Posted by: @cathoderay

Posted by: @hughf

the defrost requirement is quite interesting

The defrost cycles appear to be a particular nuisance, because they kick in, as I understand it, at around 5 degrees ambient (and stop at minus something, no longer needed for a reason I can't remember) but the key point is they reduce output when it is most needed. Very crudely, again as I understand it, the unit becomes a cooling unit, sucking heat from the house to achieve the defrost. Clever, or what? Again, it is not always clear whether manufacturers include the defrost effect in their output data. If you plot output by ambient, and see a dip around 0 to 5 degrees ambient, that is most likely the defrost cycles kicking in.

What's odd about that TUV (TUV = ?) table is that there is only one column showing a defrost cycle. But it is also the column with the longest data collection period, 4 hours vs 2 hours for the rest. If my 5 degree threshold is correct, the A7 and A12 tests wouldn't have defrost cycles anyway. One way of getting rid of embarrassing defrost effects at lower ambients would be to run tests that last less than the interval between defrost cycles. 

I wonder how many installers tell customers that their ASHP will periodically turn itself into a fridge unit in colder weather.

 

I thought it impressive that the only condition where a defrost cycle was required, was pushing 55 deg water out at -10deg air temp, after running for 4 hrs. And then it only defrosted once.

It’s all dependent on the humidity of the air of course.

Btw, on the subject of Midea, I got hold of their official (not rewritten by GH) installation manual and all the rating charts are in there, pages of them in fact 🙂

And GH has mentioned that they might sell me one, so I’ll give them a bell later and see what the story is about that.

I will bow to the experts, but I thought defrost cycles were most needed between plus five degrees and minus whatever, and a unit that didn't defrost at those ambients would sooner or later get into trouble. The main question is whether a manufacturer's output data includes defrost cycle effects.

The official Midea documentation ('Engineering Data') came up earlier in the thread, and yes it is all there, pages of it. But does it say whether those capacity (output) tables do or don't include defrost effects? It don't think it does. You have to plot the data, and make a guess.

I sometimes think GH has a rather optimistic view of Freedom, based on what he did when he was there, rather than how they behave now. They very clearly told me they considered themselves B2B, and weren't prepared to talk to me directly. Extremely short-sighted in this day and age. It will be very interesting to hear what your experience is when you get in touch with them.

This is (I think) a defrost cycle.  The unit sucks warm water back to melt the ice so the flow temp drops.  It then has to use energy to warm it up again before settling back down.  Because I'm using weather compensation to control things and not thermostats, the house will get a tiny bit cooler when this happens and then warm up again as and when.  If I were using thermostats, I think the additional power used would be more. I think the increase in outdoor temp is probably the defrosting warming things up near the sensor. 

This was at 3C ambient.  The Ecodan databook includes defrost in all its outputs at 2C.  (P60 or thereabouts in the link I posted earlier)  

Posted by: @cathoderay

I will bow to the experts, but I thought defrost cycles were most needed between plus five degrees and minus whatever, and a unit that didn't defrost at those ambients would sooner or later get into trouble. The main question is whether a manufacturer's output data includes defrost cycle effects.

The official Midea documentation ('Engineering Data') came up earlier in the thread, and yes it is all there, pages of it. But does it say whether those capacity (output) tables do or don't include defrost effects? It don't think it does. You have to plot the data, and make a guess.

I sometimes think GH has a rather optimistic view of Freedom, based on what he did when he was there, rather than how they behave now. They very clearly told me they considered themselves B2B, and weren't prepared to talk to me directly. Extremely short-sighted in this day and age. It will be very interesting to hear what your experience is when you get in touch with them.

Defrost is purely a function of evaporator size and airflow. Units need to fit in small spaces, so manufacturers will size the evap coils to be 'large enough' without being massive. Ideally you'd buy a unit twice the size as you need, so that the airflow required is much less (for a given heat output) but this brings the issue of modulation range. A large unit won't modulate down low enough when the heat demand is low and this will result in cycling.

The Midea units, with 16kW on a single fan are probably (just a guess here) going to defrost more than a unit with double height evap coil and twin fans.

Posted by: @cathoderay

I sometimes think GH has a rather optimistic view of Freedom, based on what he did when he was there, rather than how they behave now. They very clearly told me they considered themselves B2B, and weren't prepared to talk to me directly. Extremely short-sighted in this day and age. It will be very interesting to hear what your experience is when you get in touch with them.

Email sent, asking for price and availability of a 10kW and a handful of bits from their price list (that I probably could get from screwfix, but can't be bothered)

EDIT: Email back, they won't sell me one, but they have offered to point me to the plumbers merchants who stock one if I want to self install.

@cathoderay to be fair, many many business are not B2C and the reason is exactly what you are doing. They don't want the cost or time to deal with end users so they provide a product to end sellers so they can deal with the customers. As any business would say, the worst part of any business is the customers and things would be much easier without them

Posted by: @hughf

they have offered to point me to the plumbers merchants who stock one if I want to self install

The thing i would be wary of is having no access to technical support. This forum is excellent, but they maybe something only Midea/Freedom know (particular to the unit) and i doubt a plumbers merchant will know or want to get involved.

Posted by: @batalto

things would be much easier without them

But then there wouldn't be a business either! I do understand the B2B thinking, keep the punters at arms length, but as a punter it is very frustrating. There are many many business who could adopt the B2B model, but who choose to have publicly accessible technical departments, and when it works, it can work very well. 

Posted by: @cathoderay

Posted by: @hughf

they have offered to point me to the plumbers merchants who stock one if I want to self install

The thing i would be wary of is having no access to technical support. This forum is excellent, but they maybe something only Midea/Freedom know (particular to the unit) and i doubt a plumbers merchant will know or want to get involved.

Posted by: @batalto

things would be much easier without them

But then there wouldn't be a business either! I do understand the B2B thinking, keep the punters at arms length, but as a punter it is very frustrating. There are many many business who could adopt the B2B model, but who choose to have publicly accessible technical departments, and when it works, it can work very well. 

The fact they won’t sell me one direct and only want me to buy through their merchants has struck them off my list. Plus, the unit is too wide. I’m going to stick with cool energy I think. They’re super helpful on the phone and their 9kW unit is a slightly better size for our space.

Posted by: @hughf

The fact they won’t sell me one direct and only want me to buy through their merchants has struck them off my list.

Freedom will probably if asked say losing one sale doesn't matter, but they haven't just lost the sale, they have also lost some general goodwill. Obstructionist policies never go down well with punters.

By the bye, the form factor, wider rather than taller, was one of the main reasons I chose the Midea unit, because my property is listed (which means you need LBC and because of that you also need planning permission), and being low profile lessens the visual impact of what is at the end of the day a large steel box with a big grill over a fan on the front. Even if the property wasn't listed, I might well have still chosen the Midea unit because it is low profile, after all, the building is the same whether listed or not. But horses for courses, of course.  

Posted by: @cathoderay

Posted by: @hughf

The fact they won’t sell me one direct and only want me to buy through their merchants has struck them off my list.

Freedom will probably if asked say losing one sale doesn't matter, but they haven't just lost the sale, they have also lost some general goodwill. Obstructionist policies never go down well with punters.

Exactly - I'm pretty active over on buildhub where I've just talked up the Freedom spreadsheet for someone who is doing their own design for their apartment. I said 'don't bother choosing a Midea, they won't sell you one even if it was suitable'...

Posted by: @hughf

Posted by: @cathoderay

Posted by: @hughf

The fact they won’t sell me one direct and only want me to buy through their merchants has struck them off my list.

Freedom will probably if asked say losing one sale doesn't matter, but they haven't just lost the sale, they have also lost some general goodwill. Obstructionist policies never go down well with punters.

Exactly - I'm pretty active over on buildhub where I've just talked up the Freedom spreadsheet for someone who is doing their own design for their apartment. I said 'don't bother choosing a Midea, they won't sell you one even if it was suitable'...

In fairness, it's probably a contractual thing. My guess is that, with Midea trying to gain market share against the likes of Daikin, Mitsubishi, Vaillant and LG, competing means offering some significant incentives to installers to choose Midea by preference. One of those will likely be a contractual agreement stating Midea won't compete directly with their own installers for customers.

Also, in fairness, anyone building their own house will still likely be buying their materials from a builder's merchant rather than approaching the brick, tile or cement manufacturer directly, so buying through a distribution network is a pretty well established sales model and hardly deliberately obstructionist. Not that I'm defending Midea or any other heat pump manufacturer; I just prefer to pick my fights and there are far more questionable antics the manufacturers get up to than not selling direct to consumers.

@majordennisbloodnok exactly. Very few things you actually buy direct from the supplier. I'm surprised people take it so personally.