Danny42

Thanks james, that makes a lots of sense! I just watched a video from: https://www.intatec.co.uk/product/anti-freeze-valves/#:~:text=Designed+to+discharge+when+the,costly+damage+to+the+system. And their one explicitely says it triggers from the water temp, so I think it'll be fine. Interestingly, another video (by altecnik, I think, probably spelling that wrong), says to NOT insulate it, while the one I link above not only say you can but actually sell a little custom insulation jacket for the thing. I think I'll err on the side of not insulating it. The parts inside the heat pump aren't insulated very much and can see them freezing pretty quickly, would rather the dump valve got cold faster and dropped the water quickly in the event of cold+powercut. Even if that does mean a tiny bit of heat loss just there.

Does anyone know either way if frost protection valves are triggered by air or water? If by the air temp then it seems that the frost-protection mode of running water through the pipes all the time when the temp is low outside is a bit pointless as the valves will dump all the water. Thing is, I'm still working on the system, I have got it up and running to get hot water (we only had oil before this and it was £1.70 a litre due to awkward narrow road, so couldn't afford to do anything but rappidly swap out system - now have lots of cheap hot water from ecodan, yay!) but the heating side is still a work in progress, it works, but need to swap out all the rads (they are tiny, pinholed, single skinned and hugly as hell), and a lot of pipework (micro currently). Anyway, thats a lot of babbling, essentially I still have work to do and will be emptying and refilling a lot over the next 6 months, so £200 each time to get to 25% glycol, only to also reduce the efficiency seems a bit much, so I'd have to be pumping it out rather than dumping it etc. All a total pain. Seems a lot of folks just use frost protection and frost protection valves. If the power fails while its -4 outside the valves save the outside unit from ice damage by dumping the water, from the lowest, coldest most exposed bit of pipework. Sounds like a great idea. They only concern I have, is that having watched a video from altecnic about how you SHOULDN'T insulate the valve, however counter-intuitive that is, to ensure it's sensors are exposed, that rather implies they go by the air temp. Well if thats the case even though the mains is up or the batteries still charged and despite the frost protection mode or the actual normal heating cycles keeping the water warm despite all that, the valves will dump the water because the air is 3C. Seems silly. I'm clearly missing something here, like either thats not how they work, or maybe it is and people only put them on houses which never go below 3 (but thats nowhere in UK isnt it, we always get to below 3 many times each winter even in south). One thing I do know, or at least have been told: having read online that mitusbishi warranty still fine if frost protection mode enabled and set to 6C trigger, and valves in place, I called them, they confirmed, enabled at 6C and valves installed and warranty fine.

I think you may be misunderstanding, I was explaining why I came to this site for better answers. It was a compliment and explanation, I wasn't suggesting they were good sources of data, I was just trying to say that the first few hits on google for 'grid-tie vs hybrid' sent me to places that contradicted specs and hence I came to this site. Regarding: "you are correct", yes, I know I'm correct about use of that term within this context. I intentionally referred to using function generators at uni. in the hope that you might better judge the context of my statement. 4 years at university studying physics and then various technical careers have not left me in the position of asking people for the definition of the word 'generating'. I was trying to explain to you that your statement was a little confusing. You wrote that: "At night when the inverter isnt generating, a small amount of power flows TO the inverter" I found this to be a tad unclear, and was explaining to you that perhaps you didn't really mean 'generating' and was hoping you might clarify what you had meant. For instance you could have written: "I meant that when the solar panels aren't generating your invertor will draw a small current from the grid." Also, above you wrote that the invertor's output in a grid-tied system is not connected to the busbars, but is connected to the consumer unit just all other load circuits are, "via an MCB(or fuse)". I get that a circuit breaker will likely be involved, I wasn't really enquiring about the minutia of protective circuitry present when I asked if: the invertor output is hooked up to the busbars. What I meant was: is it connected in parallel to the grid connection and hence all the load circuits. And I think the answer is yes. Anywho, I think I've taken this line of enquiry as far as I can just here. Thank you to everyone for your help, its really appreciated.

You write that "At night when the inverter isnt generating, a small amount of power flows TO the inverter" Do you mean that at night the solar panels aren't 'generating'? I don't think of an inverter 'generating' power, just transforming it. I guess we used to use 'function generators' at uni to create arbitrary waveforms, it just sounds a bit odd in this context to refer to an invertor as 'generating'; I certainly do think of the solar panels or wind turbine as 'generating' power. >> If you've read that grid tied systems cant have batteries you need to be a bit more choosy where you get your info as that is wrong. https://www.solarreviews.com/blog/grid-tied-off-grid-and-hybrid-solar-systems First section contrasts 'grid tied' as a definition only applying to systems wihtout batteries. Also: https://skyelectric.com/blog/hybrid-vs-grid-tied-solar-energy-systems/#:~:text=2- GRID-TIED SOLAR ENERGY SOLUTIONS&text=These systems are less effective,be stored for future consumption. Again it explicitly states that: Grid-tied solar energy systems also lack energy backups. So excess energy cannot be stored for future consumption. They both seemed well written but were promptly contradicted by the specs on devices advertised as 'grid tied'. Please understand: I'm not saying they're right and you're wrong, I expect you are absolutely correct. I'm just saying that I did check a couple of sites, before finding the information rather contradictory! As for telling me to 'be a bit more choosy where you get your info', well I read quite a bit, found it contradictory and then came here, here is where I chose to get some more definitive info, as I think should be clear from all the questions

Sorry not to give you time to answer, but again, I need clarity on the nomenclature. You write that if my invertor is hooked up to my consumer board and able to suppliment the grid (and rely on the grid to cope with surge demands higher than its rated output), that is called 'grid tied'. According to a few (very likely to be wrong) articles, there is some distinction that grid tied systems cannot have batteries. And that the only systems with batteries are 'hybrid'. I was rather hoping to: - Have solar charging my batteries if there is an excess of solar generation. - Charge batteries from the grid at night if the sun didn't fill them up. - Use the grid to fill in the gaps when my inverter capacity cant cope, or batteries too flat solar not supplying enough. While I absolutely accept your definition that the invertor is defined as 'grid tied' if it is connected in parallel to the grid supply, does this also mean that it can't use batteries? Perhaps the articles I have read are out of date and that inverter-charger equipment can these days handle everything someone might conceivably want to do.

Thanks Dillsue. Do you know if the 'extra' passes through the invertor, or if it is just supplied by dint of the invertor being hooked up in parallel to mains supply to the busbars on my consumer unit?

Hi guys, Thanks for trying to help. I'm afraid I didn't really phrase my questions quite right, let me try again from the point that Dillsue got to: >> "If the inverter is feeding the house and the house is connected to the grid, then youve got a grid tied inverter." My invertor would certainly feed the house, my plan for it would be to be connected to my consumer board and able to feed (at least partially) everything I use. >> "Your heat pump is only going to pull 10kw for a few seconds during startup and a fraction of that once its running. Unless you cook on full power..." I know the draw might only be very high for a short while, and I certainly don't want to oversize the system based on the temporary max draw. I do get that, I just want to know what happens when the draw does, innevitably, however briefly, go over my system's limit. I know you might not like the numbers, but if you wouldn't mind indulging me and assuming these are realistic: I have a temporary demand for 10kW, but I have only a 5kW invertor. Pretend I don't have solar at all, but instead a vast battery that is currently fully charged, lets say I charge it when Octopus are billing me 7p/kwh at night, and now I want to use the battery and invertor while my steady state during the day is around 4kW. But right at this moment it has blipped up to 10kW because I have two rings on the oven going, have just opened the oven door and heat pump is battling the snow outside and is just winding up the compressor. I get that that is rare, and hence wont design the system for it, so have just a 5kW invertor. My question is this: What happens? Does the invertor shutdown completely? Does it supply the 5kW it is rated to and let the grid supply the rest? And if the latter (I'm hoping the latter), does the inbound grid connection have to somehow go 'through' the invertor, or is it just hooked up in parallel to the grid? Sorry for the pedantry and I really do appreciate the help! Thanks, Danny

Hi apologies for the silly question: Assume I don't want to do a grid-tie (I believe is the phrase for the ability to feed power back into the grid, current rate averaging 4p, vs 52p they charge me...) If I have an inverter that can supply a maximum of 5kw, and say I have full batteries, or the sun is out and I'm generating 5kw, but then my heat pump kicks in with a compressor startup inductive load (10kW), plus I'm charging my EV(7kW) and my cooker(4kW) is on plus 3 computers(0.7kW) and a bunch of lights(0.3kW), so say I need 22Kw for a while, I need another 17kW. I know some invertors (although I'm struggling to wrap my rubbish brains about whether this requires them to be a hybrid or a grid tie-in or what designation), have a mains input that can help charge the batteries, or perhaps it can top up the supply. Here's my question: If the electronics in my invertor are rated to supply 5kW, and then any topping up I need from the mains cant come 'through' the inverting circuits. Does it get 'mixed-in' somehow, and does that mean that the invertor is always syncing the voltage, frequency and phase with the mains to allow for that? I've been looking at specs for invertors and combined 'solar charge controller & invertor' beasts, and they'll give you all the ratings for the invertor but wont say what the limit of how much they can top up the supply wiht mains is. Maybe no one does that? But for a house with heat pumps and 32A EV chargers and electric cookers, you'd need an impossibly large PV array and giant invertor to cope with the occasional loads of all of that at once. Please note, I did ask for some clarification on the subject to the people who just charged my dad 24k for a grid tied system on his roof, and they couldn't answer the question. Figured you guys would know! Thanks, and again apologies for stupid questions.

In our case, air source can go on the far side of a garage, and definitely not audible from in the house and likely very very quiet even if we are outside. When I wrote that I wasn't put off by the noise, I didn't mean that I thought it was noisy and I'd cope, I meant that from a lot of research it seems that they really aren't that noisy at all and I wouldn't be put off. The plant for our GSHP would go in the garage in a dedicated space, so I'm pretty sure that wouldn't cause any noise issues either.

Hi all, I could do with a little advice from those in the know. I have just bought a house. It has about half an acre of land and I had been looking at GSHP. Between looking at the size of heat pumps people use here, the advice relating to heat loss calculations, various rules of thumb, that somewhere between a 5kw and 15kw system is likely to be the result of a proper heat loss calculation. If I assume the higher number (and I know that many will say its far too high), but if I understand correctly from the Kensa website's various rules-of-thumb, I'd need about 10m of slinky per kw, so perhaps 150m, so 3x50m or perhaps 4x40m. Now I've seen a lot of youtubes of people with far, far bigger houses than me, with 3x30m slinky trenches and being fine. I have laid it out, following rules of 5m between slinky trenches, and we can definitely get 4x40m slinky trenches in. Thats including avoiding the 2.5 next to boundaries, and the property, enough room for turns, and that would use about 2/3 of my garden. I've just been told by an installer that: - air source will be about 17kw all in, installed. - ground source from the last person I spoke to was 35k for the install. We have a 3 bed bungalow with okayish insulation (300m loft insulation + cavity wall + double glazing) but it is an old building so not like a new one. From all my reading, from scouring this forum, I think I can get a brand new Kensa ground source heat pump for about 8k, if I do all the trenches myself, I'm a mechanical engineer by trade I have plumbed in every house I've lived in etc. I really don't think (given lots of time) I'd have a problem doing the install myself for about 10k. Obviously if I do that I cant get back the RHI, but with air source I believe the most I'd get over 7 years would be 15k and maybe 30k for ground source, so they JUST maybe draw even. If you factor in the oportunity cost (i.e. the money I wouldn't be making on the money I'd be spending on the installation, e.g. investing in stocks), then paying someone to fit either ground source or air source is a non-starter. They also tell me its impossible to get the system signed off by an MCS installer, even if I say paid them 3k to do the last day of install, hook everything up. They might just be lying because the want all the money, but it just doesn't make sense. Financially I mean. If I do it myself, then I break even with just the savings (from oil) from either system in about 10 years. If I do air source then I think I may well break even after just 5, as I can see heat pumps on ebay for just a few thousand. I dunno, I'm going round in circles. I think the only thing really putting me off GSHP isn't the hard work and tearing up our garden, I'm quite happy to do that, its the risk of it not working long term. The installer I just spoke to said you need at least 2 acres for a small bungalow (what we have), otherwise the ground cant warm up enough in the summer. But that goes against the advice I've seen in papers. I can see studies which tend to agree with the Kensa advice, that you need between 3 and 5 times the floor space for the ground array (assuming horrizontal piping). Well my house is 170sqm and my garden is 2000sqm, thats more than 10 times. In winter the soil is very wet which should be good for conduction. I have access to a mini-digger, I run my own business so I have plenty of time to dedicate.... Any advice welcome. And I do get that lots of folks go for air source, and believe me, I haven't ruled that out either yet - I'm not put off by the noise and I totally get the advantages, its just that at the moment I'm leaning towards ground source - if anything as an engineering project. So while I 100% welcome any advice, including "just use AS!" I'd love it if anyone who has done a GSHP install or had one done can let me know their thoughts. Thanks, Danny