Beelbeebub

Apparently you can write values to the Grant heatpump Via modbus. See https://github.com/aerona-chofu-ashp/modbus So theoretically you could use a Raspberry pi or Arduino to calculate the optimum flow temp at any given moment using whatever scheme you want and command the HP to use that set point.

How about if A2A installs got some subsidy, say £3k, as long as the cooling function was locked off at 30C (or whatever) so you couldn't set a cooling temp below that. The we would have cooling for proper heat waves where people start to have real heath concerns, which is worth the extra energy hit, but it wouldn't get used for most of the time. If you chucked in a noise level limit to qualify but removed the planning permission requirement for "approved" units that would go a long way to helping

Yeah, it's a bit of a minefield. Seems a bit weird that one qualification expires and the the other doesn't. What do C&G courses do that stop you forgetting?

It is a shame we need fgas cert to install A2A units. I can see why it's done as people would be pissing redridgerant about all over the place, or not properly flushing the system and getting problems. R290 wouldn't be an issue *except* for the flammability. If we could sort that, and maybe that can be done by checking how likely the fire/explosion risk actually is¹, then it would be brilliant if we could DIY install. I would be 100% doing it. I'm pondering getting an f-gas cert. ¹i believe r290 units have been in extensive use in India and China for a while now. I didn't know how rigorous their installation regulations are or how well they adhered to or what they deem an acceptable level of accidents, but it would seem if they can do it without blowing themselves up on regular basis we could

Yes, but using the meter readings is a viable way of doing it. Smart gas meters should record half hourly usage which would give you a good idea. Conceivably, octopus or whoever could use that to calculate what size heatpump you needed. There is a company that sticks some sensors and heaters in your house and measures heat loss directly, but it's not cheap.

If some sort of really compact heat meter and logger could be developed, with a really compact flow meter (or even an noninvasive one) that can simply be retro fitted to the boiler flow and return then we could subsidise the fitting (say it was £50 fixed fee). This would then monitor the actual heat delivered (minus DHW for combis) and also flow temps. It could then suggest what size HP is needed and also what flow temp is possible.

I agree. They could have been sneaky and mandated dT20 be used in the calculations (don't think they did) Also the 55C is the limit for HPs as well, so a shitty developer might fit a 55C system so they can get away with rads all around rather than UFH. Technically compliant but poor for SCOP. A 45C limit for HP systems would have been nice. Still, as you say not half bad considering

Yeah, for some reason I had 50/30 in my head. The point is that a system designed for a boiler flow temp of X will need a slightly lower than X flow temp when run with a HP. Assuming the various flown rates can be maintained) Personally I'd like to see the mandatory max flow temp set a bit lower, say 50C or ideally 45C. Maybe even mandatory 22mm primaries with 15mm reserved for the drops/rises to each rad. That would make straight swaps to HPs easy.

I think you're right. Modern boiler controls are significantly more flexible than the early generation so can run lower dTs. The point is: the calculations for sizing the radiators assume the larger dT values (I have seen 10C as an option but at higher temps) and that HPs generally use a lower dT than boilers so the same mean radiator temp can be achieved at a (slightly) lower flow temp.

I thought part L said 55C flow for new builds? As condensing boilers have a delta t of around 20C, this is a mean rad temp of 40C, which is equivilent to a heatpump flow/return of 42/37 The newer HPs eg Arotherm can start to hit Scops of greater than 3.5 at nominal 45C max flow temps. Ironically the rads can be smaller and cheaper if you design your new build for a 55C flow HP than if you use a 55C boiler! 😁

I mean it woukd be great if the industry had an open common communication bus and any thermostat could work with any heat provider. Ironically the closest we have to that is the dumb "on/off" volt free contact system. It just happens to be crap at doing the clever things we want to do for better efficency and comfort! And I do worry about heating control systems that rely on the Internet to operate. The market is littered with smart devices that are obsolete or crippled since the provider shut down. That said, a function where the installer could remote diagnose and tweak the settings (say they connect it to the jtnernt before they handover and can "log in" with a password and app afterwards - function dependent on a hardware switch on the unit so the customer can block the option after a while). That might make the call back problem less of an issue.

That's the key bit, the installer having to come back and adjust. With gas boilers the installer can wind it up to max, and then the thermostat on/offs to control the temp. Which installer love because they don't have spend an hour to drive back to your house to twist a dial on the boiler. With HPs that leads to poor cop and low output which gives high running costs and not enough heat output. Ideally, the HP woiod be set up perfectly from day one, but realistically it will require a little tuning to get right. Users are used to a thermostat so we need a similarly simple interface. Maybe a simple dial with no temps just "warmer/colder" and the controller working things out from there. The controllers goal being to flow a temp sufficient that the user doesn't feel the need to fiddle the dial. If it consistently being turned up then in should adjust for a higher flow temp for those internal and external temps and vice versa

Grant provide some basic "retrofit" schemes but they also seem happy for installers to deviate. The Chofu HP thry rebrand as grant actually seems like a really good unit. It has loads of flexibility for setting up how you like it. We have a (gas powered) 130m2 bungalow with wet UFH in a concrete slab (exposed). It's pretty highly insulated but our flow temps are in the low 30's which easily keeps the place at 20-21C even down to below zero. We did have individual zones but found they didn't really work well. So have switched to the entire slab as one zone and adjust the bedrooms to be a bit cooler by tweaking the flow down a bit in those loops. The Chofu/Grant units have pretty powerful inbuilt pumps (10m head for 10kw IIRC) so you might not need a separate heating system pump. This would suggest your place would be a good fit for a very simple scheme with no buffer and no external pump. IIRC grant are fairly relaxed about not needing a big volumiser, certainly no more than the 30l internal one (useful as it can have an immersion back up/booster in) and possibly not needing one at all if you have a big system volume from the UFH.

That's. Pretty much Podesta's method. I'm pretty sure modern boilers can record their output. The Worcester Bosch units have KW output. All they need is to record that along with the external temps. Should be able to calculate the heat losses from that.

It doesn't exist. There is no reason it can't exist. The tech is there. The numbers roughly work, and it would have the effect of guaranteeing the consumer doesn't pay more (for the 5 years) which woukd be a big block out of the way.

Pushed the button on this, let's see how it goes.

I think that's right. People now have a slightly distorted view of how big a heat provider thry need. They look at their little 30kw combi in the corner of their kitchen then Google a 30kw HP and are put off by the cost and size of one, unaware they probably only need a 9kw unit. IIRC the median peak heat demand for UK housing is around the 10-12kw mark, so a 10kw with 3kw booster heater would d do the majority of UK houses.

Yeah but 99% of people don't notice or care. As long as the house is warm and the hot water comes out of the tap they don't actually care what the boiler does. Most don't even know if it's running or not. To be fair, most won't care if their HP is short cycling as long as the house is warm and the water is hot. The issue is that *we* know it's bad and probably costing them money.

The advantage of gas (aside from the space saving advantage with combos) is thry have so much reserve power and high temps that they can pull the insaller out of any problem. If you undersize the rads or pipes or have poor flow or whatever, you can just wind them up and away you go. I"ve just come back from odd jobbing at a friend's place and their new boiler in a new refurb and extend house was set to a flow of 80C. Easy for the plumber, no call backs for cold rads or not warm enough. It was a 30kw system boiler for a small and fairly well insulated house. No way they will ever need 30kw. But a 30kw boiler costs not much more than a 20lw or even 15kw boiler and isn't any bigger. So from the installers POV, why not. Makes it much easier. So we have a whole industry devoted to chucking in gas boilers by eye and a fi get in the air and forgetting about them. But that approach comes unstuck with HPs.

But you would have to build more RE generation, say 2.5x assuming a national scop of 2.5. And more upgrades to the local grid to move even more power around.

A proposal I made for a different model of subsidy from the current lump sum for install. In short, the HP is installed with a "smart heat meter" basically the heat version of the smart gas and electric meters. It records the kwh heat delivered. It also records the electricity used (thus generating Cop as well). The energy Co rebate the consumer for the difference in price between the cost of the heat delivered assuming a modern gas boiler (let's say 110% of gas price to allow for inefficiencies) and the cost of the ekectricity used to produce that with a HP assuming Cop of 2.5 (the carbon break even cop). This lasts for 5 years then tapers out over the next 5 so after 10 years there is no subsidy (or the assumed scop climbs over 10 years) So the consumer is guaranteed (assuming their installation is at least SCOP 2.5) not to pay more than gas. In fact if their system is better than 2.5 they "make" money. That is the incentive to upgrade stuff like rads or insulation to boost the performance. The scheme is paid for via a levy on the gas price. There are some variation that can be played with like the starting scop, the taper rate etc. Also you coukd have it just make it so the cost is always the same as gas for the period, though that removes some of the incentive to upgrade. D You also continue to offer subsidised upgrades like insulation or (say) a radiator scrappage scheme with money off new high performance rads when replacing old ones.

Absolutely, but the capability to hit that higher temp is a good marketing point in this soundbite age. "heatpump can't get hot enough"...... "yes they can, they can produce 75C down to -20C outside". Yes the nuance of efficency is lost, but the opponents don't do nunace. They gloss over fact that you can heat your house using 50C water. It"s also why I like my tapering price guarentee subsidy scheme. It removes the "but they cost more" argument. Once installed the system can be tuned over a period of actual operating conditions to become more efficient. Which spreads the upgrade cost of the emitters.

Nice to see some positive press for once.

Thanks. I had a look at the manual and the wiring to the controller seems to have many connections but they are labeled "valve 1", "valve 2", "min" etc. I think they are just switched lives to activate the 2 way valve, or the min/med/max fan speed. If that is the case the it should be pretty easy to integrate into the. Existing system. The system already has a 2 way valve per zone. All I need to do is turn the fan on.

Let's pretend out government was actually interested in doing something useful rather than whatever it's up to at the moment.... A2A systems can be installed alongside existing gas systems. This sidesteps the "what if it's too cold" issue and also the "wahg if it costs more to run". The A2A system can just be run when it is cheaper than gas. Hopefully over time the householder realises that the fgas system is very rarely used and can retire it. So the market for installing these systems could be huge. With some appropriate subsidies and import tariffs, local manufacturers would be in incentivised to appear. With a strong local market they could gain size and experience. The presence of a successful UK regulatory framework would pressure the EU to cut and paste the UK standards and practise into their own standards (albeit this is less certain now UK is out). If this were to happen you would have a strong UK base making EU compliant products ready to sell into a massive EU market. Or we could have pints of wine that nobody actually wants.