Testing underfloor heating
- Thread starter Milleniumaire
- Start date
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Hi Stephen,
When the CH calls for heat from the boiler, the supply and return pipes get hot very quickly. So thats the pipe leading up to the white thermostatic valve on the left (supply) and the right most pipe with the small white cap (return).
(Please note: I'm not labelling these pipes for your benefit, but for my own understanding and if I'm wrong please tell me).
The bottom bar (return) gets hot quickly. This morning, with the manifold thermostat set at 2, the gauge on the bottom bar read 50 degrees and it is very hot to the touch. The top bar (supply) gets luke warm and the gauge was reading 35 degrees. The white supply pipes for the 3 loops at the top bar don't really get warm at all and the bottom white return pipes only get warm close to the manifold, which may therefore be radiated heat, rather hot water in the pipes.
If I follow all the white pipes into the wall below the manifold they are all (supply and return) cold, regardless of how hot any part of the manifold gets.
What would happen if I attach a hose to the drainhose at the top right and opened the blue valve? This seems to be the only way to empty the UFH, so is this the only way to allow water out, so that new water can be forced in. The problem is how to force in new water.
I keep unscrewing the small venting nipple at the top right and invariably a small amount of air is always released.
http://www.wundafloorheating.co.uk/downloads/M02 manifold + 22kw pump station combo.pdf
View media item 80579
When the CH calls for heat from the boiler, the supply and return pipes get hot very quickly. So thats the pipe leading up to the white thermostatic valve on the left (supply) and the right most pipe with the small white cap (return).
(Please note: I'm not labelling these pipes for your benefit, but for my own understanding and if I'm wrong please tell me).
The bottom bar (return) gets hot quickly. This morning, with the manifold thermostat set at 2, the gauge on the bottom bar read 50 degrees and it is very hot to the touch. The top bar (supply) gets luke warm and the gauge was reading 35 degrees. The white supply pipes for the 3 loops at the top bar don't really get warm at all and the bottom white return pipes only get warm close to the manifold, which may therefore be radiated heat, rather hot water in the pipes.
If I follow all the white pipes into the wall below the manifold they are all (supply and return) cold, regardless of how hot any part of the manifold gets.
What would happen if I attach a hose to the drainhose at the top right and opened the blue valve? This seems to be the only way to empty the UFH, so is this the only way to allow water out, so that new water can be forced in. The problem is how to force in new water.
I keep unscrewing the small venting nipple at the top right and invariably a small amount of air is always released.
http://www.wundafloorheating.co.uk/downloads/M02 manifold + 22kw pump station combo.pdf
View media item 80579
Well that rings a few alarm bells.
The bottom rail is the return rail so should not be the first to get hot. The top rail should - which is the flow rail (supply from boiler).
Which connection pipe on the manifold (to & from the boiler) gets hot first?
If it is the left connection the flow is correct, if it is the right the flow is incorrect.
One more thing to try is to remove the blending valve control - this is the large knob on the left side of the manifold - it unscrews from the valve body - usually finger tight but you may initially need to loosen with a grip.
This is a dry connection so you will not hurt anything or get wet! Removing this control knob should open the blending valve allowing the flow water (assuming it is plumbed the right way round) to flow to the top rail.
I'm just trying to eliminate things one by one.
The bottom rail is the return rail so should not be the first to get hot. The top rail should - which is the flow rail (supply from boiler).
Which connection pipe on the manifold (to & from the boiler) gets hot first?
If it is the left connection the flow is correct, if it is the right the flow is incorrect.
One more thing to try is to remove the blending valve control - this is the large knob on the left side of the manifold - it unscrews from the valve body - usually finger tight but you may initially need to loosen with a grip.
This is a dry connection so you will not hurt anything or get wet! Removing this control knob should open the blending valve allowing the flow water (assuming it is plumbed the right way round) to flow to the top rail.
I'm just trying to eliminate things one by one.
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looking closer at the blending valve head - if it is not obvious that it can be unscrewed with ease do not remove it as I cant tell from the info sheet if it can be removed - usually the connection is the same as a TRV on a radiator - a threaded ring with a centre pin.
If its been made as a sealed unit you will get wet! If so its not a good design. Initially check the pipework.
If its been made as a sealed unit you will get wet! If so its not a good design. Initially check the pipework.
Stephen,
Both the supply and return pipes get hot at the same time, I can't distinguish between them.
I have followed them back to the boiler and they are connected up to the existing supply and return for the radiators using a T connection. Even at this point both pipes seem to get hot at the same time. I assume this is possibly because most of the radiators in the house have been turned off or are on very low settings (all have thermostatic valves). The only radiator on is the one in the hall, which controls the hall temperature and hence affects the hall thermostat. Is it possible therefore that there isn't much heat being lost from the CH, so the return feels just as hot as the supply (at least that's my theory)?
Regarding the blending control valve, it does screw off and I've already had that off (and all the other valves on the return bar) to check the pins were moving freely, which they are.
St0rmer66, it's interesting that you say the air vent should be open, which explains the "automatic air vent" as this was fully closed, so no air could ever escape! As I've said before, the plumber also left the manifold with all flow valves fully closed! I guess, the fact that no water could flow through the loops and the air valve was closed could be the cause of air getting trapped in the manifold/UFH pipes during the last couple of months.
When I originally explained the issue to the builder last weekend he told me he thought it would be trapped air and that this had also happened to his last UFH installation!
Both the supply and return pipes get hot at the same time, I can't distinguish between them.
I have followed them back to the boiler and they are connected up to the existing supply and return for the radiators using a T connection. Even at this point both pipes seem to get hot at the same time. I assume this is possibly because most of the radiators in the house have been turned off or are on very low settings (all have thermostatic valves). The only radiator on is the one in the hall, which controls the hall temperature and hence affects the hall thermostat. Is it possible therefore that there isn't much heat being lost from the CH, so the return feels just as hot as the supply (at least that's my theory)?
Regarding the blending control valve, it does screw off and I've already had that off (and all the other valves on the return bar) to check the pins were moving freely, which they are.
St0rmer66, it's interesting that you say the air vent should be open, which explains the "automatic air vent" as this was fully closed, so no air could ever escape! As I've said before, the plumber also left the manifold with all flow valves fully closed! I guess, the fact that no water could flow through the loops and the air valve was closed could be the cause of air getting trapped in the manifold/UFH pipes during the last couple of months.
When I originally explained the issue to the builder last weekend he told me he thought it would be trapped air and that this had also happened to his last UFH installation!
Hi Stephen,
As I'm at work, I've just asked my son to trace the UFH pipes back to the boiler and what he has just told me is interesting, but I need to confirm it when I get home.
He's telling me the pipe connected to the left side of the manifold (supply to the pump) is connected to the CH Return at the boiler and the pipe connected to the right side of the manifold (return) is connected to the CH Flow at the boiler.
Now, I believe "CH Return" and "CH Flow" are actually written on the lagging around the pipes at the point where they connect to the boiler, so I need to be sure this is correct and that what my son is telling me is correct as the new UFH pipes are connected to the old CH pipes and there are a number of T-joints etc (for the magneclean etc) between the connections and the boiler.
However, based on what he has just told me, this seems to match the fact that the return bar is heating up more than the flow bar.
Also, I would guess the CH flow from the boiler would be the one connected to the boiler pump, so if the CH return is connected to the manifold pump they would be working against each other?
As I say, I will need to double check this information when I get home as I find it difficult to believe the plumber has made such an elementary error.
As I'm at work, I've just asked my son to trace the UFH pipes back to the boiler and what he has just told me is interesting, but I need to confirm it when I get home.
He's telling me the pipe connected to the left side of the manifold (supply to the pump) is connected to the CH Return at the boiler and the pipe connected to the right side of the manifold (return) is connected to the CH Flow at the boiler.
Now, I believe "CH Return" and "CH Flow" are actually written on the lagging around the pipes at the point where they connect to the boiler, so I need to be sure this is correct and that what my son is telling me is correct as the new UFH pipes are connected to the old CH pipes and there are a number of T-joints etc (for the magneclean etc) between the connections and the boiler.
However, based on what he has just told me, this seems to match the fact that the return bar is heating up more than the flow bar.
Also, I would guess the CH flow from the boiler would be the one connected to the boiler pump, so if the CH return is connected to the manifold pump they would be working against each other?
As I say, I will need to double check this information when I get home as I find it difficult to believe the plumber has made such an elementary error.
That will be the problem.
(Engage smug face)
Which I think I suggested a few pages ago. Not sure if someone else suggested it earlier though
(Engage smug face)
Which I think I suggested a few pages ago. Not sure if someone else suggested it earlier though
Obviously it's yet to be confirmed, but I didn't take these suggestions too seriously as I was more focused on everything else that appears to be wrong (flow valves not opened, automatic air vent not opened, not having it's own zone/thermostat,symptoms of trapped air) and I assumed a plumber would know the difference between flow and return and wouldn't make such a trivial mistake.
On another note, is is usual for CH installers/plumbers to use 15mm lagging on 22mm pipe?
On another note, is is usual for CH installers/plumbers to use 15mm lagging on 22mm pipe?
I would say it happens when that is all he has got on the van - but no it should not happen - the whole idea of insulation is to reduce transmission heatloss; if the insulation does not fit then it will not do a proper job.
Anyone ever tried pi55ing up a tree in a gale?
Well, I finally got home and checked the piping and from what I can tell my son is correct, at least I'm 90% sure of this and would appreciate confirmation.
The reason I'm not 100% sure is that the manual for the Vaillant ecoTEC plus 637 System Boiler that we have shows more pipes than are actually connected to the boiler and they are slightly different, however this may be because we also have a Vaillant uniSTOR unvented cylinder to provide hot water.
Here's a photo of what I see under the boiler:
View media item 80805
Here's the relevant diagram from the installation manual:
View media item 80806
The two lagged 22mm pipes are the supply and return according to the sticker and the manual and this appears to be correct as the left hand (flow) pipe is connected to a Salus motorised valve, which appears to split between the hot water cylinder and the CH. The right hand (return) pipe has a magnaclean connected to it, so I assume it's normal for this type of thing to be connected to the return.
However, according to the sticker, the middle pipe is the gas supply and this isn't the case as I'm fairly sure that is the right hand 15mm pipe which appears to go through the garage wall to the gas meter. Hence I'm a little confused about how accurate the manual and stickers are as they don't completely match the actual pipe connections.
So, following the pipes from the boiler to the manifold, the left hand flow pipe connects at the right hand return side of the manifold and the right hand return pipe connects at the left hand flow side of the manifold. They are the wrong way around!
I did a little more testing and turned the heating on and could feel the left hand flow pipe at the boiler heat up quickly, while the right hand return pipe stayed relatively cool. I could follow this difference in heat along the pipes to the manifold, where as expected, the return bar was much hotter than the supply bar.
The reason I'm not 100% sure is that the manual for the Vaillant ecoTEC plus 637 System Boiler that we have shows more pipes than are actually connected to the boiler and they are slightly different, however this may be because we also have a Vaillant uniSTOR unvented cylinder to provide hot water.
Here's a photo of what I see under the boiler:
View media item 80805
Here's the relevant diagram from the installation manual:
View media item 80806
The two lagged 22mm pipes are the supply and return according to the sticker and the manual and this appears to be correct as the left hand (flow) pipe is connected to a Salus motorised valve, which appears to split between the hot water cylinder and the CH. The right hand (return) pipe has a magnaclean connected to it, so I assume it's normal for this type of thing to be connected to the return.
However, according to the sticker, the middle pipe is the gas supply and this isn't the case as I'm fairly sure that is the right hand 15mm pipe which appears to go through the garage wall to the gas meter. Hence I'm a little confused about how accurate the manual and stickers are as they don't completely match the actual pipe connections.
So, following the pipes from the boiler to the manifold, the left hand flow pipe connects at the right hand return side of the manifold and the right hand return pipe connects at the left hand flow side of the manifold. They are the wrong way around!
I did a little more testing and turned the heating on and could feel the left hand flow pipe at the boiler heat up quickly, while the right hand return pipe stayed relatively cool. I could follow this difference in heat along the pipes to the manifold, where as expected, the return bar was much hotter than the supply bar.
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