Home energy saving tips /ideas...

[mrcharly-YHT]

The control units - why the heck aren't these ASHP just working off a 'call for heat/call for hot water'?

It's not like a gas burner where either the flame is lit or it isn't, though: as its efficiency is so closely tied to the temperature difference it creates, the control needs to modulate the system output to match heat demand without cycling on and off, rather than just throwing heat into the pipes. New installations use weather compensation, so the output is set by an outdoor thermometer which estimates the requirement from a preprogrammed heat curve.  And the unit has at least two pumps to coordinate, for the refrigerant and the primary water circuit. The whole setup is unavoidably fiddly.

But all of that should be in a control unit either in the ASHP, or wired to it. The controller that the householder touches should just be a 'heat to this temp at these times', 'boost' controller. That is hardly different from a system that has a heat reading from the hot water cyl, a heat reading from the rooms, an out temp and a return temp.

Sure, the logic has to be more complex, but the signal wiring really isn't any more complex. Actually, the sensible way to design this would be to have a logic unit in the house, and the outdoor therm signal to that. Then the logic unit just needs to drive the ASHP - which wouldn't need more than the standard 5 core.

My point is that Flite shouldn't need the house rewiring to replace the ASHP part. Maybe Mitsubishi decided to not use standard

[Kim]

To be fair, it's not like gas boilers aren't a mess of incompatible standards, once you get into weather compensation or load compensation rather than a simple open/closed thermostat.

[JellyLegs]

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My point is that Flite shouldn't need the house rewiring to replace the ASHP part. Maybe Mitsubishi decided to not use standard

Assuming similar setup to me, he won’t.  Broken bit for me was somewhere in the actual ASHP outside.  All the Mitsubishi control units (several different panels worth) and clever gubbins lived in the garage with the hot water cylinder and several other bits that I dont pretend I understood.  There was a lot of rather untidy wiring and electronics there!  Heating controls / thermostat etc that I set temperature and hot water programmes on lived on the wall by the living room door.  I could buy a new version of the Mitsubishi pump unit for, iirc, in the region of £3.8k which would have been my way to go if that was it, but unfortunately I was told that pump is not compatible with all the Mitsubishi controls in the garage so I needed to rip out and replace that which is where the price spiralled out of control.  I glazed over at that point, but there was also some reason given as to why I would need some re plumbing done in the garage / outside as some requirements there had also changed and that added another few hundred to the cost.  I presume just a case of the manufacturer moving inlet / outlet positions or changing pipe size requirements but it added to the already unacceptable cost.

[chrisbainbridge]

I get the impression that ground source is both more efficient and longer lasting with companies quoting 20+ years and zero servicing costs.
We have a large garden which would allow a borehole and we have a garage which already has the solar controls and boiler in it.
The plan would be to use the solar/gshp for hot water and most domestic heating with the gas for winter.
Has anybody got a similar system and any views on manufacturers etc.

[quixoticgeek]

one of the issues with heating systems, is that for most people it's a distress purchase. Most people don't replace their boiler cos it's 20 years old and it's a good idea. They do it cos it's 20 years old and it just broke.

Ten years from a ASHP doesn't feel totally unreasonable if it's 7k, that's 58 quid a month. Stick that in a savings account each month, and after ten years you have the money anyway. Yes, there is the issue with non interoperability of parts from the first generations. Unfortunately that's common with most technologies. (try plugging in a 100 year old electrical appliance). As the tech becomes more pervasive, and more mature, the interoperability will improve.

Sorry to say that some of you are paying the price for being early adopters, but I would hope it's improving.

J

[barakta]

I think the issue that Flite is reporting is the constant breakdowns, stress and costs incurred even within that 10 years, seems very shoddy service from Mitsubishi to be honest. I'd be making "consumer rights act 2015" noises about some of those costs myself but that's a stress and hassle to enforce in itself.

It hasn't been a smooth 10 years for some folk, and having to undergo a whole reinstallation down the line which was not clearly indicated as a possibility smells like misselling at best. I'd be pissed off. Councils need to ensure their installations are secured properly and that if the company goes bust there is high quality followup, or maybe in-house it.

[chrisbainbridge]

I too think Flite has been really badly done by.  As I understand it an ASHP is basically the guts of an air-conditioning unit connected to some hot water.  I have had an air-conditioning unit in my office for about 15 years with no servicing for about 8+ as we forgot and I presume the company forgot/went bust/etc.  It still works perfectly well to both heat and cool.  I suspect that Flite and others were sold some seriously shoddy kit.

This for me is the biggest worry along with getting cowboys to do the installation.  I know of one failed builder who has reinvented himself as a heat pump installer with no experience!

[JellyLegs]

Ten years from a ASHP doesn't feel totally unreasonable if it's 7k, that's 58 quid a month. Stick that in a savings account each month, and after ten years you have the money anyway.

That was an additional £7k over and above the cost to replace an oil boiler.  To cover the whole cost would be just over £75 a month.  Yes, doable but that comes close to doubling the running costs of the system in my case taking into account the electricity I fed it of around £80 per month averaged over the year and an annual service cost of about £150 depending on whether the antifreeze needed topping up or not.  Plus there was the very ungreen creation of a lot of probably unnecessary electronic waste which dented the environmental credentials of the whole venture, at least for me. And the doubt factor of how long it would actually last.  I had nothing in writing when I checked but my recollection is I was told 15-20 year’s anticipated lifespan and I got 10.  Guess what, they still verbally say 15-20 years but are only willing to offer a much much shorter guarantee.  Don’t get me wrong, I really liked the technology but didn’t enjoy being shafted by Mitsubishi who washed their hands of me.  I don’t blame the installer, they followed all the advice from Mitsubishi and they serviced it regularly throughout its life.