Heat pump and voltage

We have an air/eau heat pump that we installed a couple of years ago to replace our old fuel oil central heating.
This year it’s been playing up, and we had its annual service advanced to check it out.
Nothing wrong with it but the technician said that the voltage was low causing it to turn off periodically.
Called in our electrician who confirms the voltage varies between 198 and 233, the norm is apparently 220 to 240, and the legal minimum is 207.
See. S this is a problem in remote areas where the power network is running at a lower level for economies sake, and being a long way from the source we see a large voltage drop.

Welcome @roger_tedman and thank you for your post. It strikes a chord with me as we have 2 air to air heat pumps and the newer one has started behaving as yours is and all I can get out of the installer is a demand for payment before they will offer advice.

Maybe an electrician is the next move rather than arguing with people who don’t want to know. :thinking:

Funnily enough…

EDF are supposed to deliver 230V ± 10% (so 207 to 253V) at your PDL (point de Livraison - or the EDF main disjoncteur).

As long as the voltage is low at the PDL the right people to argue with, unfortunately, are EDF/Enedis.

I might have to go down that route myself (see posts passim).

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Fundamentally it is an ENEDis issue.

Ask your spark about a voltage stabiliser - they,re not stupidly expensive - although they don’t always solve problems - yours is varying so you probably can stabilise at 210-220v.

I’ve only really used big expensive ones in industrial settings so not an expert in the domestic ones

Such things exist, of course…

Depends on your definition of “stupid” - a 12kVA unit is likely to be well ovr 1000€

I’ve just looked at the specs of some and they seem to offer very tight output voltage control - within 0.3% (so less than 1 volt variance).

However the fact remains that if the voltage delivered by ENEDIS is < 207V, assuming you are not pulling more than your agreed power/current limit it is their job to spend money fixing the problem, not yours (persuading them however…)


Low supply voltage has always been an issue for people living at the tail end of a rural spur.

I have a friend involved in discussions with EDF/Enerdis at the moment for this very issue. He has a 9KW subscription, but if he fires up his 3KW pottery kiln, his mains voltage drops to 197V AC.

I’ll ask him how he’s getting on tomorrow.


But we’re in the main village.

Domestic voltage stabilisers for the tableau are 30’ish to 150’ish dependant on brand/power capability. May solve the issue whilst the OP spends eternity arguing with ENEDis.

He only needs to stabilise the voltage to the heat pump.

Regardless of what level of abonnement you have ENEDIS’s deal is to supply 230V +/- 10% at the PDL (as you’ve said).

If you have a 45A/9kVA maximum branchement, but only a 6kVA puissance souscrite, ENEDIS still have to be able to keep within the voltage limits for a 45A load. Likewise, a 12kVA/60A branchement has to be capable of that, even if you only have a 9kVA abonnement.

I’ve mentioned the following story before, but it illustrates the problem that the OP has run into…

If I were the OP I’d definitely get ENEDIS to stick a monitor on the supply. They are in breach of contract if your equipment can’t run on their flaky supply.

Which might easily be drawing 5 or 6kW

Got a link? I’m not sure we’re talking about the same product.

Indeed. In my case I probably have to be pulling 40A to really get below spec which means it’s not actually low enough to complain that often. But I might consider sticking a datalogger on the supply and seeing if I can get some evidence to send their way at some point.

“‘It’s tough to make predictions, especially about the future’” Yogi Berra.

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An update, for what it’s worth. After going through the heat pump tech, and an electrician, got hold of Total (the supplier) and it took three days for the client service guys to get the technical service people to talk to me. All they could do was give me contact details for Enedis. Called them, Their technicians came out and confirmed an AA battery would be better. They suggested linking us to one of the other phases in the main cables, but measured them and they are just as bad.
They will have to do work to reinforce the line, though I have my doubts that this will do anything, and I have a dossier number.
Chasing several times, and am now just waiting for something to happen.

Why do you think that?

If the ENEDIS conductor sizes are enlarged then your volt drop problem goes away & your heat pump will work correctly. This assumes that everything on your side of things is up to the job.

This is the second winter with the heat pump installed. Last year there was no problems at all. I think ENEDIS are simply not putting enough into the line. The line was reinforced a few years ago.
It could be a simple thing that several of the empty houses up the line are now occupied; a hameau that was desetred now has five occupied houses, so there is an increased drain on the supply.
We are the very end house.
We shall see.

Given what you say the line is not sufficient to supply the enlarged demand, & you suffer most, being at the end of things.