Should the pump for the underfloor heating run constantly?

FaceHead

The pump for my underfloor heating runs constantly - it only has a live/neutral/earth lead, so when you give it power it just runs. 

Running a 60W pump 24/7 will consume a chunk of electricity, will reduce the life of it and just seems wasteful when the system only seems to need to call for heat ~2 hours/day in winter (based on the Nest's records). 

Is it normal practice to set up the pump to just run constantly? 

The pump is a Grundfos UPM3 Flex AS 25-75 130 AZA, which circulates water around a two ~70m loops, which are on their own heating zone, controlled by a nest thermostat.

You can open up up the pump and get access to some further terminals, where the pump can take a signal to control its speed, but this hasn't been done either by the manufacturer (A lead came attached to the L/N/E terminals, which has been wired into a fused spur) or the guy who did the controls for the heating system - not that I trust him much as he needed several visits to get it right, so on the final repeat visit could have been a bit fed up with the job. 

I think it would be achievable to bring 0V and switched 12V (if that's available in the boiler or nest's heatlink) to the pump if needed, but it doesn't seem that the person wiring it thought it was necessary. It's possible that the pump just need to be on the right setting if it has, e.g. a temperature sensor in it, by the manual for it is very uninformative. 

Welcome some views on how these pumps are normally controlled. 

NSG666

FaceHead said:

The pump for my underfloor heating runs constantly - it only has a live/neutral/earth lead, so when you give it power it just runs. 

Running a 60W pump 24/7 will consume a chunk of electricity, will reduce the life of it and just seems wasteful when the system only seems to need to call for heat ~2 hours/day in winter (based on the Nest's records). 

Is it normal practice to set up the pump to just run constantly? 

The pump is a Grundfos UPM3 Flex AS 25-75 130 AZA, which circulates water around a two ~70m loops, which are on their own heating zone, controlled by a nest thermostat.

You can open up up the pump and get access to some further terminals, where the pump can take a signal to control its speed, but this hasn't been done either by the manufacturer (A lead came attached to the L/N/E terminals, which has been wired into a fused spur) or the guy who did the controls for the heating system - not that I trust him much as he needed several visits to get it right, so on the final repeat visit could have been a bit fed up with the job. 

I think it would be achievable to bring 0V and switched 12V (if that's available in the boiler or nest's heatlink) to the pump if needed, but it doesn't seem that the person wiring it thought it was necessary. It's possible that the pump just need to be on the right setting if it has, e.g. a temperature sensor in it, by the manual for it is very uninformative. 

Welcome some views on how these pumps are normally controlled. 

No it should not run 24/7 it should all be wired so that it's on it's own zone and will only come on when there is a call for heat. Do you have something like this somewhere?

Wet Underfloor Heating Kit Builder (soleheat.co.uk)

Rosa_Damascena

FaceHead said:

Is it normal practice to set up the pump to just run constantly? 

I don't think so! Take another look at the settings on your control panel, is there a frost-free setting that might be triggering it?

It sounds like you lack confidence in your fitter - join the club!

FaceHead

Thanks for the replies. 

So clearly something isn't right, as the pump runs constantly. The manual for the pump says that it will just run if there's no low voltage signal attached. 

Ideally I'd find 12V which switches on and off as the downstairs thermostat calls for heat, and bring it to the pump, so that the pump only runs when needed. 

In the meantime I've turned the pump down the minimum (25%) setting, but I think that's unlikely to be sufficient when needed, and still a waste to be running the whole time. 

There is the hub pictured - basically it appears to just be a whole load of wago connectors where the 2x two port values, 2x nest heatlinks (one for upstairs, and one for the downstairs UFH) and the boiler come together. 

Is there likely to be switched 12V in there somewhere? 

I could get in touch with the installer, but I'm not confident he'll get it right on the 4th try.

fenwick458

why do you need a switched 12V? is the pump not 240V?
if you find the UFH zone valve, trace the black flex back to that wiring centre above and find the brown wire and connect the UFH circulation pump to that. 
that is, assuming it's wired how I think it is. 
I'd be prepared for some trial and error unless you know what you're doing, or just got someone in

Bendy_House

FaceHead is right - this pump can seemingly be controlled by a low voltage PWM signal; "UPM3 are speed-controlled, high-efficiency pumps fitted with an electronically commutated motor (ECM) with permanent-magnet rotor and frequency converter. They are either externally controlled by digital pulse-width modulation (PWM) low-voltage signal, LIN bus signal or internally controlled in constant pressure, proportional pressure or constant speed mode defined by a smart operating panel or factory presetting."

I suspect, tho', that it isn't using this type of LV control, but is internally controlled, so just requires mains power as and when (except it's seemingly permanently 'as'!) I think it then should have various settings that'll provide 'auto' control, so it'll vary its performance to suit demand. But, it certainly shouldn't be running all the time.

F'Head, are there cables going to both sockets on the pump? Can you trace the pump cable back to that wiring centre, and try a wider, straight-on pic of it? Is there no wiring guide on the inside of the lid or anywhere?!

https://product-selection.grundfos.com/products/up-oem-north-america/upm3-oem/upm3-flex-as-59C97302?tab=documentation

NSG666

Your initial post threw me when you said it had been wired to a fused spur I thought it was some kind of bodged system without the proper manifold etc.

Anyway you might want to look at this:

Plumbing - How To Wire Underfloor Heating - Wet Underfloor Heating - YouTube

I think you need a proper UFH wiring centre that prevents one part of the system making the other part run? I also thought the wiring centre came as part of the UFH bundle but seemingly not.
On a standard S-plan the 2 switched lives from the 2-port valves will go in to the same block along with the wire that tells the boiler or system to run. The fact that one can back feed the other doesn't matter.
That's no good with UFH as the 2-port valve switched live also tells the UFH pump to run so if wired as above the UFH pump would run regardless of which 2-port valve was activated.

Sounds like he's not wired UFH before.

FaceHead

Thanks all for the very helpful responses. 

Bendy_House said:

 are there cables going to both sockets on the pump? 

No, just the HV. The HV is wired to permanent live, neutral, earth, via a fused spur. There is nothing coming from the PWM socket on the pump. There is a 3-core and earth back to the boiler, so it's not impossible to do something else. 

Bendy_House said:

Is there no wiring guide on the inside of the lid or anywhere?!

Picture of the inside of the lid below, but it really doesn't make much sense to me. I'll just have to figure out what's what with a multimeter. 

fenwick458 said:

why do you need a switched 12V? is the pump not 240V?
if you find the UFH zone valve, trace the black flex back to that wiring centre above and find the brown wire and connect the UFH circulation pump to that. 
that is, assuming it's wired how I think it is. 
I'd be prepared for some trial and error unless you know what you're doing, or just got someone in

Thanks. This is what I'm going to do. I think the manufacturer's intent is you provide the pump permanent 240V (as it has) and also a low voltage control, so that it can overrun for a bit after the call for heat stops. I think I could use the 3 core and earth to the pump to bring permanent 240V, neutral, 12V switched (if available) and 0V, but that would mean utilising the CPC in that 3 core+earth flex, and then earthing the pump to a nearby pipe that is earth bonded. Things would probably need extending too to reach the PWM sockets on the pump. A bit of a messy bodge, that I'm not quite comfortable with. 

The setup you suggest - which I'll do - will mean the pump goes off as soon as the thermostat stops calling for heat. Whilst I don't think that's ideal, I'll go with it. 

Once I have a free morning I'll work out what's going on in that wiring hub with a multimeter, put the live to the pump in the right place, and report back (perhaps a couple of weeks as I'm going on holiday at the weekend).