Water flow in Under Floor Heating

[athlonoc]

I have just had my Heating System serviced and asked the question about flow through my UFH

 

I have attached two images showing the flow is not making it around the complete circuit and I have no idea why.

 

Its a two year old system, run by a Mitsubushi Ecodan 8.5kW ASHP. I have 5 zones downstairs ( Hall, WC, Utility, Lounge, Kitchen ) and both the kitchen and lounge have what looks like two separate pipe feeds.

My thermal image for the lounge shows even after the heat is pumped into the pipes for over 6 hours it still doesn't manage to flow all the way. The two blue coloured pipes in my thermal images as expected are cold but the two behind it for the lounge are warm.

The heating engineer said I should try and run it with the actuators off. I'm advised that this will render the wall thermostats non operational and the flow will just continue. He also states that this will highlight if the actuator is working.

 

Does this sound right? I also have a dense green solution dripping from both the large valves on the left in the non thermal images. It's not a constant drip, but I wiped the floor about 3 months ago and the leakage is there again. 

 

Before I fork out to get them back on a fault finding mission does anyone have any thoughts on what might be happening?

[ProDave]

Post a close up picture of the flow meters (the red things on the top manifold) with ALL thermostats turned up and heating running.

 

Chances are the "cold" loops just have the flow set too low.

[athlonoc]

All 5 zones are now calling for heat and on

[ProDave]

All are flowing at a similar rate.  It is not that the water is not getting all the way round, it is that some loops (the longer ones probably) have given up all their heat to the room before the water gets back to the return manifold.

 

I don't see a pump on this manifold so is is using just the pump built into the ASHP?  Is there another circulating pump anywhere?  I would start by turning up the pump speed if it is not already on full speed.

 

Ignoring the technicalities, is the heating working properly and all rooms getting hot enough?

[athlonoc]

There is a circulating pump in the loft. 

The rooms get warm enough, so technically I guess it's working correctly.

Is there any value in just removing the actuators so the heat flow continues and then I would see if the colder elements of the pipe work do in fact warm up?

 

I bought a thermal camera to highlight to my builder there were some issues and by chance I noticed the larger heating runs had cold areas, where I guess I was to assume the pipework would all heat up.

 

 

[JohnMo]

You definitely have flow because the hot pipes are hot and the flow shows flow.

 

Reasons for being cooler

 

It's been balanced to give the heat required - dT changed.

 

Bigger dT than the other loops. Easy way to fix is open the flow slightly. But if rooms are up to temperature are just making problems?

Edited February 10 by JohnMo

[athlonoc]

As a side issue which wasn't dealt with by the service engineer due to time restrictions.

Due to water flow noise in our system we have decided to turn off our heating when we go to bed at night as the noise stops us sleeping. Its been two years of poor sleep.

We just turn the stats down a few degrees to ensure it doesn't call for heat. This is not the way in which we should or want to run our ASHP fuelled central heating.

What I do notice other than it takes much longer to get the house to temperature 😠, is the pressure gauge every morning reads zero. Then after 20 minutes or so after the house calls for and starts flowing heat around the pipes the pressure goes up to the set bar of between 1 and 1.5bar.

Is it normal for a pressured system like this to drop to zero overnight, then go up when the system kicks in?

 

[ProDave]

1 hour ago, athlonoc said:

As a side issue which wasn't dealt with by the service engineer due to time restrictions.

Due to water flow noise in our system we have decided to turn off our heating when we go to bed at night as the noise stops us sleeping. Its been two years of poor sleep.

We just turn the stats down a few degrees to ensure it doesn't call for heat. This is not the way in which we should or want to run our ASHP fuelled central heating.

 

Do you not have any sort of timer or programmer?

 

Most people seem to just use the timer built into the ASHP but some can be fiendishly complicated and hard to understand or adjust, so my system is controlled by an ordinary central heating programmer that everyone understands so it is easy to set on and off times etc. 

 

 

1 hour ago, athlonoc said:

What I do notice other than it takes much longer to get the house to temperature 😠, is the pressure gauge every morning reads zero. Then after 20 minutes or so after the house calls for and starts flowing heat around the pipes the pressure goes up to the set bar of between 1 and 1.5bar.

Is it normal for a pressured system like this to drop to zero overnight, then go up when the system kicks in?

 

Have you ever topped up the system pressure with the fill loop?  did your service man not even do that?

 

The behaviour you have shows there is not enough water in the system.  If it has never been topped up since it was installed this will be due to air in the system bleeding through automatic air vents. 

 

If you don't know how to do this, get your service person back.  Turn the heating off before he gets there so it is cold and he can see the lack of pressure then get him to show you how to top up the water, and how to let any residual air out of the vents.

 

You should keep on venting air and topping up the pressure until there is no air left in the system and hopefully it will run a lot quieter.

[SimonD]

Sounds like the system needs purging which could also account for poor flow through some of the loops. Then a need to balance the loops. If this is a new/ish system is there a technical manual showing the theoretical flow rate through each loop? Setting them to this would be a great start.

[athlonoc]

Well, in terms of a programmer, I have set just the hot water on a timer. Twice a day, 3pm and 3am.

The 3am kicks in when we are in a deep sleep and this doesn't wake us up. It's no problem changing just the stats. It does the same thing. Its controllable via the Heatmiser App so all 6 stats can be changed in a matter of seconds. The FTC6 controller is where I have programmed the HW and know I could program the CH that way too. My big issue was not being able to leave it on, while using weather compensation and forgetting it. The noise just prevents this from happening. We still get a COP of over 3 which I'm more than happy with.

 

I have topped it up many times using the fill loop. However, its only recently that I have noticed this first thing in the morning. Since it gets up to pressure within 15 to 20 minutes I now leave it alone and no longer repressure it. I'm convinced none of this should be happening. Maybe once a year check the pressure and fill as required but not every day in the morning. Any explanation why its zero when its not been on for a few hours and then pressurises itself when the system is up and running? Also is it being suggested I keep topping up every morning to 1 bar until the day comes when the system doesn't need doing in the morning. If I keep topping it up, does this cause any issues if it gets to pressure when the system is running?

 

There doesn't appear to be any air in the system. The two bleed valves in my original picture at the manifolds have no air. The valves in the loft of which there are about 9 dont let any air out.

 

 

Edited February 10 by athlonoc

[sharpener]

15 minutes ago, athlonoc said:

Since it gets up to pressure within 15 to 20 minutes I now leave it alone and no longer repressure it. I'm convinced none of this should be happening.

 

Might be wrong pressure setting in the expansion vessel. My installers left it at factory 3 bar setting so it wasn't accepting any expansion volume and the pressure fluctuated a lot.

Solution was to let the system pressure down to atmosphere, then let the EV precharge down to 1.2 bar, then pressurise the system back to 1.5 bar which leaves 4/5 of the volume available for expansion.

[athlonoc]

2 minutes ago, sharpener said:

 

Might be wrong pressure setting in the expansion vessel. My installers left it at factory 3 bar setting so it wasn't accepting any expansion volume and the pressure fluctuated a lot.

Solution was to let the system pressure down to atmosphere, then let the EV precharge down to 1.2 bar, then pressurise the system back to 1.5 bar which leaves 4/5 of the volume available for expansion.

 

Well, the engineer did say the pressure in the expansion vessel was low and has re-pressurised it. So I will find out tomorrow morning.

On that point, has anyone used a Bluetooth pressure sensor over the valve, so you can check instantly on an app and even get alerted when it drops below a certain level. As the valves are the same as those on cars, would a permanent pressure reading cap work?

 

[sharpener]

9 minutes ago, athlonoc said:

As the valves are the same as those on cars, would a permanent pressure reading cap work?

 

Can you not see the pressure on the FTC6? I am a bit surprised your Ecodan will start up with zero system pressure, my Arotherm plus won't hence my discovering the EV problem in the first place.

 

But no pressure measurement will tell you what the proportions of air and water in the vessel are. And you cannot achieve the correct pressurisation of the vessel without letting the system down to atmosphere first to ensure it is empty of water, did your "engineer" do that?

 

 

Edited February 10 by sharpener

[athlonoc]

30 minutes ago, sharpener said:

 

Can you not see the pressure on the FTC6? I am a bit surprised your Ecodan will start up with zero system pressure, my Arotherm plus won't hence my discovering the EV problem in the first place.

 

But no pressure measurement will tell you what the proportions of air and water in the vessel are. And you cannot achieve the correct pressurisation of the vessel without letting the system down to atmosphere first to ensure it is empty of water, did your "engineer" do that?

 

 

I'm not aware that the FTC6 shows pressure but I could be wrong. Skipping through the menu I never came across it. 

My system is in the loft and I left the engineer to it. So I couldn't comment but I'd like to think he did it this way.

 

[sharpener]

17 minutes ago, athlonoc said:

I'm not aware that the FTC6 shows pressure but I could be wrong. Skipping through the menu I never came across it. 

 

@JohnMo will be along to tell us soon enough.

 

17 minutes ago, athlonoc said:

My system is in the loft and I left the engineer to it. So I couldn't comment but I'd like to think he did it this way.

 

If he needs to come back ask him to tell or show you, then you will know for sure.

 

[Alan Ambrose]

Neat the way the thermal camera show what's going on...