Air to Water Heat Pump

Katz83

Hi i am just wondering how much more expensive is it to go with an Air to Water heat pump and underfloor heating compaired to an oil condensing boiler rads and a stove with back boiler and solar panels . Would they be much of a difference between the two, Also if anyone has an air to water heat pump how do they find the bills ect . I have heard alot of horror stories has anyone hear experienced these.

galwaytt

What type of construction are you using ?

The reason I ask is that we built a pair of semi's with NIBE air-water units, and they work well, with a mix of rads/ufh............but in a very high spec, highly airtight house.

If you're not doing that, then I'd be afraid that it would run too long, too often, and ESB bills would be what you'd expect...........it's a low-grade heat appliance, so I'm not sure how it would cope with a big big heat demand on an on-going basis.

They're also not cheap to buy.

flash333

thinking about about air to water heat pump with underfloor heating on ground floor,radiators on first floor. has anyone installed this in the last 12 months, how hot do the radiators get,what about the esb bills,esp for the winter have you a back up system?

fclauson

is this a new build or renovation
are you building to Part L 2011 ?

citywide

flash333 wrote: »

thinking about about air to water heat pump with underfloor heating on ground floor,radiators on first floor. has anyone installed this in the last 12 months, how hot do the radiators get,what about the esb bills,esp for the winter have you a back up system?

Hi did you get any advice or information on air to water heat pump I am thinking of using the same but under floor heating up & down. Stairs

blast06

Moved into my new house Aug 31st. ..... its part L 2011 compliant, BER A2.

Have a Danfoss air to water heat pump with underfloor downstairs (downstairs being 75% of total living area) and rads upstairs. Also have a BEAM MHRV.

I find the comfort of living absolutely fantastic. I have not turned on the rads for the 2 upstairs bedrooms yet (have double height front hall) and temp upstairs has never once deviated from 20 or 21 degrees.

Total price of underfloor, plus 3 rads upstairs plus heat pump including hot water tank etc was 16K.
If you're house is part L compliant then i think you'd be bonkers to go with oil burner, rads, stove back burner and solar panles.

fclauson

blast06 wrote: »

Moved into my new house Aug 31st. ..... its part L 2011 compliant, BER A2.

Have a Danfoss air to water heat pump with underfloor downstairs (downstairs being 75% of total living area) and rads upstairs. Also have a BEAM MHRV.

I find the comfort of living absolutely fantastic. I have not turned on the rads for the 2 upstairs bedrooms yet (have double height front hall) and temp upstairs has never once deviated from 20 or 21 degrees.

Total price of underfloor, plus 3 rads upstairs plus heat pump including hot water tank etc was 16K.
If you're house is part L compliant then i think you'd be bonkers to go with oil burner, rads, stove back burner and solar panles.

really intersted in your performance numbers - I used more heating than I should have done last year (around 1500Kwh)
a) the problem described here - https://www.facebook.com/Passive.House.Wexford/posts/174801372724975?comment_id=251690&offset=0&total_comments=1&notif_t=feed_comment
b) because I set the heat curve to 28 degrees but this is still too much - take the last couple of days - floor is at 21.5 deg - but the heat curve detected the cold weather overnight and run the HP for about 2hrs. The sun the next day was warm and heated the house up - so the HP efforts were wated

I need to do some more clever monitoring to resolve this issue

blast06

Yes - i know the problem ! .... albeit that it was only really in the warm spell in September i had this problem. For past couple of weeks, everything has been great. I think part of this is due to it only being now that MRHV is offering full value ...... i only connected a drainage pipe to it 2-3 weeks ago so i think humidity levels in the house were a small big higher than they might otherwise have been until i done this.
It is only my upstairs that has the very consistent temperature. I still have not turned on heating up there and it was 19 degrees this morning (0 degrees outside at 7am) - perfect for bedrooms.

I have only started loking at my stats closely since i saw your reply. I have been too busy with work and a million and 1 other things since i moved in to worry about this. I am also waiting on an app from Danfoss supplier to monitor this on the fly.
My stats for last few days as per below. I will (obviously!) use a lot more kWh than you for heating (my assumption is that 50% of heating will be daytime and 50% nighttime) but i still think the bill here is for next to nothing for keeping a 2600 sq ft house at contant 20-21 degrees 24/7 (although maybe i should hold my smoke on that statement until after a really cold spell !)

Compressor Heating Hot Water Heating Units kWh Hot Water Units kWh Heating cost Hot Water cost Total Cost
2013-10-30 217 152 63
2013-10-31 223 157 63 11.25 0 1.42 0.00 1.42
2013-11-01 228 162 64 11.25 3.15 1.42 0.53 1.95
2013-11-02 234 167 65 11.25 3.15 1.42 0.53 1.95
2013-11-03 241 173 65 13.5 0 1.70 0.00 1.70


PS ... i set my heat curve to 29 from the day i moved in and haven't changed that yet

BarneyMc

blast06 wrote: »

I have not turned on the rads for the 2 upstairs bedrooms yet (have double height front hall) and temp upstairs has never once deviated from 20 or 21 degrees.

Would this suggest that for a very low energy house UFH upstairs is unnecessary and low energy rads are the way to go? Is there much price difference?

BarneyMc

blast06 wrote: »

Yes - i know the problem ! .... albeit that it was only really in the warm spell in September i had this problem. For past couple of weeks, everything has been great. I think part of this is due to it only being now that MRHV is offering full value ...... i only connected a drainage pipe to it 2-3 weeks ago so i think humidity levels in the house were a small big higher than they might otherwise have been until i done this.
It is only my upstairs that has the very consistent temperature. I still have not turned on heating up there and it was 19 degrees this morning (0 degrees outside at 7am) - perfect for bedrooms.

I have only started loking at my stats closely since i saw your reply. I have been too busy with work and a million and 1 other things since i moved in to worry about this. I am also waiting on an app from Danfoss supplier to monitor this on the fly.
My stats for last few days as per below. I will (obviously!) use a lot more kWh than you for heating (my assumption is that 50% of heating will be daytime and 50% nighttime) but i still think the bill here is for next to nothing for keeping a 2600 sq ft house at contant 20-21 degrees 24/7 (although maybe i should hold my smoke on that statement until after a really cold spell !)

Compressor Heating Hot Water Heating Units kWh Hot Water Units kWh Heating cost Hot Water cost Total Cost
2013-10-30 217 152 63
2013-10-31 223 157 63 11.25 0 1.42 0.00 1.42
2013-11-01 228 162 64 11.25 3.15 1.42 0.53 1.95
2013-11-02 234 167 65 11.25 3.15 1.42 0.53 1.95
2013-11-03 241 173 65 13.5 0 1.70 0.00 1.70


PS ... i set my heat curve to 29 from the day i moved in and haven't changed that yet

Very impressive figures! How come you hot water costs are zero some days?

blast06

I couldn't say re low energy rads.
First of all i wouldn't say i have a very low energy house - it is just about A2.
I have normal rads in the 2 bedrooms upstairs and bathroom upstairs with 1 mid-sized skylight per room. Walls and sloped ceilings have 100mm rafterloc, then air-tightness membrane then 62.5mm insulated slab. On flat ceiling part it is normal slab, air-tightness membrane, 100mm rafterloc plus 200mm wool.
I priced the cost of the low energy rads but i didn't think the cost-benefit figures could justify it and so far i am right .... the payback would be a ridiculous number of years.
However, by the end of next March, i would be in a better position to fully comment.

Re the hot water figures ..... OK, the zero figures aren't strictly correct ! Take the figures for the 31st Oct - the number of hours the compressor had been running in total for hot water was 63 by end of that day. By end of the following day it hadn't ticked over to the 64th hour .... so it was probably a case of 63 hours and a few minutes by end of 31st and by end of Nov 1st it was probably just a few minutes shy of 64 hours in total (or else we're a smelly family and didn't wash that day ). It will balance out over a week or more.

fclauson

blast06 wrote: »

- it is just about A2.

ok

Re the hot water figures ..... OK, the zero figures aren't strictly correct ! Take the figures for the 31st Oct - the number of hours the compressor had been running in total for hot water was 63 by end of that day. By end of the following day it hadn't ticked over to the 64th hour .... so it was probably a case of 63 hours and a few minutes by end of 31st and by end of Nov 1st it was probably just a few minutes shy of 64 hours in total (or else we're a smelly family and didn't wash that day ). It will balance out over a week or more.

Yes this happens

Can I suggest a couple of things
1 - set the heating at a set back temp of say 18 from 06am -> 23pm - and see how you get on this will force you onto night rate and save a bit

you can look at the supply/return temps to see how things went - I turned of a week ago and have lost just 0.5 degrees but will run it tonight to top it up again - love to do this programmatically one day

2 - same with the h/w - turn it off (of course depending on usage) from say 4pm->11pm - this again will cause the top up to happen on cheap elec


question: how did you get the Kw vs hrs - what factor did you multiply by for each of the hrs

BarneyMc

So you both use the night rate electric meter?

blast06

Thanks FC. I need to check this..... i didn't know i could do it. I presume of course you do not mean to manually turn it on/off at those times.....

Re Kw versus hours ..... just multiply the number of hours compressor was running by the kWh rate, i.e.: 2.5 for the heating and 3.5 for the hot water. Note, since i posted, i know i got my usage rates wrong, i.e.: i was assuming 2.25 for heating and 3.15 for hot water but was corrected when i was on the phone to the supplier today.

Barney - yes, night rate for sure

fclauson

blast06 wrote: »

Thanks FC. I need to check this..... i didn't know i could do it. I presume of course you do not mean to manually turn it on/off at those times.....

not use the calendar function on the unit (assuming its an AQ)

Re Kw versus hours ..... just multiply the number of hours compressor was running by the kWh rate, i.e.: 2.5 for the heating and 3.5 for the hot water. Note, since i posted, i know i got my usage rates wrong, i.e.: i was assuming 2.25 for heating and 3.15 for hot water but was corrected when i was on the phone to the supplier today.

Barney - yes, night rate for sure

where did you get those numbers from ?

BarneyMc

Just did a bit of digging and it seems like these are the current figures when using a night meter:

Normal 24 Hour Meter
Annual Standing Charge of €165
Unit Price of 15.3 cent per unit

Night Saver Meter
Annual Standing Charge of €218
Unit Price of 16.3 cent per unit from 8AM to 11PM
Unit Price of 8.1 cent per unit from 11PM to 8AM

Yip, makes sense to me to use a Night Saver meter if going down the heat pump route. Seems like this would favour a slab rather than screed floor finish for the UFH so the HP could use cheap units at night? Would a ground source HP be better when used with a ground source HP also?

fclauson

BarneyMc wrote: »

Would a ground source HP be better when used with a ground source HP also?

??

blast06

fclauson wrote: »

where did you get those numbers from ?

From the supplier .... he detailed these rates in the original quote and more or less clarified today when i gave him a call on a few points.
Given that you are asking though i am now asking myself again ..... so i had a look here (the 11 KwH one).... http://heating.danfoss.com/PCMPDF/dhp-aq_VDGFE402.pdf
The 3.5 figure i guess comes from the compressor (3.3) and fan (0.2) but now i am now sure where he is getting the 2.5 for for heating. I need to get in touch with him again.

PS .... thanks re the tips. I figured out the 'blocking' for hot water. Presuming this could say result in 50% of hot water heating happening between 11pm and 7am instead of 100% during daylight hours then i estimate this will save me ~€50-60 per annum. Cheers !
I'm a bit nervous about playing with the heating just yet though cos herself is beginning to come round to the idea that it was worthwhile pumping so much of the budget into securing an A2 house with this heating system, HRV, etc with not enough money left for all the furnitute she wanted (she only realised this when i had already committed to securing an A2!!) ..... so i don't want to find the house "not warm enough" by playing with the settings just yet !!

fclauson

blast06 wrote: »

From the supplier .... he detailed these rates in the original quote and more or less clarified today when i gave him a call on a few points.
Given that you are asking though i am now asking myself again ..... so i had a look here (the 11 KwH one).... http://heating.danfoss.com/PCMPDF/dhp-aq_VDGFE402.pdf
The 3.5 figure i guess comes from the compressor (3.3) and fan (0.2) but now i am now sure where he is getting the 2.5 for for heating. I need to get in touch with him again.

you will also find this info in your installation manual for the DHQA

PS .... thanks re the tips. I figured out the 'blocking' for hot water. Presuming this could say result in 50% of hot water heating happening between 11pm and 7am instead of 100% during daylight hours then i estimate this will save me ~€50-60 per annum. Cheers !

Your round next time we meet then :P

I'm a bit nervous about playing with the heating just yet though cos herself is beginning to come round to the idea that it was worthwhile pumping so much of the budget into securing an A2 house with this heating system, HRV, etc with not enough money left for all the furnitute she wanted (she only realised this when i had already committed to securing an A2!!) ..... so i don't want to find the house "not warm enough" by playing with the settings just yet !!

Chicken -- but do let the house settle down before you tweek - remember you do have (assuming you have a screed/concrete floor) @ 2600 sqm ft - something like 25 tones of thermal mass let alone the walls to hold you heat - you can do the maths to see just how much that is

one last thing - its published by Danfoss - but some useful info in the attached

BarneyMc

BarneyMc wrote: »

Would a ground source HP be better when used with a ground source HP also?

Sorry, not sure what was going on there!

What I wanted to say was, when a HP is working away it's producing hot water for the UFH system. However does that mean the hot water has to be circulated around the UFH system at the same time. In other words is it possible to have your HP run on the night saver rate but have the water circulated later in the day?

fclauson

BarneyMc wrote: »

Sorry, not sure what was going on there!

What I wanted to say was, when a HP is working away it's producing hot water for the UFH system. However does that mean the hot water has to be circulated around the UFH system at the same time. In other words is it possible to have your HP run on the night saver rate but have the water circulated later in the day?

Barney - HP works like an old boiler
for h/w production the heating circ goes HP->tank->HP
for UFH production it goes HP->UFH->HP

You screed - depending on size is around 1.8 Tones per M3 - you use this as the thermal store - warm it a little and these it slowly ooses heat - in reality in a well insulated house the screed temp might move 20.5 -to 22 and back again - hence why Zones, or heating coming on in the morning no longer makes sense

So to answer you question - yes - heat the floor 11pm->6am - and then hope you can coast for the rests of the day - which is what I am doing except I have it back on at 10am to make use of the PV - but I am now questioning this judgement and might not do so

blast06

Jes, those figures look impresive FC - even if they are published by Danfoss themselves.
With all this talk of 25 tonnes of thermal mass (i have 18m3 of screed so probably closer to 30 tonnes) i'm getting more tempted to start playing with the heating settings !!
One question on your reply below: "except I have it back on at 10am to make use of the PV" .... what is PV ?

Cheers,
Beers on me!

fclauson

blast06 wrote: »

Jes, those figures look impresive FC - even if they are published by Danfoss themselves.
With all this talk of 25 tonnes of thermal mass (i have 18m3 of screed so probably closer to 30 tonnes) i'm getting more tempted to start playing with the heating settings !!
One question on your reply below: "except I have it back on at 10am to make use of the PV" .... what is PV ?

Cheers,
Beers on me!

PV - photo voltaic-

BarneyMc

fclauson wrote: »

So to answer you question - yes - heat the floor 11pm->6am - and then hope you can coast for the rests of the day

I'm not sure of the dynamics of heat release from UFH in screed v concrete but having a slower release concrete floor might work better using the above approach?

fclauson

BarneyMc wrote: »

I'm not sure of the dynamics of heat release from UFH in screed v concrete but having a slower release concrete floor might work better using the above approach?

its all physics - density and thermal capacity -do the maths :pac:

blast06

OK, i've made the switch .... heating and hot water now only running between 11pm and 7am. If i can get away with this on an ongoing basis then my running costs would be almost ridiculously small ..... below would be the figures for the last 7 days if all electricity was from 11pm to 7am



Date Heating Units kWh Hot Water Units kWh Heating cost Hot Water cost Total Cost
2013-10-31 13.25 0 1.11 0.00 1.05
2013-11-01 13.25 3.5 1.11 0.29 1.34
2013-11-02 13.25 3.5 1.11 0.29 1.34
2013-11-03 15.9 0 1.34 0.00 1.26
2013-11-04 15.9 7 1.34 0.59 1.85
2013-11-05 15.9 0 1.34 0.00 1.26
2013-11-06 5.3 7 0.45 0.59 1.01

blast06

Barney .... i replied to your DM but i have had problems in the past with DM's so if you don't get the DM reply then send me your mail ID and i can mail you.

dfader

blast06 wrote: »

OK, i've made the switch .... heating and hot water now only running between 11pm and 7am. If i can get away with this on an ongoing basis then my running costs would be almost ridiculously small ..... below would be the figures for the last 7 days if all electricity was from 11pm to 7am



Date Heating Units kWh Hot Water Units kWh Heating cost Hot Water cost Total Cost
2013-10-31 13.25 0 1.11 0.00 1.05
2013-11-01 13.25 3.5 1.11 0.29 1.34
2013-11-02 13.25 3.5 1.11 0.29 1.34
2013-11-03 15.9 0 1.34 0.00 1.26
2013-11-04 15.9 7 1.34 0.59 1.85
2013-11-05 15.9 0 1.34 0.00 1.26
2013-11-06 5.3 7 0.45 0.59 1.01

Blast,
Thanks for this info - its very useful to those planning similar builds. I know you said your house is A2 and so this question might be somewhat academic and I don't wish to derail the tread, but since ye brought up the topic of thermal mass in the floor, I am curious as to what is your external wall build up exactly?

fclauson

blast06 wrote: »

Barney .... i replied to your DM but i have had problems in the past with DM's so if you don't get the DM reply then send me your mail ID and i can mail you.

clear you "sent box " is the trick

BarneyMc

blast06 wrote: »

Barney .... i replied to your DM but i have had problems in the past with DM's so if you don't get the DM reply then send me your mail ID and i can mail you.

Message received

exaisle

blast06 wrote: »

OK, i've made the switch .... heating and hot water now only running between 11pm and 7am.

Did you do this via a timer on the HP circuit or is there a setting in the HP itself? I have a night rate meter but I haven't tweaked the HP system at all....yet!