Flow pipe - part hot and part cold

[iMCaan]

Hi

 

We have three heating zones of which groundfloor ufh is not heating up. All ufh components appear to be working fine. The boiler is working, it's heating up the water. The manifold side also appears to be working. However, the flow pipe to manifold/pump is always cold when the boiler has kicked in. So it appears the hot water is not reaching the manifold pump.
 
The flow pipe from the boiler has 3 branches (one for each heating zones that are controlled by Danfoss motorised valves), attic (radiators), 1st floor ufh and groundfloor ufh. The motorised valves are close to the boiler. The attic and 1st floor zones work as they should. When they request the boiler comes on, the motorised valves open and the hot water starts flowing to those zones and the rooms warm up. The water is hot either side of those motorsied valves as it should be. 
 
Now the mind boggling bit.
Whether the groundfloor heating zone (motorised valve) is open or closed, the flow pipe on both sides of the motorised valve are COLD but ONLY the branch part of the flow pipe, which is about a foot long. Nothing else is between motorised valve and the boiler just like other branches. The rest of the flow pipe from the boiler to the other motorised valves are hot (untouchable). The groundfloor ufh branch is the middle branch. How could it be that only the branch is cold but the rest of the flow pipe is hot?

 

Thanks

[Big Jimbo]

A knackered, stuck shut motorised valve ? That would be my guess.

[JohnMo]

Few things, motorised valve not opening valve.

A manual valve closed in that circuit.

UFH pump not starting 

UFH mixing valve stuck and not sucking any new hot fluids in.

[iMCaan]

Thanks, motorised valve is in auto position and lever can be manually moved to auto or manual position. I'm not sure how to test it at what state the valve is (open or closed). Surely, the water pipe on right towards the boiler should be hot just like the rest of flow pipe.

The UFH pump is all lit up and goes off when there's no heating request.

The flow pipe near UFH mixing valve is cold. It seems the hot water is not reaching to the mixing valve.

When you say "manual valve", is that motorised valve in manual position you are referring to?

 

Edited 21 hours ago by iMCaan

[JohnMo]

1 hour ago, iMCaan said:

motorised valve is in auto position and lever can be manually moved to auto or manual position

Remove actuator from valve and truly to rotate the valve with your finger. It should be easy to move. 

 

Manual valve is an isolation valve, so likely to have a handle on it. May look similar to this

 

Do you have any drain valves upstream of the UFH but after the motorised valve. Will look like this?

[iMCaan]

I had an electrician, who wired the ufh, to come out to investigate. He concluded that the flow and return pipes are wrongly connected. The flow pipe is connected to the return connection on the pump and the return pipe is connected to the flow connection. Therefore,  the pump is circulating the cold water in the ufh pipe loop. On return, the pump (manifold side) is pushing the return (cooler) water back to to boiler to heat up and at the same time the boiler is pushing hot water on this same (flow) pipe towards the manifold. (hope this makes sense). This creates a conflict, which is why the heating is not working. He says the flow and return pipes need swapping on the pump.

 

He said to contact the heating company to confirm that flow pipe and return pipes are correct. I contacted the heating company and they said that's rubbish (as in they don't make a mistake - probably typical response when one company says it's another company's fault) but they will come out next week to take a look.

 

Yesterday, I did notice that the return pipe was more hotter than the flow pipe. This was when only when only one thermostat was requesting heating. If other thermostats kicked in the flow/return pipes got cooler, near the manifold and near the boiler.

[ProDave]

Question.  Has the downstairs UFH ever worked properly?

 

i.e. are we trying to solve a fault (it used to work but has stopped working) or is it a new install that has never yet worked on the ground floor?

 

Post some pictures of the ground floor UFH manifold please.

[iMCaan]

It's a Danfoss motorised valve with a manual and auto setting. It's set on auto.

Yes, there's a drain valve.

 

Orange - Flow pipe from boiler

Yellow Radiators - branch 1 

Green Groundfloor UFH - branch 2

Blue 1st floor UFH - branch 3

Light Blue hot Water

 

[JohnMo]

28 minutes ago, iMCaan said:

contacted the heating company and they said that's rubbish (as in they don't make a mistake

Is this a new install? If so, tell them the UFH not working and needs to be fixed.

[iMCaan]

3 minutes ago, ProDave said:

Question.  Has the downstairs UFH ever worked properly?

 

i.e. are we trying to solve a fault (it used to work but has stopped working) or is it a new install that has never yet worked on the ground floor?

 

Post some pictures of the ground floor UFH manifold please.

 

It's a new UFH system. I would say it has never worked properly. Nothing has changed since it was commissioned. It has heated the rooms before but we never had it on continuously as we haven't moved in yet. 

 

The photo was taken a few months back but nothing has changed in this system. 

 

[ProDave]

14 minutes ago, iMCaan said:

 

Can we have a closer / clearer picture of the jumble of pipes coming out of the floor bottom left of the photo.

 

Following the copper pipes between the 2 manifolds, the left manifold has the hot pipe connecting to the right hand manifold cold.

 

These are the flow and return to / from the manifold.  So either one is connected with flow and return swapped (which is wrong) or they are connected in series, which I have never seen before.

[iMCaan]

1 minute ago, JohnMo said:

Is this a new install? If so, tell them the UFH not working and needs to be fixed.

 

Yes.

They are coming out to take a look next week. I will ask them to fix it as they laid the flow and return pipe and connected it to the pump. The flow and return should be connected to the correct pump connection, if incorrectly connected. The heating request does work as it starts the boiler.

 

Three companies setup the ufh system, ufh company laid out the plastic pipe and installed the manifold, electrician installed the thermostats and wired it all up to manifold, and the heating company fitted the boiler/cylinder.

[iMCaan]

Have loads of old installation photos but not of the finished installation. Will share the photo later. 

Edited 2 hours ago by iMCaan