Anyone here have a clue about underfloor heating?

[swee'pea99]

Most pumps have a big chrome centre key, with a flat slot. If you remove this a bit of water will come out, but you can see the motor spindle. It should be spinning. If it's not, something is jammed in the motor or the motor itself has seized. Lock off valves either side of the motor for removal/replacement

Looking at the direction of the Motor, the chrome key is facing the cabinet side on the left, difficult to access. I would loosen the fittings and rotate the motor so you can remove keyto check motor rotation

See images https://www.google.com/search?q=cen...=_d4fEY7XfGLTE8gKl4474DQ_31:22.85714340209961

The interesting keeps coming! Many thanks.

Managed to get this:

...which clearly shows the 'chrome key' you mention. How do you actually go about removing it? (I can definitely get access to it one way or another, even if it means cutting a chunk out of the MDF.) Does it just screw out? And was I right in thinking that if I shut off those big red & blue taps, I can then work on the pump without fear of a full on flood?

Thanks again.

 

[figbat]

The interesting keeps coming! Many thanks.

Managed to get this:

View attachment 674568

...which clearly shows the 'chrome key' you mention. How do you actually go about removing it? (I can definitely get access to it one way or another, even if it means cutting a chunk out of the MDF.) Does it just screw out? And was I right in thinking that if I shut off those big red & blue taps, I can then work on the pump without fear of a full on flood?

Thanks again.

I'm not sure about those isolators - there is a manifold after the blue one which makes me think it might not just isolate the pump.

You may be able to slightly loosen the big nuts holding the pump enough to turn it to afford better access to the large screw cap - this may result in a little water loss but containable with towels or whatever. Assuming the supply cable won't prevent this.

 

[ClichéGuevara]

It died again.

And there was me thinking it was one thing sorted. Nope. Same symptoms - cold room, flow rate stuck on zero - but this time the couple of taps on the pump with a hammer haven't made any difference. It just sits there, humming gently to itself...

It's hot, and if I put a long screwdriver to it and my ear to t'other end I can hear it humming quite urgently...like it's trying to do something, but can't. If I switch between the three settings (and contrary to what I said above, setting three is not off) I can hear/feel the hum changing frequency - but the flow rate remains zero.

Last time, when someone suggested a few taps with a hammer, I applied same and almost immediately there was this strange brief rumbling sound, like a 40-a-day smoker clearing his pipes in the morning, and the flow indicators immediately went to 3ish, and I thought that was that. And so it was. But now the low rates are stuck on zero again, but when I tap it, the magic trick no longer works...

What baffles me is, if the pump is burned out, why isn't it totally dead/quiet, and if it isn't, why won't it pump? Could it be blocked? (We've never had the rads/system flushed in the 25 years we've been here, and when I took the radiator out in the bedroom upstairs, the black filth that came out was truly grim.)

Is this the kind of thing a halfwit like me might be able to fix, or is it time to Get A Man In? At a glance, it doesn't look that challenging. Drain down the system, remove pump, proceed depending on revelations sort of thing...

Any thoughts/advice/handy hints & tips much appreciated.

Brrr!

Sometimes the impeller linkage from the motor gives up, so the motor is spinning, but not moving the water round, so removing the large nut can be deceiving. You can just get a replacement head, or at least you could a few years back.

It could be worth draining the system to change the pump, and flushing it all out in the process.

 

[swee'pea99]

The plot thickens...

Or, I finally got round to doing what I should have done way back - ie, taking out the shelf so I can get a proper look at the beast. Now I have...

...it seems pretty clear that the blue & red valves are between the pump and the underfloor system, so would not isolate the pump from the mains/rest of the central heating one tiny bit. But I did find that valve-looking thing on the top:

...which comes before the pump/between it & the rest of the system. Does that look like something I could use to isolate the pump before loosening off the nut under MIX, and its partner at t'other end, to swivel the pump a bit? And then...? (I'm still not clear about this here chrome cap. I can see it. Is it actually a cap, like a lid? Do I unscrew it using the slot, and it unscrews and exposes a hole so I can see the innards?)

Oh, and...

You can just get a replacement head, or at least you could a few years back.

That would be nice.

Oh, you mean for the pump. What is this 'head' of which you speak?

Thanks again.

 

[newts]

There should also be isolating valves on the primary flow/return (boiler) that closes off the underfloor circuit before the blending valve, somewhere off to the left of your picture.
If you've not had the system cleaned in 25 years, i'd recommend getting in a pro to clean thoroughly & balance the system correctly. It'll be much more efficient.

 

[ClichéGuevara]

The plot thickens...

Or, I finally got round to doing what I should have done way back - ie, taking out the shelf so I can get a proper look at the beast. Now I have...

View attachment 674627

...it seems pretty clear that the blue & red valves are between the pump and the underfloor system, so would not isolate the pump from the mains/rest of the central heating one tiny bit. But I did find that valve-looking thing on the top:

View attachment 674628

...which comes before the pump/between it & the rest of the system. Does that look like something I could use to isolate the pump before loosening off the nut under MIX, and its partner at t'other end, to swivel the pump a bit? And then...? (I'm still not clear about this here chrome cap. I can see it. Is it actually a cap, like a lid? Do I unscrew it using the slot, and it unscrews and exposes a hole so I can see the innards?)

Oh, and...



That would be nice.

Oh, you mean for the pump. What is this 'head' of which you speak?

Thanks again.

The head is the bit of the pump (which is a misnomer, as they don't pump) that does the work, and can be replaced by undoing the four Allen screws for less cost than a full pump, but you would still need to isolate it or drain the system, which I think has other advantages anyway.
https://www.heatingcontrolsonline.co.uk/pump-head-for-grundfos.html

 

[CXRAndy]

The white valve ontop is just a bleed off when the water is too hot it is fed directly back into the return.

You should be feel some heat on the pipes just below the white valve. This indicates hot water is getting to the motor. The next step is to check if the spindle is spinning. If it is but the pipes are cold on the lower part of the pump, this would indicate the impeller has come off the motor spindle. A new pump would be my choice in the latter case. . If the pump spindle is seized try a pair of pliers to free it off, if it starts spinning, and the underfloor start heating then consider getting a new pump anyway.

 

[swee'pea99]

Thanks very much, lots of food for thought. The system's off at the moment but it's certainly hot below the white valve - and indeed down to and through the pump, to the underfloor pipework (with the valves); the entire pump is hot to the touch...to the extent it would be uncomfortable if not painful to grip it tightly...and hums.

One thing that seems a no-brainer is to remove the chrome screw and see what if anything I can learn. I'm still not clear tho' about whether I need to isolate the pump before unscrewing it. One or two of the vids on YouTube seemed to be suggesting having an old tea towel or similar to hand for the inevitable leaks, but they seemed to be suggesting dribbles, not torrents. If I take the chrome screw out, will I find a bit of water on the other side or mains pressure? (I can't see any really obvious valves 'to the left'...the only possible candidate is this, right under the boiler:

But would that do the job? And/or, does 'the job' need doing? Or can I just remove the chrome cap, keeping me tea towel handy?

I'm going in thru' the side wall, using my swiss army knife as a padsaw. Wish me luck...

Thanks again.

 

[swee'pea99]

Found me answer, made me 'ole...

...wish me luck, I'm going in

 

[swee'pea99]

Hmmm. Well. Took the screw off, the central shaft is whizzing round like billyo. But the biscuit-coloured 'bit' immediately surrounding it

isn't. On the face of it this would seem to suggest that the impellor's come off, as suggested upthread, but

The next step is to check if the spindle is spinning. If it is but the pipes are cold on the lower part of the pump, this would indicate the impeller has come off the motor spindle.

...the pipes below the pump aren't cold at all. All the pipework, up to and including all this:

..is toasty warm. There's just no flow.



Thanks all.

 

[CXRAndy]

Well it's either a blockage or the impeller isn't pushing the water around the underfloor loops. It now needs a bit of disassembly. I would be 'best practice ' to also fit isolation valves to aid motor removal or flushing underfloor loops separately

 

[CXRAndy]

The only other thing is the blending valve is causing the problem by restricting return flow from the underfloor circuits

 

[swee'pea99]

Popped back to say thanks to all contributors and update: boringly, I've decided to postpone until the summer, when I had some plumbing scheduled anyway so I think I'll kill two birds, drain down the whole system, and remove the pump, which I'm fairly sure is the root of the problem. Then I can maybe try to disassemble and (if it proves possible/easy/economical) fix the pump. And if not, there's someone selling them brand new on the bay for not far north of the ton, so a straight swap is definitely an option. May? June? Something like that. In the meantime, we like slippers .

Thanks again.