Discussion ... ASHP(Air/Air) with Solar pv ....

Exiled_Tyke

zeupater wrote: »

Hi

Yes, but if the boiler already exists the question revolves around simply changing the pipework to accommodate the cylinder and installing a 3-way valve being a cheaper alternative to replacing the entire system .. after-all, that's the situation described ...

From the referenced post it looks like the point has been missed ... a situation exists where due to there being no DHW storage it's currently impossible to use proportional diversion to heat water from an installed solar array, so in the case where a DHW cylinder is installed what would the fallback heat source be when a number of consecutive dull days impact on PV generation, and of course when daily generation if poor in the winter months ....

We live with the very issue as we already have solar thermal for the DHW, however with our storage being around double that being considered by Costalwatch we have the ability to cope with a longer poor weather period before needing to use a secondary heat-source (ours is standard boiler GCH to a secondary cylinder coil heating the upper portion of a high insulation solar DHW cylinder) , but that simply effects the frequency of heat provision ...

On heating water with the boiler (point 2) ... with a 3 way valve setup if there's demand from space heating and DHW then the installer has the ability to design & set the priority - water or heating, or potentially both - however, it's unlikely to really be an issue as a proposed 170l cylinder would only require around 10kWh to heat from completely cold, so around 5kWh as a top-up to whatever has been collect through solar diversion should be more typical, which should be much of an issue as the heat-transfer is a factor of boiler flow/temperature and cylinder coil surface area ... of course, it's also typical for solar diversion to be topped-up in the evening after sunset on a timed & thermostatic basis which can be scheduled for after the space heating requirement has reduced & the boiler has pre-heated the pipe-work & raised room temperatures ... then again, there's nothing to stop anyone doing this manually as required by flicking a switch!

Anyway, it's not an issue as a decision has already been made! ... :cool:

HTH
Z

Just to clarify. My point was that using a combi boiler to heat a cylinder is not terribly effective as it's not been designed to do this job. I lived with this arrangement for a few years and it was an absolute pain in the neck.

But as you say, not really relevant to this particular decision now.

Coastalwatch

Exiled_Tyke wrote: »

Just to clarify. My point was that using a combi boiler to heat a cylinder is not terribly effective as it's not been designed to do this job. I lived with this arrangement for a few years and it was an absolute pain in the neck.

But as you say, not really relevant to this particular decision now.

Thanks for further hypotheses chaps, I can just about follow what is being suggested. The jury is still out on how the plumbing will be sorted as I'll leave it to the professional who'll install it. From my point I wish to get the hotwater tank up and running on Solar energy only with the option of switching/isolating it to run the hot water direct from the gas combi boiler when the tank temperature isn't hot enough.

According to pvgis there are just three months each year when there will not be in excess of 6 kWh spare daily from which to heat it. Understanding that added to this will be days of poor generation until a suitable sized storage battery(or EV) can be utilised to cover for them.

From my simple viewpoint this option should derive the least capital outlay and running cost
.
As usual I'm open to be persuaded otherwise if a greener and/or more cost efficient method is readily practised.

ASavvyBuyer

Coastalwatch wrote: »

Thanks for further hypotheses chaps, I can just about follow what is being suggested. The jury is still out on how the plumbing will be sorted as I'll leave it to the professional who'll install it. From my point I wish to get the hotwater tank up and running on Solar energy only with the option of switching/isolating it to run the hot water direct from the gas combi boiler when the tank temperature isn't hot enough.

According to pvgis there are just three months each year when there will not be in excess of 6 kWh spare daily from which to heat it. Understanding that added to this will be days of poor generation until a suitable sized storage battery(or EV) can be utilised to cover for them.

From my simple viewpoint this option should derive the least capital outlay and running cost
.
As usual I'm open to be persuaded otherwise if a greener and/or more cost efficient method is readily practised.

We have a hot water cylinder with an immersion heater and also a combi boiler.
The plumbing is done so that in the winter we use the combi, but in the summer we use the hot water tank.
Changeover is done by opening and closing some isolator valves so that the hot water supply is either direct from the combi or the hot water tank.
We usually get all the solar PV heated water we need from May till September and switch over when we notice that there is not enough supplus to get the tank upto temperature.

Coastalwatch

ASavvyBuyer wrote: »

We have a hot water cylinder with an immersion heater and also a combi boiler.
The plumbing is done so that in the winter we use the combi, but in the summer we use the hot water tank.
Changeover is done by opening and closing some isolator valves so that the hot water supply is either direct from the combi or the hot water tank.
We usually get all the solar PV heated water we need from May till September and switch over when we notice that there is not enough supplus to get the tank upto temperature.

Thanks ASB that's the style of system I have in mind with perhaps switching more frequently than just the once in spring and autumn depending on water temperature come the hours of darkness on a daily basis!

Strangely, since his visit I've heard nothing further from the prospective installer, so it looks like I'll be seeking alternative quotations hoping eventually they will actually result in seeing the task through to completion.:(

Coastalwatch

Finally we've arrived at a satisfactory quotation for the installation of a single ASHP. It started out as two but upon receipt of a first quotation was quickly reduced to just the one, for now at least. Unfortunately the guy who first came to size up and provide a quote never came back! I'd had another online quote at reasonable cost for the smallest available base model, an additional cost of £125 was required for the larger unit we needed which I had no problem with. I enquired further about the minimum power input the unit would run at but heard nothing in response.

I should perhaps explain that we are in a bungalow and there was no other wall to place the outer unit against other than one room away from the inner. Hence, the outer unit is to be placed on a gable end wall above a flat roofed garage. The pipework then has to go through the cavity wall into the loft and travel approx 4 metres before descending into the lounge and the inner unit.
Because of this descent an additional pump is required to send the condensate back to the outer unit where it can be disposed of. The units are to be the latest top of the range Mitsubishi SRK35ZSX inner, & SRC35ZSX outer installed for a total cost around £1600. There was some negotiation that took place to arrive here and based on those quotes posted earlier in this post I'm satisfied as it comes with a 5 years parts and labour warranty from a local guy who is well respected. He'd been very open to the many questions asked and options discussed centred around the invaluable advice received by the wonderful contributors on this Forum. We agreed the final price yesterday and received an install date of 18/19 Oct. In the meantime he arrived this morning to place the outer unit on the garage roof to see if our neighbours would notice it before I consult them about it's proposed position. Fortunately there are only likely to be two affected minimally by any visual presence and with any noise restricted to just the nearest. This being quoted as 61/62 dB(A).

Initially the installer was opposed to the outer unit being wall mounted, especially as it was adjacent the bedroom. However, Z had already advised that wall mounting had little noise issues for him and with us being unlikely to have the unit running during the hours of darkness then any noise/vibration should have a limited effect upon us and he succumbed to our preference.

Now we can't wait for when it's supplying daytime heat to raise the temperature of thermal mass within the property.

We have to thank Mart and Zeup in particular for their encouragement and sound advice for arriving at this point. What a shame the odd poster has to lower the tone of this wonderful forum with their negative and contradictory statements. What sad individuals, have they nothing better to do!
Long live Renewables!:j

Martyn1981

Coastalwatch wrote: »

Now we can't wait for when it's supplying daytime heat to raise the temperature of thermal mass within the property.

Good timing. I've just started using ours again this week. The clear skies have brought lovely sunshine, but also cold crisp mornings, and rapid falls in evening temps, so a bit of hot air has been nice.

ASavvyBuyer

Martyn1981 wrote: »

Good timing. I've just started using ours again this week. The clear skies have brought lovely sunshine, but also cold crisp mornings, and rapid falls in evening temps, so a bit of hot air has been nice.

Same with us, the heat pump is working a treat warming up the lounge, but using less than 200 watts (apart from when it first starts up).

zeupater

Hi All

We've also taken advantage of the late September sun over the past few days and ramped the heat-pump thermostat & fan up to charge-up the house's thermal mass a little more than normal before those pesky clouds return! ...

@Coastalwatch ... good to see another convert, hope it works as well for you as it has for us ... 22.3C where I'm sitting at the moment with the average though the rest of the house probably being close to ~20C despite a run of chilly nights & it being just a couple of days until October, but this is the time of year and exactly the kind of conditions that spurred the initial thought process a few years back! .... anyway, looking forward to seeing your initial impressions when you've settled the new system in!


HTH
Z

Coastalwatch

zeupater wrote: »

Hi All

We've also taken advantage of the late September sun over the past few days and ramped the heat-pump thermostat & fan up to charge-up the house's thermal mass a little more than normal before those pesky clouds return! ...

@Coastalwatch ... good to see another convert, hope it works as well for you as it has for us ... 22.3C where I'm sitting at the moment with the average though the rest of the house probably being close to ~20C despite a run of chilly nights & it being just a couple of days until October, but this is the time of year and exactly the kind of conditions that spurred the initial thought process a few years back! .... anyway, looking forward to seeing your initial impressions when you've settled the new system in!

HTH
Z

Thanks Zeup, the chap who's installing it has the same system set up in his home and, like you, is already charging up the warmth in the fabric of the building by leaving it on all day while at work.
He also has this cunning plan of taking a duct from inside the conservatory across to the colder part of the house, driving the air by an extracctor fan thermostatically controlled! Without Solar it may not prove worthwhile but with it, I think it's genius. Forgive me if it's been listed elsewhere before but it's the first time I've come across it.
I reckon I could get about three ducts, strategically placed, along the length of ours and directed to the rooms in the north side of the property via the loft. Hopefully the standard loft insulation being sufficient to prevent too much heat escaping.
I wonder if anyone else has something already in place who could share their experience with us?

Coastalwatch

Up and running! Completed around lunchtime today is our Air to Air Heat Source Pump. Impressive in it's delivery it is too. Our installer was not keen on mounting the external unit on brackets bolted to the gable end wall due to the possibility of noise/vibration perculating through the wall and into the bedroom shaking us out of bed! In reality it's barely audible and, so far, quieter than the combination boiler similarly mounted in the loft. Thanks Zeup for giving us the confidence to pursue this. Once switched on it didn't take long to raise the room temperature to a comfortable 23C from the 19C starting point. With the door open into the hall the warming effects were soon apparent in there also. An impressive start but of course autumn temperatures are reasonable at the moment so a real test is yet to come.

The installer has thoughtfully installed a three pin socket and plug for the units supply, thus I have the option of placing an energy monitor between the two in order to keep a check on how much energy is being consumed by this unit independently.
In his home our installer has two such units, one 18years old with a cop of approx 3.5 and a modern unit with a cop around 5. The modern unit being relied upon to maintain the heat in the property for much of the year with the former only being pressed into action in severe weather as a top up. Further more these two are the only forms of heat to keep the property warm, the gas supply being capped a couple of years after their installation. He has a 4kW PV system installed and his annual energy bill being around £220.

At the outset I'd followed this thread purely to supply additional heating in the spring and autumn just as Zeup had envisaged. I'll see how the ASHP performs in the coming months with perhaps a view to having a second unit installed next year so we too can reduce our FF use even further!

Thanks to all contributors for guiding me through the process and allowing us to arrive here today.:D:T