Beelbeebub

I guess it would be technically possible for a gshp to act as a combi if it was rated at a high enough power (18kw minimum) at 45C. An ASHP couldn't do that as it needs defrost cycles every now and then. So I guess if you were to try and make a "combi" HP, effectively a box on the wall like a gas boiler, then a GSHP would be the way forward. Doesn't mean it's sensible.

That's my question. Standard sized indoor units can kick out about 3kw of cooling. Which means they must be kicking out about 4kw of heat to the "outdoor" unit. So if we literally switched them over, the wall mounted unit outside, the "main" unit inside we'd have a roughly 4kw heater. If we cut the fan and coil off the inside unit and used a PHX, we'd have a pretty small indoor unit ready tonsoateibute heat about the place and the outdoor unit woukd be pretty discreet

Not quite, that just makes for 3 working fluid loops! It was more a thought that the outside units could be made smaller, sleeker and modular for much easier fitment. Imagine, instead of a big box stood off the wall, there were 1 or 2 of these type of things (suitably designed for outside use etc) stuck to the wall a bit above head height. They'd be coated black or maybe even matched to your exterior. Inside would be a bix much like your boiler in size with the compressor and a plate heat exchanger, possibly a central heating circulator pump as well. It would hum a bit like a fridge when running but then so do boilers.

But about 100th that of aluminium and the ice will be thicker. Maybe if you had some sort of sonic de-icer, vibrate the ice off the fins?

I like it! 😁 they basically looked at the frost and deicing problem and went " fu*k it!"

Yeah, though even slimmer by using a crossflow fan.

yes, the samsung 5kw units were about 800x800x400 but i'm pretty sure they didnt have any pumps etc inside. But it's the thickness that's the problem. none seem to be much below 400 and many are towards 500. Coupled with the 300mm standoff means you effectively have a 700-800mm block sticking out from the wall, this is pretty big at ground level and can preclude alot of side mounts between houses something with side inlet and top outlet that could be fitted to a wall would be much easier to site (think overgrown meter box) and possibly planning (again, think meter box) If the units were 4kw units and pretty small, wall mounted things (again think meter box) that could be twinned up to provide 8kw, that would cover alot of cases and provide better modulation.

stupidly small houses on stupidly small plots with poor insulation pretty much describes the UK housing stock! I get the arguments that it's just as easy to stick the gubbins outside and in the case of monoblock units you get the massive advantage of no messing with refrigerant lines. It was more a thought about how the usual format for outside units of horizontal axial fans sucking from the back and blowing out the front whilst the same thermal flow inside is serviced by a crossflow fan sucking and blowing planar to the wall. What advantages could we get by utilitising the indoor format for the outdoor unit (even with a compressor and phx)

Pretty much, but with an outdoor unit that was more like a wall mounted air con internal unit than some sorry of picnic table/korean BBQ 😁

Yes I have. 😁 The main point is the airflow/coil size for an indoor unit must be similar to the outdoor unit (given they are both transferring similar amounts of heat with similar DTs) and the indoor units are much quieter and more compact than the outdoor units. Inside units use crossflow fans which are very quiet and would lend themselves to a flatter device. If a HP could be fairly slender (say 200mm thick) and could be set against a wall because it is sucking top to bottom or side to side or bottom to top rather then front to back then the size in other directions isn't so much of an issue. You could probably stick a 2000x1000x250 box on a wall fairly easily but a 1400x800x400 unit that needs to be 300 off the wall is a bit trickier.

Usually an error because he'd left a semicolon out.

I remember complaining to my dad how long some app or other was taking to run on my computer and he replied his first interactions with a computer required the program to be put on punched tape and then physically posted to the comoutt facility, where it would eventually be run and an output tape posted back. Round trip was about a fortnight if you were lucky. 😁

If you really wanted to be radical, whay if each "head unit" was entirely self contained with a small compressor and the inside unjt purely held the controller, a PHX and pump, maybe a booster heater. Then each external unit woukd be capable of producing (say) 3kw, and you just double, triple, quadruple up for 3,6,9 and 12 kW demands This woukd proably add some cost through duplication, but that might be offset by economies of scale as the same outside unit is being produced in larger numbers. The really bug advantage thought would be that your modulation woukd be genuinely huge. In shoulder months you could run a single unit at low power (say sub 1kw for a 3kw peak unit) and then just spin up extra units as the demand increased up to however many you needed, say 12kw.

OK, another random thought. Currently there is general anxiety about the size, visual and acoustic footprint of the external parts of heat pumps. Usually they are a big white box sat outside the building (cough octopus cosy cough) Air to Air systems are a little smaller as they don't need the air to water heatexchanger etc and split A2W are essentially a a2a outside unit with an internal heat exchanger. But the inside units of a2a units (the boxes on the wall) are small and quiet, because of their location. They tend to use crossflow fans and are very compact. It occurred to me the heat exchange capability of the inside unit must be similar to the outside unit. Usually 2-3kw per head unit. What if (in essence) used the form factor of an inside unit as the external heat exchangers and what is effectively the outdoor unit was inside? As we would be going to water, the inside unit woukd replace the bulky fan and coil with a PHX and circulation pump. So inside we woukd have a boiler sized (and probably sited) unit with a compressor, PHX and pump. Outside you would have a wall mounted head units, say 2 for a 6kw system. Coloured to blend in. So in essence my pitch is: why not use crossflow fans and compact coils for the outside unit?

Please! Booting from floppy was for peasants! When you rolled one of these it booted from it's 200Gb hard drive whilst you sipped your morning latte. As a side note the typical noise levels generated by those things was around 50db. Not far off where some of the quieter HPs are now.

And 8gb of RAM! What luxury!

Not a cheap one! 😁 The O2 was about £15k when new. The onyx2 was closer to £100k 😲

Possibly, the angled top fan is a reasonable idea and maybe the entire back and both sides are intakes for max coil area. But the design is very "fisher price" as someone put it. It looks like a late 90's computer design to be honest, think iMac or a SGI workstation. It just seems odd. Straighten the sides, make the edges crisper, lose the typical fan mesh for setting else and, for the love of God, make it black.

I have to say, it is pretty awful looking - looks cheap and tacky. I don't think you need to go much away from a box. Changing the colour away from the default off white would be good, offering a colour choice also. Detailing the case so it doesn't look like a tin box with rivets etc.

Isn't part of the idea of WC that, because the flow temps are low, the change in output from any temp deviation (solar gain or opening a door) has a disproportionately large effect on the power delivery? Eg when your radiator temps are 65ish, then the change in power output to the room at 17C vs 20C is negligible, Delta T goes from 50 to 53, 6% difference. But if your rads were 35C then the DT goes from 15 to 18, a 20% increase in power delivery. Likewise if the sun comes out and your room heats up to 25C, the DT drops to 10 and the power delivered drops by 30% Basically the lower the design DT, the more self regulating the system is?

I, for one, welcome our new overlords...

That debris appears to be the inner part of the pipe that has just dissolved away! The bit that worries me is about 2/3 of the downstairs is cast into screed under tiles. If the issue was simply abrasion of the pipes from the outside, i'd be reasonably confident the slab pipes would be OK. But if the pipes are corroding from the inside, it's only a matter of time before they go. My choices are to abandon UFH entirely and fit rads throughout or to rip out room at a time and replace, which I can do in the upper floors but the cast in sections are done for.

... But worse than that is the inside of the pipes....

First off, I am a big fan of UFH but this is a cautionary tale of what can go wrong. My parents built their own home about 25years ago. For various reasons itvs bloody massive, over 3 floors with UFH on every floor, under reclaimed floorboards. They went for the red rubber santoprene system, which was a mistake. Flash forward to now and the system is plagued by leaks. I am converting the downstairs office to a bedroom for my dad who sadly has dementia and have been ripping up the UFH. Here are some pics. One of the 4 splits we found in one room. It appears the pipes have been abrading against the floorboards (company recommended the pipes were pressed in contact with the floorboards for better heat transfer). When my dad fiddled with the hearing system last winter he pressurised it to 1.5bar (we have been running sub 1 bar for many years) and caused these thin patches to rupture.