Green Schemes - Handle With Care.
Posted 25 November 2013 - 04:15 PM
ASHP at timing 35:38 - approach with care.
(Use your cursor to move the timer along to that point in the programme.)
Posted 25 November 2013 - 04:43 PM
Even here near Inverness, over 100 miles south of the Orkney's I have been advised that an ASHP is not the best choice, which is why I am considering a GSHP.
Add in the cold draughty 1940's house and I think she was given bad advice.
On the plus side, with the economy 19 tariff she should be able to work it to get most of the heating at the cheap rate, especially if it had been designed properly with a big buffer tank (but I'll bet it hasn't)
Posted 25 November 2013 - 05:15 PM
If you live in an area that's cold and wet a lot of the time then they're probably not the best choice, but generally they will work at around the same performance as a GSHP if properly sized. The secret is sizing the pump so that it doesn't need to do too many defrost cycles in normal use. It's defrost that kills the COP, and so causes poor performance. One odd feature of some ASHPs is that they will do less defrost cycles if run at a higher delta T (i.e. higher flow temperature). This does lower the COP a bit, but there is a "sweet spot" where the lowering of the COP by the higher flow temperature is less than the lowering of the COP by the higher number of defrost cycles would be. Worth looking at, as it one of the things that is catching out some of the less knowledgeable installers.
The other caution is for those living in exposed coastal areas, where there may be a high salt content in the air. Some ASHPs have been known to corrode quite badly when used in such an environment.
Edited by jsharris, 25 November 2013 - 05:15 PM.
Posted 25 November 2013 - 05:17 PM
Posted 25 November 2013 - 06:22 PM
"Yes, it is cold here now and for some reason we are surprised that it came so early, I guess we have been spoiled. They say that we will get some light snow today but tomorrow we will be getting 10 to 15 cms, which is early for such a large amount. Many areas particularly in the States have been inundated already and in some instances where they don't usually get snow. The temp has been hovering around minus 20 Celsius and that means burning expensive oil since the heat pump cuts out at minus 12."
That's an ASHP.
Posted 25 November 2013 - 07:17 PM
The Ecodan we're going for, for example, still works OK at -15 deg C (not a great COP, admittedly, but at least it carries on working). Add a buffer tank that can run the heating load for a few hours, and because it doesn't often stay very cold for more than a few hours per day you can still get a viable system with a simple ASHP.
Edited by jsharris, 25 November 2013 - 08:51 PM.
Posted 25 November 2013 - 07:22 PM
Posted 25 November 2013 - 08:18 PM
Posted 25 November 2013 - 09:06 PM
[snip] The temp has been hovering around minus 20 Celsius and that means burning expensive oil since the heat pump cuts out at minus 12."
I am from the same climate, but in the English - speaking part.... It gets below minus 12 so often that I take it he bought the ASHP because he is not on the gas network?
Posted 25 November 2013 - 09:13 PM
When homes were heated by gas or oil boilers, or even electric storage heaters, the majority of engineers were OK, they could use "rules of thumb" to size boilers and rads, and the tolerances were such that 99% of the time these systems worked as customers expected.
Heat pumps (of whatever flavour) are a very different kettle of fish. They need to be selected and sized, together with ancillary items, like buffer tanks, with far, far more care and attention. Get the heat pump selection wrong, the buffer tank size wrong, or the heating system design wrong, and the chances are that the system will seriously fail to meet the expectations of the consumer.
There are some companies that are up to speed with heat pump and system design, but regretfully there are stlll some companies around that simply have little comprehension as to how to design an efficient and effective system using a heat pump (and GSHPs are just as intolerant of poor system design as ASHPs).
Posted 25 November 2013 - 09:49 PM
Edited by joiner, 25 November 2013 - 09:50 PM.
Posted 26 November 2013 - 02:55 PM
Lengthy follow-up to that programme over on the other place and it's best to post this initial response...
"My first forum post, having read the content of this forum for a couple of years I finally have felt the urge to join and contribute to this thread as there are a number of assumptions being made that are somewhat remote from the reality
"I was directly involved with the installation mentioned during the BBC segment, and to be blunt they have had the wool pulled over their eyes - here are the facts.
"The pump installation was carried out under one of the Gov's energy efficiency schemes (I forget the exact name) the scope of which was limited to the grant funded installation of a high efficiency oil fired boiler or ASHP combined with the separate provision of top up loft insulation and extensive draft proofing. The grant amount allowed, where needed, for the installation of a complete CH system, where none had been present at the time of initial contact.
"Other grant schemes were running in parallel which provided EWI and other measures for hard to treat homes, as was the case with this property.
"The householder featured was informed at the initial (non technical) assessment for grant eligibility that the house was not currently suitable for being heated by an ASHP, she was also informed (and signed to accept the fact) that an ASHP was currently not the best means of heating her house at the time of the technical assessment.
"The grant application was allowed to proceed as the applicant stated that there were plans to dramatically improve the thermal performance of the house such that using an ASHP as the prime source of heat would be suitable, and that the quality of the thermal improvements made would ensure the running costs would be reasonable.
"These thermal improvements were apparently to be made by taking advantage of other grants and self funded works. The householder was informed, by a number of people that the running costs would be high until these improvements had been completed, this fact was fully understood and accepted by the applicant.
"The lady in question was portrayed in the segment as a frail, poverty stricken soul, whose only source of warmth was dependent on neighbours leaving a few twigs on her doorstep, and one who has been taken advantage of by the grant providers, the assessors and the installers. The reality is that she is a highly informed, very intelligent, very locally vocal lady who manages to keep a house and large garden neat and trim and until recently owned a number of properties.
"Mention was made during the segment that it took 11 months for the installation to be completed, blaming the installers incompetence.
"Again the reality is somewhat less entertaining.
"The entire process, from initial grant application, through the grant eligibility assessments, through the numerous site visits, through the planning process, through the materials procurement and actual installation may well have extended to some length - but the installation of the complete CH system took approximately 5 days, with a few revisits to replace some scratched rads (damaged in transit).
"The system consisted of a 6Kw EcoDan, over sized wall mounted rads, with a store, backed up with immersions along with the necessary controls etc - a simple, non complex installation.
"The sizing of the unit, and the anticipated end of project thermal performance of the house were independently checked by the local BCO department and others - a process that has resulted in numerous other very content recipients of grant funded ASHP installations in the area.
"In hindsight, perhaps the grant should not have been allowed to proceed until the promised improvements had been made to the property, that was outwith our control and the applicant was more than keen to take advantage of the time limited opportunity.
"I will leave you all to speculate as to which of the above mentioned works have not been completed, or in fact commenced."
Posted by 'Sean'.
There is a little more and if anyone wants to follow that thread...
Edited by joiner, 26 November 2013 - 02:56 PM.
Posted 26 November 2013 - 05:30 PM
Posted 26 November 2013 - 07:17 PM
If you choose to post to that forum you need to be aware that you will/may be quoted in the magazine, with selective editing in some cases. I wouldn't be at all surprised to find that the GB magazine ignores much of the seemingly genuine comment fro Sean and presents w view about heat pumps that is generally negative. This is supported by the fact that discussion of heat pumps was banned, or discouraged, on the GBF for several years. Members there were subject to moderation/editing of posts if they discussed heat pumps in fact.
Posted 26 November 2013 - 07:26 PM
If not, then the Devil will be looking for something to keep him warm when Hell freezes over.
Posted 27 December 2013 - 06:12 PM
Posted 27 December 2013 - 06:53 PM
The local authorities running these schemes are invariably poorly informed as to the technical nuances of them, just like the clients. Those trying to sell the stuff just want the grant cash, and couldn't give a stuff as to whether the system will work as promised.
The installer (in this case a sub sub contractor) ends up copping some of the blame when the system doesn't work well, which is frankly unfair, but the bottom line is that the installer is the person ho the client will see the most of, and is often the easiest person to blame if there's a complaint.