Air to water system

marcobass

We have an A rated house of 240 square metres, it's a detachable bungalow built in 2014. We currently have oil heating with radiators, no underfloor heating and also have a solid fuel stove that can heat our water for the rads, we are looking into changing to an air to water system. Has anyone done similar looks for pros and cons and general thoughts on air to water system?

Lenar3556

https://www.boards.ie/discussion/2058432169/air-to-water-system

I’d be slow to go down that road.

Radiators may not be large enough for lower flow rates on A2W.

Electricity supply to house may be undersized. You really need 16KVA.

It will probably be more expensive to run, when you consider current kerosene and electricity prices.

marcobass

Much appreciated....they forecasting a 13kw system and they think that radiator size are ok....thank you.

ongarite

What heat pump are they recommending to install? Is it a R290 refrigerant model which is better suited to radiators as it has higher flow temperatures?

Lenar3556

https://www.boards.ie/discussion/comment/124207096#Comment_124207096

Your high insulation levels will be favourable.
What is the total cost?

Cyrus

https://www.boards.ie/discussion/comment/124206864#Comment_124206864

why would you need 16kva? for a heat pump?

sydthebeat

https://www.boards.ie/discussion/comment/124207194#Comment_124207194

Quote possible that would be required where you have a heat pump, electric shower and electric cooker.

High load + instant demand = higher risk of tripping out

Lenar3556

https://www.boards.ie/discussion/comment/124207194#Comment_124207194

Because of the demand. A 13KW (output) air to water heat pump can be a 7KW electrical load at times. That’s 30A alone.

A standard 12KVA supply is rated for a maximum of 52A continuous. So there wouldn’t be headroom for an electric shower, induction hob or effective EV charging for example.

Cyrus

https://www.boards.ie/discussion/comment/124207251#Comment_124207251

That heatpump sounds over sized for a start, our house is 192 sqm and i think we have a 5KW samsung system that never goes over 2.5KW load. Id be amazed if you needed 7kw to heat a 240sqm a1 rated house. Also why would someone with a heatpump / modern house have an electric shower, thought they were gone since the 90s?

Wearb

https://www.boards.ie/discussion/comment/124207366#Comment_124207366

I dont think the op stated A1, just A. Also the house is 25% larger than yours.

Cyrus

https://www.boards.ie/discussion/comment/124207390#Comment_124207390

Ok sorry thought i read A1, yes its 25% larger, would that require 200% more heat output? And electric showers? are they still a thing?

greenbin2

I love my electric shower, use it all summer

I only use it on the lower power

But I am a miserably cheap person

marcobass

Hi guys

No electric shower need, also cooker is gas....only oven is electric.

We do not use too much power through the day and we have solar system for 4.5kw... once out of the winter tunnel quiet self sufficient in the power side.

We just worried about do a 20k( new grant coming inj)ob on air to water and the house will not be warm- insulation seem good enough,is a passive house and h-l-i is just below 1.9

Cyrus

https://www.boards.ie/discussion/comment/124207483#Comment_124207483

whats prompting the move? 20k will buy a lot of oil, and heat pumps work best with UFH which you dont have.

Water John

The only reason to make the switch would be for environmental reasons. With the good grants, it is the optimum time to consider it. A priority switch would solve any load issues. I'd be getting a second opinion on A2W size required. Any A rated house is easily heated.

ImTiredOfItAll

You need an airtight home for a heatpump. Heatpumps heat the rads to a much lower tempeture. Little more that luke warm. Designed corectly this is fine. Without airtightness on days like today the heat will be sucked out of the home. Because heatpumps run the rads at such a low tempeture it takes a long time to get rooms back up to tempeture.

ongarite

https://www.boards.ie/discussion/comment/124208402#Comment_124208402

Not if they are being recommended to install of r290 heat pump system. These run with water temperatures comparable to oil,gas boiler so can work with existing radiators.

I asked earlier what system they were recommended but haven’t got answer so far.

Jonnyc135

https://www.boards.ie/discussion/comment/124208414#Comment_124208414

I think the SEAI are only piloting these heat pumps now in order to see if they will issue them with grants down the line.

If I was th OP, I would hold off let the technologies develop. At the end of the day they are in an A rated house already with high insulation value which would mean low usage of solid fuel and oil to run the house as is. There are already doing their bit for the environment.

Low temp air to water hp are better suited to Underfloor heating, I would let the high temperature HP develop and when they approve it for the grant then it may well be a good option

Lenar3556

https://www.boards.ie/discussion/comment/124207366#Comment_124207366

I couldn’t comment on the sizing without seeing it. But it’s a big house, and a 2014 build would have been in the earlier stages of the energy efficient construction methods that are common today.

Again I don’t know the specific case, but a house of that size would typically have an annual domestic hot water requirement in the region of 6000 Kwh.

But I was to hazard a guess, 13KW would seem comfortable. Many of these units have defrost and purification heaters which push up the instantaneous current consumption considerably when they are active.

marcobass

Viessmann 13 kw heat pump. They suggesting a buffer tank for the back boiler of the fireplace ( not to interfere with the system)

The reason we looking at it is that we have heating on for 3h a day but for the 6 month a year is taking 1000 lt of oil.

If I have to pay these money I like to have the house warm for most of the day and not only 3 h

Cyrus

https://www.boards.ie/discussion/comment/124208598#Comment_124208598

6000kwh for DHW? that would be 16kwh per day for DHW, sorry that's way off.

Lenar3556

https://www.boards.ie/discussion/comment/124208414#Comment_124208414

R290 units can run at temps coming close to oil/gas boilers, but with significant COP degradation.

Water John

A2W needs to be left on at a regular temp, in our case 19/20c, all the time through the winter. They are not meant to be used intermittently. They don't have the capacity to raise room temp quickly. These systems already do the DHW at a higher temp, and go higher again once a week to prevent Legionaires.

Lenar3556

https://www.boards.ie/discussion/comment/124208610#Comment_124208610

Why do you think it’s way off? It’s actually quite conservative if you consider a family of 5 which would be a reasonable assumption for a house of that size.

To put it in perspective, 16Kw/h a day will give you a combined daily total of 20 - 25 minutes of power shower. So 5 No. 4 minute showers, without considering any handwashing, kitchen sink wash up etc.

Cyrus

https://www.boards.ie/discussion/comment/124208778#Comment_124208778

if i pick a month where there was no heating say last June July or August, we used 55kwh on average in those months which was all DHW basically, family of 4.

Now my kids are pre teen so they arent showering daily but even if they were its a big jump from less than 2kwh per day on average to 16 wouldnt you agree?

Lenar3556

https://www.boards.ie/discussion/comment/124208881#Comment_124208881

If it works for you, great.

But I’m telling you that isn’t representative of a typical household’s hot water requirements. And it would be misleading to tell a family that putting 55Kw/h a month into a cylinder is going to give them a reasonable quantity of hot water - it isn’t.

You are taking about one 3-4 minute shower a day at that rate.

When you say you used 55Kw/h - where are you getting this figure from and what precisely is it this figure representing?

Cyrus

https://www.boards.ie/discussion/comment/124209436#Comment_124209436

We aren't, there are two adults a day taking showers and using whatever hot water is needed from taps at the least with one or both of the kids being showered on some days too.

I have a shelly energy monitor on the heat pump , that figure represents the total energy consumed by the heatpump in the months I stated , I am making the reasonable assumption that there is no heating required in those months , if there is then the dhw usage would be lower.

Given I am the one providing actual figures and you are maintaining I am wrong do you care to offer any data yourself ?

Few others reporting their monthly usage as well in this thread no one reporting dhw usage like that

https://www.boards.ie/discussion/2058281726/heat-pump-running-costs/p22

Lenar3556

https://www.boards.ie/discussion/comment/124210108#Comment_124210108

So that’s a different scenario entirely.
The shelly energy monitor will tell you the electrical energy your heat pump is consuming, not what heat it is producing. In the middle of summer the heat pump should easily have a COP of 4. So the 55Kw/h input energy will be about 220Kw/h output, and that is your monthly domestic hot water heating requirement, not 55Kw/h.

Multiply that out across the year, and make an allowance for colder supply water temperatures in winter and you are looking at about 3,000Kw/h+ of annual DHW heat requirement, which is on the lower end of the normal range.

Cyrus

https://www.boards.ie/discussion/comment/124210337#Comment_124210337

Fair enough that wasn't clear to me from your post, my system is a bit older and doesnt report COP so my only focus is on a) maintaining a comfortable temp in the house and b) minimising the amount of energy used to achieve that / or at least minimising the cost of that energy by using it when electricity is cheap.

Lenar3556

https://www.boards.ie/discussion/comment/124210415#Comment_124210415

And you’re doing very well by all accounts. You have something that’s working for you and you’re keeping an eye on it.

I’m just giving some broader perspective on the the scenarios that sometimes arise in other cases.