Air Source HeatPump or Biomass?!

Hi,

Looking a new build heating systems, and currently due to have Biomass but am being tempted by AirSource Pumps. (Low load needed for out property and no Flue installation costs!)

Being STW I assume with all the woodburner talk, some of you must have Biomass or AirSource installed!!

Are there any obvious negatives to either, only I can see to AirSource is potential noise. Can’t find a genuine figure or comparison as to how noisy they are?!

Cheers

Are you on mains gas? If so, they are a waste of time. You will be better off installing more efficient heating controls, such as those that give you a visual indication of how much it is costing you and learns your habits so the systems don’t run when not needed.

I really don’t think the prolonged payback period and added complexity make ASHP and biomass boilers viable for ordinary homes.

PS: I know, because I have just been involved in a domestic project where the M&E engineer specced an ASHP.

As ^ said, if you have gas don’t bother, if you don’t then be very very careful about picking your installer as some of them don’t know what they are doing, which leads to systems using ten times the fuel they need too (this is from personal experience).

Hi,

Yeh I’m off main gas grid. So only options are oil, LPG or the biomass/heat pump! Otherwise I’d be going for straight gas as it’s much cheaper install and an easier fix!

ASHP are rubbish in properly cold weather, ie when you need them. We had 2 houses with ducted ASHP systems and they never really felt ‘warm’.

We have a fairly small load at 9-10 kW, through underfloor heating and only three radiators upstairs, plus hot water. Seems to be overkill for most boilers, as been advised that the house will run too hot due to the amount of underfloor pipe work. So a lower heat level running ASHP might be more suited?!

Check the minimum external ambient temperature in which it will work – which is a fancy way of saying what NZCol said.

I wouldn’t get a heat pump without a heat store (large well insulated hot water tank) so it can chunter away through the warmer times building up heat for you to use later and I’d go ground or water source heat pump not air – far better when you need them and not so affected by warmer/colder times.

As I understand it a lot of heat pumps kick over to pure resistive when it gets cold, vastly increasing your bills, and “cold” might we’ll be 4C or so.

Cheers guys, few questions to ask the installers there.

Originally we had planned Biomass, but now having to put the boiler inside due to flue restrictions outside and the small load, have been swaying to an alternative?!

They will make exaggerated claims over cold weather performance for ASHP, all i know is the lowest temps we got were above freezing and it would regularly need to defrost itself and leave the house feeling cold. Heating air is inefficient and they are noisy, vents mainly, the inverters are almost silent. This was a new install in 2011 as well.

I run a back boiler on a stove. Stovax 8hb with 9 radiators and a water tank, it uses about 8 cubic metres of wood a year, and the house is generally at about 18 degrees. It’s a little dusty but its a renewable energy source and i generally source a lot of free wood so its cheap for me to run.

It uses in an evening what our old open fire did but heats a whole house and hot water.

Noise is one of the things as well as performance that’s bothering us! If LPG wasn’t so expensive we’d just do that!

Seems all the non mains gas alternatives are massively expensive and have a far amount of drawbacks!! Boilers is the most expensive and the boilers are huge! ASHP seems ineffective and noisy, GSHP needs massive drilling, and solar has no way of storing energy when most is produced when your not in those during the day!

I know of an ASHP in Scotland that was removed after 2 years, as it never really got going properly on a cold day. It’s replacement did work on a cold day, but consumed ‘interesting’ amounts of electricity to do so.
If the load genuinely is low, and you are off mains gas, then some simple biomass install as PePPer suggests is ideal.

Solar (water or PV) can be used via a heat exchanger to heat a heat store – which as I said is just a large hot water tank really.

But biomass or oil would be my preference if GSHP or water source HP is not an option. Oil with a modern condensing boiler is reasonably effective and efficient.

ASHP’s can be good and bad in my experience, but from talking to house builders they’re not that impressed as they’re getting a lot of call backs in the winter when they ice up.

With biomass, presuming we are talking pellets, not logs, in my opinion they are only viable if you have a large enough store that would allow bulk delivery (blown in by lorry), otherwise it’s just too expensive and too much hassle.

At the moment with oil prices as they are then oil is probably the best option.
Failing that look at the Firewin from Windhager if you are interested in biomass as it is a reasonably pretty room heater.

ASHP are rubbish in properly cold weather, ie when you need them.

They can be, but if properly designed, they can be fine. They are comparatively low grade heat, but it shouldn’t be a huge issue with UF heating. I can see where engineersd are tempted; they comply with part L and CSH and are cost effective. They really aren’t great with normal heat emitters (rads).
Biomass can also be good, but again need to be designed well and you will also need to consider operational constraints. I looked at a site who couldn’t get fuel deliveries in harsh winter conditions due to poor access. They will also need quite an intensive maintenance regime; consider your biofuel source and type wisely. If it’s cheap, it’s highly likely to be crap.

The biomass was Pellet, not log/pellet.
Was looking at windhager but purely biomass pellets not logs. As I don’t want the hassle of loading logs to keep the water going!

Phil – was the log reference to me as the Firewin is pellet only anyway.

The devil with ASHP is in the design. You can’t just do a heat demand calc for the house and bash one in like you would a boiler.

As the air temperature drops, so does the available heat for the pump to recover, so you have to effectively over spec them to compensate. As it works harder to pass more air over its heat exchanger, they get iced up and effectively have to backwash a portion of the reovered head to de-ice them selves. Which adds to the double whammy. I’m simplifying a great deal, but its all about the coefficient of performance. When it gets down to 1:1, they effectively become electric boilers. If the system is specced properly, it shouldn’t get to this point more than a couple of time a year.

The other issue with ASHP, which has already been mentioned, is that its a low temperature system and works way better as a steady state system running 24 hours a dayvwith large emitters. (Which is why they’re well suited to underfloor heating). They’re not good at delivering high demand heat over short periods, because their heat ‘harvesting rate’ is relatively low compared to more traditional combustion heat sources.

Get your insulation right and understand the limitations of the system then get an installer who knows their onions and you’ll be fine.

Biomass I have less experience with, but the R&D my lot did shoed it to be huge, expensive capital cost and unless you have space for decent storage and and autofeeder, its a pain to constantly load.

GSHP not an option? You don’t have to drill deep if you have some land you can run the collection loop shallow over a wider area.

When it gets down to 1:1they effectively become electricboilersheaters.

Nearly! But in essence correct. Look at the systems with a wet tope up immersion. Sounds pricey, but at a COP of 1, its the same but a bit more effective. The Mitsi altherma things do it.
Or you could just look at normal DX air con (which are air source heat pumps without a wet circuit).Not very pretty though and don’t provide DHW.

Have you enquired as to the possibility of being connected to mains gas? Even if it costs several thousand to connect, I’d still go down that route than solar, biomass or ASHP.

I’m all for renewable energy sources but not when they become so inefficient that they result in the use of even more energy. A simple gas system with intelligent operation will be more efficient than most renewable options at this current time.

How well is your house insulated? That is something that could be looked into as well.

If you do go down the ASHP route, make sure the designer allows for a decent heat store and you have the room inside to fit another airing cupboard.

Another thing to think about is it’s location: They may not make that much noise but they do create vibration, which can be worse than actual noise, so make sure it is isolated from the house structure.

Heat recovery is another option worth looking into (as augmentation to another system), although it helps if your house is well insulated and fairly air tight.

Not run any myself, but some experience of systems through work and friends.

Pellet boilers work with RHI payments, but are otherwise the same cost to run as oil but take a lot more space and we are yet to trust the one in the staff house to run for more than a month without breakdown.

Chip, the supply quality is erratic, swapped for pellets at another office.

Batch boiler, great if you have the time, space and a lot of stuff to heat. Our sawyer has one and has burnt about 50t in 12 months to heat 2 farms and has enough capacity to add kilns at a later date. He could burn less, but wants to pay back the boiler as quick as possible with the RHI.

ASHP, our office is on a dry system and has kept it warm in -10 and has the potential for it to be solar driven. Friend has a wet system in a new build farm house. Always seems toasty, but well insulated with large store plus under floor heating with a woodburner for additional top up.

GSHP, in another friends cottage bored/drilled as a small plot. Been in for years and you could add solar to help run it.

We’ve had an ASHP for 5 or 6 years and think it’s great. Don’t notice noise really. Only struggles to heat the house when it’s windy (which is the fault of wind chill/draughty windows etc. One room on under floor and the rest radiators. With the £650+/year payback etc, it’s worked out well (rural, non-gas Cumbria). We have wood burner too for cold days. I figured that electricity prices won’t be allowed to climb too far and there are many ways to generate it. We have PV panels too.

At the moment with oil prices as they are then oil is probably the best option.

This ^ I’ve read in a couple of places that oil is currently cheaper than mains gas for hw and ch.

Even more info!

There’s no way of main connection, it’s nowhere near our road!

The Firewin looks an interesting one, as it can be used to heat a particular room and CH/Water. But does have a heat guard that can be raised to block room heat in the summer. Might look into this one further.

The noise problem with the ASHP is the neighbour it is close to, it won’t affect us as it would be away from the living areas. It would be within about 4 metres of his backdoor though, other than that just unsightly.
GSHP is a no go, as the land has already been excavated and landscaped, also heat recovery was crossed off due to space limitations in a dormer bungalow.
House is a new build, so no problems with insulation and why our load will be so small (9kw ish).
Already have a concrete-pad with insulated underground CH piping, electric and cold water feed to the main house, for when the biomass was supposed going outside. So this would be a prime place for the ASHP to go. Just not great visually or seemingly on the electric charges front.

Hopefully more info from the installers on its way, will be back soon….

Vertical GSHP would need little relandscaping

I’m amazed at that Phil, with your house being a new-build. Have you seen the services maps from your local supplier?

IME GSHP aren’t much better: High installation costs and full of nasty chemicals.

Just not great visually or seemingly on the electric charges front.

Some qualify for the RHI (mitsubishi, daikin) leave the Nibe crap well alone (but the calculator is pretty good; http://www.nibe.co.uk/Calculator/ )

High installation costs and full of nasty chemicals.

What nasty chemicals?

What nasty chemicals?

Refrigerants. They aren’t as bad as they used to be, but they are still pollutants.

Refrigerants. They aren’t as bad as they used to be, but they are still pollutants.

They will never be brilliant, but the system shouldn’t leak and should be tested for leaks at regular intervals in accordance with the F-Gas regs.

It’s not just leaks, it’s the whole life cycle of the products.

It’s not just leaks, it’s the whole life cycle of the products.

Considering that Refrigerant isn’t/shouldn’t be a consumable; it’s impact is fairly minor.

Yeh Mains has nowhere near.
Although it’s a New build, it’s only a new build as we demolished an existence building and building a new one from ground up

ASHP are changing quite a lot, as the market place for them is changing, and becoming more popular.
If you find a good manufacturer, and more importantly an installer, they will be able to guide to which would suit your needs better.

The system shouldn’t leak, if it does, you need to contact your installer/supplier to sort that out.
Systems that have MCS certificates, have been through a rigorous testing/manufacturing procedure.

Split systems are better than mono blocks, but it all depends on how much you want to pay.