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EBAY ASHP


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6 hours ago, vfrdave said:

It escaped me that it was 9 years old I'm guessing not as efficient as a newer one. As you say @PeterW wouldn't want to pay that much, they are open to offers it seems.

 

TBH I was a little sceptical but applying 240v to the unit and 24v to the controls soon kicked it into life. I’m surprised at the low flow rate that it needs - wilo pump on a static head of 2.5m and 16w works perfectly as I know some have had to put double pumps in to get heat pumps to work. 

 

The actual unit is a rebadged PUHZ-W90VHA which is designed as far as I can see to be part of a hot water tank system as they state they can do up to 60c from the heat pump. Not sure what this does to the CoP but it seems pretty good from first look. 

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There another cheap one here but only 5kwh

 

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F232943320938

 

I don’t know what they mean by “The cooling function option is not available with this listing”

Surely it’s just a control parameter rather than another piece of hardware?

 

I’ve noticed some of these sellers are trying  to seriously profiteer from “extras” i.e. “fitting kits” at £600 !! 

 

 

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31 minutes ago, Barney12 said:

There another cheap one here but only 5kwh

 

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F232943320938

 

I don’t know what they mean by “The cooling function option is not available with this listing”

Surely it’s just a control parameter rather than another peice of hardware?

 

I’ve noticed some of these sellers are trying  to seriously profiteer from “extras” i.e. “fitting kits” at £600 !! 

 

 

 

 

These were the Chinese, non-inverter control, units that ESP were importing and selling at one time, I believe.  I have a feeling that Navitron may have imported and sold some too.  They are pretty basic, can only run flat out or off, have a high starting surge current and pretty rudimentary controls.  The comment about cooling is interesting, as they have a four way reversing valve, for defrosting the evaporator, which means they can physically run in cooling mode.

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As per @JSHarris it you search for these we discussed them back in July. They did list them on Navitrons website for a while - they are a standard Chinese unit although they do list being inverter controller elsewhere but for that price I think they are worth a punt anyway. 

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The next two models up have a soft motor starter, but this model doesn't, hence the 20 A starting current for a unit that draws less than 6 A without the integral immersion heater running.  Looking at the tech data sheet none of this range have inverter control, it seems, as they all have a pretty high starting current listed.

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27 minutes ago, Barney12 said:

I only wish I knew what “inverter control” meant. ?

 

It's not really an accurate description, either, unfortunately.  Perhaps worth looking at how a non-inverter control ASHP works  There are three moving parts internally (excluding the water circulation pump and assuming that the unit doesn't have an electronically controlled variable expansion valve).

 

The main component is a powerful rotary compressor, driven by either a single phase or three phase motor, often with a rating of several horse power.  This motor is a synchronous machine, so can only run at a  fixed speed, which in turn means the compressor runs at a fixed speed, and as compressor speed is directly linked to the heat pump capacity for any given conditions, the heat pump can only run at either maximum output or zero output, a bit like an older, non-modulating, gas or oil boiler.

 

An ASHP normally has to have a fan to blow air through the evaporator, and that too will be driven by a synchronous motor, so can only run at full flow rate or no flow rate.

 

An inverter controlled ASHP, whether single phase powered or three phase powered, rectifies the fixed frequency AC supply to DC and then electronically generates a variable frequency (usually three phase) to drive the compressor motor, and separately, generates another variable frequency to drive the fan motor.

 

The advantage of this is that, as frequency controls motor speed, and as heat output is proportional to compressor speed, the ASHP has the ability to vary it's heat output over a wide range.  Similarly, the fan speed can also be varied, often using the evaporator temperature, so that the fan never needs to run faster than is needed for a give heat output.

 

This ability to modulate the output of the heat pump is really useful, as it means it can run very quietly most of the time, when it isn't being asked to deliver it's maximum output.  A secondary advantage is that the heat pump controls can include a slow start for the compressor motor, which then completely eliminates the starting surge current that an "all or nothing" heat pump compressor motor has.

 

Inverter controlled heat pumps are a bit more complex that that, as they also have to modulate the expansion valve along with the compressor speed, in order to maintain best efficiency, but overall they tend to be more efficient, quieter and pose less stress on the local electricity supply network.  As an example, our 7 kW maximum ASHP has a maximum current draw of 8 A, but in practice it rarely seems to draw more than about 2 A when running.

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1 hour ago, Barney12 said:

I don’t know what they mean by “The cooling function option is not available with this listing”

Surely it’s just a control parameter rather than another peice of hardware?

 

Isn't there something about cooling being made more awkward to get at somehow to comply with RHI?

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15 minutes ago, Ed Davies said:

 

Isn't there something about cooling being made more awkward to get at somehow to comply with RHI?

 

 

Yes, there is, but it seems that the degree of difficulty in being able to access cooling mode is highly variable.  For example, the re-badged Carrier ASHPs that a few of us have, default to cooling mode if the dry contact "on" connection is made.  The way that they get these to comply with the MCS/RHI rules is to just add a note in the installation instructions saying that as well as terminal 6 being connected to terminal 3 turn the ASHP on, a wire link must be added between terminal 3 (0 V) and terminal 7.  It doesn't say what terminal 7 does, but in fact that's the connection that tells the ASHP to run in heating mode.

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I wondered about this listing. It's much more expensive but the seller is MCS approved and says that they provide the following service:

 

We are offering a complete delivery and installation advise service no other seller on eBay has offered before. A free special next day delivery service if you reside within a 70 miles radius from Grimsby.

One of our qualified engineers will run through the system design with you and advise on the whole installation, wiring, plumbing etc to ensure a smooth installation.

 

They also say:

 

Cool Energy are MCS approved and can audit your installation as required

 

So I wondered if it was a cheap(er) way of getting an MCS / RHI eligible install potentially by doing a bit of DIY and then getting it signed off. Not sure how much that would cost in addition to the equipment mind ... I know RHI wouldn't amount to much for those of you in passive houses but for those people who are not, or have large houses it might be an option. For example, the amount I would get from RHI payments here would make it worth it if I could get someone to install it for less than a second mortgage. 

 

https://www.ebay.co.uk/itm/Air-Source-Heat-Pump-Complete-Hot-Water-System-Home-Office-Business/113053977495?hash=item1a528acb97:g:HgcAAOSwStdbHj~9

 

 

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On 10/11/2018 at 10:20, Gav_P said:

This one is being advertised again, but now at £750.

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5 hours ago, joe90 said:

That’s the same as I bought and I paid £850 delivered two years ago.

Do you think it’s the 4Kw version ? It has a different shaped fan grill to mine, so wondered if it was a bigger output.

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5 minutes ago, Gav_P said:

Do you think it’s the 4Kw version ? It has a different shaped fan grill to mine, so wondered if it was a bigger output.

The add isn't very clear it states something like 4000 - 7999w as the power so is it the 8Kw?

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24 minutes ago, vfrdave said:

The add isn't very clear it states something like 4000 - 7999w as the power so is it the 8Kw?

If it is 8kw then it’s a real bargain! 

 

Both @joe90 and I have the 4kw versions which seem to do the job.

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