do you have air to water heat pump

caitb1

do any of ye have air to water heating system?? iv seen some things in other threads and i have a few questions about it

1. with air to water do you also need oil or solar panals or other heating source?

2. how do you find it works well in really cold weather, iv read that it doesnt work well below 2 degrees and doesnt work at below -15 degrees, did ye have it in the bad winters of 2009 or 2010 when it was -17

3. how high is your electricty bill with it?would you be spending more if you had oil?

4.is it worth it?

mike_2009

Don't have one yet but have read up on them a lot:

1. Depends on use case, just for under floor heating you should be ok if sized appropriately but if you need hot water too then this reduces COP and you might benefit but additional renewable sources of heating. Solar Thermal (drainback preferably) or Solar PV & Sumamp PV might be worth checking out if your roof faces south / off south ideally.

2. The issue is between 0 and 4 degrees the defrost cycle kicks in a LOT. Reduces COP significantly. This isn't the case as much in Scandinavian countries as much as milder countries like ours. Check out the following study for a good analysis:
Google this title as I can't post URLs yet:
"Influence of Outdoor Air Conditions on the Air Source Heat Pumps Performance"

3. The great thing about heat pumps is the COP factor so you get more for your buck. I know of increasing efficiency in gas boilers over the years but not heard much about oil ones. I don't have any costs but I know one person runs his under floor heating system all the time to balance the temperature around the house even when the ASHP isn't operating. The main issue is cost of electricity and the increasing surcharges (public service obligation levy and renewable levy). They are good technology. Look at TCO also, if not a monoblock you'll need a service engineer to deal with the refrigerant. Factor than into your running costs too.

4. I think it's a serious contender - you can get combination ASHP and MHRV units but I wonder if they are as efficient as separate units and you didn't mention a need for MHVR. There are lots of options of course to heat a home but much of your heat demand is going to be for hot water which needs higher temperatures, that's where ASHP doesn't alway shine. There are those Energie panels that are specifically designed to generate hot water, there was one thread on there somewhere that showed the calculations of running it over 1-2 years that might prove interesting if you can find it....

I hope someone else here will give you more concrete experiences from using a live system shortly.....

ferryman35

1. You don't have to have another energy source....but the size of the heatpump you use will depend on how much heat you need, and if you go above a certain size then you would need a 3 phase unit. However, most domestic houses (new builds at least) will be fine with single phase units.

Of course, some systems will allow you to combine other energy sources, and some will then choose the most efficient source of energy at the time for you. The sove is the best one I see.....virtually every new house has one but very few use a boiler....a boiler stove could make a very useful contribution to the load especially when the demand is highest, and isn't all that more expensive to add in.

2. Some will work down as low as -22'C but the colder it gets the harder they have to work. They all have back up immersions which supplement the heatpump at times of extraload (but the immersions would kick in at different times on different heatpumps). That's what Mike means by getting a lower COP in cold weather. Cold and dry is one thing, cold and damp is another - so -10 and 'dry' might not be as difficult as -5 and damp. In our weather it might only be 1/2 days per year that some systems would need the help of the immersions.

3. The first step in reducing your bills is good insulation and good airtightness (they go hand in hand) and attention to detail in this regard is important. Air source does well in our climate because our weather is relatively mild most of the year. A ground source pump costs a little more to install the first day but is even more economical to run. You can get a comparison done between what you would expect your house to cost on a heatpump vs different technologies. But the price of oil has swung so dramatically in the last few years you need to keep this in mind....in the worst of the recession heating oil was costing €1 / l - its probably at least 25-30% cheaper at the moment.

4. if you take the time to figure it out it most probably is. You don't have to get bogged down in the science but it is worth considering what a heatpump and the alternatives will do, weigh up the capital cost and the running costs.

Gas boilers have come along way and now are modulating and will condense (depending on how they are set up). Oil boilers have not come as far in Ireland as quickly but that is beginning to change. The technology is also changing for heatpumps and is now heading down the road of modulating heatumps as well!

Belkin1975

Can anyone confirm if building 70m from the sea if the salt water affects the outdoor unit?

gooner99

I'd be interested to know this also. One thing I can say is that the salt water has played havoc with the calipers and disks on my cars. So my guess is that it would affect the outdoor unit.

ferryman35

Some units have a what's called a 'bluefin' coating that protects some components at least from corrosion. 70m is very close to the sea so you'd have to assess the product suitability to your site more carefully, but it's not impossible. Good chance you'd never have to worry about defrost!! A lot would depend where on the coast you'd be talking about too.