Air Source Heat Pumps

richardc1983

Geotherm wrote: »

Should really go for max 10% undersize for best operating and money saving.

Fair enough matey you know best. I was just under the impression it is best to have the extra duty. Couple of KWs over wont harm.

lovesgshp

richardc1983 wrote: »

Fair enough matey you know best. I was just under the impression it is best to have the extra duty. Couple of KWs over wont harm.

Never the best solution to oversize. Why use more energy when it is not really needed?

richardc1983

Geotherm wrote: »

Never the best solution to oversize. Why use more energy when it is not really needed?

As the inverter compressors will adjust to the load required and having a few extra kw's (just few not talking massive oversize) you have the extra capacity required for extreme temps.

My air con system at home is oversized by about 3kws, majority of the time it just ticks over once indoor temps are satisfied however at start up if a very cold day with have extra capacity to reach the set points quickly.

henryc148

Hello Samtheman,
You must be lucky or you are selling Heat pumps?
I have one ,an Ecodan. We were mis sold this awful contraption.
Although we are not in our home (as we can not live there at present) I tested the running costs.
All windows and doors closed, nobody in the property i.e. not opening and closing doors, I sealed the windows with tape and any gaps covered them with tape as well.
Over a 24 hour period I calculated a cost of £6.45p equalling a quarterly cost of approx £600-00 I don't think that cheap!
This was heat only in April and both floors did not heat up!
Judge for yourselves. A word of warning thought BE CAREFUL
BE VERY CAREFUL there are companies out there whom would sell anything without care and dont don't give a dam. And dont think you safe with an accreditted company, we got this from a so call accreditted company they do not even acknoledge that we exist.and forget it, It's worth the cost of this e-mail .... NOTHING

Cardew

henryc148 wrote: »

Hello Samtheman,
You must be lucky or you are selling Heat pumps?
I have one ,an Ecodan. We were mis sold this awful contraption.
Although we are not in our home (as we can not live there at present) I tested the running costs.
All windows and doors closed, nobody in the property i.e. not opening and closing doors, I sealed the windows with tape and any gaps covered them with tape as well.
Over a 24 hour period I calculated a cost of £6.45p equalling a quarterly cost of approx £600-00 I don't think that cheap!
This was heat only in April and both floors did not heat up!
Judge for yourselves. A word of warning thought BE CAREFUL
BE VERY CAREFUL there are companies out there whom would sell anything without care and dont don't give a dam. And dont think you safe with an accreditted company, we got this from a so call accreditted company they do not even acknoledge that we exist.and forget it, It's worth the cost of this e-mail .... NOTHING

https://forums.moneysavingexpert.com/discussion/2968958

lovesgshp

henryc148 wrote: »

Hello Samtheman,
You must be lucky or you are selling Heat pumps?
I have one ,an Ecodan. We were mis sold this awful contraption.
Although we are not in our home (as we can not live there at present) I tested the running costs.
All windows and doors closed, nobody in the property i.e. not opening and closing doors, I sealed the windows with tape and any gaps covered them with tape as well.
Over a 24 hour period I calculated a cost of £6.45p equalling a quarterly cost of approx £600-00 I don't think that cheap!
This was heat only in April and both floors did not heat up!
Judge for yourselves. A word of warning thought BE CAREFUL
BE VERY CAREFUL there are companies out there whom would sell anything without care and dont don't give a dam. And dont think you safe with an accreditted company, we got this from a so call accreditted company they do not even acknoledge that we exist.and forget it, It's worth the cost of this e-mail .... NOTHING

A few questions:
Was the 24hr period from start-up?
Room temp setting?
Size of house, pump size, outside air temp?

rogerbanana

has anyone thought of useing a small tank, say about 25litres, installed inside the property, connected in line with the cold water inlet to the DHW tank?

---

this would raise the inlet temperature (it would be room temperature) instead of allowing the outside temperature to affect the performance (temp. raising requirement) of the system?

also, whats the latest on the RHI and associated payments?

giscool

Hi I am new to this forum, but I have read this whole thread and have found some useful information and encouraging information about ASHPs but not the answers to my confusion.
I have been getting very different solutions offered from providers of ASHP systems in terms of size and would be very grateful for some views.
Property:
SW England, 1980’s 4 bed brick cavity insulation, 150mm loft insulation, 10yr old double glazing throughout, integral double garage (ceiling insulated). 142 m2 heated floor space (conservatory not included). No gas available. Electricity is two rate tariff of 4.5/9.5p currently, most recent consumption 23,000kw pa and cost of about £1600 pa for all electricity.
I want to replace my 20+ yr old storage heaters and install a new wet radiator system with ASHP which I would also want for DHW.
1) I have had a SAP report done by an energy consultant who has provided a figure of 446 watts as the “heat losss coefficient”. Energy consultant says multiply coefficient by the temperature difference between desired room temp and lowest outside air temp, usually 21 and -5. 26 x 446 = 11.6 KW. This does not include DHW. He says I will not be happy with ASHP and should consider linking to additional source eg wood burning stove with boiler.
2) Radiator sizing web site taking into account dimensions, window area, insulation, etc etc gives radiator size for property of 9KW assuming ~56 degree temp differential.
3) I have had quotes from installers varying from 8.5Kw to 16 Kw for stand alone ASHP.
I hear that you should not oversize but cannot see how you can avoid it if you design for -7 or even -5 when the average temperature is 7 and sub zero temperatures occur for less than 5-10% of the winter. How do you take into account DHW demand? What temperature do you design to? Which is best variable speed or fixed speed HPs?
Is a wood burner a good option to work with an ASHP assuming it would be lit for 3-4 hours per day. How you do factor this into the HP size?
I don’t really want the upheaval and cost of under-floor heating installation. How do you correctly size the radiators assuming a flow temperature of 45-50. One web site gives radiator performance figures for different temperature differentials with coefficient of 1 at 56 deg. They don’t give figures for a difference of only 24-30 degrees (for ASHP temps) but if a linear relationship the coefficient would be 0.4. Does this mean that to size radiators for an 11.6Kw heat loss I would need radiators equivalent to 29 kw output (11.6/0.4)?
I am getting quotes of £17-20K. I am certainly not going to invest that sort of money when faced with so many uncertainties over sizing and performance. Am I better off just replacing the old storage heaters with new ones?
Thanks in advance for your ideas

Cardew

jeepjunkie wrote: »

For example this is a very old large cottage with 9ft/10ft ceilings and is maintained at 21c regardless with the ashp barely ticking over hence the bulk of the year is £20-25pm to run. All we have is CWI/Loft Insulation/DG sash windows and good doors so no drafts.

QUOTE]

Surely it is pertinent to point out that you had your system fitted recently - i.e. after winter.

Winter results will be a while away yet but spring/summer/autum costs us £20-30 per month for heating and hot water. Hard to tell exactly as I know what we paid monthly before ASHP

Cardew

Hi JJ
I was making the point that any heat pump should work well when used in Spring and Summer when outside temperatures are normally over 10C or 15C and the inside temperature of houses only requires raising a few degrees.

The 'acid test' will be in winter which is when most problems occur - icing up etc.

It may well be that your system will function well in winter(and I hope it does); but as shown in the Energy Saving Trust 12 month trial of 29 systems - many had very poor performance.