Heat Pump Sizing?

michaels

So this would seem to be my baby.  On the underside of the controller circuit board.



Still not easy, it appears to be soldered (via tabs?) top and bottom and it i snot a button battery I am immediately familiar with.  So time for some soldering but I am loathe to remove it in case the whole thing stops working when i don't have a replacement to hand.

All good learning I guess....

Reed_Richards

Surely that's a pressure plate on the top?  And the battery seems to be held within a transparent container.  I wouldn't have thought either would be necessary if it is soldered in place.  But then again I'm only looking at your photograph whilst you can see it from a variety of angles. Can I see some writing on the battery which might identify it?    

QrizB

Reed_Richards said:

Surely that's a pressure plate on the top?

Looks more like spot welds on a tag terminal to me, rather than a pressure plate. And I've no idea how the positive terminal is attached.

@michaels I'm fascinated by your DIY installation of a second-hand heat pump. I've wondered about doing something similar but I keep finding excuses not to   Do keep us updated with how you get on. It might even be worth a thread all of its own?

FreeBear

QrizB said:

Reed_Richards said:

Surely that's a pressure plate on the top?

Looks more like spot welds on a tag terminal to me, rather than a pressure plate. And I've no idea how the positive terminal is attached.

The positive terminal is probably spot welded on the other side - I've had to replace a few of these types of button cells in the past..
One example -> https://cpc.farnell.com/panasonic-electronic-components/vl2020-1hfe/battery-lithium-vl2020-horizontal/dp/BT03239

Reed_Richards

You could well be right, @QrizB.  It's just that the technology for mounting a small removable battery is so well-established that it's hard for me to believe the somebody would ignore that and devise a circuit board that required spot welds in its construction.

michaels

QrizB said:

Reed_Richards said:

Surely that's a pressure plate on the top?

Looks more like spot welds on a tag terminal to me, rather than a pressure plate. And I've no idea how the positive terminal is attached.

@michaels I'm fascinated by your DIY installation of a second-hand heat pump. I've wondered about doing something similar but I keep finding excuses not to   Do keep us updated with how you get on. It might even be worth a thread all of its own?

It is remarkably working beautifully at the moment, had to boost it a bit as with the wind and rain simultaneously our heat loss crept up a bit, indoor temp that had been steady between about 21.3 and 20.8 slipped down to 20.2.  I was not at all convinced it would work as the way it is plumbed into the rad circuit is 'rudimentary' but adding the second pump has made a real difference (obviously at the cost of higher energy use).  Spent some of today finishing the replacement of the two tank immersions in the loft (one had long been not working and the other developed a thermostat fault) so replaced both, one of the new ones was obviously not brand new and was missing a connecter screw but managed to find a suitable one and then also added a wifi switch to this one (the other one is controlled by an iBoost working both as a diverter and a timer : funny fact, the iBoost timer does not support timed periods that go over midnight so I am running with an offset on the unit set time to support heating during our cheap rate window from 23:30 - 06:30)

I do a lot with my 15 year old son - he volunteered today that perhaps we should 'do it properly' and run some 'tube' along the side of the house and in where the gas boiler hot water rad circuits are, fit a diverter valve and not only circulate through all the rads (currently 2 are on the 'closed' half of the circuit as the boiler end is valved off to make sure the flow goes through the remaining 14 rads) but also heat the hot water. 

The 12kw heat pump is oversized as we know the max heating requirement is about 7.5kw but we have the auxiliary immersion in the heat pump itself turned off, not sure if it is included in the rated 12kw output when outside temp is low and anyway our rads can probably only output a max of about 8kw at max heat pump flow temp (57c) and we are also circulation limited in terms of max heat output with long stretches of 15mm piping.

michaels

QrizB said:

Reed_Richards said:

Surely that's a pressure plate on the top?

Looks more like spot welds on a tag terminal to me, rather than a pressure plate. And I've no idea how the positive terminal is attached.

@michaels I'm fascinated by your DIY installation of a second-hand heat pump. I've wondered about doing something similar but I keep finding excuses not to   Do keep us updated with how you get on. It might even be worth a thread all of its own?

FreeBear said:

QrizB said:

Reed_Richards said:

Surely that's a pressure plate on the top?

Looks more like spot welds on a tag terminal to me, rather than a pressure plate. And I've no idea how the positive terminal is attached.

The positive terminal is probably spot welded on the other side - I've had to replace a few of these types of button cells in the past..
One example -> https://cpc.farnell.com/panasonic-electronic-components/vl2020-1hfe/battery-lithium-vl2020-horizontal/dp/BT03239

You are both correct, annoyingly I did not see the label on the battery until looking at the pics after closing it up again and the pics only have have half the code so not sure exactly what battery it is.  May get a TV/electronics repair guy to actually do the battery swap.  There is a second hand controller for sale on eBay for 50 which might be cost effective but then again it might also have the same dead battery problem.

Reed_Richards

My 12 kW LG heat pump never had an auxiliary heater connected and that has never caused a problem.

FreeBear

michaels said: Spent some of today finishing the replacement of the two tank immersions in the loft (one had long been not working and the other developed a thermostat fault) so replaced both, one of the new ones was obviously not brand new and was missing a connecter screw but managed to find a suitable one and then also added a wifi switch to this one

Be careful with some of those WiFi switches. Many of them only have a relay optimistically rated at 10A and should be derated to 5A or less. Ideally, for an immersion heater, you want to be using a contactor rather than a relay.

michaels

FreeBear said:

michaels said: Spent some of today finishing the replacement of the two tank immersions in the loft (one had long been not working and the other developed a thermostat fault) so replaced both, one of the new ones was obviously not brand new and was missing a connecter screw but managed to find a suitable one and then also added a wifi switch to this one

Be careful with some of those WiFi switches. Many of them only have a relay optimistically rated at 10A and should be derated to 5A or less. Ideally, for an immersion heater, you want to be using a contactor rather than a relay.

Claims to be 40A and even has a 'hot water' symbol on it.  Hopefully being only 13A and a resistive load it will be OK.  I do worry that in the roof space as well as the tank with immersions I also have a TV signal booster, lan switch, wifi hub, iBoost and now this wifi switch but no smoke detector!!!

This one:
Acmerota Smart Immersion Heater Timer Switch, 40A 2.4G WIFI Smart Wall Touch Boiler Switch Water Heater Timer Switch Works with Alexa Google Home and Smart Life APP Tuya : Amazon.co.uk: DIY & Tools

Edit:  Just seen it has had one scary sounding review added since I bought it!!!