Beelbeebub

Preventing recirculation is the key, and the only way to really be sure would be to butt the unit against some sort of enclosure so it sealed (some sort of flexible rubber of foam seal against the face) the two air flows. My worry is that this would also channel the noise out, possibly even acting as megaphone and making it worse!

This is an oft overlooked point. As the designer and builder of an overly complicated homebrew tank thermostat I worry about this. 😁 My approach was to build the system for extreme simplicity. It basically runs on an Arduino with no internet dependence and all components off the shelf and modular. I also did a fair bit of documentation. It actually runs really well, 8 years of solid service through power cuts and all weather. One important function it does is control the overheat protection - in winter it activates the UFH and in summer (or if the UFH dumpmis insufficient) it will dump DHW down the drain. I'm currently faffing around upgrading it to put in weather compensation whilst preserving the UFH dump function. The existing on/off thermostat does seem to be doing a pretty good job though, so I wonder if there will be any noticeable improvement. Still it's a nice intellectual exercise.

I reckon it *might* work with some big caveats... First, you need to makes sure there is no recirculation of air from the inlet to the exhaust. The inlet for heatpumps is the back and one side (usually the left as you look at them). That is where air is sucked in over the heat exchanger coil. The exhaust is the circular (sometimes square) opening at the front. You need to make sure no air ejected out if the exhaust can find it's way back into the inlet. You then also need to make sure there is adequate air flow throught the machine. So *if* you were able to mount the HP so the exhaust blew straight out of the building or the inlet drew from outside, you might have a chance. Imagine mounting the HP against a partition wall with a hole cut in it. To prevent flow issues, the openings into and out of your building would need to be *at least* as large as you HP, againimagine being able to push your HP easily through the hole.

I belive it is as the mechanism is physically the same. It's just the valve actuator - the motor bit) is different. Even then it's not that different. A 3 or mispositioning valve has a resting position (when no power is applied) where all the water goes one way, an end position where power is supplied, the motor drives to the end position and stalls sending all the water the another way, and a mid position where some.swi4ches and electrical jiggery pokery make the motor stall half way so it "hovers" and water goes both ways. You could wire up a 3 position valve to effectively be a diverter by simply not wiring up the mid position. That said, I've never actually "converted" one as it's never been necessary.

If the installer used a 3 way valve that has a mid position, that might be the cause. Traditional hearing systems would have a mid position where heat went to cylinder and radiators at the same time, not a problem when your boiler is set to a single high temp (eg 75c). A HP should either run the heating OR the cylinder. It's the same physical valve, just a different actuator head and wiring.

Assuming you bought online/over the phone the distance selling regs apply and you have a bunch of rights. You can cancel your order *for any reason* up to 14 days from delivery for a full refund including shipping. I'd the item is faulty you have 6 months to return it even if you've altered it. You don't have to pay shipping. The item not being as described, would be faulty - ie if it says it has inverter drive and doesn't etc It sounds like a bit of a lemon TBH https://www.gov.uk/accepting-returns-and-giving-refunds

I don't think so, here's a video with one unit being opened up EXternal air is contained within the unit, rather like a room sealed boiler. That said, a unit that deliberately took the outside air and heated it up using extracted air from the room might not be a bad thing. Basically a standalone heatpump powered MHRV unit. Would definitely help with preventing humidity and pollutant buildup

Good spot. That'll teach me to rely on the Q&A section!😁

I imagine defrost is a big issue with these monoblocks

Sadly they say heating down to 7C only!

Noise level, good point. Yeah, if they were £500 a unit that would definitely get very attractive

https://www.powrmatic.co.uk/products/air-conditioning/airco290/ Does anyone have experience of these units (or their predecessors which were r32)? I am thinking about replacing some storage heaters using these. The particular tenant is experiencing very high elec bills. We've traced this down to his electricity company charging him standard rate for all electricity. Eon claim they can't provide economy 7 for him due to "a complex meter setup". This is bollocks, it's a standard, albeit old, system. A standard rate meter and a night rate meter serving a dedicated heater circuit switched on and off by a clock. So instead of paying 36/12p he's stuck paying 28p. I estimate it's costing him and extra £700 or so a year. (Actually more because they are billing him 2 standing charges) One option is to try and get the meters ripped out and replaced with a single smart meter dual rate one. Physically simple, but apparently the bureaucratic equivilent of a mars mission. The other option would be to replace a few of his units with the above. Given he's paying flat rate any CoP above 1 will be a win. If it can achieve a SCoP of about 2.3 he will be back to where E7 would be, except maybe a bit better as his regular elec will be 28p not 36p. If we can better 2.3 we'll be ahead. The 3re option is a mini split. That should achieve higher cops and a single unit should be able to serve 2 or 3 rooms, but the outside unit may be more problematic.

You might be right. I think the Grant/Chofu units so have that function, though as an undocumented (from Grant's perspective) feature. They seem very capable units. Grant have made them as simple as possible for existing boiler installers to use which ignores a lot of functionality. I'm really intested in what the next gen r290 units will do.

Don't most HP controllers allow for different zones of heating with different WC curves?

Even with new control units fitted tenants still complain of poor marching between heat output and demand. You cannot argue that storage heating is a nicer heating system to use Vs gas boilers. Only a lunatic would take out a gas boiler and replace with storage heaters. There are some limited situations where they might make sense but for the majority a well set up HP will provide a better end result. And from a high level perspective of national policy heatpumps make the problem of generating all that extra electricity tonreplqce direct gas much easier than storage heaters would.

Yeah, but you still have to hump 100kg or so of bricks up/down stairs (in my case up to 5 flights). Plus, if you are unlucky enough to have one of the asbestos models, dismantling and disposing of them is a whole other level of bother. Dunno about your area, but here (midlands) I'm getting gas around 6.5pkwh and the tenants seem to be around 9pkwh for their off peak. A fair point and, in my experience, the average level of knowledge regarding heating is really poor regardless of the heating system. With gas systems invert often get call outs "no heating" and it's because they are trying to hear outside the timer hearing periods. In one case the old lady complained of her hearing nitncoming on, or coming on when she didn't want it. When I went to look at the thermostat I couldn't find it and she looked blankly when I asked where it was. When I described it she thought for a minute, then rummaged around in the kitchen drawer by the oven. That said, people expect their hearing system to at least get warm when they want and the idea of storing it at night then using it later really seems to throw a lot of people.

"That's not a bug, guv. That's a feature!" 😁 I don't buy that. Imagine being told that you can't shut your heatpump off even if you're plenty warm enough. There is nothing engineered about the heat leak, it's just the poor seal. Some units leak more than others because the metal flap fits better on some units. The newer units are designed to keep heat in better, with more insulation and a fan powered design that leaks less heat. If heat leaking was a deliberate feature what would they be going to great lengths to eliminate it? you are absolutely right that we don't necessarily need to store excess electricity as electricity (or rather chemical potential). Thermal storage makes a good deal of sense. but even then heatpumps are a better option as you still get to store more heat than you consume. Even at high temps like 65, the COP can be greater than 1. The only time direct electric would be useful would be for really transient use, so if the time of use tariffs were minute by minute or even faster. In that scenario the spin up time of a heat pump might be too long but flicking an immersion heater on for 60nsefonds to take advantage of a brief drop in price might be possible.

^^^^ this, so much! 😁

At a higher level the issue is that E7 only makes sense from a cost perspective and it is all based on the idea of cheap rate night electricity. Night rate electricity is only cheap because there is less demand for electricity at night. If everyone switched to E7, demand would go up and it would no longer be cheaper* From a carbon perspective, whilst electricity is now lower carbon (on average) than gas, storage heaters only have a COP of 1. This means a nation using storage heaters will produce more carbon, and require more generating capacity, than a nation using heat pumps. They aren't even that cheap, a typical unit will cost £600-£1,000 before fitting (and they are pigs to fit given the weight). A 3 bed house might need at least 5. So you are looking at a minimum of £3k just for the most basic storage heaters. Go for the better and bigger ones and you're at £5k. And all that assumes you don't need a rewire. If you already have storage heaters, then sticking with them may be rational for now. But as a technology for replacing other methods of heating, they are a dead end. *and with the uptake of electric cars and tariffs for charging them at night the demand for "off peak "electricity is growing. E7 tariffs won't last forever.

The big issue is the units leak heat. The control is a bimetallic strip and a little metal flap. Even when closed shut a significant amount of heat leaks out. Most of the occupants are out during the day, so the heat is not useful (though from a maintenance perspective it does help keep the properties drier) and when they come home at night and actually want heat there isn't enough left. If they wind up the store temp it helps, but then they get even more wasted heat during the day. We fitted some newer units, which are better insulated and use a fan to move the heat so leak less. The big issue with those units was the inflexibility. It was very difficult for the users to control them requiring diving into multiple setting menus rather than a simple "warmer/colder" setting.

Simplicity is about the only thing storage heaters have going for them. Everything else about them sucks. I look after a few properties with them and nobody likes them. Expensive to run, hot in the mornings, cold in the evenings and god help you and your back if you have to change one.

Is this a simple on/off pool unit? In which case isn't it run just like a boiler? All the "logic" is done via the wiring center of the heating system (standard timer, thermostats, 5 wire valves etc) and all the unit gets is on or off signal.

I think that paper was looking at using the same physical equipment but swapping fluids. It is relevent because a chunk of the market is retrofitting older units with newer refrigerants. So effort has gone into working out which new refidgerant to use in a given set of circumstances. As they point out the compressor specs for r290 differ from those of a similarly spec'd r410a unit. R32 is a better "drop in" than r290 But when it comes to a unit designed for r290's properties i think the picture is different. Efficiency wise similar, but with wider operating range, higher max temps.

The problem with bard and other chatbots is they produce something that sounds plausible but is not necessarily true. So if you feed it a bunch of inputs from sales brochures it will simply come up with something that could plausibly be a sales brochure for heatpumps. Little things like the accuracy of numbers quoted are less important than numbers being quoted. All things being equal, R290 can achieve higher water temps than r32 and operate at lower external temps. The efficiencies are similar with system design being more important than the refrigerant. The downside of r290 is it's very flammable, whilst r32 is only mildly. R290 needs special attention to what could happen if it leaks from a fire/explosion perspective. R32 much less so. The downside of r32 is it has a global warming potential in the many hundreds (better than told stuff that was in the thousands tho). If you let the r32 escape from a typical monobloc it it the equivalent of about 1t of co2. R290 has negligible GWP. The r290 from a typical heatpump is equivalent to a few kg of co2.

You could use a multimeter to check if the control signal to the radiator valve is going live or not, and then if the valve is moving when it gets that live signal. What you described sounds like a dodgy valve actuator and/or valve. Regarding your expansion vessel, I assume you mean the one for your hot water tank. The pressure on that should be set when the mains are shut off and the pressure in the water system is relieved. The "at rest" pressure can be calculated by your plumber.