Underfloor heating conundrum - return hot and feed cold?

[Chestnuts]

Recently moved into a house - about 3 years old. Heating system is water underfloor on ground floor, radiators upstairs.

About 2 weeks ago got someone out to service the (oil fired) boiler before the winter. He dealt with a small leak at the time, and ended up having to drain the system.

Immediately after, the kitchen UFH didn't work. Seemed likely it was an air blockage so I did some internet searching and found out you need to flush air out by connecting to mains with a hose.

Did this, but realise now I connected mains hose to the return manifold so water flowed in the reverse to the normal operating direction. Can't see this would make any difference, but....

Since then the whole UHF seems messed up. The return manifold is very hot, and the supply manifold is cold. System seems to be running "backwards" although I can't see how that is possible.

Anyone got any bright ideas about what may be happening?

 

[Chestnuts]

The boiler service also involved removing the main circulation pump by the boiler, and the pressure gauge on the UFH shows zero at all times despite the boiler gauge showing about 1 bar.

Anyone?

 

[Nige F]

Since then the whole UHF seems messed up. The return manifold is very hot, and the supply manifold is cold. System seems to be running "backwards" although I can't see how that is possible.

Anyone got any bright ideas about what may be happening?

Maybe the pump was fitted the wrong way round There was a thread here recently

 

[Chestnuts]

Did wonder if that might have happened but seemed unlikely - wouldn't that also affect the radiators in the rest of the system? I'll call the engineer to ask if that may have happened and see if he'll come back.

Anyon e know any other options to investigate?

 

[RUBICON52]

Try flushing again, the right way round this time, can't hurt.

 

[Chestnuts]

Latest newsflash.

Looks like pump may well be installed backwards. Thanks for suggestion - engineer coming back tomorrow to check but looks like that's the issue...

 

[dcawkwell]

Latest newsflash.

Looks like pump may well be installed backwards. Thanks for suggestion - engineer coming back tomorrow to check but looks like that's the issue...

good grief.
can't they put in a pump the right way round.
Wouldn't have that engineer near my boiler.

 

[ukmatt]

Hi All

Answer to this post seems very obvious now but at the time of me finding it it wasn't! I was having the same problem!

It's actually a little more logical than you think to fit the pump around the wrong way. Polypipe manifolds all have their pipes fitted upside down to the side. Logical when you actually think which way it should be flowing to the manifold, but not logical when you fit up with the wording on the pump up the right way, wrongly assuming that's the way it goes! Refer back to the diagrams and you then feel very foolish when you see it shown upside down and actually take two minutes to think well it would need to be for flow direction!!

Anyway greatful for this post as saved me hours of confusion!

Thank you.

 

[Natineah]

Hmmm..Got this kind of problem also. And I think I got the answer already from here. Thanks!

 

[shockfreesince93]

Having similar problem with new system. Can't get ufh pipes to return heat to manifold. Temp gauges on main valves to/from pump mixer set seem to fluctuate wildly, occasionally flipping entirely. Have tried flushing from boiler end with inlet valve open, return valve closed, filler/drain tap on bottom of manifold open with a bucket. Then opened and closed each loop one at a time while whacking up the boiler pressure and letting it fall back to 1 bar as the loops filled.
This replaced all the water in each loop with warm water and got rid of any bubbles, but when I opened the return valve, I watched the return temperature drop away again steadily. aaaaah!!!!

I'm going to double check I've got flow and return pipes fitted to the right ports on the mixer set in the morning (just to make sure) but I was sure I had it the right way round. Only other thing I can think of is some kind of air lock in the mixer. Ecomix installation guide says there is an air vent on the pump outlet elbow, but I just can't see it.

Anyone with helpful suggestions, philosophical ponderings or just wise-ass comments welcome! Could do with a laugh