assuming these are like radiator TRV's where sometimes the pins get stuck down in the closed position)

 

 

Also you didn't mention spreader plates in your buildup - there has to be a way for the UFH pipes to conduct their heat to the floor surface. The way you describe it there's nothing around the pipes to do that.

I tried pressing the pins but they all look okay. 

 

Unsure about spreader plates tbh. The thermal cameras clearly show hot loops on the floor but only the loops. Would I see a bigger spread with spreads plates?

[rhymecheat]

3 hours ago, ProDave said:

So you are putting as much heat in as you can constantly, and the temperature in the room has dropped as the outside temperature has dropped.

 

So as @Radian said above you have reached thermal equilibrium and this is as hot as the room is ever going to get with this outside temperature and the UFH system you have.

 

All you can really do is supplement it with some other heat source in the very cold weather.

Also keep in mind this is every room. The ones exposed to external walls, the ones that are not, the hallways. It’s all suffering. 
 

also, the upstairs has rads instead and it’s always hot with the same insulation and exposed to the same elements. 

[Radian]

37 minutes ago, rhymecheat said:

Unsure about spreader plates tbh. The thermal cameras clearly show hot loops on the floor but only the loops. Would I see a bigger spread with spreads plates?

 

Do you have a Flir type imager? Post a photo. Even with spreaders it would still tend to show up hottest on top of the pipes but I'm guessing the temperature in between loops shouldn't be more than a few degrees lower. I only know what it looks like in 50mm screed and it's even to about 2.5^oC

 

[rhymecheat]

1 hour ago, Radian said:

 

Do you have a Flir type imager? Post a photo. Even with spreaders it would still tend to show up hottest on top of the pipes but I'm guessing the temperature in between loops shouldn't be more than a few degrees lower. I only know what it looks like in 50mm screed and it's even to about 2.5^oC

 

What’s your flow temp and how the hell are them loops so hot? My flow is at 55C and the loop is only at 24C max

 

[Radian]

1 hour ago, rhymecheat said:

What’s your flow temp and how the hell are them loops so hot?

The flow after the mixer is 43^oC which is the minimum set point for my buffer so probably a bit less. It has been taking 6 or 7 hours to get the room comfortable since it went sub-zero recently.

 

Incidentally, if you use the Flir tools App you can call up multiple spot readings retrospectively. Lousiest bit of software imaginable apart from that but that one facility is worth having.

[rhymecheat]

3 hours ago, Radian said:

The flow after the mixer is 43^oC which is the minimum set point for my buffer so probably a bit less. It has been taking 6 or 7 hours to get the room comfortable since it went sub-zero recently.

 

Incidentally, if you use the Flir tools App you can call up multiple spot readings retrospectively. Lousiest bit of software imaginable apart from that but that one facility is worth having.

Thanks for the FLIR tip!

 

Are your flow tubes clear? Mine are all brown so I’m guessing there’s some funk in there. I’m gonna go ahead and drain them tomorrow then refill. I’m convinced there’s crap/air in there preventing them from heating fully. 

[Radian]

3 minutes ago, rhymecheat said:

Are your flow tubes clear?

 

I honestly don't like to think about it. I added the loop to an existing rad only system and all the advice was to have the rads power flushed before connection - but I hooked it up last November just when it went sub-zero and I decided not to take any risks with the main heating. Seems OK but I never quite get all the air out (open vented system). I was going to seal it this year but didn't get around to it. I always seem to end up in November when I have time to do big jobs like that - then chicken out for fear of leaving everyone shivering.

[Super_Paulie]

On 10/12/2022 at 21:08, rhymecheat said:

Hi there,

 

I’ve had UFH installed about a year ago but this is the first proper winter that it’s going through. Long story short, I can’t get it to go anywhere above 18C (-2 outside). 
 

the manifold is being supplied with 55C (actual value oscillates between 48/55) flow temperature. And the return is around 40/45C targeted by Salus auto balancing actuators.

 

I’ve used a thermal camera and can see the loops actually heating up under the floor so I know the water is flowing to the zones, but still it remains cold. It’s been running like this for about 48h straight and the temperature doesn’t go up (or down for that matter). Any suggestions of what to check or try?

 

 

out of interest how did this pan out, did you get it resolved?