Under floor heating problem

[kurtuk]

My underfloor heating manifold is the "pump mixing modular manifold" as per the link below:

http://www.warmafloor.co.uk/pdfs/std-pmp-manifolds.pdf

The problem being that, when the pump is on, the hot water gets as far as the injector valve but doesnt continue around the manifold and hence heat up the pipes. I have taken the thermostatic control head off to make sure that the valve is open and it seems to be. Furthermore, if the pump is switched off, the water passes the valve and the manifold becomes hot but as the pump is off, the water is not being moved around the pipes so does not heat up the floor. If the valve was not working then would the hot water pass through with the pump off?

The main question is: what is the reason that the hot water is not being circulated around the manifold by the pump when the pump is on?

 

[crockett]

Hi. You say that the injector valve "seems" to be open..... I would suggest that this is your first port of call for checking. Isolate the manual caps on the return manifold, isolate the pump on the lower valve, isolate the regulating valve on the main heating return. Then where the pipework tees up to the pump, undo a nut carefully, to see if there is any water coming through. If not much water comes through, then the injector valve may be at fault. Hope this helps

 

[kurtuk]

Thanks.
If the valve is faulty, then would it let through the hot water when the pump was turned off?
There doesnt seem to be any relation between the pump and the valve so I dont understand how the water flows if the pump is off but doesnt if the pump is on. Any suggestions?

 

[croydoncorgi]

...assume you have checked that the pump is the right way round! (arrow on pump casing pointing upwards.)

 

[kurtuk]

I did think the pump was the wrong way but the arrow on the front is pointing up which is the correct way.

Is there any chance that the pump is working in reverse?

When the pump is on, I can see that there is water travelling through the underfloor pipes as the glass guages show this. However, for whatever reason the hot water is not being drawn through by the pump.

 

[croydoncorgi]

Is there any chance that the pump is working in reverse

No

Given it's a standard 3-speed pump, try it on the lowest speed (1). Then check what flow-rate you're getting through the floor loops - should be 1 to 2 litres per minute in each loop. (different UFH suppliers recommend differing rates in that range.)

I can't immediately visualise what could be going on - especially if the Return manifold warms up a bit when only the boiler pump is running. That indicates that the injector valve IS open.

 

[kurtuk]

The temperature guage is showing around 30 degrees when the manifold pump is on. When the manifold pump is off, the temperature shows around 60-70 degrees which is the approx temp that the boiler is set to.

 

[picasso]

what number have you got the thermostatic control valve set to?

 

[kurtuk]

As i stated, the thermostat head was removed and therefore there should be no hinderance to the hot water coming through.

 

[Norcon]

The temperature guage is showing around 30 degrees when the manifold pump is on

So the UF loops (flow) are reaching 30C OK and UF pump working satisfactorily?

 

[kurtuk]

yes it seems that the loops are reaching 30 degrees and the pump seems to be working.
the loops may be at 30 degrees but this is not enough to heat the rooms.
is it possible that the pump is not working full force hence unable to pull through the hot water?

 

[picasso]

As i stated, the thermostat head was removed and therefore there should be no hinderance to the hot water coming through.

I stupidly assumed you had put it back as it made no difference with it off , either the sensor or the injection valve is faulty, assuming you havent disconnected the sensor.

 

[kurtuk]

which sensor are we talking about?
if the valve is faulty, would it let through the hot water when the pump is switched off?

 

[Norcon]

Flow passing through the valve with the UF pump off is not the fault of the valve.

When there is no MV fitted then the primary pump when in operation heating other areas of the property will make the valve create a by pass back to return.
A TMV will do the same but an nrv prevents any by-pass flow.

 

[picasso]

on the thermostatic injector valve there is a thin metal tube connected to a sensor that sits in a pocket just above the pump, this senses the flow temp of the mixed flow and return water and opens or closes the injector valve,

if the ufh is running at 30c then the pump is ok