Heat pumps etc.

[GordonTarling]

Trying to decide on a heating system for our recently purchased bungalow. There's no gas in the village and we desperately would like to get away from oil, so have been considering air source heat pumps. We've concluded that these heat pumps are probably best when allied to wet underfloor heating, but we don't really want to install that, for numerous reasons. So, we're looking at using the heatpump with radiators - they'll all be new and sized to suit, but we've read conflicting reports about them. Some say they need to be oversize, but will work just fine, whilst others pretty much say to avoid them! Has anyone any real life experience of using rads with air source heatpumps? We need to make a decision ASAP. Thanks!

 

[PXW]

I've only looked at air source heat pumps for swimming pools, but was put off by the relatively low efficiency at low air temperatures; the impressive numbers quoted (4 or 5 to one) were simply not available below about 18 degrees air temperature and they basically didn't work below about 5 degrees. However, that was pool heaters rather than domestic heating, so while the technology is I think the same the products may be better - worth asking about efficiency at different ambient temperatures though.

If you don't want oil, have you considered LPG? Tanks can now be buried and have telemetry for automatic scheduling of deliveries etc.

 

[mattc]

try this forum greenbuildingforum.co.uk and use the search facility (you dont have to be a member to search). Look for "ASHP" or for "heat pump". the stuff some of the guys on that forum know leaves my brain frazzled. once you have had your brain fried you will come away with 2 key themes - make your house airtight and insulate. Good luck!

 

[PXW]

Also, I suspect the reason people are sceptical about heat pumps and rads is that the heat pump is likely to produce a plentiful supply of warm water but will have challenges getting that up to rad temperatures. iirc rad run significantly hotter than underfloor wet systems, so it may be you air source pump cannot generate that temperature - hence some advice that you need oversize rads (because they will only ever be warm, not hot)

 

[Shacks]

As I understand it, heat pumps do not heat the water to a high temperature. This is why it is recommended to have it under the floor. It needs a lot of pipe work to carry the (not very hot) water around the whole floor area, as the whole floor has to become the radiator/heat sink. If you use radiators, you will need very large radiators because the water in them is not very hot.

If you were to go away on holiday in the winter and turned the system off, on your arrival home, the house would be very cold and it would take up to a day to get the house warm.

These systems consist of a lot of hardware, one of my friends has it installed and it is enormous, it has IMHO far too many parts to potentially go wrong and is very expensive to install. Your average plumber won't have a clue how to fix it.

Use a wood burning stove or 2. If you can supply your own wood, they cost nothing to run. At a guess, I spend about 2 weeks in total over a period of time in the summer chopping up the wood and storing it for the winter and being retired I use mine for about 14 hours a day.

 

[ItalianTuneUp]

Sounds like over engineering to me, dubious use when cold (when you need it) and problematic if, or more likely when it breaks down.

 

[flango]

I had this exact same problem, we have only fairly recently got gas in our village my solution was one that would definitely upset the greenies I went for an automatic coal fired boiler similar to the ones HERE being in the mining business I got free fuel but even so it was very economical only burning approx 3 tonnes per year. These can now burn wood pellets as well making them even more cost effective, only downside is you need to remove the ash every few days.

I've since switched to gas mainly for convenience as with working away from home a lot I cant really expect SWMBO to load 25Kg bags of coal into the hopper If I found myself in the same position again with no gas I wouldn't hesitate to install another far better than oil, lpg or heat source pumps.

 

[ItalianTuneUp]

Yes coal tends to make greenies hyperventilate due to increased levels of plant food output.

They also hate the idea of fracking for gas, despite half the plant food output.

I think if it comes to the crunch and the lights go out, greenies can keep their windmills, and the rest of us can stay nice and warm with our coal, gas and nuclear.

 

[del320]

I would be glad to hear the opinions of others, but while gas and electricity prices continue to rise inexorably, our domestic heating oil cost has come down by 12% over the past year.

Having looked at heat pumps, it's the old story of huge capital outlay and probable upheaval for dubious returns. Underfloor heating really only works with new-builds. Would you want to tear up your floorboards and lay a screed?

We also have a stove and unlimited supplies of wood.

 

[Piff]

Underfloor heating works ok with a joisted floor.
Either aluminium trays to carry the pipes or celotex between joists, pipes clipped to celotex & then filled between celotex & floor boards with a 25mm dryish screed mix.
There are also "thin" systems to go over joists - google nu-heat.

Have to agree that ASHP works best with underfloor heating. I believe there are low surface temperature radiators designed for use in places such as care homes/schools.

We put in underfloor heating downstairs & upstairs & it is run 24 hours/day, just controlled on individual room stats. The place is constantly warm and although we don't yet have final figures for the year, it's looking like it's cheaper to run than our previous abode where we had gas.

Don't forget for ASHP & other "green" systems there is the RHI where the gov't are offering to pay you. It looks like I could be getting in the region of £1000 per year for the next 7 years which helps with the higher installation cost.

Critical - as mentioned above - draft proof & insulate as a priority.

As for complicated systems, ours initially looks complicated, but when you analyse it is essentially several simple systems.
There is a pump & 2 separate zone valves on the heat pump. One zone valve for a buffer tank for the underfloor heating controlled by a time clock & the master heat pump controller. The other zone valve controlled by a separate time clock for the hot water cylinder.
The underfloor heating has a separate pump for circulation.
Heated towel rails have another pump & time clock
If there were any radiators, again these would have another pump & time clock.
Finally we circulate hot water with another pump & time clock.

Have a look here for independent energy cost comparisons.

 

[GordonTarling]

Thanks for the replies chaps!
We know that a heat pump will only give water at about 50C, but it appears that by sizing the radiators correctly, this should be sufficient to heat the house. The problem with researching things like this on t'interweb is that everyone wants to sell you their product, so you don't get to hear the negatives.

PXW - yes we thought about LPG, but it's more expensive than oil and we don't really want either a big tank in the front garden, or a big hole dug for one.

Shacks - It seems the key to efficient use is just to leave it running all the time and insulate well. We will be installing two woodburners as well, so these should take a lot of load off the main system.

flanaia1 - have ruled out both coal and pellets, due to storage and health considerations.

del320 - I hear you about the cost of oil, but who knows what might happen in future? We'd rather not rely on it if at all possible. Yes, underfloor heating and heat pumps seem to be the almost perfect combination, but not easy to do in an '80's bungalow with solid floors. We did visit a nearby new-build with this system and it was all very neat and professionally done, but that would be difficult to achieve in our house.

We're planning to have at least 4kW of PV solar panels on the roof, so these should help offset a large proportion of the running cost of a heatpump. We also know that insulation is key - the walls already have cavity wall insulation, so difficult to improve that without huge expense. However, the loft insulation is down for an upgrade when all the building work is complete - pointless doing it before. I'd dearly love to rip up the floor screed and lay some decent insulation under a new screed, but the cost of doing that is beyond our means right now. I guess the answer is to get some sort of performance guarantee from the company doing the install and then hope they don't go out of business!

Piff - Thanks for that - the link is very handy! Not bothered too much about complication - Concorde was far more complicated than any heating system!

 

[marty359]

I just typed up a lengthy reply but it timed out and I lost it


You can get high temp ASHP's Gordon, think they supply water up to 80degrees.

The thing is to get them sized properly I've done some work round a massive house that has zoned under floor heating and he says it works really well. It's a 3 phase 40kw jobby Yet in a 4 bed house round the corner from me the owners not a happy chappy as his electricity bill was £4k last year and his system struggles to reach 19d throughout the house.

 

[Piff]

Mine came with a g'tee from the supplier of the kit that it would work.
The first supplier I selected for the underfloor started introducing disclaimers in their quote so we switched supplier even though we had paid a small deposit.
We used an approved installer. You have to have use MCS accredited people to get the RHI payments.
I have found Nu-Heat to be very good, both in design & aftersales. They even sent an engineer for a day to check the system through when I complained that we were overshooting the requested heat level.
That's been our only issue. I don't think Nu-Heat believed the level of insulation & air tightness we were going to achieve and over designed their system. Initially one of the parameters in the main controller was set too high and we initially requested 18 degrees, when I returned the following day it was like a sauna at 25 degrees.
Parameters have been changed but we are still overshooting. We currently request 19 degrees and according to the controller we are getting 22 degrees.

We expected warm feet with the underfloor heating, but because it runs (on room stats) all day, the floor is only slightly warmer than the room as it is only topping up heat loss, not heating the house from cold.

 

[GordonTarling]

Useful replies, thanks chaps!

Marty - We've all been there with timeouts! I did briefly investigate high temp ASHP's but concluded that they are working harder and using more energy to achieve those temperatures, which is a less desirable aspect from out point of view. This 4 bed house where the owner is not happy - any idea what sort of system he has?

Piff - Yes, looking for some sort of performance guarantee from whoever supplies and fits the system. We've heard of Nu-Heat, but it seems they specialise in underfloor systems and we've pretty much ruled that out.

Just about concluded now that with two log burners and a suitably specified ASHP system with radiators, we won't be cold, providing we insulate and draught-proof as much as we can.

 

[ItalianTuneUp]

As this subject interests me but I currently know virtually nothing about costs, implementation details, gotchas etc, could someone knowledgeable give an idea on the following, regarding heat pumps / underfloor heating etc:

- upfront costs
- total costs to implement a properly working system over its projected lifetime
- how many systems actually achieve stated lifetime
- any problems encountered / reliability
- costs to repair / difficulty finding qualified repair personnel
- costs compared to using an existing gas fired central heating system, based on today's gas price (yes, I know gas price will go up or down: e.g. fracking could reduce gas prices if plenty of gas found etc)

Costs should reflect all the costs of buying components, fitting, running costs including any government subsidies/payments, if any)

I understand this may be difficult, but a ballpark figure would be useful to get an idea of any possible savings.

Edit:
Also, if there are any health issues to be aware of: e.g. what happens to materials like laminate flooring / plastics / pvc /glues used etc when heated from underneath?

 

[Satch]

If you are hoping to tap into the Renewable Heat Incentive which applies to off-grid residential properties after 1 April 2014, move quickly to get signed up.

It is a prime candidate to be crimped because it is part of a badly thought out policy and pretty soon that will be splashed all over the press. (Landed gentry to be paid to heat their country piles by levies on freezing pensioners!!!)

It is bonkers: being paid real money by other energy users to burn woodchips shipped from North America or wood from your own estate at a level that with a large residential property can easily result in a £10k per annum excess over fuel cost

Applies to heat pumps as well:

Ice Energy - Renewable Heat Incentive (RHI): Get paid for the heat you generate

 

[ItalianTuneUp]

It sounds crazy and unjust on the poor, especially pensioners.

 

[balge]

It sounds crazy and unjust on the poor, especially pensioners.

Especially when you realise that while we are doing it the rest of Europe doesn't seem to be quite so concerned

Germany's clean energy drive fails to curb dirty brown coal | Reuters

Dirtiest Coal?s Rebirth in Europe Flattens Medieval Towns - Businessweek

We are closing perfectly good highly efficient coal powered stations while they are expanding the use of brown coals, even lignite and peat...

Ever get the feeling you've been conned?

 

[ItalianTuneUp]

Yes, I do feel we have been conned:

https://www.youtube.com/watch?v=JUdgiehz9dU

 

[74merc]

Useful replies, thanks chaps!

Marty - We've all been there with timeouts! I did briefly investigate high temp ASHP's but concluded that they are working harder and using more energy to achieve those temperatures, which is a less desirable aspect from out point of view. This 4 bed house where the owner is not happy - any idea what sort of system he has?

Piff - Yes, looking for some sort of performance guarantee from whoever supplies and fits the system. We've heard of Nu-Heat, but it seems they specialise in underfloor systems and we've pretty much ruled that out.

Just about concluded now that with two log burners and a suitably specified ASHP system with radiators, we won't be cold, providing we insulate and draught-proof as much as we can.

The only problem with this is that the stoves will need a fresh air feed into the room to satisfy the latest regulations. We installed one recently and were left with 10cm hole in the wall! I know that some stoves can have a direct fresh air feed plumbed into them, but I don't know if that is sufficient.