Dillsue

We've got friends living in a large solid walled 1800s house and their ASHP works well for them. They've got insulated UFH, fairly recent DG and deep loft insulation. No IWI or EWI so they've not gone mad with insulation but are still happy.

There's only you that can decide on any prep mods for an ASHP. All the previous posts have started to scratch the surface on the things you need to consider before you make the decisions. The problem you have is many of those posting will have their own preference so what one person says is right for them isn't necessarily the right thing for you, or others, the size of rads being a classic example. I want the best system efficiency so have designed for a low flow temp and large radiators as I'm not bothered about large rads but dont want the cost and disruption of removing floors to install UFH. Others don't want or can't have large rads so are running with smaller rads/higher flow temps and living with higher running costs but lower installation costs. Neither option is right for everyone.

Are the 2 strings of 5 getting wired to separate MPPT inputs?

Care to share how it failed?? Intrigued to know to avoid repeating the cause, if possible

If your designing for a low flow temp then yes, just move the pipes from the rad to the UFH.

A large emitters surface area is what works best with a HP so that it can work at low temperatures. UFH gives a large area without being intrusive but radiators can give a big enough surface area too. Retro fitting UFH is more involved, intrusive and costly than radiators so it's up to you what you go for depending on your preference for the type of emitter versus your budget. If you've already got usable plumbing for radiators then that's a plus for rads. Hopefully you already know what's involved in installing wet UFH so you'll appreciate that it's pretty disruptive to install. If youve sized your rads to operate at low temperature, the plumbing involved in swapping from rads to UFH is a small proportion of the work to install UFH. The other consideration is to look at your insulation and draught proofing before you spec a new heating system.

If your boiler is now defunct, my advice would be to have a look on ebay or marketplace and get a secondhand replacement to repair or replace what you've already got. That will buy you time to answer all your questions and work out what you need/want rather than rushing into throwing an ASHP under pressure to get the heating back on.

No problem fitting a bigger expansion vessel, but if this EV is in an existing and previously working system, why do you and your plumber think its suddenly become to small??

If it's a new system then it could be an undersized expansion vessel but if it's been in service for a while the much more likely the expansion vessel has lost its pressure or the diaphragm has failed.

Another potential quirk may have happened this morning. It's been too warm during the day recently for the HP to modulate down enough so it doesn't short cycle so we've used the thermostat to turn it off during the day but leave it to run in the cheap overnight period which finishes around 5 am. When I looked at the controller first thing this morning the inlet and outlet temperatures were around 19/20 degrees having cooled from 30 degrees that would have been running at up til 5.30. An hour or so later the inlet and outlet were both at 22 degrees which is room temperature so I think the circulation pump must have fired up?? It was pretty cold outside but no where near freezing, maybe 10-12 degrees, so no need for any freeze protection but maybe it's an anti condensation feature to keep the section with the PCBs dry?? Antifreeze protection seems OTT at those temperatures but anti condensation seems more plausible??

If the ivt9 stops the pump then that seems to be different to the Therma V?? A bit of experimentation needed

I'm guessing that if there's some knocking when the diverter changes over that there's a short period when it's closed to both DHW and CH which is causing the knocking?? Slowing the flow might be the easiest fix but if that doesn't work then a change of valve or securing the pipework could be the next step. I think you've got a display of flow rate on the series 4 so can see if you're maintaining a decent flow if you back off the pump

What series have you got? I'm guessing that the DIP switch to enable DHW functionality is set correctly or you'd likely not have any DHW options at all. Assuming the switch is set correctly, any options for DHW settings should be showing in the installer menu but I dont remember seeing anything about settings during changeover. If you've got rattling pipework options I'd look at would be- Secure the pipework Throttle the pumps maximum output in the installer menu Change your diverter for one that doesn't block the flow when it's changing from one port to the other

I assume Chris has a DHW heating schedule that avoids peak times?? Do you have the Energy State function on your early version?

Not sure what series HP you have but on our series 3 I could use a timed contact to switch the thermostat input to turn the HP off during peak cost periods. Although Ive not used it yet, the Energy State function seems to allow you to turn off or set back heating and hot water setpoint temperatures by switching a pair of digital inputs. If it's available on your HP you could use that feature to set back flow temp during peak times and boost flow temp during the Cosy periods

I've started this topic to document some of the quirks I'm finding in getting our Therma V installed and up and running. There's lots of other topics covering some of the quirks which I've read several times to try and understand how Heat pumps work and in particular how the Therma V works. Some of what's said elsewhere will likely be repeated here! Our HP is a secondhand 7kw unit built in late 2020. The part number ending in U43 says its a series 3 unit as that's what the last digit denotes. Our software version from the remote controller is 3056. The first quirk is the installation manual says the transition from series 3 to series 4 was from August 2020 to Setember 2020. The date on our HP is 20 October 2020 yet it's a 3 series! Double check the manual/HP model to make sure your reading the correct info applicable to your series. Next quirk is that I've seen a number of posts where one person is describing a feature and another person doesn't seem to have that feature. What I have found is that what the remote controller displays/how it acts can be dependant on DIP switch/ link settings. If you enable the use of a third party thermostat the On/Off button on the controller stops working and displays function blocked if you try to switch the heating off from the remote control panel. Similarly our HP had previously been used with glycol and there was a DIP switch AND a linked plug that had been set to use glycol. This then gave an "antifreeze" option within the installer menu. I'm not using glycol so have reset the DIP switch and link to reflect this. The "antifreeze" option has now disappeared from the installer menu. Be conscious that if there's differences in features between your system and others of seemingly the same model, it can be just that the settings are different that either add or remove features!! Resetting CH14 low flow errors can be achieved by cycling the thermostat input On, Off then back On rather than power cycling. Whilst commissiong our system I've had the HP hydraulically isolated which stopped the HP circulating water and generated a CH14 error a few times. I'm intending to run with WC and use the thermostat as a temperature limiter rather than for control but switching it seems to be able to reset faults. The HP has a "forced run" feature to stop the pump seizing up which was configured to run the pump every day for a few minutes. I think it was this routine that caused the CH14 fault whilst I had the HP powered up but the water circuit isolated?? Not had the fault since so I'm making this diagnosis but keeping my fingers crossed!! On the subject of low flow, I've read few posts where people talk about cleaning the strainer inside the HP but very little mention of cleaning the magnetic filter that should be on the return pipework to the HP. If youve not got a mag filter, get one as they pick up lots of bits. Ours also has a fine mesh, much finer than the strainer in the HP so pretty much renders the HP strainer redundant. LGs documentation says a mag filter is mandatory, so if you've not got one ask your installer why not!!. I've seen few posts asking if it's possible to set back the HP flow temp overnight with the answer seemingly no. I'm not sure this is correct but I haven't tried it yet. There's a feature called "Energy state" which allows you to increase or decrease flow temperature/DHW temperature based on switching a pair of digital inputs or over modbus. This feature seems to be intended to be used dependant on a battery state but no reason the digital inputs can't be triggered by a timer to increase or decrease flow temps overnight or to match up with a TOU tariff? More investigation needed but looks viable. On the remote controller there's a button with a symbol of what I thought was a pointing finger with 2 hills in the background. I couldn't for the life of me work out what it was but it's a pair of lips and a finger saying "shhh"......puts the HP into quiet mode!! Couldn't see this in the user manual!! If you want a quick boost to DHW temp and have the HP set up to control your cylinder immersion you can activate the immersion from the remote control panel. Scroll through though the buttons to get the DHW selected(shower symbol) then use the On/Off button to switch on the DHW. Now press and hold the back button. After a few seconds a lightning bolt/electrical hazard symbol appears on the DHW button. I believe the the immersion will now be powered. Press and hold the DHW button again to turn it off. I don't have my immersion connected to the HP but this feature works anyway on my remote controller. Hope that helps anyone scratching their heads over their Therma V or at least points you in the right direction for some further research. More to follow as and when I come across them but feel free to add any quirks you've found but dont forget to reference your series number to make things meaningful.

Don't get too excited as I think that filter is for standalone devices only, not G100 certified inverters!

The ENA type test register allows you to filter by G100 device to that's worth having a look through

If youre not bothered about export why cant you select another inverter with a G100 cert? You can have your 10kw array and batteries but not the un certified multiplus. I beleive you can get third party G100 devices to sit between an uncertified inverter and the grid but I don't think they are cheap and there's a good chance your DNO will want to witness test something that's not mainstream, at further cost!!

If and when you build the second house put in a meter box and ducting to your consumer unit for a future grid connection. If you decide to sell in the future, spending a few grand on a grid connection for the next owner will likely be more than recouped in the sale price versus an off grid setup. Piggy back off the existing house in the meantime if that works for you. If you put PV on the new house any surplus will go to the grid via the existing house connection. Remember that any DNO limits for the existing house will apply to the combined output from both houses! Make sure the cable between the 2 houses is big enough to carry the max any PV could generate without causing to much of a voltage rise.

According to the Therma V manual, 3rd party boiler, immersion and inline backup heater are all separate features with separate wiring and settings. The settings for the 3rd party boiler only offer an OAT trip point and a hyteresis value so the HP doesnt restart until its warmed up a bit. Won't be testing til the winter so will see how accurate the manual is then!!

The missing insulation is on the pipes within the HP omitted by LG, presumably because they expect the HP to run continuously, even though they have a feature to enable a backup boiler in cold weather. With all the bends, strainers, sensors and other pipework it would be difficult to get it all effectively insulated The trace heating manufacturer gave a table of insulation thicknesses needed for a particular size of pipe giving 25mm of insulation for 28mm pipe so that's what we've got. A genny powers it in anything but a short power cut. Having the trace heating is more for if we shut the HP down in very cold weather to run on the WBS rather than flog the HP. It will also protect it if it fails in cold weather and can't get fixed quickly. At £48 it's probably cheaper than antifreeze valves or glycol??

An alternative to glycol or antifreeze valves is trace heating. A £50/4metre length runs through our insulation around the outdoor pipes with a loop coiled up in the bottom of the HP under the water pipework. Our HP isn't particularly well insulated and most of the water pipework wasnt insulated at all. Ive added some insulation but there's still plenty exposed so hopefully the trace heating will keep any freezing at bay

The original part of the house had 8mm copper drops from ceiling to floor on 5 rads and I couldn't get any flow to 3 of them without shutting down the lockshield on the rest of the house. A small pump on the 22mm pipe feeding them has sorted that. Still got another rad with a long 10mm run to get flowing but Im confident Ill get that with balancing. Everything is plumbed direct so no separation

Balancing and WC setup can be done now. I wouldn't wait til winter to set things up in case you hit problems.....I couldn't balance the whole house and have had to shut the heating down to add a pump and control for it. Potentially could have been without heat for a couple of days which isn't a problem now but would have been in the winter