CADjockey Posted June 19, 2018 Author Share Posted June 19, 2018 4 minutes ago, ProDave said: fear of noise Not so much fear, but have just never heard an ASHP in action. My assumption is that it's no worse that a gas boiler which you wouldn't site next to a bedroom for example. How far away can you site it, far side of my garage would be 8m minimum from the house, do the fan units have to be sited close to all the internal tanks etc... A friend of mine has just installed a couple so might pop round this week to have a listen. Till now he hasn't had power connected to run them. Link to comment Share on other sites More sharing options...
CADjockey Posted June 19, 2018 Author Share Posted June 19, 2018 16 minutes ago, SteamyTea said: There are certain noises I really hate Where I live the sound of petrol driven garden tools denotes the sound of a summer weekend. It should be highly irritating, but it's strangely therapeutic! Link to comment Share on other sites More sharing options...
Jeremy Harris Posted June 19, 2018 Share Posted June 19, 2018 9 minutes ago, CADjockey said: Not so much fear, but have just never heard an ASHP in action. My assumption is that it's no worse that a gas boiler which you wouldn't site next to a bedroom for example. How far away can you site it, far side of my garage would be 8m minimum from the house, do the fan units have to be sited close to all the internal tanks etc... A friend of mine has just installed a couple so might pop round this week to have a listen. Till now he hasn't had power connected to run them. Ours is tucked around the back of the house, about a 18" from the rear wall, and about 4 ft from the back door. The area is very quiet, no traffic noise and really just wildlife (and the sound of the occasional mower). It's inaudible from the back door, and there's no way of knowing from inside the house as to whether it's running or not, other than by looking at the command unit on the wall. It can't be heard in the garden, or by the neighbours, either. 1 Link to comment Share on other sites More sharing options...
le-cerveau Posted June 19, 2018 Share Posted June 19, 2018 15 minutes ago, CADjockey said: How far away can you site it, far side of my garage would be 8m minimum from the house, do the fan units have to be sited close to all the internal tanks etc... Depends on the type, a split will have a maximum distance between the Fan unit and internal unit, ours was 3m - 30m though there are performance penalties Heating 9.25kW - 8.1kW and cooling 7kW - 5.25kW (though cooling capacity max was at 7m). A mono-block (simple install unit) it depends how well you insulate the pipework as to heat loss/gain (equivalent Mono block to my split has no limit on distance and no performance figures suggesting it is down to the installation). Link to comment Share on other sites More sharing options...
jack Posted June 19, 2018 Share Posted June 19, 2018 26 minutes ago, CADjockey said: How far away can you site it, far side of my garage would be 8m minimum from the house, do the fan units have to be sited close to all the internal tanks etc... Our ASHP is on the far side of our attached garage. The pipework runs through the centre layer of the insulation under our slab. The total distance from ASHP to cylinder is around 8-9 metres. It works perfectly fine, although I'm sure that's at least partly because it's so well insulated. Our ASHP is rated to 55 deg C, and the tank reaches that temperature every morning without fail even in the middle of winter. Ours is a monobloc (single exterior unit outputs hot water). A split system (or bi-bloc) has the fan and refrigerant unit outside, and outputs hot refrigerant to an internal unit that heats water. Split systems tend to be more expensive and require installation by a refrigeration engineer due to the use of refrigerant connections. Link to comment Share on other sites More sharing options...
SteamyTea Posted June 19, 2018 Share Posted June 19, 2018 5 minutes ago, jack said: Our ASHP is rated to 55 deg C, and the tank reaches that temperature every morning without fail even in the middle of winter. Does the built in immersion heater kick in at all? Link to comment Share on other sites More sharing options...
jack Posted June 19, 2018 Share Posted June 19, 2018 22 minutes ago, SteamyTea said: Does the built in immersion heater kick in at all? No, it's disabled in the software. Link to comment Share on other sites More sharing options...
joe90 Posted June 19, 2018 Share Posted June 19, 2018 1 minute ago, jack said: No, it's disabled in the software. That’s pretty good, I notice you are in the S.E. , not next to the Atlantic like me so your RH should be lower to help with the COP.. Link to comment Share on other sites More sharing options...
CADjockey Posted June 19, 2018 Author Share Posted June 19, 2018 So at 1Kw/10m2 for ASHP (found this on the web) I roughly calculate I'd need about 45Kw supply. I could do 35Kw if I exclude the garage. My quote for GSHP kit says 49Kwh/yr, but GSHP is probably a different calculation or it includes 10% over spec. How much should you over spec the requirement? 10%? None at all? Link to comment Share on other sites More sharing options...
SteamyTea Posted June 19, 2018 Share Posted June 19, 2018 1 minute ago, CADjockey said: 1Kw/10m2 for ASHP That is 100W/m2, which seems high to me. Or maybe I am just tough and like the cold (which I don't). My space heating is 21 kWh/m2.year, which is 2.4W/m2 on average or 10W/m2 during the heating season. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted June 19, 2018 Share Posted June 19, 2018 3 minutes ago, CADjockey said: So at 1Kw/10m2 for ASHP (found this on the web) I roughly calculate I'd need about 45Kw supply. I could do 35Kw if I exclude the garage. My quote for GSHP kit says 49Kwh/yr, but GSHP is probably a different calculation or it includes 10% over spec. How much should you over spec the requirement? 10%? None at all? That sounds like a massive heating requirement to me, way, way more than I think is realistic, even for a house that is only built to "just" comply with building regs. Our house very worst case (house empty, no appliances etc running, maintained at 21 deg C) only needs 1.6 kW to maintain that internal temperature when it's -10 deg C outside. In reality, with two occupants plus the odd appliance, PC etc running, it rarely, if ever, needs as much as 1 kW of heating. Most of the time in winter it only needs a few hundred watts, if that, and we often have winter days when the heating doesn't come on at all. To specify the requirement, you first need to define the heat loss, for the worst likely case. There are several ways to do this, but I wrote a fairly simple spreadsheet that works OK, although it was only intended to be a "what if?" tool, to allow the quick comparison of changing design elements, when looking at the cost/complexity/benefit. The spreadsheet is here, if you want to play around with it: http://www.mayfly.eu/wp-content/uploads/2017/01/Fabric-and-ventilation-heat-loss-calculator-Master.xls 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted June 19, 2018 Share Posted June 19, 2018 12 minutes ago, joe90 said: not next to the Atlantic like me so your RH should be lower to help with the COP.. I don't think it makes a huge difference as with lower RH you also have lower energy (all that latent heat of fusion and stuff). When I look at RH levels across the country, they don't vary that much as our weather is predominately affected by South Westerly winds, which are high in RH. Link to comment Share on other sites More sharing options...
A_L Posted June 19, 2018 Share Posted June 19, 2018 23 minutes ago, CADjockey said: So at 1Kw/10m2 for ASHP (found this on the web) I roughly calculate I'd need about 45Kw supply. I could do 35Kw if I exclude the garage. Assuming from this a 450m2 house to current building regs with mvhr levels of air tightness then 15kW would be plenty at -3°C Link to comment Share on other sites More sharing options...
CADjockey Posted June 19, 2018 Author Share Posted June 19, 2018 1 minute ago, A_L said: 15kW would be plenty That's 1-2 units for a 450m2 build based on the 8-14Kw ratings I've seen. That's good from where I sit, I don't want to end up with an vast array of grey boxes even if behind the garage. On the other hand it was -14 on a few times this past winter! Link to comment Share on other sites More sharing options...
jack Posted June 19, 2018 Share Posted June 19, 2018 24 minutes ago, JSHarris said: Our house very worst case (house empty, no appliances etc running, maintained at 21 deg C) only needs 1.6 kW to maintain that internal temperature when it's -10 deg C outside. In reality, with two occupants plus the odd appliance, PC etc running, it rarely, if ever, needs as much as 1 kW of heating. Most of the time in winter it only needs a few hundred watts, if that, and we often have winter days when the heating doesn't come on at all. Our 289m2 house on the Hampshire/Surrey border doesn't have the solar gain that Jeremy's does, and has some large windows to the north, so despite the similar construction, we need a little more heat input than him. As an example, when our ASHP went on the blink at the start of last winter, we used a single electric column heater to heat the entire house. Bathrooms were a little too cool (no heating in the bathrooms - that's another story), but for most of winter, the house was perfectly comfortable running the column heater on medium (which I assume is somewhere between 1000-1300W). During really cold spells, we would run the heater on full (2000W) overnight. I wouldn't describe the house as being "toasty" during this period, but it was perfectly comfortable. It would have been better if our entire downstairs wasn't polished concrete, which tends to make the house seem cooler, on average, than the air temperature would suggest. Edited to add: our ASHP is a 5kW Panasonic unit, and it's more than up to the task of keeping the house warm while also providing hot water. Link to comment Share on other sites More sharing options...
joe90 Posted June 19, 2018 Share Posted June 19, 2018 14 minutes ago, jack said: our ASHP is a 5kW Panasonic unit, and it's more than up to the task of keeping the house warm while also providing hot water. Thats good to hear as ours is 4Kw and is a bit of a punt regarding being adequate ?( it was cheap on Ebay). 1 Link to comment Share on other sites More sharing options...
joe90 Posted June 19, 2018 Share Posted June 19, 2018 28 minutes ago, SteamyTea said: I don't think it makes a huge difference as with lower RH you also have lower energy (all that latent heat of fusion and stuff). When I look at RH levels across the country, they don't vary that much as our weather is predominately affected by South Westerly winds, which are high in RH. I thought lower temps and high RH led to more defrosting cycles for an ASHP? Link to comment Share on other sites More sharing options...
PeterW Posted June 19, 2018 Share Posted June 19, 2018 I’ve just put a 9kw one in where the heat load is 3.2kw at -5c and that’s just so it doesn’t get stressed (and it was cheap..!) The kw/m2 call you have found is for oil boiler replacements in houses built to 2003 regs and is still barking mad ... If I was going ASHP (and Aga...) then I would go with a 12kw unit as it’s the max you can go on single phase and up size the buffer and the UVC / Sunamp for hot water and run it overnight on E7 and then use PV during the day. Link to comment Share on other sites More sharing options...
JamesP Posted June 19, 2018 Share Posted June 19, 2018 1 hour ago, jack said: Our ASHP is rated to 55 deg C, and the tank reaches that temperature every morning without fail even in the middle of winter. Does this temperature meet the legionella issue as you have disabled the immersion. Do you know how an ASHP can be used for cooling UFH, I am looking at the new, (quieter) Mitsubishi Ecodan PUHZ-W85VAA. Thanks. Link to comment Share on other sites More sharing options...
CADjockey Posted June 19, 2018 Author Share Posted June 19, 2018 23 minutes ago, PeterW said: 12kw unit as it’s the max you can go on single phase Interesting to know. Thanks for that. Link to comment Share on other sites More sharing options...
CADjockey Posted June 19, 2018 Author Share Posted June 19, 2018 OK, as I'm in season for stupid questions... What happens when you get a foot of snow or more with an ASHP? GSHP is obviously insulated from the weather give or take. Link to comment Share on other sites More sharing options...
joe90 Posted June 19, 2018 Share Posted June 19, 2018 (edited) 2 minutes ago, CADjockey said: OK, as I'm in season for stupid questions... What happens when you get a foot of snow or more with an ASHP? GSHP is obviously insulated from the weather give or take. Snow insulates, as long as the air can get to the fan it’s not a problem. I am building a louvred cover for mine as it faces SW and we are exposed and near the Atlantic. p.s. No such thing as a stupid question, stupid is not asking! Edited June 19, 2018 by joe90 Link to comment Share on other sites More sharing options...
ProDave Posted June 19, 2018 Share Posted June 19, 2018 33 minutes ago, PeterW said: If I was going ASHP (and Aga...) then I would go with a 12kw unit as it’s the max you can go on single phase I think you are getting confused. 12KW might be the maximum amount of electrical power you would want to use on one appliance on single phase, but a 12KW heat pump will probably only use 4KW of power. So on that basis if the heat pump were to use 12KW of electric power it would be a monster with an output of over 40KW Re heating power requirements, our house is not as good as some on here, but not bad, needing about 2.5KW of heat to maintain 20 degrees inside when it's -10 outside. And that will be provided by a 5KW ASHP. Link to comment Share on other sites More sharing options...
PeterW Posted June 19, 2018 Share Posted June 19, 2018 17 minutes ago, ProDave said: I think you are getting confused. 12KW might be the maximum amount of electrical power you would want to use on one appliance on single phase, but a 12KW heat pump will probably only use 4KW of power. So on that basis if the heat pump were to use 12KW of electric power it would be a monster with an output of over 40KW Nope - I spoke to both Mitsubishi and Panasonic and both step from 1 to 3 phase over 14kw. Whilst at a decent CoP (A7/W35) you will be pulling only 3.5kw on the 14kw Ecodan, outside of this the CoP falls away and there is a point at which parity is reached. Add to this that the 12kw Panasonic has a 6kw in built immersion and the max draw on most of the bigger units is towards 30A. Most commercial units on 3 phase have much lower draw - Panasonic used to make a 3 phase unit that is 12kw but it’s purely for commercial use where 3P is available. A 35-40Kw ASHP would be a 3 phase unit or preferably a pair of smaller units to allow for redundancy. Link to comment Share on other sites More sharing options...
jack Posted June 19, 2018 Share Posted June 19, 2018 28 minutes ago, JamesP said: Does this temperature meet the legionella issue as you have disabled the immersion. We've only disabled the inbuilt immersion in the ASHP. We have two immersions on the unvented cylinder, and they are used with a PV diverter. The entire tank reaches 75+ deg C on many days during the sunnier half of the year. As for winter, after a lot of research, I concluded that our situation involves a low risk of Legionella: domestic situation with smallish-tank for the size of the house (= complete turnover of tank water every couple of days) no iron or steel components (= no sludge or rust for Legionella to live in) softened water (= reduced build-up of calcium deposits in which Legionella might live) a sealed system (gravity fed systems with open header tanks are a potential vector) occupants who are not at high risk (no elderly and infirm occupants, or regular visitors who might use showers). I therefore don't run a Legionella cycle. We do have one relatively long dead leg, which is the run to the guest room ensuite. The shower in that room is never used, and in theory that could be a problem, but a Legionella cycle at the hot water tank wouldn't really reduce that risk much. Within the next year or two I can see this bathroom being commandeered by one of the kids, which will remove this potential issue. 44 minutes ago, JamesP said: Do you know how an ASHP can be used for cooling UFH, Some units just have a code you input via the service menu. It's done that way because the Renewable Heat Incentive doesn't pay out for units with a cooling mode. The lockout is a way of getting around this. Personally I haven't bothered with cooling mode on mine. The main place we have issues with heat is upstairs, and there's no UFH there. 36 minutes ago, CADjockey said: What happens when you get a foot of snow or more with an ASHP? A foot of snow sits on top of the unit and on the ground around it? Makes no operational difference as far as I can tell. 1 Link to comment Share on other sites More sharing options...
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