is the nibe fighter systems cost effective?

[spotty.trog]

I have recently moved into a eco house, and we have had installed a nibe fighter 2005, which is running with a  nibe vvm 300 boiler.
We are not having a very good experience with these systems at present, and i just wondered if anyone could either confirm our findings ( as nobody ever seems to have any bad words to say about nibe systems) or if they are so brilliant, could someone please try helping us in finding  what is wrong with ours.
Firstly, we are finding that it is uncontrollable with our room stats. The system is underfloor and air source rads in upper floors.
We find that the underfloor does not stay on, unless the room stats are turned round to at least 20 degrees. this seems to be the only thing they do. Like a on/off switch that comes on at 20 degrees. then basicially its too hot! it does what it thinks temperature wise, the sensor outside just takes over and does what it thinks, and it seems to cycle at anything under 20 degrees (usually being off totally overnight)
We are not having much joy consumption wise either, as it is totally using loads of electric!
The installers have flushed the system, reset the paramaters, tweaked this an that, but we still still seem to have no control? is there a way to bypass the auto sensor outside? I dont want to live in george orwells "big borother" house... I would like to be in control of my own heat.
PLEASE HELP!! anyone have any ideas?

[dhaslam]

Not familiar with the Nobe system  but it looks like you  have  one of two  problems. 

The first problem could be just the way the system is wired.  Normally all the thermostats are wired into a simple control box which is just a multi input relay.    This just turns on the circulating pump when  any one of the rooms calls for heat.  You can test this by turning down all the thermostats  so that the pump stops and then turn one on to see if the pump starts.

The other problem  could be  a seasonal problem.  The  VM 300 has  controls the  auxiliary  immersion.   In the present weather conditions the heat pump is not going to take much heat from the air, specially at night  but the  VM 300 may be programmed not to turn on the immersion unless there is  a biggish temperature gap between the  required water temperature and the  actual water temperature.  The company describes it the control as intelligent weather control, although that may mean just about anything.   With underfloor heating it is difficult to detect any heat when the circulation temperature is below about 30C  so there may be some heat circulation when the thermostats are set lower.   You need to  be able to test the flow temperatures with a thermometer  to see if there is some heat circulating when the thermostats are turned down.


In general air source heat pumps do not work well in very cold conditions.  In normal winters the immersion is probably a reasonable alternative for a week or two when the nights are frosty but this year there has been frost at night for nearly three months.      I had planned on using an underground air feet to my heat pump for frosty conditions but this year has made me think  that an air input of aroound 20C would be preferable so I am going to make a more sophisticated air pre-heater.       

[martin]

My  googling suggests that what you have is an air-source heat pump and an electric boiler  (a tank with 2 immersion heaters!)
In my opinion ashps are grossly oversold, they don't work well at temperatures below 8-10 degrees C (which is when you actually need the blessed things), they're not at their happiest in the damp conditions in the UK, and use gobbets of the highest grade and most expensive form of energy going (electricity) - to ally that to immersion heaters makes me think "stitched up like a kipper"............that system is an eco-disaster!
 If you're on mains gas it would be loads cheaper to junk the superannuated 'fridge and electric boiler (whoever flogged you that should be shot!) and replace it with a small high-efficiency condensing gas boiler and proper heat store - or if you want an eco-friendlier solution, a woodburner with back boiler, either allied to a tubed solar hot water system for spring to autumn hot water...........

[desperate]

Sorry Spotty Trog,

but I agree with martin, I am no expert on the heat pump systems, but regarding the weather compensation baloney, I,ve yet to come across one that works as it was designed to, in a domestic property.
Personally I feel that weather compensation is vastly overcomplicated for a pretty marginal saving, it can work ok if the users understand the principle and how to program it all to perfection, BUT there is the rub, most people dont and end up overiding the thing, which ends up being worse than a simple stat and timer.

Is it possible to get one of the installers, or better the designer of the system, to explain exactly how it should work in theory, post that up here, and expose it to the collective "NAVIFOR"  brain.

Good luck

Desperate

[Ted]

See http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5383&page=1#Item_0

One of my neighbours has the self same system that you do - but allied with solar. Their installer has told them that they need to leave the ASHP on 24/7 all year round - in which case the solar is never going to get a chance to do anything useful.

My understanding is that this model turns itself off at -8C and then relies entirely on the immersion heaters - with a COP of 1 - and results in electricity usage of around 100kWh a day. I'm not sure if that temperature is the ambient air temp or the exhaust from the ASHP (which will be lower) but given the recent weather conditions it is hardly surprising that people are not happy with this particular model of ASHP.

[martin]

Trading standards job - unfit for purpose (or just plain threaten them with widespread reporting of the problems to all the local papers, BBC local radio etc. unless they give you a FULL refund and compensation, or rip out the useless equipment, and "make good" with a system that actually works properly, and you can afford to switch on!..............)

ps my temptation would be to press for the refund, then go to a company with the honesty/competency to "get it right"

[Baz]

This is just a case of not understanding the way the system works.
With underfloor heating the thermal mass is huge so unlike a gas ch system it will take a long time to respond, and if you have carpets that gets longer as they are meant to be in houses with parquet or stone floors.
 The theory is that at a particular external temperature the heat requirement is predictable so the system sets up a heat flow to match that. If you force it to provide more heat that energy will go into the 2 tons of concrete first and then leak out into the room, by which time if you have overdone it you can't turn it back.
You didn't mention the most imortant part - the controller. It probably has a feature to control the operation relative to the outside temperature. you need to make adjustments to that not the room 'stat and only make one very small change per day max until you find the correct setting.
Read the manual again. Do not expect your installer to have any idea how to set it. He did not become an installer because he has 5 A levels and a Cambridge Science degree.

[desperate]

Baz,

So,............if you dont have the required qualifications, or the weather changes quickly or the sun comes out, with that huge thermal mass, and your fancy compensator.......your cattled

Desperate

[Brandon]

I would argue that the thermal mass on the underflooor negates the need for weather compensation, as the floor doesn't have a snowballs chance (pun intended) of reacting in time.

I have to agree though, that ASHPs are the "in thing" at the moment, but basically wholly unsuitable to most domestic applications, GSHP have their place, but again they are being mercilessly (and ill-advisedly) sold into any four walls by unscrupulous sales men who have little or no understanding of building design and thermal performance.

[dhaslam]

Underfloor heating will always cause an overheating problem in south facing rooms when/if  the sun comes out.    It doesn't matter what heat source is used it is important that thermostats set time and temperature.   I have all thermostats off  during the day in south facing rooms regardless of weather, also the water flow temperature is set to the lowest setting so that when the heating is on it is at a low level.  I have used the heat pump for  nine hours at night  and six hours during the warmest part of the day so the cost is one euro for night time use and 1.5 euro  during the day but the latter only since the cold spell started in December.   I should be able to eliminate the day time running next winter if the heat store works and also if the output temperature is higher the immersion won't be needed to top up the DHW water temperature.       

[martin]

Baz, it's a case of the fact that we understand the way it doesn't work...... (at all satisfactorily or economically), the "lag" intrinsic in underfloor heating has precisely bog all to do with it........ it matters not a jot how long the heat takes to escape into the home, what is of importance is that (as I said)
"ashps are grossly oversold, they don't work well at temperatures below 8-10 degrees C (which is when you actually need the blessed things), they're not at their happiest in the damp conditions in the UK, and use gobbets of the highest grade and most expensive form of energy going (electricity) - to ally that to immersion heaters makes me think "stitched up like a kipper"............that system is an eco-disaster!"..........

Electricity is being used to heat the water and the home, in a disastrously inefficient manner - it is gross misrepresentation for any company to suggest there is the slightest element of "greenness" in the system - it ranks alongside Swindlesave as a heartless con!

The original question was "are the systems cost-effective" to which the honest answer must be a resounding "no" (from all reports, several people have discovered the same shortcomings). As a minor, and completely secondary problem, it may take a while to get used to living with the "timelag" in heating a large chunk of concrete, but there's no escaping the fact that an ASHP and immersion heaters is a frighteningly expensive way of heating it!
With the country of origin that's advertised, I doubt the equipment is exactly cheap either..........

[dinitro]

Martin, contrary to what you say, ASHP works better in the damp air than in dry air (read in HVP magazine article).

The selling point is that its better than immersion although the question is by how much.

Yes there are a lot of inflated claims and counter claims but there is a little bit of truth.....

I have weather compensation, no underfloor, no GSHP or ASHP.  Yes system response is slow, my hands do not burn on my rads which sometimes are lukewarm.  I have programmable room stats.  The system has been set that at peak occupancy there is a predefined rise.. okay not as fast as an on/off system but comfortable.

So we wear sweaters, socks, slippers..... I grew up in a house with no central heating.  We heated the room or part of the room we occupied...why heat the empty room?

I have been graphing my system using 1-wire sensors, am still expanding the 1-wire network and contrary to what 'professionals' say with charts and calculations, I still am tinkering with the wet side (valves) and control side (timers, stat settings).  Have I reached a perfect equilibrium.... no.
Can a heating engineer reach a equilibrium in 1hr on a particular day.... no

Who better than the end user, the one paying the bills, the one listening to the moans to tinker with the settings!

dinitro

[martin]

I think the whole point of the original question is being lost - "is it cost-effective? - no!
It may well take a while to get used to underfloor heating with the "lag" involved, what's important here is that it is probably costing the poor bloke £100 a week in electricity, whereas he could have the same amount of heat from mains gas at a fraction of the price........ ASHPs are NOT efficient at low temperatures (the much-vaunted "cop" figures plummet), whether the air is dry or damp........., and to add immersion heaters into the equation is completely laughable as being "green" in anyway whatsoever-however it's weaselled.......... (electric boiler-what tosh!)

[martin]

http://www.bbc.co.uk/blogs/theoneshow/consumer/2009/07/03/sale_of_goods_act_letter_downl.html

[KenB]

Spotty.trog,

Sorry to hear of your tale of woes regarding the ASHP system.

May I suggest that you compile some figures of your energy consumption, over the heating season. This will be useful evidence should you have to prove that this ASHP system is not fit for purpose. You may then be able to get some recompense from the suppliers.

As Martin says an "eco-house" which runs predominantly on high grade electricity, is a contradiction in terms.

What other options do you have?   If you have access to mains gas, then this is probably the most cost effective option for the next few years - but the price of gas will undoubtedly fluctuate.

If your eco-house has been built to the highest standards of insulation, then you should not need a huge amount of heat to keep it comfortable.

There is a German building standard which says 7 litres of heating oil/ 6m3 of natural gas (70kWh) per year per m2 of floor area.  This should be a good yardstick to compare your consumption.  My heat-leaky old 1905 solid brick house runs at about 2 to 3 times this ideal - so I have  a long way still to go. I know we are not Germany, and British builders are notorious for barely meeting minimum standards of construction - but it should prove what is possible.

Other options, other than gas,  are  wood-pellet boiler (Try 3G Energi in Melrose) or possibly if you have a suitable flue a wood fired stove with back boiler.



Ken