Wet Underfloor heating system not working

[Masher]

Hi folks
New to the forum so hello to all.
I'm hoping someone can point me in the right direction. Our underfloor heating has not worked properly since we bought the house over a year ago now. We are getting limited hot spots on the floor close to the manifold but nothing much else. I don't think the warm water is getting forced through the circuits as all the flow meters are permanently at zero and I can't adjust the flow at either the flow meters or on the return manifold.
I have flushed each circuit out by hose and there was no air pockets, the flow meters did drop down when you flush each circuit individually to the max at 4. I have had the mixer value and pump replaced, to no avail.
The system itself heats from a multi fuel stove up to the cyclinder.
The system was installed by the previous owner who had no prior knowledge I am lead to believe. I am not convinced the system has ever worked properly.
Thanks in advance for any advice any one can suggest.
Masher

 

[townfanjon]

Me too pal , thats not a straight forward job. Can you post some pics of manifold , mixer etc etc

 

[Chuck]

Can you supply some photographs, please?

Is there a zone valve somewhere that controls flow to (or from) the manifold? If the pump is okay, and the underfloor pipes are not blocked the list of remaining possibilities is rather short.

 

[Masher]

Hi
The last image is a ladomat pump which circulates the water from the stove to the cylinder which is a McDonald's Thermflow vented mains system. The manifold is Myson.
I have had plumbers out to it and they added an additional pump to the hot inlet at the manifold in the hope that this would help but has done nothing either.

 

[Masher]

Can you supply some photographs, please?

Is there a zone valve somewhere that controls flow to (or from) the manifold? If the pump is okay, and the underfloor pipes are not blocked the list of remaining possibilities is rather short.

No other zone valve I'm aware of mate.

 

[townfanjon]

No other zone valve I'm aware of mate.

There must be one somewhere it turns off the flow pipe to the manifold otherwise theres no way of controlling the UFL .
In otherwords it would be on all summer , Its possibly behind the cupboard , but I am guessing .

 

[Chalked]

Hi
The thermostatic mixing valve ( white knob at the base of the pump) has probably seized.

 

[Masher]

There are the blue and red valves on the manifold itself, is this it. They are currently both in the open position.

 

[Masher]

Hi
The thermostatic mixing valve ( white knob at the base of the pump) has probably seized.

Hi Chalked. I have just had the mixing valve swapped over.

 

[Chalked]

To the right side of the blue valve. White head , that's against the wood.

 

[Chalked]

Looks closed to me. Can you turn it ?
It should have been fitted on the other end to aid control.

 

[Masher]

View attachment 31132 Looks closed to me. Can you turn it ?
It should have been fitted on the other end to aid control.

Yes I can turn the mixer value, I've just had it replaced!

 

[Masher]

Hi Folks
Still not got this one resolved! Any further advice would be appreciated. As noted the mixer valves and flow and return pipes are on the right hand side of my manifold. Can it make any difference which side it's on? The install book doesn't explicitly state it goes on the left side but the picture shows it this way. I have emailed Myson on Sunday but they have not got back to me as yet.
When the system is on it runs between 1 to 1.5 bar however the flow meters do not move. If I run water through the loops manually via a hose/tap on the left side of the manifold the flow meters will move, this is at around the same pressure.

 

[Ric2013]

You can't adjust the flow at manifolds? How do you flush one circuit at a time then? Please explain the exact procedure you used for flushing and I'll see if I can see the problem. I had airlock problems when commissioning my own UFH. It was annoying...

Also, I assume the top manifold is flow and that the pump is pumping upwards?

 

[Masher]

Hi Ric2013
Yes top manifold is the flow.
When the system is running under the pump pressure the flow meters will read zero.
When I flush out a circuit I will close the flow and return valves on the right hand side of manifold (butterfly valves?)
Next I will close all the flow meters and return valves for each circuit.
I then open up the circuit furthest from the pump by opening flow meter and return valve on that single circuit (all the others are closed.
I then attach a hose to the flow manifold on the left side from the tap and a hose from the return to a bucket.
Once the water is running through the circuit I can check for air etc.
Like I say, when I put water through each circuit this way the flow meters move right down to the max. This is leading me suspect hot water is not getting through when it is under the pump pressure. Like I said, there is not much difference between the tap and the pump pressure.
Hope this makes sense?

 

[ShaunCorbs]

If the system is running and flow meters arnt showing anything you either have a blockage or air lock or there shut

 

[Ric2013]

You're flushing it correctly. Problem I had was that when I'd done flushing I found I either had to shut the drain and fill valves (leading to a hose coming off with a pop and consequent flooding) or I could leave it draining but in the time it took me to get back from turning off the hose air had got in.

Did the flow meters not even wobble when pump came on?

In the end I worked out I either needed an assistant, or a strategy. I opted for the latter and, since my system is open vented, I worked out I could open the blue valve as I closed the drain valve and then nip off and turn off the hose. Did this for each circuit, making sure flushed each circuit for a minute longer [edit - I think I waited for 30 litres - 3 pailfuls - to come out of each circuit] than seemed necessary (since it takes 7 minutes for water to run the length of each circuit in my house under normal flow conditions). Then, after flushing, I set my pump to full speed (thus developing a good head of pressure - it is a fancy electronic pump so I set it to fixed speed and maximum for the purposes of getting things moving), opened one circuit fully and switched on the pump, let it run for a few minutes (I had a good flow), then opened the second circuit as I shut the first. When each circuit was flowing individually, I opened them all up, set the pump correctly, balanced, etc.

If you try this and don't get any of the circuits working even for a short time, then probably not an airlock. As you say, did it ever work?

I like the idea that it might run all summer - I think he missed the bit about it being heated by a multi-fuel stove

 

[SaraCampbell]

It should have been fitted on the other end to aid control.

 

[Uheat – Jake]

The side the pumps mounted on shouldn't make a difference, the pump looks to be mounted the correct way with the ball valves open as well. When calling for heat are the flow pipes to the floor getting hot?

 

[Masher]

The flow pipes to the floor get marginally warmer when calling for heat but I would not say they are warm.