ASHP - Wet system

[Biggles..]

If you realisticly think you can achieve 55degc from a hfc ashp specifically altherma without any electrical backup your in trouble.

Reality above 8deg c is about 45 hence why ufh is the preferred option as there's no need to blend the water temp down.

If it was cost that motivated you,then by the time you've oversized your rads,paid for the electric top up heating and had no heating in winter you'll reconsider how wise a choice altherma actually was when actually
Not having saved you that much in the initial payout.

I learnt how bad they were the hard way,hence why I'm throwing alot of my companies money to prove what actually is what.

 

[D_Hailsham]

After a fairly frank discussion with the engineer who has contacted Diakin (...) it would appear that they maintain a mean water temperature of 50 degrees is correct. The engineer has fitted several others and knows that the mean water temperature of 50 is achievable with the system and can be used for calculation purposes.

I would require something in writing from the installer and Daikin stating that the system will be able to achieve a flow temp of 55C when the outside temp was -1C before I even considered signing the contract.

 

[Biggles..]

Daikin won't do that because it doesn't.they don't even state figures that low.
+5 to 8 is as low as they go before tuning at defrost,thats where the unit requires all its got to stop itself freezing,at which point it doesn't care if you freeze.The ht system is a casade that use two
Compressors and refrigerant circuits,the out door unit still uses r410a but the indoor unit uses another gas with much better properies.it's still the 410a that is floored in performance.surprisingly daikins spec sheetperformance figures based around both properties of both gases,therefore the second gas may work to -20 but the first stage of R410a won't,so it's irrelevant how low the second stage can operate I'd the first stage has stopped producing heat.

The other downside is daikin units have an indoor and outdoor unit plus
the cylinder/store.More space to find to go along with your oversized rads.
The industry consider the installation of cascade refrigeration systems into domestic properties to be a step to far.

 

[Norcon]

Icgs wrote

I've just agreed to fit ashp in a clients home at the cost I would have installed a shiney Vaillant boiler and aurostor.

And the shiny vaillants output? Probably at least 24kw to the ashp's 9kw.
Multiply your ashp installation cost by three to equal the gas boiler.

 

[Biggles..]

Spot on with the size sir,624 running a 300 aurostor with wireless weather comp and dhw priority supplying split heating comprising ground floor ufh,upstairs radiators.

That compared to 1 9kw ashp with a 230litre store.

 

[ArgyllMC]

O.K. thank you all for your views.

Can I deduce from the above that Diakin Altherma is NOT the way forward and looking at something like a Sanyo system would be the way forward

I think having digested all this information I may well abandon the plans and live with the very expensive gas system for another 1-2 years until the performance of these units has been proved or CO2 technology has advanced further as it would appear to be the emerging winner in the long run?

Thank you all for your time if nothing else I have learnt what a useful resource the internet can be when you find a good forum

 

[Agile]

I dont think that you are in a position to come to any conclusion at this stage of the development of ASHP units.

Its not so much what the manufacturers tell you as what they DONT tell you.

In the UK climate the most important aspect of any heating system is how it performs during the worst weather conditions, i.e. -1°C outside.

Current units can look very good when its 8° outside and they drive UFH at 40°C. But its what they do when its -3°C outside which will worry you.

It always surprises me that there is no common development of Peltier effect units and we are still using 1930s/1940s compressor driven heat pump units.

Have you looked at wood pellet boilers if you have lots of space?

Tony

 

[Biggles..]

Biomass, if you've got space and deep pockets then off you go.

why not try the baxi ecogen,just been released for general sale at circa £6200.

 

[Agile]

I dont know whats happened over the last two weeks but when I enquired at their show two weeks ago they said they were still undergoing field trials and no date had been set for making them available commercially.

I also asked about the price and got the usual that its not decided yet but perhaps about £4500.

If you look more closely at the specs its not as wonderful as one might hope. It will not give electricity unless there is a demand for heat.

You would have to fiddle it to give a demand for heat but prevent the main gas burner coming on as well.

The efficiency of the generator is lowish, about 30%, if you dont take account of the waste heat from the sterling engine.

They are also heavy and apparently rather noisy by boiler standards although no one has shown me a working one yet.

Tony

 

[Biggles..]

ive got a couple of CHP's on the books,not ecogen or whispergen as theyre scaled down domestic efforts.

i'll put some photos up later in the week of the setups.

 

[vulcancontinental]

The efficiency of a radiator is always 100%

Not if their covered over with clothes as many people do

That's not a fault of the radiator and the efficiency will not alter.

or sludged up inside with gunk.

The radiator may not give off the same amount of heat but the efficiency will still be the same.

Efficiency is defined as output ÷ input. If the rad is covered/sludged, both will decrease by the same proportion.

Can't contribute anything to the ASHP posts which are fascinating but if a radiator had an efficiency of 100% the return would be leaving at room temp.

quote: I had read up and there were arguments for both putting them below windows and not. The arguement for not putting them below windows seemed to be more relevant to our house. We have long curtains so all heat rising from the radiators beneath windows would be getting pushed up behind the curtain and not emitting into the room as such.

Lot of debate over this for years by my take is put the heat where the cold is. If you do not you'll be sitting in a good temperature in the middle of the room but believing you're cold at your back because there's a window behind you. It's not just physics it's also perception.

 

[ArgyllMC]

O.K. then guys, clean sheet what would you fit to heat the house?

100 sqm floor area bugalow, insulated to the hilt and set in just under 1 acre of ground, budget for install about £8K. No mains gas supply and no existing system build on.

Incase it makes any difference I am in coastal area of scotland which is very wet however does not often have sustained periods of cold weather due to sea breezes. House is facing south (ish).

Oh and I intend on living there for 15-20 years..........

 

[Perfectionist]

Why do you think that speedfit is dramatically reduced?

Have you ever looked at the inside of a rad valve?

Have you done fuel cost calcs to compare the different costs?

Its quite likely an ASHP will be comparable as you dont have NG and can only choose oil, LPG or off peak electricity as alternatives. Usually oil is the cheapest both to install and run.

Part of the problem is that heat pump performance is not well documented and makers claims are usually very over rated.

Worse when its cold outside the performance usually falls off severely. The makers and installers dont want to discuss that!

Tony

1. A rad valve is reduced at the appliance, the rad, with full flow and pressure to the valve. This is not the same as a restriction 20 foot away in the pipe.

2. Speedfits inserts collectively can restrict a system's flow. This has to be taken into account.

3. Since when has oil been cheaper to run and fit than NG?

4. The claims of ASHPs are mainly exaggerated. Standards are being tightened to performance claims.

 

[Perfectionist]

In comparasion to other fuels the proven sustainability wouldlace place fuels in the following order (best to worst)
ASHP/GSHP-NG-OIL-LPG this takes into account,extraction,refining,transportation,installation,running etc.

The end user does not care about transportation or extraction, only on how much it costs to run. ASHPs do outdo NG condensing boilers. The new ATAG A325EC combi with the integral GasSaver is very efficient. The same can be got by using a GasSaver top box.

ASHPs rarely are cheaper to run than NG or oil. They can be effective when heating low temperature underfloor heating combined with a solar panel, to cut it out when enough solar gain.

The best heat source for a heat pumps is running water, after that a vertical bore hole, after than horizontal slinkies on ground which the sun shines on.

There is a lot of greenwash spouted over ASHPs. Despite, there are ASHP products that are efficient when fitted as a complete well designed system. The lacks of testing standards is a problem with wild claims.

ASHPs are improving and the Mitsubishi "was" regarded as the most efficient.
I like the sound of the Sanyo.

 

[Perfectionist]

ive got a couple of CHP's on the books,not ecogen or whispergen as theyre scaled down domestic efforts.

i'll put some photos up later in the week of the setups.

Thanks. Explanations would be appreciated.

Lgcs, you claim it cheaper to run the Sanyo ASHP, than an NG boiler and also cheaper to install.

Is that so? If so, some more info would be appreciated, as this would be a leap.