Air to water heat pump system - Advice !

blast06 · 02-02-2013 1:33am #1

Hi,

I'm trying to decide on heating system for a new build (part L 2011 compliant). Details are 187 m2 ground floor and 61 m2 1st floor. Will have air tightness and HRV system (still figuring out what to go with here from a mix of different quotes for different systems). Walls are 4" concrete, 150mm pumped bead (highest spec available) and 4" Quinn lite on inside-leaf (u-value = 0.16). Attic will have 400mm wool and floors 125 mm Polyiso.
Im thinking of going with a Danfoss 11 kW system or else an 11kW Thermia Atec with underfloor downstairs and rads upstairs (i'm hoping that 35-40 water constantly in upstairs rads would be sufficient.... upstairs is only ~1/3 size of downstairs and i will have double height front hall so might get away without heating need at all upstairs ?

My brain is fried reading up on it for past week or 2. Anyone any last snippets of info/advice to put my mind at ease !

Cheers.

Tommyboy08 · 11-02-2013 3:32pm

blast06 wrote: »

Hi,

I'm trying to decide on heating system for a new build (part L 2011 compliant). Details are 187 m2 ground floor and 61 m2 1st floor. Will have air tightness and HRV system (still figuring out what to go with here from a mix of different quotes for different systems). Walls are 4" concrete, 150mm pumped bead (highest spec available) and 4" Quinn lite on inside-leaf (u-value = 0.16). Attic will have 400mm wool and floors 125 mm Polyiso.
Im thinking of going with a Danfoss 11 kW system or else an 11kW Thermia Atec with underfloor downstairs and rads upstairs (i'm hoping that 35-40 water constantly in upstairs rads would be sufficient.... upstairs is only ~1/3 size of downstairs and i will have double height front hall so might get away without heating need at all upstairs ?

My brain is fried reading up on it for past week or 2. Anyone any last snippets of info/advice to put my mind at ease !

Cheers.

Ouch, who told you that 35-40 degree water through rads was a good idea clearly doesn't have to pay your esb bills, you have 61 mtrs upstairs that's gonna govern the flow temps on your heat pump system,
In English, your going to be heating water to an unnecessary high temp for your ufh in order to get some duty out of the rads, put in Dimplex smart rads or similar and run them at the same temps as your underfloor, approx 32 degrees or your bills will be terrible, you should be able heat that size of house for about €400 per year if you do it right,
Crazy salesman giving you rubbish advice as he obviously doesn't know what he's talking about, any wonder heat pumps have a bad rep in this joke of a country

Condenser · 11-02-2013 5:52pm

I would add to that and say if you use any type of rad you will need a buffer tank installed on the system as the rads have no thermal storage and will therefore call on the heat pump when the ufh would not do so for hours. By the time you pay for a buffer it would have been cheaper and more efficient to use ufh.

With your insulation you should be aiming for a flow temp of no more than 30C (dependant on correctly designed underfloor), going up to 40C will drop the efficiency you could have achieved by at least 20%.

yop · 12-02-2013 3:00pm

blast06 wrote: »

Hi,

I'm trying to decide on heating system for a new build (part L 2011 compliant). Details are 187 m2 ground floor and 61 m2 1st floor. Will have air tightness and HRV system (still figuring out what to go with here from a mix of different quotes for different systems). Walls are 4" concrete, 150mm pumped bead (highest spec available) and 4" Quinn lite on inside-leaf (u-value = 0.16). Attic will have 400mm wool and floors 125 mm Polyiso.
Im thinking of going with a Danfoss 11 kW system or else an 11kW Thermia Atec with underfloor downstairs and rads upstairs (i'm hoping that 35-40 water constantly in upstairs rads would be sufficient.... upstairs is only ~1/3 size of downstairs and i will have double height front hall so might get away without heating need at all upstairs ?

My brain is fried reading up on it for past week or 2. Anyone any last snippets of info/advice to put my mind at ease !

Cheers.

Why not have UFH upstairs or does the first floor structure not support this?

blast06 · 14-02-2013 11:34am

Thanks for the comments folks.
My 'problem' is i have joists so not really suitable for UFH.
I didn't get my figures exactly right on the upstair size...... in total it is 55 m2 but 15 of this is a void over the front hall plus upstairs 'landing' ... so 'just' 40 m2 upstairs in reality to be heated (i.e.: 2 bedrooms and a shared en-suite) as the void space and 'landing' will be heated from the groundfloor UFH.

My understanding is that if the rads call on the heating (and it should only be a couple of hours in the evenings and say 1 in the morning for say 4-6 months a year) then the heat pump will work harder for that duration but this hotter water will not be feeding into the UFH system.

So, would i still need a buffer tank even with the dimplex smart rads ?
Would i nearly be better off with electrictity storage heaters or something in the 2 upstairs rooms running of the nightsaver rate ?

As for the heating system .... its actually an air to water system. I know, i know - but ground conditions are not suitable (completely gravel to big depths) ..... couldn't justify the say 4K for the drilling alternative plus an unknown amount of steel casing for the hole depending on the depth of the gravel. I know the shelf life will be more like 10-15 years rather than 15-25 but i guess technology would have advanced far enough in 10-15 years to justify getting the next generation ore efficient heat pump then anyway.

Cheers.

Tommyboy08 · 14-02-2013 11:53am

blast06 wrote: »

Thanks for the comments folks.
My 'problem' is i have joists so not really suitable for UFH.
I didn't get my figures exactly right on the upstair size...... in total it is 55 m2 but 15 of this is a void over the front hall plus upstairs 'landing' ... so 'just' 40 m2 upstairs in reality to be heated (i.e.: 2 bedrooms and a shared en-suite) as the void space and 'landing' will be heated from the groundfloor UFH.

My understanding is that if the rads call on the heating (and it should only be a couple of hours in the evenings and say 1 in the morning for say 4-6 months a year) then the heat pump will work harder for that duration but this hotter water will not be feeding into the UFH system.

So, would i still need a buffer tank even with the dimplex smart rads ?
Would i nearly be better off with electrictity storage heaters or something in the 2 upstairs rooms running of the nightsaver rate ?

As for the heating system .... its actually an air to water system. I know, i know - but ground conditions are not suitable (completely gravel to big depths) ..... couldn't justify the say 4K for the drilling alternative plus an unknown amount of steel casing for the hole depending on the depth of the gravel. I know the shelf life will be more like 10-15 years rather than 15-25 but i guess technology would have advanced far enough in 10-15 years to justify getting the next generation ore efficient heat pump then anyway.

Cheers.

Stick with the smart rads for upstairs, your going to need a buffer tank anyway if using air to water for defrosting purposes, it's better in the long run than using an immersion heater to defrost the outdoor, and you'll have no problems heating the rooms with 35 degree water with those rads, I know their expensive but cheaper to run and better for the life of your system,
But please be wary of the make of unit you choose, I spend 6 days a week fixing heat pumps and don't listen to the salesman bull, some units are very bad, pm me the makes your thinking of using and I can give you the benefit of other people's mistakes.

blast06 · 14-02-2013 1:04pm

Thanks Tommyboy !
I have been having some problems sending PM's (not sure what i am doing wrong) but i can reply to one when i get it .... so could you just send a message to me an i will reply with the details.
Thanks.

housebuilder1 · 19-05-2013 12:39am

HI,
Listen, i have prob 1500 heat pumps installed in house with all UFH, UFH and rads and all rads too... smart rads, aluminium rads and std steel rads...

The bull out there is so frustrating from people who "think" they know... well i have seen it all guys...

A house with standard steel rads will work absolutely at 35-45 degC if on a weather compensated curve ie. on "ALL" the time.

We have retro-fitted heat pumps into 100's of houses with UFH on GF and standard steel double rads on FF.. unless the people have been drugged or are delusional - the houses are warm... all the time.

PLEASE PLEASE dont listen to wanna be's or know it all's...

ASK someone who has it installed, go to their house and see it for real...

Afterall half the population of Sweden have heat pump with - YES - std steel rads... i bet they are warm..!!

Cheers.

:-)

Apologies for sounding blunt, but im sick of hearing stories what heat pumps can and cant do.

BryanF · 19-05-2013 12:59am

housebuilder1 wrote: »

HI,
Listen, i have prob 1500 heat pumps installed in house with all UFH, UFH and rads and all rads too... smart rads, aluminium rads and std steel rads...

The bull out there is so frustrating from people who "think" they know... well i have seen it all guys...

A house with standard steel rads will work absolutely at 35-45 degC if on a weather compensated curve ie. on "ALL" the time.

We have retro-fitted heat pumps into 100's of houses with UFH on GF and standard steel double rads on FF.. unless the people have been drugged or are delusional - the houses are warm... all the time.

PLEASE PLEASE dont listen to wanna be's or know it all's...

ASK someone who has it installed, go to their house and see it for real...

Afterall half the population of Sweden have heat pump with - YES - std steel rads... i bet they are warm..!!

Cheers.

:-)

Apologies for sounding blunt, but im sick of hearing stories what heat pumps can and cant do.

Do you ever install a sensor to check the performance? I'm not knocking ashp just keen to know their annum performance. Do you think the performance of ashp is connected to the fabric? And if so what Is your experience of poorly insulated homes?

Condenser · 19-05-2013 8:20pm

housebuilder1 wrote: »

HI,
Listen, i have prob 1500 heat pumps installed in house with all UFH, UFH and rads and all rads too... smart rads, aluminium rads and std steel rads...

The bull out there is so frustrating from people who "think" they know... well i have seen it all guys...

A house with standard steel rads will work absolutely at 35-45 degC if on a weather compensated curve ie. on "ALL" the time.

We have retro-fitted heat pumps into 100's of houses with UFH on GF and standard steel double rads on FF.. unless the people have been drugged or are delusional - the houses are warm... all the time.

PLEASE PLEASE dont listen to wanna be's or know it all's...

ASK someone who has it installed, go to their house and see it for real...

Afterall half the population of Sweden have heat pump with - YES - std steel rads... i bet they are warm..!!

Cheers.

:-)

Apologies for sounding blunt, but im sick of hearing stories what heat pumps can and cant do.

Who said they don't work? They just don't work efficiently and if you don't know why that is then you don't know anything about heat pumps.

What influence does the SST and the SCT have on the performance and therefore efficiency of a heat pump may I ask.

housebuilder1 · 20-05-2013 12:26am

Hi guys. Again apologies for bluntness of first post.
I do agree that radiators are not as good as say underfloor heating when used with air or geo heat pumps.

All I was trying to say is that heat pumps can besuccessful with standard rads . We just completed 10 no. 30 year old council houses that had std rads in them. They were on solid fuel and oil.

We used air source heat pumps because of the lack of space and the limited budget etc.
The savings are approx 40% to 50% and the residents are happy.

The radiators run between 20 and 45 deg depending on the outdoor temp. 45 at -3 outside temp and the warmer it gets the cooler the rads get etc.

The hours on the additional heater (electric) is almost zero since last October. So good result. The heat pump also produces all the hot water.

Smart rads are better again as we can reduce the temp a little more but people find them a bit noisy in bedrooms during middle of the night.

Also remember air source heat pumps need to defrost and they do this by reverse cycle. So we need to ensure a large volume of water in the heating system. Smart rads have very little water so we need to increase using a buffer or volume tank.

Using double panelled steel rads in some cases reduces the need for buffer size due to the larger volume in them.

I guess its a balancing act at the end of the day.

The fabric is also important with any heating system but especially with heat pumps as the are designed to match the buildings actual heart loss. So the more insulation the better as always. :-)

JD6910 · 20-05-2013 8:10am

i am very interested in this debate on geothermal heat pumps and standard steel rads.

i am also told that the system will work perfect. a buffer tank is needed so that the HP can heat it at night on the cheap rate and be ready to dump into the rads when required. any thoughts?

Condenser · 20-05-2013 9:42am

JD6910 wrote: »

i am very interested in this debate on geothermal heat pumps and standard steel rads.

i am also told that the system will work perfect. a buffer tank is needed so that the HP can heat it at night on the cheap rate and be ready to dump into the rads when required. any thoughts?

You'll get about 20mins of heat from a 500L buffer before its too cold to offer any energy. The only purpose of the buffer in this case is to cut down the amount of start stop cycles. Anyone saying you'll heat the house up based on the buffer storage is talking through their proverbial.

sas · 20-05-2013 12:06pm

Condenser wrote: »

You'll get about 20mins of heat from a 500L buffer before its too cold to offer any energy. The only purpose of the buffer in this case is to cut down the amount of start stop cycles. Anyone saying you'll heat the house up based on the buffer storage is talking through their proverbial.

This would be my experience based on my own house too.
We've 1000 litre tank with the bottom 500 litres targetted for heating.

The UFH circuit will pull any usable heat out of that in 2 hours. This doesn't suffice at all in winter.

Tommyboy08 · 20-05-2013 9:55pm

housebuilder1 wrote: »

Hi guys. Again apologies for bluntness of first post.
I do agree that radiators are not as good as say underfloor heating when used with air or geo heat pumps.

All I was trying to say is that heat pumps can besuccessful with standard rads . We just completed 10 no. 30 year old council houses that had std rads in them. They were on solid fuel and oil.

We used air source heat pumps because of the lack of space and the limited budget etc.
The savings are approx 40% to 50% and the residents are happy.

The radiators run between 20 and 45 deg depending on the outdoor temp. 45 at -3 outside temp and the warmer it gets the cooler the rads get etc.

The hours on the additional heater (electric) is almost zero since last October. So good result. The heat pump also produces all the hot water.

Smart rads are better again as we can reduce the temp a little more but people find them a bit noisy in bedrooms during middle of the night.

Also remember air source heat pumps need to defrost and they do this by reverse cycle. So we need to ensure a large volume of water in the heating system. Smart rads have very little water so we need to increase using a buffer or volume tank.

Using double panelled steel rads in some cases reduces the need for buffer size due to the larger volume in them.

I guess its a balancing act at the end of the day.

The fabric is also important with any heating system but especially with heat pumps as the are designed to match the buildings actual heart loss. So the more insulation the better as always. :-)

Rads at 20 degrees! you'd get more heat in the room if you stood in the nip

Why would you run rads during the night when your under a duvet?

Can you not answer condensers questions, if he's such a wannabe or know it all, you being the guru it should be easy to you ;-)

housebuilder1 · 20-05-2013 11:04pm

I'm not saying you would have your radiators at 20 when outdoor is cold. Obviously that won't work. The radiator is weather compensated. If out side is like 18 or 19 the the rads will be 20. Of outside is 0 the rads may be 40 and a curve in between. I just checked on line on some live house feeds from old houses on rads and air source heat pumps and outside is 14 deg and the rads are at about 27. The house is 20 DegC so it works fine. See screen shot of the online live feed. If your system is sized correctly and the house is suitable there is no reason for steel rads not to work.

The house in the screen shot is 100m2 council house and was fitted with a 6kw air source heat pump in November last year. You can see at bottom of screen the run hours etc.

Smart rads and ufh are better in most csses but sometimes its too expensive to chane all the rads or there is no room for buffer.

On the buffer question I agree. Not used for charging but to limit the start and stop of compressor too often. This will only shorten the life of the compressor and make your pocket hurt Lol.

Buffers work well on very large houses too as you csn have your 8 DegC delta on your condensor and 5 DegC on under floor if you like etc... it also allows for heavy zoning if the client requests as it protects the compressor cycling.

All heat pumps are fairly similar and its slight controls diff that makes one manufacturer diff than the next. Air source and geo have their places and each have their own slight sizing diff too.

Always go see one c installed and ask are they Happy and has the system ran as promised etc.

Heat Pumps that run on full weather compensation will have lower discharge gas temp and the condensor temp can be kept as low as possible reducing life cycle and energy costs. Then when hot water is needed they can let rip for 20 min and get to the 69 DegC flow needed for hot water.

The second screen shot is air to water with smart rads in an office 2300 sqft. Outoor 7 DegC and flow temp is only 29 DegC.

Hopefully heat pumps will get a better name with better installations and all installers and manufacturers can make a living from it. Too many bad jobs out there and too many old wives tales.

Cheers. :-)

Tommyboy08 · 20-05-2013 11:42pm

housebuilder1 wrote: »

Heat Pumps that run on full weather compensation will have lower discharge gas temp and the condensor temp can be kept as low as possible reducing life cycle and energy costs. Then when hot water is needed they can let rip for 20 min and get to the 69 DegC flow needed for hot water.

Cheers. :-)

I presume your taking the piss about 69 degC flow

housebuilder1 · 21-05-2013 12:12am

Oops. 60 DegC I should have said. Sorry.

Condenser · 21-05-2013 11:43pm

housebuilder1 wrote: »

Oops. 60 DegC I should have said. Sorry.

Anyone that runs a compressor up to 60c needs their head examined or just loves the smell of burnt windings. Guaranteed compressor replacement in 6 to 8 years

housebuilder1 · 22-05-2013 8:31am

Well not the case.

we have been producing hot water with heat pumps for 40 years now using the compressor to heat hot water. how come all they ones ive been using over the last 12 years are still alive and kicking..!

The time spent on hot water is very short, approx 20 min and it starts at 40 deg C and runs to 60 Deg C.

We have heat pumps doing this in houses and commercial building lasting more then 20 years. So Please don't say that they will not last 5-6 years when they actually do. My own one is now 12 years old and guess what.. i still have some compressor...

The Copeland compressors used are designed to work between say 25 and 60-62 Deg C and at 60 for as short a time as possible. we don't go making hot water 24/7.

This is the problem when people say things about heat pumps. Granted some manufactures don't do hot water and running their machines to 60 deg c is not possible and, yes, they wont last, but a lot of modern heat pumps can make hot water very easily and efficiently.

Heat pumps are not at their best making hot water but like i was saying its for such a short time in the year of the heat pump. On average most heat pumps will have approx 2500 - 3000 hrs a year and approx 300 - 400 hrs on hot water.

Condenser · 22-05-2013 9:34am

housebuilder1 wrote: »

Well not the case.

we have been producing hot water with heat pumps for 40 years now using the compressor to heat hot water. how come all they ones ive been using over the last 12 years are still alive and kicking..!

The time spent on hot water is very short, approx 20 min and it starts at 40 deg C and runs to 60 Deg C.

We have heat pumps doing this in houses and commercial building lasting more then 20 years. So Please don't say that they will not last 5-6 years when they actually do. My own one is now 12 years old and guess what.. i still have some compressor...

The Copeland compressors used are designed to work between say 25 and 60-62 Deg C and at 60 for as short a time as possible. we don't go making hot water 24/7.

This is the problem when people say things about heat pumps. Granted some manufactures don't do hot water and running their machines to 60 deg c is not possible and, yes, they wont last, but a lot of modern heat pumps can make hot water very easily and efficiently.

Heat pumps are not at their best making hot water but like i was saying its for such a short time in the year of the heat pump. On average most heat pumps will have approx 2500 - 3000 hrs a year and approx 300 - 400 hrs on hot water.

Well as a refrigeration engineer with close to 20yrs experience I will tell you you're talking rubbish. I've spent a considerable amount of time replacing compressors in units ran exactly like you say where salesmen have said exactly as you've said.
With a flow temp of 60C you'll be running discharge temps exceeding 90C, possibly even 100C depending on your evaporating temperature and neither Copeland, nor Danfoss, nor Bitzer, nor Bristol or any other manufacturer you wish to mention manufacturers scrolls to operate at those temperatures repeatedly and to say it can be done efficiently is simply not true. Whats the COP at B0/W60 or even B4/W60 and don't even try to tell me an A2W can even do that temp when its below 0C.

housebuilder1 · 22-05-2013 8:16pm

I can see what you are saying but how come I have several hundred systems installed over the last 12 years and none of them have failed. I must be seeing things so.

Nibe. Danfoss. Thermia. IVT. All have the same systems and all have been fine for me. Im nit familiar with other systems so I cant comment on them.

Where I have seen compressor failures and alot of them is where too many stats and no buffer is installed. Stop and start is bad news as you know yourself im sure.

I do agree with you about runnung heat pumps at 60 degc for long periods but on a rare occasion for a few min a day seems to have been fine for hundreds of thousands of scandaniavian heat pumps.

housebuilder1 · 22-05-2013 9:22pm

This is a spread sheet of our air to water heat pump making hot water.

you can see outdoor was between 0 and -2

Look at the supply line.

I can give you a link to live feeds if you like?

They can do 60DegC at minus temps.

Condenser · 22-05-2013 9:38pm

housebuilder1 wrote: »

I can see what you are saying but how come I have several hundred systems installed over the last 12 years and none of them have failed. I must be seeing things so.

Nibe. Danfoss. Thermia. IVT. All have the same systems and all have been fine for me. Im nit familiar with other systems so I cant comment on them.

Where I have seen compressor failures and alot of them is where too many stats and no buffer is installed. Stop and start is bad news as you know yourself im sure.

I do agree with you about runnung heat pumps at 60 degc for long periods but on a rare occasion for a few min a day seems to have been fine for hundreds of thousands of scandaniavian heat pumps.

Several hundred heat pumps and never a compressor failure? I think I'll end this discussion here because theres no reasoning with that level of bs

housebuilder1 · 22-05-2013 10:12pm

There was of course compressor failures. I've had approx 6. Two were a cause of loose neutral and the rest were because of too many stats and too many starts.

If its bs then all of my customers are delusional and they all have cold hot water.

I'd be more than happy to meet you too show you systems etc. Im not a bull ****ter if you knew me.

Anyway. That's ok.

Cheers.

muffler · 22-05-2013 10:26pm

Careful lads

housebuilder1 · 22-05-2013 10:51pm

I'm grand. Just don't like being called a bs.. when I'm not.

Its ok..
Cheers. :-)

muffler · 22-05-2013 11:06pm

Temperatures will be back to normal tomorrow (hopefully)

Tommyboy08 · 22-05-2013 11:09pm

housebuilder1 wrote: »

This is a spread sheet of our air to water heat pump making hot water.

you can see outdoor was between 0 and -2

Look at the supply line.

I can give you a link to live feeds if you like?

They can do 60DegC at minus temps.

It's taking almost 45 mins to get from 50 to 60 degC which is not a small time for a scroll compressor running between 22 and 26.5bar on R407c. If that comp was on any other fridge system it would have tripped out on HP ages ago

Just as well its not on 410a, it'd be nearly hitting 40 bar, stand back lads its gonna blow ;-)

housebuilder1 · 22-05-2013 11:22pm

Lol. Yes well it was -2 outside.. The pressure stat cut out is 28.5 bar for DHW and the HP alarm is 31.5 bar

normally at +5 or 6 it takes about 25 to 30 min. That last post was just to prove a point.

This was an 11kw at A7 heating a 300l tank. prob 8 to 9 kw at A zero. but that's the nature of AW heart pumps. That's why I prefer Geothermal.

housebuilder1 · 22-05-2013 11:24pm

muffler wrote: »

Temperatures will be back to normal tomorrow (hopefully)

please god. Lol :-)

Air to water heat pump system - Advice !

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