Air to Water

soundskin

For those trying to choose heat pumps. Think 5-10 years down the line

1. Will the company installing exist in 5 years plus
2. Have they a dedicated service team
3. Ask the company what is the cost of replacing a compressor, inverter card (if it has one) and
4. What are the most common faults on your heat pump (if they don't have any then they have created a miracle machine)
5. Every heat pump will be replaced someday or will get a new compressor in 5-15 years. Plan for it. It will happen.

exaisle

MENACE2010 wrote: »

Hi

we have a Airsource heatpump for 3 yrs now and I can share my experiences .. ( so far)

our Pump (thermia) has a calendar setting for the following things ..( these are our settings , by no means correct before someone jumps on my post)

Hot water
Hot generation only happens at night - 11PM - 09 Am Mon - fri , 11PM - 10 AM Sunday / Saturday to cover for sports


Heating
We have a reduced heat setting from 09 AM - 17:00 PM - 18*C , 17:00 - 09:00 its is 20*C
now here is wher i went wrong initially , its the temperature curve setting. The Underfloor heating and heat-pump provide a Climate rather than instant heat if that makes sense. (underfloor heating does not respond as fast as a radiator) to get to the achieve temperature.

You can set the temperature of the water on the heat-pump in other words you can tell the pump how hot the water should be for the equivalent temperature outside to get the temperature in the house.

initially I had the temperature curve to high = very high water temperature versus outside temperature , what meant sometimes the house "over shot " the temperature i wanted , eg 23 - 24 degrees.

After two winters i know applied a different strategy . Aim as low as possible turn water temperature low as possible , the house will get cold, now in small steps everyday increase the temperature of the water till the house is warm enough ( 19- 20*C for us) . now what is happening is that the house is "nippy" around 5PM through heatloss , but that changes in an hour (underfloor heating needs to kick in) and alternatively we light a fire in the stove if we need a heat fix.

we leave the thermostats open .. we don't use them , I have altered the flow rate of certain zones. though .. for example the downstairs bath room was very cosy , only to discover the flow rate was high and i turned it down a notch, same for the boys bedrooms . its lower as they don't need that much heat. I increased the living areas were we spend the most time.

again its taken time to get here .. you need a cold winter to tweak it to your liking

Good luck , if needed PM me ;o}

I think you might be as well off leaving the system running 24 hours a day. The difficulty in producing heat at night is that you're running the system when it's at its most inefficient (ie when the outside temp is at its lowest) so the system has to work harder (and use more electricity) and its starting from a lower temp. I'm open to correction but with warmer air running through the outdoor unit, it may need to defrost less regularly too...
I agree with having a low heat curve though...and interesting that you use the flow rate to adjust the heat in certain rooms although the thermostats do the same thing but just in a different way...

darkdave265

I put my heap pump in early last year and i can honestly say its one of the best investments ive ever made. I suppose the fact that i was using oil before, would make it easy to see my payback on my investment. My outdoor unit is a Toshiba variable speed compressor which comes with a 10year manufactures warranty and i believe its one of the best out there.

zulutango

If you're building from scratch make sure to really spend on insulation, air tightness and lowest possible u-values for windows especially. If you do that then your heating system is less of an issue, and you'll save much more money in the long run.

mark11original

Calahonda52 wrote: »

For the benefit of others, including me, can you elaborate on this point please?
Thank you

Thermia and Danfoss would not pass part L for me as not enough of kw of renewable energy produced. A wood burning stove (burns wood only) was then required. A new build must create 10kw of renewable energy

adrianm1234

halfforward wrote: »

FiOT wrote: »

My two pence, however much it's worth, is to think about who is supplying your heat pump as well as what heat pump you're getting.

A well - reviewed company with good customer service definitely won it for us between two similar heat pumps in the end. No point in having a fabulous product if there's nobody to come and see it if it needs to be fixed in the future!

Who did you go with? PM please
Trying to decide?

ME TOO pm please

rolion

zulutango wrote: »

If you're building from scratch make sure to really spend on insulation, air tightness and lowest possible u-values for windows especially. If you do that then your heating system is less of an issue, and you'll save much more money in the long run.

Well put it,Sir !
I dont know how to quiet say it...but i've seen and heard people spending a fortune off their budget in heating systems but ignoring the thermal envelope !

Doorcase

Have talked to so many people who have heat pumps and underfloor and to be honest a good majority say they would not go with it again if given the chance. I am thinking of putting it in but it seems impossible almost to pass with solar and oil

air

A lot of people put in heat pumps 10 years ago or more into houses that didn't have enough insulation. Underfloor can be very expensive to run in a poorly insulated house for obvious reasons - heat losses through the floor and wall footings as well as a higher average temperature within the house.
With a house well built to current building regulations this should not be an issue.

BarneyMc

Doorcase wrote: »

Have talked to so many people who have heat pumps and underfloor and to be honest a good majority say they would not go with it again if given the chance. I am thinking of putting it in but it seems impossible almost to pass with solar and oil

What levels of insulation and air tightness do they have?

If you can install a hybrid system of wind and solar P.V then it doesn't really matter the air tightness and the insulation , well it matters but if your energy is free it's a lot less of an issue.

In fact if you got enough wind and solar PV you can probably save a lot of money by eliminating the heat pump altogether and use storage heaters.

Hopefully a feed in tariff will be introduced in 2018 and it will make wind and solar PV a lot more viable, there needs to be grants for this also. It's ridiculous there's no grant either.

A turbine and Solar P.V is the ideal way to go. Just a 3 Kw turbine has the potential to generate possibly 72 Kwh at max production in 24 hrs. Or at 2 Kw 48 Kwh in 24 hrs.

There's a huge limit in our grid, we can only send 5 Kw max to the grid, this needs to improve.

If you really want to harvest as much energy as possible from solar PV then a tesla powerwall might be your solution, I question the economics of it.

Water John

The reality for most builds is high insulation and sealed envelope. Heating bill then will actually be quite low €4/600 per year.
Also with a sealed envelope be sure to install MHRV costing about 5K. Very little operating cost.
With those low annual running costs, the diff in COP between A2W and Geothermal doesn't justify the extra capital cost.
The use of UFH or Alu Rads is a personal choice. Certainly would not bother with UFH upstairs, just alu rads.
Set Thermostats in living area to 20/21 C. Bedrooms at 18 and can drop to 16 c at night.

Water solar heating is a complete waste of money and very poor ROI. Saves about €170/year and costs 3/5K. Just think how much hot water you actually use?

Doorcase

A much as i agree with your views on HRV i am trying to build on a budget. Have the new regulations put a end to building a good house at a reasonable price. HRV is addition 5k...its not peanuts. will be taping windows and doors and making house as air tight as possible. And does anyone know anything about completion cert ? seem to hear more about commencment notice than cpmpletion cert. Do you need it

KCross

Water John wrote: »

With those low annual running costs, the diff in COP between A2W and Geothermal doesn't justify the extra capital cost.



Set Thermostats in living area to 20/21 C. Bedrooms at 18 and can drop to 16 c at night.

What are typical A2W quotes like these days?
The difference in capital costs wasn't that different when I was buying(2011).

And I think it's worth pointing out that the capital cost isn't the only factor, you also have to consider how long the HP will last. Obviously A2W will die long before a geothermal will. Any savings day 1 could then be lost.


On the temps... If I dropped my bedrooms to that level I'd be handed divorce papers!!

Water John

Ah K you must not be cuddlly enough!!!.
Well bedroom temps can be done the other way round. 16 by day and raise to 18 in the evening.
Not sure why you say A2w will die much sooner than geo. Both are basically reverse fridges.
Because of the sealed building, HRV is required. The building and the stale air in it will not be healthy. To my mind a sealed building and HRV go together. Otherwise you will have sick building syndrome and a real headache.
I know its 5K, but consider it as an integral part of you heating budget.
I don't see it as an optional extra in this case.
I'm not anti geo, would prefer it in fact but you must have the correct subsoil not stony or shale. Just think the plug and play aspect of A2W makes it more accessible for many people. I know some poor units were sold here in the past which froze up in cold weather but I'd say most now on the market are fine.
I would have a back up dry stove for safety.

KCross

Water John wrote: »

Ah K you must not be cuddlly enough!!!.
Well bedroom temps can be done the other way round. 16 by day and raise to 18 in the evening.
Not sure why you say A2w will die much sooner than geo. Both are basically reverse fridges.
Because of the sealed building, HRV is required. The building and the stale air in it will not be healthy. To my mind a sealed building and HRV go together. Otherwise you will have sick building syndrome and a real headache.
I know its 5K, but consider it as an integral part of you heating budget.
I don't see it as an optional extra in this case.
I'm not anti geo, would prefer it in fact but you must have the correct subsoil not stony or shale. Just think the plug and play aspect of A2W makes it more accessible for many people. I know some poor units were sold here in the past which froze up in cold weather but I'd say most now on the market are fine.
I would have a back up dry stove for safety.

HRV is a must have if you have an air tight house.

Geo and A2W are based on the same tech but the A2W is physically outside and open to the elements and they still have the frosting issues where they have to use energy to defrost which means the unit has to work harder to achieve the same result as Geo. A2W also has more components to go wrong. This gives it a shorter lifespan and more maintenance.

Whether the extra initial cost for Geo is worth it is the big debate. It wasn't much extra for me as I had a relative do the digging for me so that only cost a few hundred. It remains to be seen how long the A2W units survive but cheapest isn't necessarily best is the point I'm making.

air

Geothermal doesn't really make sense any longer for new homes as the total heat demand through the year is so small that you're not going to make back the capital cost of the boreholes or trenching through increased efficiency. You would need a huge house or swimming pool or other high heat demand use to justify it now. The outdoor unit of an ASHP may have to be replaced after 10 years and you do need a secondary heat source for extreme conditions, but overall air source still makes more sense than putting a lot of capital into the civils works required for ground source.

Water John

Water to water would make sense for many rural houses with a good well supply. COP up to six, with a stainless steel exchanger. Small second borehole is all that is needed for water disposal.
Only a few do them. Would be interested in hearing on them.

KCross

air wrote: »

Geothermal doesn't really make sense any longer for new homes as the total heat demand through the year is so small that you're not going to make back the capital cost of the boreholes or trenching through increased efficiency. You would need a huge house or swimming pool or other high heat demand use to justify it now. The outdoor unit of an ASHP may have to be replaced after 10 years and you do need a secondary heat source for extreme conditions, but overall air source still makes more sense than putting a lot of capital into the civils works required for ground source.

Boreholes are expensive, I'll give you that. Horizontal pipes are not. I know they are ground conditions dependent. A few days in an excavator is in the hundreds, not thousands.

Admitting that you might have to replace an ASHP after 10 years should sound some alarm bells! How much is it to replace that?

And the need for secondary heat source adds to your capital as well

I'm not saying GSHP is always the way to go but I would recommend you get quotes for both and weigh up the lifetime costs and not just the initial costs.

How much is an ASHP today?

Heat pumps make perfect sense with renewable energy set ups, can run it for almost free, a hybrid, wind + Solar PV and in particularly when the Feed-In-Tariff returns you will sell all the excess to the grid and buy it back when you need to , if they can give you at least the night rate for electricity then you will pay back the installation a lot faster.

If you can get enough renewable energy you might not even need the heat pump....... All depends on the feed-in-tariff.

The Government need to provide grants also, but they want us consuming energy because it's too easy to tax...... though you'll be taxed on renewable energy you send to the grid also but it's going to make pay back a lot faster.

Is there a grant for a heat pump and how much ?

The Heat Pump in my EV is very efficient so I am quiet interested in air to water pumps, as a potential retrofit option.

KCross

[Deleted User] wrote: »

The Heat Pump in my EV is very efficient so I am quiet interested in air to water pumps, as a potential retrofit option.

Not sure they make much sense as retrofit as they don't work at rated efficiency if you stick with your standard steel rads.

HP's are more suitable for low temp underfloor heating or high efficiency alu rads. So unless you have either of those retrofitting a HP might not be a good investment.

Water John

Would work, as said, with alu rads.
Would want to be careful as you could end up with a high electricity bill.
Probably would need to heat a large storage tank 1 to 2,000 litres on night rate.
Run rads then on secondary loop with Wilo pump connected to timer thermostat.

An alt for such a system would be wood gasification as a heat source, fired up every second day. Then you would not need to change the rads.

air

As you say, you need a suitable site for horizontal loops and you need to factor in the cost of the pipe, connectors, pump, sand, glycol, flow and pressure gauges as well as a high speed pump for commissioning. It's not quite as simple as letting a guy with an excavator off and hey presto.
Also ground loops aren't going to give as good a COP as boreholes as they will lose more temp during the heating season. Finally remember that a ground source system will only have a COP benefit over an air source when the air temperature is below that of the ground.

You really need to have an accurate estimate of the heat demand of your home and do a degree days analysis to work out the precise running costs of each system. I'm all for ground source where it can be justified as being worthwhile.
An ASHP may require an outdoor unit replacement but a GSHP will require replacement of circulation pumps occasionally too.
With respect to the capital cost of the alternative heat source this could be as simple as a few resistive heaters - negligible cost and would last pretty much indefinitely especially if used infrequently.

Walter John, a bit of care needs to be taken with a pump and dump system like that, there is potential to create a sink hole in some ground conditions!
Also I've never heard of someone achieving a COP of 6 in practice, a pump and dump in particular would have higher pumping losses than a standard closed loop system. It would also be far more likely to involve higher maintenance with a requirement for filters and potentially more regular replacement of the heat exchanger.

Mad Lad, if you are interested in retrofitting an ASHP to an existing relatively standard home I think a simple mini split system probably makes most sense. Just use it to heat your most used room in the same manner that people use stoves etc.

KCross

air wrote: »

As you say, you need a suitable site for horizontal loops and you need to factor in the cost of the pipe, connectors, pump, sand, glycol, flow and pressure gauges as well as a high speed pump for commissioning. It's not quite as simple as letting a guy with an excavator off and hey presto.
Also ground loops aren't going to give as good a COP as boreholes as they will lose more temp during the heating season. Finally remember that a ground source system will only have a COP benefit over an air source when the air temperature is below that of the ground.

It just didn't appear to me that GSHP was that much more expensive than ASHP when I was buying. The items you mentioned are included in the quotes, the excavation usually isn't which is why I singled that out.

What is the COP difference between borehole and ground collector? In the greater scheme of things I'd say it's a small difference in running costs. In any case the ground condition itself will make that decision.

I agree GSHP will only surpass ASHP during lower air temp but that's exactly when you need it, surely?

Regardless of all that, if you have to replace the ASHP within 10-15yrs that's surely a major red flag? How much will that cost?

A compressor or circ pump change in a GSHP is not huge money.

air

It will depend on what model you are talking about obviously but I certainly wouldn't be banking on any outdoor unit lasting longer than 15 years in Ireland.
I'd suggest that your air source quotes must have been very over priced if they were similar to those for ground source.

I'm just thinking along the lines when the Feed-In-tariff is reintroduced that it doesn't really matter much if your home is air tight or well insulated, the solar PV/Wind turbine can provide free electricity to drive the heat pump. The heat pump will improve efficiency regardless. You sell the excess in Summer and buy it back in winter. It may not provide all you need but could greatly reduce the need for fossil fuel backup. Even wood stoves are not clean.

You could also dump the renewable energy into storage heaters.

A 4 Kw/p solar PV system will generate an average of 5,500 Kwh per year in Ireland.

http://pvwatts.nrel.gov/pvwatts.php

The Key is a Feed-In-tariff, the grid then becomes your unlimited free storage battery for Summer when you can't use all that energy you can generate.

air

That's a terrible argument, air tightness and insulation are important regardless of how your home is heated.

air

air wrote: »

That's a terrible argument, air tightness and insulation are important regardless of how your home is heated.

It's not a terrible argument if your energy to drive the heat pump is practically free.

If you have enough renewable energy then you can save on the heat pump and just dump that energy into storage heaters.

Water John

There is a massive capital cost to both solar PV or domestic wind turbine.
You may go with them but the vast majority would not.
The FIT would have to be very good, sadly unlikely, given our past record in RE.
With modern houses and HP, cost of space heating can be around €400/year.

air

It's far from practically free as you have to invest the money in the equipment in order to harvest the energy. Also the manufacture of the equipment generates carbon and it would be far better to export excess electricity to the grid than squander it needlessly through poor insulation or air tightness.