Underfloor heating lukewarm

[Mark p]

Looking for some help! I am having problems with my underfloor heating only getting lukewarm, even when on for 8-12hrs constantly (see pictures) . It is currently costing £25 to £30 a day and using 150 to 200kw a day to not even be warm and is driving me crazy. I am struggling to get above 16 degrees in some rooms but others i have got up to 19 degrees. I have had heat in the system before. As set out in the background below I have had a Heatmiser system installed and currently having a plumber coming back to try to solve the issue.  Any suggestions?

 

Some background

I moved into a property just over a year ago. I have underfloor heating in all rooms with one radiator downstairs and one towel rail upstairs. The existing underfloor heating Manifold was upside down and thermostats didnt work very well. Before Christmas last year I had the manifold corrected and a Heatmiser system installed. The system seemed to work although I was spending quite a lot during the winter months. I found that I had less than 100mm of insulation in the loft and assumed that was where I was losing lots of heat. The rest of the property is pretty well insulated, with double glazed windows and doors, insulated cavity walls and now topped up insulation.  

 

The system (see picture - system off in picture)

• 10 port manifold
• Heatmiser UH8-RF 8 zone
• Heatmiser Neoair v2 wireless
• 8 actulators but 9 systems
• Grundfos pump
• 2 radiators
• All rooms underfloor 
• Heatmiser plug boosters - ordered additional ones. 
• Neohub Gen2
• Floor is engineered oak through out
• I have had the boiler at varying temperatures from 60 to 75 degrees
• Mixing valve - set at 55 degrees 

 

Specific problems

• One of the flowmeters seems stuck - Ordered new one
• Occasional knocking and clicking sounds
• Heatmiser thermostats keep going off line
• Heating switching on during the night
• Heatmiser thermostats jumping between auto, hold, standby 
• Advised by Heatmiser not to use direct

 

I have borrowed a thermal imaging camera and can see the loops heating up although in most places there is no heat in the floor. Most rooms downstairs have plenty of loops whilst upstairs some rooms are limited. 

 

It seems that the system is getting up to a temperature but not full temperature.  

 

I would appreciate any advice to get the system to heat up to previous heating levels. Or do I need to install electric radiators???

 

Mark

[Conor]

I've the neoair stats. Useless, range is terrible. I have one sitting directly above the receiver on the floor above (literally less than 3m straight line distance) and it doesn't connect half the time. That could be your problem if the stats aren't communicating with the hub and therefore failing to call fo heat. I'm getting rid of mine and hoping for a refund as not fit for purpose. Not even attempted to install the top floor one. All three are currently sitting in the plant room beside the hubs.

 

But... The high gas usage seems to suggest that the boiler is working hard, so the heat is going somewhere. You mentioned that pipes are heating up but not the floor? Or is it that some floors heat up, but not others?

 

Do you know the ground floor build up? How much insulation is under the floor? If there was only 100mm insulation in the loft, my money is on very little or nothing on the ground floor and you're basically heating the earth.

[JohnMo]

Just looking at the dotted line on your graphs, which looks to be the thermostat set points.  And the red part where it states heating is on.

 

A couple of observations based on experience with my house.

 

You have the heating on at various times and various temperature throughout the day.  Looking at the red parts of the graphic your room temp is just about getting to temp and you switch it to a lower temp, then a few hours later a higher temp.  So with floor inertia you boiler is playing catch up all the time.

 

The other thing that may be happening you have multiple zone all programmed at differing times of the day. This is great, but in practice, you can have periods where you only have the lounge switched on, so the boiler is only being asked to do a couple couple of kWs of work, but the boiler may have a min output of 10kW.  In practice this leads to the boiler short cycling. So boiler starts, a few minutes later trips on high return temps or minimum flow. Boiler is locked out for 10 mins, and this repeats until more zones are opened up.

 

So why does this lead to poor heating performance and high consumption of gas.

 

Short cycling, every time your boiler starts, the efficiency is low, it's heating a slug of cold water and lots of metal, once the boiler has been running for a 5 mins the efficiency climbs quickly. Continuous on off cycle means the boiler is in a low efficiency mode, the 10 min lock means no hot water is being pumped around.

 

Timing efficiency, your floor is heating, you can see in the lounge at about 10am a big jump in temperature. So big it look like the flow temp is way too high.

 

My recommendation as a trial, set all your thermostats to manual at say 19 degrees, and the boiler will have the whole UFH system to heat, see what happens. I suspect it will be fine and heat up quite quickly.  If the temperature overshoots 19 then your flow temp is too high.

[ProDave]

8 hours ago, Mark p said:

Can you explain the context of this picture?

 

Is it the right way up?

 

If so most of your pipe loops go UP from the manifold.  That is not normal.  Usually the manifold is on the wall and the pipes come out of the bottom and into the floor.

 

Pipes going up will need provision for bleeding air out of them at the highest point, otherwise air will collect and you might get air locks which could explain some parts of the floor remaining cold.

[Mark p]

36 minutes ago, ProDave said:

Can you explain the context of this picture?

 

Is it the right way up?

 

If so most of your pipe loops go UP from the manifold.  That is not normal.  Usually the manifold is on the wall and the pipes come out of the bottom and into the floor.

 

Pipes going up will need provision for bleeding air out of them at the highest point, otherwise air will collect and you might get air locks which could explain some parts of the floor remaining cold.

This is a picture of the manifold now. The right way up! Previously the whole thing was the other way up with the flow release valves pointing down. Ports 1, 2, 3 and 10 feed downstairs, whilst upstairs are port is 5 to 9, with 4 not being used. The upstairs ports go up the wall to room above and feed the rest of the house from there. I don't believe that  there is anywhere to bleed the air out upstairs. To be honest I don't know where or how we would put some in as i have oak floor everywhere. Part of the problem upstairs is there aren't enough loops. I have though had heat in these rooms so I am guessing there is some heat in the system. Downstairs seems to be better. I think my thermostats may need calibrating as two next each other say a different temperature if I take them off the wall and put them next to each other. I think I need him to flush the system and get the air out.

 

I don't know if it is relevant but when all rooms are on my radiator is only lukewarm but when only one system is nice and hot. It doesn't have its own actuator and will heat up when any system is on.  

[Conor]

4 minutes ago, Mark p said:

This is a picture of the manifold now. The right way up! Previously the whole thing was the other way up with the flow release valves pointing down. Ports 1, 2, 3 and 10 feed downstairs, whilst upstairs are port is 5 to 9, with 4 not being used. The upstairs ports go up the wall to room above and feed the rest of the house from there. I don't believe that  there is anywhere to bleed the air out upstairs. To be honest I don't know where or how we would put some in as i have oak floor everywhere. Part of the problem upstairs is there aren't enough loops. I have though had heat in these rooms so I am guessing there is some heat in the system. Downstairs seems to be better. I think my thermostats may need calibrating as two next each other say a different temperature if I take them off the wall and put them next to each other. I think I need him to flush the system and get the air out.

 

I don't know if it is relevant but when all rooms are on my radiator is only lukewarm but when only one system is nice and hot. It doesn't have its own actuator and will heat up when any system is on.  

 

There should have been a separate manifold with its own pump upstairs for those loops. Too late now. At least you can bleed the radiator.

 

What are the flow rates set at when it's all running together? The pump might be struggling to get the water upstairs when lots of zones are open, which would explain the cool rad. You'd be looking for flows of 0.5-2lpm depending on the loop length and heat loss.

[Mark p]

1 hour ago, JohnMo said:

Just looking at the dotted line on your graphs, which looks to be the thermostat set points.  And the red part where it states heating is on.

 

A couple of observations based on experience with my house.

 

You have the heating on at various times and various temperature throughout the day.  Looking at the red parts of the graphic your room temp is just about getting to temp and you switch it to a lower temp, then a few hours later a higher temp.  So with floor inertia you boiler is playing catch up all the time.

 

The other thing that may be happening you have multiple zone all programmed at differing times of the day. This is great, but in practice, you can have periods where you only have the lounge switched on, so the boiler is only being asked to do a couple couple of kWs of work, but the boiler may have a min output of 10kW.  In practice this leads to the boiler short cycling. So boiler starts, a few minutes later trips on high return temps or minimum flow. Boiler is locked out for 10 mins, and this repeats until more zones are opened up.

 

So why does this lead to poor heating performance and high consumption of gas.

 

Short cycling, every time your boiler starts, the efficiency is low, it's heating a slug of cold water and lots of metal, once the boiler has been running for a 5 mins the efficiency climbs quickly. Continuous on off cycle means the boiler is in a low efficiency mode, the 10 min lock means no hot water is being pumped around.

 

Timing efficiency, your floor is heating, you can see in the lounge at about 10am a big jump in temperature. So big it look like the flow temp is way too high.

 

My recommendation as a trial, set all your thermostats to manual at say 19 degrees, and the boiler will have the whole UFH system to heat, see what happens. I suspect it will be fine and heat up quite quickly.  If the temperature overshoots 19 then your flow temp is too high.

Thank you for you comments.  I have now changed to put on at around 19 degrees and 18.5 degrees all day and down to 16 over night to all downstairs and slightly lower upstairs see if this makes a different. Like you say it I may have been asking the boiler to heat to few zones and also on and off too much.  When it is short cycling does the boiler have an hour glass sign? I have a Valliant Ecofit pure  

 

The jump in temperature is misleading on this graph. I put the fire on in the room to get it up to a reasonable temperature as on previous days it was staying at 16 ish degrees. The room then kept up to temperature

[Mark p]

Pictures of my system now, the boiler and showing the lounge through a thermal imaging camera

 

The flow meter on port 1 appears to be stuck and I have asked the plumber to replace

[Mark p]

25 minutes ago, Conor said:

 

There should have been a separate manifold with its own pump upstairs for those loops. Too late now. At least you can bleed the radiator.

 

What are the flow rates set at when it's all running together? The pump might be struggling to get the water upstairs when lots of zones are open, which would explain the cool rad. You'd be looking for flows of 0.5-2lpm depending on the loop length and heat loss.

There is no pump upstairs. The towel rad upstairs all feels hot. It may be worth bleeding it to see if there is any air in the system. How do I top up the water if I bleed the towel rail radiator?

 

I dont know what the flow rate is. I have attached a picture of the system now while it is on. 

 

Would it be worth replacing the pump with a more powerful one?

[ProDave]

10 minutes ago, Mark p said:

Pictures of my system now, the boiler and showing the lounge through a thermal imaging camera

 

The flow meter on port 1 appears to be stuck and I have asked the plumber to replace

The immediate thing on that photo of the manifold is the numbers on the actuators are not matching the writing on the manifold You need someone to check that the actuators are really all in the correct place, otherwise you may have the actuator for one room controlled by a different thermostat.

[Mark p]

5 hours ago, Conor said:

I've the neoair stats. Useless, range is terrible. I have one sitting directly above the receiver on the floor above (literally less than 3m straight line distance) and it doesn't connect half the time. That could be your problem if the stats aren't communicating with the hub and therefore failing to call fo heat. I'm getting rid of mine and hoping for a refund as not fit for purpose. Not even attempted to install the top floor one. All three are currently sitting in the plant room beside the hubs.

 

But... The high gas usage seems to suggest that the boiler is working hard, so the heat is going somewhere. You mentioned that pipes are heating up but not the floor? Or is it that some floors heat up, but not others?

 

Do you know the ground floor build up? How much insulation is under the floor? If there was only 100mm insulation in the loft, my money is on very little or nothing on the ground floor and you're basically heating the earth.

I agree the neo air thermostats are rubbish. At the moment I cant get one connected at all to the app but is working heating the room. I spoke to Heatmiser and they told me not to use the direct connection to the hub as it is causing problems. 

 

I dont know the make up of the floor. I moved into the property a year ago and it has been extended and refurbished. I have had lost of other problems and don't trust the previous own to have done things properly. I have had heat in the floors in the past and have heat in the floor in some rooms now. The floor is the same in all rooms. 

 

The furtherest rooms from the system have the least pipe loops. if the pump isnt getting the heat to them and having less loops I have a double the problem.  I am thinking these rooms I need to install electric radiators and not use them.  

 

Is it worth me asking the plumber to change to two smaller manifolds with separate pumps? Or just just a more powerful pump?

[Mark p]

2 minutes ago, ProDave said:

The immediate thing on that photo of the manifold is the numbers on the actuators are not matching the writing on the manifold You need someone to check that the actuators are really all in the correct place, otherwise you may have the actuator for one room controlled by a different thermostat.

We realized that they weren't heating the right rooms and cooled the whole system and pumped heat into each zone and sorted the actuators for the relevant room. The plumber used the previous markings and didnt check last year. They were wrong. That is why the current photo labels dont match. I need to relabel. 

[JohnMo]

Also from the photo the flow rates look quite low.  You may be better with a higher flow rate and slightly small DP across the loops, this would give more energy to the floor, you then reduce flow rate. Option to look at later.

 

On the night set back, only drop it 2 degrees, then the boiler isn't having to work so hard to recover floor temp.

 

But just alter one thing at a time, understand the outputs before changing something else.

[Temp]

I'm a bit late but..

 

Removing an actuator head normally turns a loop on. This might be a way to test a floor loop even if the stats/elec controlling it aren't reliable. But you do need at least one stat calling for heat correctly or the manifold pump won't run.

 

So if you have one reliable stat try turning that  way up to wake the manifold permanant, then physically remove the actuator head from a "suspect" loop. Check the pin is up and you are getting flow and then wait to see if that room warms up.  If that room/floor loop warns up then the issue is with the electrics controlling that actuator. If the room doesnt warm up to at least say 21C its some sort of issue with the loop or it's installation.