New boiler v heat pump

ted1 wrote: »

I’ve an old ideal classic boiler that has probably a few years life yet. However with the boiler upgrade grant due to expiry I’m wondering should I pull the trigger now.

I’d also zone the system and upgrade the tank. As currently it’s all rads and hot water on, or all off

But I’m wondering is it worthwhile holding off and going with an air to water heat pump. Will the new grant push the prices up, what’s the retro fit cost like?

There is no boiler upgrade grant. Heat pumps will only work if it’s sized properly and your house is extremely well insulated

ted1 wrote: »

Isn’t the 700 Euro heating control upgrade grant a defacto boiler grant ?

Well u don’t need to fit a new boiler to claim it

Condenser wrote: »

This info is completely untrue yet its constantly spouted on this forum like it was gospel. The only thing you need for a heat pump to work well is low temperature heat emitters i.e. ufh, fan coil radiators, wall or ceiling heating etc. Insulation only dictates how much energy is required to heat a house and that will be the same whether its a heat pump, oil boiler or a nuclear plant you use to heat your home.

Fair enough I was unaware of that. So heat pumps used in a typical housing estate house with 8-10 rads of BER C rating are no less efficient than an oil boiler?

I have had experience of houses in Ireland that would be mid to late 2000 builds where the detailing on the insulation or air tightness is poor , or there was alot of glazing where the air source heat pumps were on underfloor heating circuits and electricity bills of 600-1000 euro were coming in the door in the winter. During the cold spell in 2010 they spent more time in defrost mode than heating the houses. I am all for their use in well insulated, relatively air tight homes but practical experience on installs has shown me again and again as soon as a tough winter hits and the bill goes sky high, and the home isnt heated properly the owner will regret ever putting it in.

Outkast_IRE wrote: »

I have had experience of houses in Ireland that would be mid to late 2000 builds where the detailing on the insulation or air tightness is poor , or there was alot of glazing where the air source heat pumps were on underfloor heating circuits and electricity bills of 600-1000 euro were coming in the door in the winter. During the cold spell in 2010 they spent more time in defrost mode than heating the houses. I am all for their use in well insulated, relatively air tight homes but practical experience on installs has shown me again and again as soon as a tough winter hits and the bill goes sky high, and the home isnt heated properly the owner will regret ever putting it in.

Then you don't really know what was causing those kind of bills on the heat pump because it wasn't the insulation.i could give you 10 reasons why but it 100% was not the insulation. It's the lazy assumption or the one taken when the true mechanics of the system or not understood.

And air to water heat pumps don't spend less time on defrost just because the house is insulated.

Condenser wrote: »

Much more efficient if the rads are changed to fan coil or wall heating is installed. Leaving on standard rad's they will be less efficient. As I said it's all about the heat emitters

Thanks for that.
So in the long term, it wouldnt suit the op, assuming their house is like the one I described, to change to heat pump unless they did a major upgrade on the system?

Dtp1979 wrote: »

Thanks for that.
So in the long term, it wouldnt suit the op, assuming their house is like the one I described, to change to heat pump unless they did a major upgrade on the system?

On standard radiators, definitely not. It's the distribution system that rules it out, not the insulation or airtightness.

Condenser wrote: »

Then you don't really know what was causing those kind of bills on the heat pump because it wasn't the insulation.i could give you 10 reasons why but it 100% was not the insulation. It's the lazy assumption or the one taken when the true mechanics of the system or not understood.

And air to water heat pumps don't spend less time on defrost just because the house is insulated.

Heres the thing I do know what was causing the issue, Building Physics and their application on determining heating and cooling loads, and thermal comfort is one the key areas I work in.

Ok for you to rule out the insulation is silly. Can I ask in all honestly do you sell, service, repair or have some affiliation with the heat pump industry in Ireland ?

Of course the insulation & airtightness of the house matters. It matters for every single heating system type you specify for any house be it gas, oil or electrical / heatpump. The heating system must be capable of heating the house. How much heat input is required from the Boiler or heatpump is determined by the heating load of the building. In a well insulated, air tight building the heating load is far less than a poorly insulated high air infiltration house. This is basic building physics.

The air to water heat pump industry has not overcome this simple fact. Can you purchase a heatpump that will overcome the heat load in the poorly insulated building ? Of course you can, but then its a larger air to water heatpump, with a greater electrical input, and you need a different distribution system to the standard setup.

The use of fan assisted convectors or low temp rads on an air to water heatpump is also not the ideal setup, the volume of water in the system ends up being quite low. On these systems you do want to minimise the stop start cycles, this is best achieved on a system with a larger volume of water and UFH with the entire slab acting as the emitter is ideal.

Now of course there are other factors that can determine the efficiency of a system, such as controls, occupant usage, control strategy, poor installation etc. But to rule out insulation and airtightness as not mattering is illogical and I honestly hope that's not advice you dole out on a daily basis.

Also about the defrost mode, nobody said they spend more time in defrost mode cause the house is poorly insulated. When you need an air source heat pump the most, is mid winter - freezing conditions - same as any heating system - this is when they spend most time in defrost cycle. Most of the heat pumps are hidden away behind the house in nearly constant shade this time of the year, when you need them most they are at their most inefficient. If they let you down in a well insulated - air tight house, you may not notice straight away as the temp in the house may stay steady for a long period - in an older house with insulation and airtightness issues they will be cold within hours.

Outkast_IRE wrote: »

Heres the thing I do know what was causing the issue, Building Physics and their application on determining heating and cooling loads, and thermal comfort is one the key areas I work in.

Ok for you to rule out the insulation is silly. Can I ask in all honestly do you sell, service, repair or have some affiliation with the heat pump industry in Ireland ?

Of course the insulation & airtightness of the house matters. It matters for every single heating system type you specify for any house be it gas, oil or electrical / heatpump. The heating system must be capable of heating the house. How much heat input is required from the Boiler or heatpump is determined by the heating load of the building. In a well insulated, air tight building the heating load is far less than a poorly insulated high air infiltration house. This is basic building physics.

The air to water heat pump industry has not overcome this simple fact. Can you purchase a heatpump that will overcome the heat load in the poorly insulated building ? Of course you can, but then its a larger air to water heatpump, with a greater electrical input, and you need a different distribution system to the standard setup.

The use of fan assisted convectors or low temp rads on an air to water heatpump is also not the ideal setup, the volume of water in the system ends up being quite low. On these systems you do want to minimise the stop start cycles, this is best achieved on a system with a larger volume of water and UFH with the entire slab acting as the emitter is ideal.

Now of course there are other factors that can determine the efficiency of a system, such as controls, occupant usage, control strategy, poor installation etc. But to rule out insulation and airtightness as not mattering is illogical and I honestly hope that's not advice you dole out on a daily basis.

Also about the defrost mode, nobody said they spend more time in defrost mode cause the house is poorly insulated. When you need an air source heat pump the most, is mid winter - freezing conditions - same as any heating system - this is when they spend most time in defrost cycle. Most of the heat pumps are hidden away behind the house in nearly constant shade this time of the year, when you need them most they are at their most inefficient. If they let you down in a well insulated - air tight house, you may not notice straight away as the temp in the house may stay steady for a long period - in an older house with insulation and airtightness issues they will be cold within hours.

My god what you know about heat pumps could be written on the back of a matchbox so here's some info on them and heating in general.

Whether you have a heat pump, a oil burner, gas boiler or any other system matters not as the insulation spec dictates the heatloss of the house. That heat loss is consistent regardless of what system heats it.

It then falls back onto the efficiency of one system vs another. Heat pumps will be more efficient producing the same kw output than all other forms of heating once the flow temperatures are kept low. Ufh is best but fan coils are still excellent options when a buffer is used.

Defrosting depends on many factors. Humidity, coil size, coil design, evaporating temperature. It has zero to do with insulation. A larger heat loss needs a larger heat pump. A larger heat pump has a larger evaporator coil and will defrost no more or no less than a smaller heat pump servicing a smaller heat loss. And to state that a heat pump will have issues defrosting as most are in the shade just goes to show how little you know.

Condenser wrote: »

My god what you know about heat pumps could be written on the back of a matchbox so here's some info on them and heating in general.

Whether you have a heat pump, a oil burner, gas boiler or any other system matters not as the insulation spec dictates the heatloss of the house. That heat loss is consistent regardless of what system heats it.

It then falls back onto the efficiency of one system vs another. Heat pumps will be more efficient producing the same kw output than all other forms of heating once the flow temperatures are kept low. Ufh is best but fan coils are still excellent options when a buffer is used.

Defrosting depends on many factors. Humidity, coil size, coil design, evaporating temperature. It has zero to do with insulation. A larger heat loss needs a larger heat pump. A larger heat pump has a larger evaporator coil and will defrost no more or no less than a smaller heat pump servicing a smaller heat loss. And to state that a heat pump will have issues defrosting as most are in the shade just goes to show how little you know.

No need to start getting personal, thats not really how civilised debate works thanks.

We are agreed on your first point - heat loss for a building determines heat load - . Heat loss is determined by insulation and airtightness you ruled these as not mattering earlier - Minimising the size of boiler, heat pump or heating source always matters.

There was a good study by N.J Kelly & J.Cockroft taking into account both detailed simulations and field data on retrofit air souce heat pump performance and the results were that the annual COP sat around 2.7 with 10% higher running costs than a gas condensing boiler.

Again you state heat pumps will be more efficient than all other forms of heating ? Heat pumps during ideal condiitons could have a COP as high as 5, but during peak winter condiitons this could fall as lower than 2.5, and lower again if electric heating element in the unit kicks in.
Also we do still need to heat the DHW cylinder to 60 degrees, if we use the ASHP to do this, then the COP will also fall off during this period or utilise an electric heater to bring up the temperature.

I never said heat pump in the shade leads to defrost issues - I said during peak winter condiitons when the heat pumps will need to run a defrost cycle, during which the house isnt being heated and unfortunately when the heat pump is located outside in the coldest location on the site, this defrost cycle can take a bit of time.

Again in a retrofit situation my main concern is peak winter condiitons and how the heatpump operates when you need it most.

For example a Daikin Altherma - which would be considered a decent choice has a seasonal operating COP of around 2.8 if outlet if 55deg C or 2.99 if 35 deg C outlet temp. If this is the seasonal COP it will be lower in winter and higher in summer - exactly as you would expect.

I am not attacking ASHP - as i believe they are a good solution for many sceanarios - i just could not reccomend them in a retrofit unless the house was undergoing serious improvement at the same time, as we have both agreed ideally a whole new distribution system is also required to get the best out of the system.

Feel free to answer my query from ealier. Are you involved in the air source heat pump industry in ireland ? Specifically sales or similar ?