Air 2 water versus pellet boiler HELP!!

[kerryblue]

Hi all first time post, any input on my dilemma is much appreciated as I find myself going around in circles in regard to which set up to choose from:

1) Air to water heat-pump circa 8 kw diakin split unit with a 260 liter water tank included for DHW and the UFH. To complement this there will be a 10 kw dry cassette stove in the living room which has extra extract hrv ducts in place which will be set to open when temp in room rises.

2) A EG -pellet 10 KW boiler or defro 10 KW which will feed into a 500 liter buffer tank with a stainless steel DHW coil and the UFH fed off the tank through a mixing valve. to complement this there will be a 14 Kw boiler cassette stove which will fed the same tank 10 kw of power.

The house is built to passive standard (269 sq meters, triple glazed, passive slab) thus load will be quite low. Both systems offer economical running but I kind of like the idea of having a redundancy with a boiler stove if you under stand me.

Once again any comments very much appreciated.
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[missplumb]

By the looks of it both well do the job well, i think it will be more of a financial choice.
Biomass requires you to get fuel and fill the store. An air source pump doesn't. Both will be eligible for domestic Rhi, which gives you the best payback?

 

[kerryblue]

Hmmm very true but my view is more on which is more likely to reliable over 10- 15 years if you get me.

 

[Sparkgap]

That's 10kW at what outside temp for the ASHP? Just putting in a 68kW commercial ASHP with UFH and manufacturers were quoting outputs for 7C outside. When I asked them to recalc for the design temps (-3C outside) we needed a bigger unit and COP went down as well. Would also check what water temps the Daikin unit will give for DHW as a lot of ASHPs normally go to max 55C and rely on immersion heater backup to boost DHW those extra few degrees to counter legionella. You can get high temp ASHP units but the COP isn't fantastic.

 

[oz-plumber]

20 years ago, I said to customers - I'll see you in 15 years for a replacement.

10 years ago, I said to customers - I'll see you in 10 years for a replacement.

3 years ago, I said to customers - I'll see you in 7 years for a replacement.

Gee I am busy at the moment!

Does this answer your question?

 

[kerryblue]

Hi Oz-plumb, I'm guessing that you would lean towards the simpler wood pellet boiler??

 

[snowhead]

Hmmm very true but my view is more on which is more likely to reliable over 10- 15 years if you get me.

Both about the same for different reasons.

Biomass require regular ash clear out with an all metal vacuum.
Pellet supply has to be carefully managed and stored.
Unless you have a large pellet store with automated feed, you'll need to top up the boiler every 3 or 4 days.
Most likely fault is the fuel auger jamming.

Heat pumps require little maintenance, but when they fail it's most likely to be electronic controls, which aren't cheap and won't be a quick fix.

So;
Biomass, easier fix but more likely to fail.
Heat pump, harder fix but less likely to fail.

Best of luck deciding.

I've worked around commercial heat pumps/refrigeration for over 20 years and around 500kw Biomass boilers for around 4 years and around a single 500kw ground source heat pumps for less than a year.

If I had to choose for myself,, I wouldn't know which way to go.

My Son has had a 45kw Biomass for around 6 months, it's jammed once and run out of fuel a few times when they've been away.

 

[Gray0689]

I'd stay away from air source expensive to run expensive to fix you will be changing after 10years when it's broke down 20 times
Bio mass can have its problems too but majority of horror story's come from heat pumps
If your on mains gas that is your best option

 

[kerryblue]

Serious food for thought there thanks for the comments. I've been in touch with one of the company's that quoted and there stating if I fit PV panels as well effectively the ASHP would be running for next to nothing...., Aww the mind boggles.

But as snow head pointed out electronics go wrong it's $$$ but the other issue in my case is I travel alot with my work so the "queen" would have to take care of the pellet boiler if it jammed.

Gary you reckon the ASHP cost alot to run do expand please as it helps knowing the down side to these units.

 

[Gray0689]

Im no expert but the ones I have seen (and have ripped out a fair few too)
All cost more than the so called experts say they will cost
Yes if you put in PV I'm sure they may pay for themselves
But then that's another say 10k
If it wasn't for grants and rocks would anyone really put these things in
For a decent bio mass boiler and the kit or ASHP let's say £10k for a decent gas boiler top spec £2k
Advantages renewables grants and RHIP payback as long as nothing goes wrong with them then let's say 5years
But big outlay up front

Disadvantages
Not a lot of people around that understand them fully
Expensive to fix parts expensive re gas compresser ect and the biggest problem wrongly sized
Wood pellet quality
Price as not a lot of choice of fuel suppliers

Gas boiler on mains gas
Easy to get fixed
Parts easy to get
Lots of engineers
Not a huge outlay and if breaks not that expensive to replace
Smaller area required
That's really the disadvantages and advantages but of course it won't give to any payments back

The best thing I can tell you is
You can have the best heating system in the world all singing all dancing
But if you can't keep the heat in the house no point at all
So spend the money on insulation good windows airtightness MVHR
And it won't cost you much to heat the house no matter what you fit

 

[Nostrum]

If your at Passive standards then a heat pump without a shadow of doubt. Install correctly of course. How bigs the house?

 

[Gray0689]

If your at Passive standards then a heat pump without a shadow of doubt. Install correctly of course. How bigs the house?

Nostrum your a clued up man in these heat pumps can you explain to me what the benefits are apart from the RHIP

 

[Nostrum]

low running costs, no need for fuel deliveries, low maintenance ( when was the last time your fridge needed a service?)

If you had a mains gas supply then you probably wouldn't choose a heat pump over that.

It is about being realistic and choosing the right technology on a case by case basis, not any one technology will fit every situation.

Personally I wouldn't fit biomass in a passive house by choice.

 

[Gray0689]

Neither would I
As for the low running costs I disagree the majority
There will be exceptions I'm sure but majority are higher running costs that the customers are led to believe take that with the height cost of installation you and me know if it wasn't for grants they would die a quick death

 

[Nostrum]

The heat pumps that don't run efficiently are most probably due to bad design and installation.

I personally think you'll be finding heat pumps becoming much more common in the future. Biomass will become less popular for domestic and predominately for commercial.

 

[Gray0689]

Yes I'd agree there due to bad design and installation
But the problem is there is good profit out of them so idiots jump on band wagon and call themselves experts
Fire them in and then once payed won't go back to fix any problems

 

[Nostrum]

Seems a shame to ridicule a technology based a bunch of muppets fitting them though.

 

[Gray0689]

But it's still a technology that if there wasn't any grants it's not cost effective to fit

 

[Nostrum]

Your argument seems to be changing on every new post! :wink_smile:

Heat pumps were being installed long before RHI payments were made available. The RHI intends to quick start the technology by incentivising the uptake at an early stage. The idea being the greater the demand the lower the production costs etc.

It's a bit like a flat screen TV, I paid over £1000 for a 42" plasma about 7 years ago. You can walk into Currys and pick a better model up now for a third of that. Supply and demand and all that.

We need to accept that gas boilers are dirt cheap, and anything by comparison is going to be expensive (partly due to the volume sold per year). In my opinion, this is the start of a massive phase out period which may last 50 years or more.

If everything wasn't about what we can get for doing nothing then it wouldn't be so bad, the technology will pay for itself over time, but most won't invest now without seeing a return on investment at an early stage, hence the RHI. The usual short sited approach as opposed to the long term gain.

And yeah there's always some idiot in a shiny suit knocking on your door trying to sell you something on false pretence, we've had double glazing, vacuum cleaners, security systems and now renewable energy!

 

[Gray0689]

My argument is always same there overpriced don't pay for themselves unless there is grants

I could pay 10k for insulation that money would be better spent than on a air to water heat pump

There overpriced tents mental technology that use electric to heat water can you tell me what's Eco about that
The dirt gas boilers are probably more Eco lol

So without the rhi what would the long term gain be ?

 

[Nostrum]

They are much more Eco compared to gas as they only use 1kw of electricity to every 3 kW of heat (basic analogy)

When you factor in the increase in zero or low carbon electricity being created through solar P.V and wind or even nuclear etc this makes it significantly less.

They would pay for themselves as I have said, it's just that it would take much longer than most people would accept if the RHI wasn't available.

A lot of the initial cost is due to a change in cylinder, change in heating pipe work, radiator sizing etc. the units themselves are reasonably priced. £10k sounds a bit steep mind.

Not sure what a tent has to do with it?

 

[Gray0689]

Temperamental that was meant to be
How long do you think the average heat pump will last without needing parts replaced
The compressor re gassed

There a hell of a lot more expensive to fit even on a new build when nothing needs changed

Let's say an average 200m2 new build
With underfloor heating at 150mm spacing 16mm pipe
I'd say total for materials
This would be with a oil boiler 300ltr unvented cylinder bundled oil tank
No labour just materials 10k to 15k depending on spec

Slightly cheaper with gas boiler

What would the price be roughly with a air to water heat pump

I've ripped out ground source and air source heat pumps because either
they cost a fortune to run
Breaking down
Or couldn't get house up to temp
As I've said before insulate and that is the best pay back you will get

 

[Nostrum]

Yep, absolutely right on the insulation. How often does your fridge or freezer need to be regassed? Never, unless it develops a leak. Other than that, there is a fan and some electronics, the same as anything now.

Air source could be installed for the same price as oil with tank and cylinder on a new build I would say. Ground source is a different story due to ground works and a slightly more complexed installation.

We fit Samsung heat pumps that include a 7 year warranty.

Like we've already said, the installs you've ripped out were probably installed or designed incorrectly.

 

[Gray0689]

Any air source I've ever seen priced is a hell of a lot more than an oil boiler and oil tank

If there so simple like a fridge/freezer why is there so many horror story's I guess I am very anti them as I've never seen a good one running well
Always cost way more in running costs than sold to the customer
And let's be honest if a fridge broke its normally just replaced
Not worth replacing compressor ect as a fridge is not that expensive
If your using the analogy of a fridge why are heat pumps so much more in cost

 

[Nostrum]

Supply and demand (hence the RHI)

Samsung probably make a million fridges a year as opposed to tens of thousand heat pumps (figures plucked out of the sky) so the cost per unit will be more expensive.

Also the compressor is bigger and it's generally a different unit in many respects but the technology is the same.

People seems to see heat pumps as some black magic or new fan-dangled technology when it's been around for years. heliotherm have been making heat pumps in Austria for over 20 years, if the technology was at fault then why are they still in business?

Most gas and oil boilers are oversized although the consequences are less disastrous. It's predicted that 60% of condensing boiler installed don't run as efficiently as they could due to installer error (or negligence)

There's more to heating design than hanging a boiler and piping it up as you most well know, but often that's what happens.

 

[missplumb]

It's still a new technology to most people and anything renewable in this country will initially be expensive.
I agree most renewables now wouldn't be taken up without the rhi. Cheapest decent biomass boiler is £10000, £1000 for a good gas boiler,

 

[Nostrum]

It's still a new technology to most people and anything renewable in this country will initially be expensive.
I agree most renewables now wouldn't be taken up without the rhi. Cheapest decent biomass boiler is £10000, £1000 for a good gas boiler,

£10k!?

I must have good terms!

 

[Gray0689]

You must be cheaper at fitting than any I have seen then

 

[Nostrum]

Maybe so mate, we don't charge Eco tax on it, just make it worth while with all the red tape involved!