Heat Pump Buffer tank

DonSke

HI,

Im looking at getting a heat pump into my house to replace expensive LPG gas boilers. I will retain the boiler to boost the temp of the water when required because the house does not have under floor heating. I am re[placeing some of my Rads with Dimplex smart-rads and hoping that in other rooms the low temp water from the heat pump will be enough to keep the room warm and the rads have thermostatic radiator valves.
My question is, should I get a buffer tank so that I can store heat produced on night rate electricity or is a buffer tank only for houses with UFH?

Thanks

fclauson

My first question is why are you replacing ?

Heat pumps are expensive - you might be better off spending the money on insulation and fabric improvements

just a thought

DonSke

Yes. Agreed. But walls are pumped and there is 300mm in the attic and my gas bill was €5500 last year (its a fairly big house with a lot of large windows). Cant get mains gas so only option is LPG or change to oil which is a step back.

Carlow52

DonSke wrote: »

Yes. Agreed. But walls are pumped and there is 300mm in the attic and my gas bill was €5500 last year (its a fairly big house with a lot of large windows). Cant get mains gas so only option is LPG or change to oil which is a step back.

What's ur estimate for the esb bill for the heat pump.

Instead of the euro cost what was the kWh purchased.

What efficiency are the lpg units?

I dont think the heat pump is the answer and neither do I think a buffer tank from nite rate is the answer

You need to start with a whole house heat requirement and work back

BryanF

DonSke wrote: »

Yes. Agreed. But walls are pumped and there is 300mm in the attic and my gas bill was €5500 last year (its a fairly big house with a lot of large windows). Cant get mains gas so only option is LPG or change to oil which is a step back.

why not start by getting a BER carried out, preferably by someone who is also an Architect that can assess your home and work with you on a list of measures that can reduce your energy spend. your spending a fortune, invest some money into why that is, then invest some money in reducing this! start with a read here

changing the heating source without a full assessment of why its costing over 5g!! to heat you home is not wise;)

btw how come your opting for a heat pump?

Outkast_IRE

you are defo going about this backwards, i wouldnt think a heat pump/ buffer tank is the answer in most retrofits also with the rads sized for a normal gas or oil system they would all be undersized for a lower temp heatpump situation.

Get a professional in and get him to calculate the best value for money savings you can get done.

Also when you say heat pump, are you talking about an air to water heatpump or are you getting bore holes done , or large garden dug up for loop , IMO none of these are a good option in a house with so much heat loss.

As i said get a pro in to calculate best way to spend your money in order to help retain heat.

fclauson

BryanF wrote: »

why not start by getting a BER carried out, preferably by someone who is also an Architect that can assess your home ....?

Also - for a couple of hundred euro get an air pressure test done - you will be amazed :mad: just where the leaks are - and reducing this will also save considerable money -check out a post by me about 6 months ago on this

DonSke

I have got the BER done. Its C3. I have calculated the whole house kWh requirements. Its 43500kWh. I have calculated the cost of alternative systems and heat pump is defo the only viable options (based on consultation with an architect and a heating consultant). I'm getting it done tomorrow so bit worried now with the doubt here:(

Stove Fan

DonSke wrote: »

I have got the BER done. Its C3. I have calculated the whole house kWh requirements. Its 43500kWh. I have calculated the cost of alternative systems and heat pump is defo the only viable options (based on consultation with an architect and a heating consultant). I'm getting it done tomorrow so bit worried now with the doubt here:(

I dont think it will heat the rads to the required temp or heat the house:( Ordinary sized rads are sized in your home for hotter water to get the heat required.

An air to water heat pump works well with low water temperature underfloor heating and very good insulation and airtightness. I would consider fan assisted radiators to help. These work at a lower temp and improves the efficiency rating of the heatpump.

The thing though is vastly spend the money on insulation.

This is the sort of thing I'm thinking. There are many others. I'm sure you could get reccommendations on the ones to use.

http://www.dimplex.co.uk/products/renewable_solutions/smartrad/index.htm


Stove Fan:)

PeteHeat

Hi,

You may have the wrong "experts" advising you by that I mean they may feel comfortable with previous installations of heat pumps or that heat pumps may be the only type of products they sell, one of the reasons I always ask people do they want a salesman or a tradesman to advise them.

The salesman is there to sell his product the tradesman is there to advise on the best system to suit the home, the tradesman has the better chance of selling one of his systems or just upgrading what the consumer has in place, also the tradesman must stand over the system, salesmen come and go.

Your heating system pipe work, rads and controls were designed for a system with high flow temperatures, unless there is a major revamp being undertaken I believe all indicators are that a heat pump is not the way to go.

Electricity is an expensive way to heat a house unless the house was originally designed to match a heat pump, your radiators were designed to heat your home with flow temperatures of 70c how can you hope to get the same level of heat from flow temperatures of max 40c?

The higher the flow temperatures you ask of a heat pump the lower the COP which is why heat pumps are best matched with underfloor heating as the flow temperatures can be as low as 30c.

From what you describe a more honest system would be to install a large storage tank and fit it with a bank of immersion heaters because only some of your radiators are being changed which means the remainder will still need the high flow temperatures to heat the rooms (COP 1).

With heat pumps it's an all or nothing job everything must match the main heat source (heat pump) we know all your rads won't match, the energy rating on your house is not even close to what I would like for a heat pump.

Also you must remember the night rate electricity is exactly that limited to between certain hours at night so the best you will get is possibly a warm house when everyone is in bed, combine that with the high rate of heat loss from your home you will have to operate either the heat pump or the gas boiler during the day.

From the system you describe I would expect a very high ESB bill combined with a high LPG bill, the only thing I see in favour of what you describe is they are leaving the LPG in place.

I haven't checked lately but my experience of LPG is it's one of the the most expensive fuels next to electricity you can use for heating, and neither products are anymore environmentally friendly than oil.

Maybe it's time to re-think before any work starts.

.

DonSke

I took the plunge and got the system installed!
So far its working very well. The house is warm all the time at half the cost of the LPG, which was used to heat the house only when we were home. Remains to be seen what effect really cold weather will have and if system can handle it. I will be providing further info here on my experience but so far it seems heat pumps are not limited in application to people with underfloor heating.

refco

good to hear positive feed back for heatpump just wondering what size house and what make and size heatpump you went with also did you get a heatpump with 40 degree flow or one with 60 degree flow and is it doing dhw
Currently sizing one and sizing it @11.5 kw with 60 degree flow @outside air temp of -5 the sales are claiming cop of 4 at -5

DonSke

Danfoss AQ, 14KW, Nominally 40C. 3000sq ft. Also heating 300L DHW tank but as just 2 in the house not consuming much each day. Heat pump worked well on 0C day last week but consumed €13 in electricity that day!.

mark2003

What temperture does the house reach to when its 0 degrees outside.€13.5 sounds very expensive. A good insulated house would only cost €2 to heat the houseto 20 degrees. You should get an airtightness test done quickly because if you get cold weather like last year,the heat pump will fail to heat the house,

DonSke

House is at 20C. I consider €13 a bargin compared to LPG. Even if weather gets cold stall have LPG to call on if needed. Can ever see it getting below €10/day in this particular house. One room in the house is 75m3!!

DonSke

Have the heat pump exactly 1 year now. 2011 heating cost was almost exactly €5000 (it was a very cold winter). Now have walls pumped and 300mm in attic and Danfoss heat pump. Total heating cost for 2012 is €1821. This is all heating and hot water for one year. Saving is €3180 per year. However I have a €15k loan which costs me in repayments and intrest. I will be payinig for the system for 5 years and after that will be in the black. HOWEVER, my home is always 20-21C so the comfort of my home has improved dramtically.

steifanc

are you using a night rate ?

mp31

DonSke wrote: »

Have the heat pump exactly 1 year now. 2011 heating cost was almost exactly €5000 (it was a very cold winter). Now have walls pumped and 300mm in attic and Danfoss heat pump. Total heating cost for 2012 is €1821. This is all heating and hot water for one year. Saving is €3180 per year. However I have a €15k loan which costs me in repayments and intrest. I will be payinig for the system for 5 years and after that will be in the black. HOWEVER, my home is always 20-21C so the comfort of my home has improved dramtically.

Wow that is excellent news and reassuring to hear it works so well ... congrats on the success of the project.

If you don't mind me asking:-
What/how did you get the original idea of a heat pump?
How did you make the choice of the Danfoss?
What type of walls do you have and what insulation material did you fill them with?