Which ASHP model / brand to go with...

Hi All,

I'm new to this forum...so hello!

I'm looking to retro-fit an air to water ASHP for all of our heating and hot water needs. We live in an 1895 cottage 90m2.

We'll be using 8 oversized radiators on 15mm pipework, ideally without a buffer tank due to space issues.

All I would like is some advice on brands of ASHP. They all seems to have different COP's but I'm not sure whether they are all tested in the same conditions, and also how relevant these are anyways.

These are the units we have been quoted for...

1. DanFoss AQ 9kw

2. Daikin Altherma High temperature (Not sure what wattage - cant find the quote right now)

3. Mitsubishi Ecodan 8.5kw

This isn't a thread to talk about if it's the right option or not - been there done that!

Any recommendations?

Climaveneta, CIAT...

Quote:

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Originally Posted by wiffola

Hi All,

I'm new to this forum...so hello!

I'm looking to retro-fit an air to water ASHP for all of our heating and hot water needs. We live in an 1895 cottage 90m2.

We'll be using 8 oversized radiators on 15mm pipework, ideally without a buffer tank due to space issues.

All I would like is some advice on brands of ASHP. They all seems to have different COP's but I'm not sure whether they are all tested in the same conditions, and also how relevant these are anyways.

These are the units we have been quoted for...

1. DanFoss AQ 9kw

2. Daikin Altherma High temperature (Not sure what wattage - cant find the quote right now)

3. Mitsubishi Ecodan 8.5kw

This isn't a thread to talk about if it's the right option or not - been there done that!

Any recommendations?

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None, unless you up the size of your main pipework to 28mm, use a convector fan such as a dimplex smartrad instead of standard rads and preferably install a buffer. Otherwise you're heading for disaster.

Hello I looking in doing the same and using daikin how did you size your rad for the kw of the unit,I spoke to daikin and they said we can put the heat pump straight on and we do not need any buffer tanks as its only doing the rads does anyone esle know

I have a Hitachi Yutaki RHUE-3AVHN (7.5 kW nominal output, I think), and this is running a radiator system in a small 2 bed bungalow (6 rads). No buffer, 22/15mm pipe. Still trying to set it up properly, but whole house consumption seems to be in the region of 30kWh/day (2-5C outside).

The controller has weather compensation, and seems not quite ideal at the moment in terms of firmware stability and suitability to this system (e.g. it can call for heat pump setpoint which causes the pump to trip out with an overheat fault).

Fan convectors might seem like a good idea, but the cost offsets the potential saving (particulalry if you have space for large rads), it's another active component to go wrong, needs more electrical work etc.

Flow temps of 45 seem to work in my property, even in the current cold weather.

We've got aDaikin 11Kw low temp split system but its feeding a PolyPipe overlay underfloor system. 140sq.M detached bungalow. Decent insulation in the loft (10-12"), cavity wall is insulated but I'm not sure how well and no insulation under the suspended floor. We heat the hot water up to 42 degrees which is just about OK and allows us to have a shower each. No buffer tank. The outdoor compensation adjusts the flow temp from 25 at 20 degrees outside to 42 when its zero and it keeps the whole bungalow at 18 dgrees. It's been running for just over a year now and we are using about 40kw/day when its about 2 degrees outside, 25kw at 9 degrees and 12kw at 12 degrees.

So we are quite happy with it's performance

Just to add a bit to the last post - I am monitoring the power usage with a British Gas freebie energy monitor clamped onto the power supply cabling to the heat pump. I am also monitoring the whole house consumption with a Current Cost unit clamped onto the whole house supply and the readings are similar except on days when the washing machine/tumble dryer are running so I suspect that the British Gas monitor is over reading by about 10-15% which makes the heat pump figures even better. The Current Cost monitor readings are surprisingly close to the tarrif meter (within an average of 1-3 kw a day).

The problem with monitoring with a clamp on unit is that it can't compensate for power factor or voltage variations .

The main criticsism that I'd have with the Daikin unit (and I'd suspect that most units are similar) is the compressor sump heater which consumes about 120w when not doing anything (heating or hot water) - I noticed this when we had the unit disconnected for a month during the summer when we had some building work done - that equates to over £100 a year just to keep it warm:mad: