Daikin Altherma HT quote advice

[wiffola]

Hi All,

We live in a 3 bed 1895 cottage in Wales, 90m2, stone rubble walls (rendered and plastered), single glazed original sash windows (secondary glazed in lounge), only insulation is in the loft 270mm.

Family of 4.

8 rads (22mm manifiold and 8/10mm microbore) sized correctly for current LPG boiler which runs off 4x47kg cylinders.

Annual LPG bill is around £1000-200 using 20-24 cylinders. That's with lean usage - and I mean lean e.g. 50-55 degrees heating on 8 hours a day.

We've had a quote for a Daikin Altherma HT with 200l tank. All in with grants (HPP £850) and Daikin cash back (£400) comes to £8750 incl. VAT. 5 year warranty on parts and labour.

Predicated annual running costs are similar to our current usage (as i mention we use LPG very carefully), but I assume we'll have a much warmer and more comfortable lifestyle with a heat pump. Also LPG prices are just going up and up so much more than elec.

ASHP is the only viable heating solution for us due to space and asthma constraints.

We also have a 2kw PV array to help when the suns out.

So am I crazy or does this sound sensible?

The offer only stands for this week and I have been researching for over a year! Please help!

[wiffola]

Sorry I mean £1000-£1200 a year

[taz24]

.

The first thing is to make sure the house is as insulated as posible.

You would get more pay back spending on insulating the walls and windows.

Don't attempt to renew the heating untill your house is fully insulated, you
will be throwing money away.

So £9000 installed??

Running costs at £1000 to £1200? If the price of gas goes up and electricity
stays the same then you would need to save about £1000 a year for 7 or 8
years to be in the profit.

But and it is a big BUT!!

But if you don't use a heat pump what alternative is there?

Gas & Electricity... Gas is going to get dearer and Heat from direct electrical
sources is never going to be efficient.

So a heatpump is the only viable option.

BUT insulate the house and double glaze the windows first.

taz

.

[r.bartlett]

Super insulate the house and the gas spend would drop dramatically too making the ASHP payback even longer. (Something ASHP's salesmen omit to point out)

[wiffola]

Thanks for the replies.

I had a feeling 'insulate first' was coming.

Unfortunately we have lovely original sash windows. So double glazing is out of the question. We could secondary glaze however. We've had a quote for £3300 for 8 windows which seems reasonable.

Insulation else where would be very difficult on the external walls. We dont want to lose the exposed stone outside and inside is small enough already not to mention a bit of a pickle to insulate, with original picture rails and cupboads etc.

We have insulated the loft but we have a loft conversion so only 50% of the roof has the full insulation to todays regs. The rest of the loft has kingspan in the rafters.

Would secondary glazing be enough to justify the heat pump installation?

[frank]

Don't fall for the old 'the quotes only good for this week' gag. As far as I'm aware (Daikin approved installer) there are no price increases due within the next 7 days.
There are changes to MCS 3005 though that require better insulation to be in place, if you are looking for the RHHP grant and the Daikin £400

[wiffola]

Thanks for the replies.

Yeah I'm not falling for the 'has to be signed this week' line but as you say the MCS rules are changing in the new year so to save £1250 now is the time to bite the bullet...well possibly.

I had forgotten about that...the installer mentioned it. I can only imagine this is where the RHI will head too.

And then I'm thinking I'll do the secondary glazing in the summer as the windows need some restoring before I do it.

I'm not kidding myself we'll qualify for the RHI, so all the more reason to get this HPP now.

Anyone care to agree or disagree?

[Jon Glanfield]

Hi Wiffola, the indoor unit on the high temp is quite noisy, I would ask your installer to demo one that he has installed for you, just in case it is going to be in a potentially intrusive location.

Also I would be a bit concerned about flow rates given your pipework sizing. The HT has an inverter driven circulator and user settable delta t which can be set to 10 degrees to take account of rads, but with microbore I would think seriously about a buffer, there are many other benefits of using one that have been debated on here before.

We have one installed that is being monitored by the EST in Manchester, the customer is very pleased with it, we don't yet have empirical data on running costs yet, but he has advised that there have been no shocks.

We used a Rotex Sanicube instantaneous hot water cylinder, this has so far outperformed a 30+kw, 2 year old condensing combi that we removed. It might be overkill for your requirements but has worked well.

As far as the RHI is concerned ASHP's have got to jump the bar first anyway!

The costing seems reasonable for an HT and the National Trust have been using quite a number according to our rep, in hard to heat properties.

[hyperion]

Definitely consider fitting a buffer tank to give the minimum water content when the TRV's shut down or you may start experiencing water flow problems, particularly as you have a microbore installation.
Some installers try to ignore the minimum flow rate and water quantity to save some costs.
If all of the TRV's close down, then you may need to incorporate a bypass valve to help maintain the minimum flow rate. This will need to be set up correctly.

[wiffola]

Thanks Guys. I really appreciate your time.

I agree a buffer makes sense, unfortunately we dont have much space available. There is potential space in the loft but it's awkward with our loft conversion.

We actually only have 2 trv's in the whole house, we can very easily replace them for normal valves during the install if it helps flow rate problems?

I'll raise this with the installer.

Basically they have agreed within the price to do whats necessary to combat the microbore e.g. whether we would benefit from a low loss header. They said though, with a 14kw unit it's not always needed.

I was planning to have the install done, see how it performs and then add a buffer in at a later date if required.

[wiffola]

the indoor unit on the high temp is quite noisy, I would ask your installer to demo one that he has installed for you, just in case it is going to be in a potentially intrusive location.

Thanks for the heads up...I've come across this in my research.

This will going outside next to the outdoor unit in a highly insulated box. I've seen a few installations like this. Work case it can go under out stairs in the cupboard, with a bit of tricky pipework.

I assume the Daikin hot water tank will be pretty quiet? As that will be in an airing cupboard in a bedroom.

[Jon Glanfield]

Can't the buffer go in a highly insulated box outside too, there are too many pros to fitting them to avoid it at the outset and costs are likely to increase if a second tranche of work has to be commissioned.

Cylinder is water noise only, but thermistor cable has a max recommended length for resistance so just check this has been factored in, pipe runs to cylinder need very good lagging and flow rate/delta t has to be maintained.

[Jon Glanfield]

Sorry also meant to say that header might not be good idea unless the pumps on either side are interlocked with the heat pump otherwise you won't have min circulation volume for defrost. If you don't interlock the size and cost of the header would justify doing a buffer which is infinitely better.

Make sure the installer fits a flow meter on the return, so that you can accurately see flow rates, and the intention to do what's required with the microbore sounds a bit woolly, you might want a decent retainer for a couple of months.

[hyperion]

It may be beneficial to fit more TRV's not less to give better temperature control throughout the house.
Normally Daikin recommend a maximum distance of 11 metres for the tank sensor cable to the control PCB, as this is the length that is supplied.
The minimum water content for the 14kW unit is 20 litres, excluding the Altherma unit.
There is also a minimum flow rate required of I believe 20litres per minute, to prevent low water flow failure. Your installing company will know these figures and be able to advise you accordingly.

[wiffola]

Thanks for the replies.

What size buffer would be recommended for this setup i.e. a 3 bed 8 rad house?

Just thinking where I can squeeze it in.

[wiffola]

And also how much should I expect this addition to be? are we talking a few hundred quid or more like £1k+?

[hyperion]

The size of the buffer tank is determined by the minimum water quantity required to satisfy the defrost cycle of the Altherma unit, which for a 14kWatt unit would be 20 litres. The additional cost would probably be about £300.00.
Your installer would be able to advise you and may already have allowed for a buffer tank in his quotation.

[Jon Glanfield]

You will find a plethora of approaches when it comes to buffer sizing and employment. With Daikins we set them up with the onboard sampling/load compensation and use a large buffer (30 litres per kw). Otherwise the contents mix and de-stratify as the pump runs to perform the load compensation.

We have been monitoring 2 that we set up like this and both are well under the Daikin simulation for Dec, 1 of them has come in 36.5% lower than what was predicted for heating usage and not all of the refurb has been completed, i.e. insulation still missing in parts and UFH uncovered in places.

Buffer costs are around £400-550 for the size you would need, but you would also need a house side circulator too.

[nec0310]

Hi Wiffola,

HT is a very good heat pump system. Some tips to help you avoid expensive problems.
You must have a buffer or balance bottle as Daikin refer to. The defrost cycle needs a minimum of 30 litres free volume- ie all rads closed. Damage to the R134a circuit will result!!! Run through a buffer (110 litres is the size we use), allow the HT to modulate, and pump separately to the radiators. Make sure you observe complete flushing of the existing heating system- the inverter pump on the indoor unit does not like dirt or magnetite!!! This is really important.
The buffer will also allow the HT inverter compressors to modulate correctly- inverter pump!
The HT unit has two compressors- thus two crankcase heaters- and two PCB boards on 24 hours per day- if you are running lpg frugally be careful with the HT. You can expect around 100-200 watts per hour electrical consumption just in standby.(
Make sure that you have a dedicated flow setter and watt meter installed with your HT system to allow you to determine energy usage- you need this to monitor set up to determine efficiency. The HT provides alot of diagnostic data but without flow rates and watt usage you will not be able to correctly determine optimal operation.

If installed correctly, the HT is very good.

[woolyback]

Interesting advice, I'd like to know the outcome of how it performs and what was done.
My 2 pence a buffer vessel would probably be required to overcome the resistance of the water pipe work (this could be calculated). With that in mind then a suggestion of a minimum of 17litres per kW is required, though more wont hurt as per Jon suggested (just not too much as this buffer will have a heat loss which we don't want). Also would suggest the three port valve for the hot water cylinder is before the buffer, if not possible using the standard piping be very careful.
Just to correct nec0310 comments, minimum water volume is 20litres (although more the better) with a good flow rate. Also standby is less than 100 watts (something like 47 watts outdoor 43 watts indoor i remember from a training course) only whilst in standby, this can only be measured with a true kW/h meter like your house meter and not one of those clamp on devices. If intending to measure actual performance then use a true power meter on the indoor and outdoor unit (or combined) as mentioned in another thread and heat meters on the flow to calculate average efficiency’s

Hope all goes well and keep us informed

[wiffola]

Our HT is all now installed - by a different (much better) company in the end. Just getting to grips with the setup. I'll be back to post pics and consumption! I'll start a new thread for that i think. thanks for everyones help.

[teebee]

Hi there,

Can you post some pics soon?

just that we're planning to go to that route as well.. we have LPG in our property and recently installed Solar PV.

We're now looking to ASHP for both DWH & CH.

Thanks