ProDave Posted November 26, 2018 Share Posted November 26, 2018 I am far from convinced about economy 7 Usage so far shows heating and DHW is a minor part of my electricity usage. I use more per week on "stuff" and can't find a way to reduce that. So even if I could do all my heating and hot water on the cheap E7 overnight rate, the penalty is the day rate is a lot more than a standard tariff so I expect the E7 saving would be wiped out by the extra daytime cost. Link to comment Share on other sites More sharing options...
Guest Alphonsox Posted November 26, 2018 Share Posted November 26, 2018 1 hour ago, ProDave said: I am far from convinced about economy 7 Usage so far shows heating and DHW is a minor part of my electricity usage. I use more per week on "stuff" and can't find a way to reduce that. So even if I could do all my heating and hot water on the cheap E7 overnight rate, the penalty is the day rate is a lot more than a standard tariff so I expect the E7 saving would be wiped out by the extra daytime cost. This depends on where you are in the UK (prices vary considerably) and whether your consumption can easily be moved to the off-peak period. We have washing machines, dish washers and tumble dryers that are all timed to work overnight, along with the UFH and DHW. Link to comment Share on other sites More sharing options...
vfrdave Posted November 26, 2018 Share Posted November 26, 2018 Like @Alphonsox says in NI it seem more reasonable. The economy 7 day rate is only 0.4pence a unit more expensive than standard with an 8p a day standing charge. I need to try and do some sums to quantify. Link to comment Share on other sites More sharing options...
Ricco Posted November 29, 2018 Author Share Posted November 29, 2018 For DHW I have been advised if going for an ASHP to have a high gain heat pump cylinder but I am still interested in a SunAmp. Can someone please explain to me the heating costs, what I mean is..... a 12kw sunamp with a 3kw immersion will take a full 12kw of electricity to charge from cold. But if running a high gain cylinder then taking the c.o.p of the ASHP into consideration then to get 12kw of heat into your cylinder it will take half or a third of the required energy. I know @Nickfromwales has referenced SunAmps in the past so hopefully someone will be able to explain it. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted November 29, 2018 Share Posted November 29, 2018 1 hour ago, Ricco said: For DHW I have been advised if going for an ASHP to have a high gain heat pump cylinder but I am still interested in a SunAmp. Can someone please explain to me the heating costs, what I mean is..... a 12kw sunamp with a 3kw immersion will take a full 12kw of electricity to charge from cold. But if running a high gain cylinder then taking the c.o.p of the ASHP into consideration then to get 12kw of heat into your cylinder it will take half or a third of the required energy. I know @Nickfromwales has referenced SunAmps in the past so hopefully someone will be able to explain it. There are two different units of measurement here, power and energy, and to compare anything they need to be separated out. Taking a Sunamp UniQ 9, or a 210 litre hot water cylinder (they have pretty much the same heat energy storage capacity) as examples, then if both had a 3 kW nominal heating element both would take about 3 hours to be fully charged with around 9 kWh of heat energy (heat energy, in kWh, is heat power in kW x time in hours). In practice both will take a bit over 3 hours to be fully charged, due to losses and slight variations between the two, but we can assume for this example that they both hold around 9 kWh of heat energy when charged. In terms of heat losses, then a typical well-insulated hot water cylinder will lose between 2 kWh and 2.5 kWh over 24 hours, whereas a Sunamp UniQ 9 would lose around 0.7 kWh, so the losses are a lot lower for the Sunamp. If heating either a hot water Sunamp or a hot water tank from a heat pump, then the heat pump performance will not be good, because of the high temperature required. I'm not even sure that many heat pumps would deliver a high enough flow temperature to charge a hot water Sunamp, as they need around 60 deg C or more. You can get away with having a hot water system that runs at around 50 deg C, but when using a hot water cylinder you'd be advised to fit a larger capacity one, because it will be running at a lower temperature, so won't get mixed down with cold water at the point of use by as big a ratio, so more water from the tank will be drawn off than might be the case if the tank was running at a higher temperature. How big a hot water tank you need really depends on your hot water needs. For example, we run two showers per day, plus washing up, hand washing etc, and use around 150 litres of water at around 58 deg C (from an electrically heated Sunamp UniQ) per day, sometimes a bit less, sometimes a bit more. I'm in the process of measuring the energy (in kWh) that we use to generate hot water, and should have a reasonable figure as a daily average by early next week. Right now it looks as if we are using around 4 kWh or so of electricity per day to heat our hot water (roughly 20% from solar panels, 80% from the grid, as it's winter), but that ignores the ASHP pre-heat system we have, which feeds warm (around 35 deg C to 40 deg C) water to the Sunamp, so reducing our electricity usage a fair bit. So, to work out the relative costs, both in terms of the initial investment plus the running cost, we need to know how much hot water you are likely to use. Heating is a different issue, and in a well-insulated and airtight house will often be lower than the hot water requirement, and is probably best dealt with separately. Link to comment Share on other sites More sharing options...
vfrdave Posted November 30, 2018 Share Posted November 30, 2018 The IVT Ecolane ASHP seem to do high temp output and at a reasonable COP based on @PeterW testing. Available on eBay currently as a 9Kw unit. Link to comment Share on other sites More sharing options...
Nickfromwales Posted November 30, 2018 Share Posted November 30, 2018 24 minutes ago, vfrdave said: The IVT Ecolane ASHP seem to do high temp output and at a reasonable COP based on @PeterW testing. Available on eBay currently as a 9Kw unit. Very much worthy of further investigation. I'd be very interested in the reliability / longevity when it's routinely driven at these higher temperatures. Higher output has to come at some price? Link to comment Share on other sites More sharing options...
ProDave Posted November 30, 2018 Share Posted November 30, 2018 1 minute ago, Nickfromwales said: Very much worthy of further investigation. I'd be very interested in the reliability / longevity when it's routinely driven at these higher temperatures. Higher output has to come at some price? And how it copes with defrosting when it gets cold. Both Jeremy and I have found our respective heat pumps never need to defrost when running at 40 degrees but above that they do when it gets cold. Link to comment Share on other sites More sharing options...
Nickfromwales Posted November 30, 2018 Share Posted November 30, 2018 As they're cheaper than shoplifting, I'd be inclined to get two and halve the duty of each unit. As the temp would still be high, I wonder how doubling up would improve things. Link to comment Share on other sites More sharing options...
newhome Posted November 30, 2018 Share Posted November 30, 2018 5 minutes ago, ProDave said: Both Jeremy and I have found our respective heat pumps never need to defrost when running at 40 degrees but above that they do when it gets cold. Do you find 40 degrees high enough to shower / bath? I find that unless the top of my TS is 50 plus then it’s not hot enough ? Link to comment Share on other sites More sharing options...
Nickfromwales Posted November 30, 2018 Share Posted November 30, 2018 6 minutes ago, newhome said: Do you find 40 degrees high enough to shower / bath? I find that unless the top of my TS is 50 plus then it’s not hot enough ? It's nowt to do with what's stored in your cylinder / other, it's to do with what your shower is set at Typically my shower is set to 38 and that's fine for me. The kids and wife have it MUCH hotter, so in order to reduce my annual energy consumption........they've got to go ?. 1 2 Link to comment Share on other sites More sharing options...
ProDave Posted November 30, 2018 Share Posted November 30, 2018 5 minutes ago, newhome said: Do you find 40 degrees high enough to shower / bath? I find that unless the top of my TS is 50 plus then it’s not hot enough ? That's the point. I heat my water to 48 degrees and if it's just sub zero the HP starts doing defrost cycles that both slows down the heating rate and uses more electricity. It can run all day if needed heating UFH water to 37 degrees and it never needs to defrost. 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted November 30, 2018 Share Posted November 30, 2018 Point being, try turning your shower up more than 38 and see how uncomfortable it becomes. Remember big shower heads will allow the water to cool slightly as it falls. Link to comment Share on other sites More sharing options...
PeterW Posted November 30, 2018 Share Posted November 30, 2018 21 minutes ago, Nickfromwales said: Very much worthy of further investigation. I'd be very interested in the reliability / longevity when it's routinely driven at these higher temperatures. Higher output has to come at some price? From the digging I’ve done, these were designed to be run as the outside unit for a prepackaged tank and heat pump system by IVT for use in Nordic countries. I expect that the units have a pre-set curve for this sort of climate so will be slightly low for this sort of region. Its been around 5-6c around here this afternoon and driving the unit at 88% it did defrost once however it seems to slow down a little but not really that much. Time will tell on reliability however they seem pretty good units. Link to comment Share on other sites More sharing options...
Nickfromwales Posted November 30, 2018 Share Posted November 30, 2018 3 minutes ago, ProDave said: That's the point. I heat my water to 48 degrees and if it's just sub zero the HP starts doing defrost cycles that both slows down the heating rate and uses more electricity. It can run all day if needed heating UFH water to 37 degrees and it never needs to defrost. In that scenario I'd just boost with the immersion as its cheap enough and cost pennies to replace compared to running the ASHP too had too long and then also ending up using an immersion for defrost anyway. Get the tank to 42/43 and then get to 50 with immersion. Link to comment Share on other sites More sharing options...
newhome Posted November 30, 2018 Share Posted November 30, 2018 22 minutes ago, Nickfromwales said: Point being, try turning your shower up more than 38 and see how uncomfortable it becomes. Remember big shower heads will allow the water to cool slightly as it falls. My shower is way above 38. 38 is like COLD! ❄️ I guess what I mean by not hot enough is unless the tank is at 50 at the top there isn't enough hot water to keep it at my preferred temperature for the duration of a shower unless the top is 50 plus, better still 60 plus ?. But then I never shower really quickly so may use more hot water than some ... Link to comment Share on other sites More sharing options...
ProDave Posted November 30, 2018 Share Posted November 30, 2018 24 minutes ago, Nickfromwales said: In that scenario I'd just boost with the immersion as its cheap enough and cost pennies to replace compared to running the ASHP too had too long and then also ending up using an immersion for defrost anyway. Get the tank to 42/43 and then get to 50 with immersion. It needs more thought. If you just said shut off the HP at 42 degrees and heat to 50 with the immersion, then when you draw water off and the temperature drops, the immersion thermostat would kick in and top it up, and the HP would never get a look in at heating the water unless you drained the tank completely. What is needed is a bit more intelligence. Like the HP needs to detect it needs to defrost, so it aborts heating the HW with the HP and uses it's internal willis heater instead. But at other times when the conditions do not dictate any need for defrosting, carry on using the HP. I might play with this later when I fit solar PV and reprogram my home made Arduino dump controller. e.g fit an outside temperature sensor, and if the outside temp drops below zero, turn off the HP demand for hot water and heat the HW entirely with the immersion heater until the temperature rises above 0 again with the arduino monitoring the tank temperature and turning it off at 50. Link to comment Share on other sites More sharing options...
ProDave Posted November 30, 2018 Share Posted November 30, 2018 5 minutes ago, newhome said: My shower is way above 38. 38 is like COLD! ❄️ I guess what I mean by not hot enough is unless the tank is at 50 at the top there isn't enough hot water to keep it at my preferred temperature for the duration of a shower unless the top is 50 plus, better still 60 plus ?. But then I never shower really quickly so may use more hot water than some ... I am willing to bet it takes you longer to wash your hair than it does me...... 1 Link to comment Share on other sites More sharing options...
Declan52 Posted November 30, 2018 Share Posted November 30, 2018 Can you not just use a pre programed setting on the hp and have it run for 2/3/4hrs each morning to get your tank to 40 degrees then have your immersion on a timer clock so it then kicks in for another 2/3 hrs to get the team up to 50. Link to comment Share on other sites More sharing options...
Nickfromwales Posted November 30, 2018 Share Posted November 30, 2018 17 minutes ago, Declan52 said: Can you not just use a pre programed setting on the hp and have it run for 2/3/4hrs each morning to get your tank to 40 degrees then have your immersion on a timer clock so it then kicks in for another 2/3 hrs to get the team up to 50. Kinda what I meant. Was just about to type that. Restrict the tanks acces to grid electricity in time with 'peak' Dhw demand. 35 minutes ago, ProDave said: It needs more thought. If you just said shut off the HP at 42 degrees and heat to 50 with the immersion, then when you draw water off and the temperature drops, the immersion thermostat would kick in and top it up, and the HP would never get a look in at heating the water unless you drained the tank completely. What is needed is a bit more intelligence. Like the HP needs to detect it needs to defrost, so it aborts heating the HW with the HP and uses it's internal willis heater instead. But at other times when the conditions do not dictate any need for defrosting, carry on using the HP. I might play with this later when I fit solar PV and reprogram my home made Arduino dump controller. e.g fit an outside temperature sensor, and if the outside temp drops below zero, turn off the HP demand for hot water and heat the HW entirely with the immersion heater until the temperature rises above 0 again with the arduino monitoring the tank temperature and turning it off at 50. Agreed. Nothing's ever straight forward is it ? Link to comment Share on other sites More sharing options...
Declan52 Posted November 30, 2018 Share Posted November 30, 2018 So it is possible to run a hp like this then. This is how I would like to run one in the future. Charge the slab up in the morning and then that's enough heat for the vast majority of the winter months. The only problem would be sizing a hp to suit the max demand in the morning if all 5 zones called for heat. My 15kw pellet stove just about keeps up at the moment. But a 15kw hp would be expensive. Link to comment Share on other sites More sharing options...
PeterW Posted November 30, 2018 Share Posted November 30, 2018 10 minutes ago, Declan52 said: So it is possible to run a hp like this then. This is how I would like to run one in the future. Charge the slab up in the morning and then that's enough heat for the vast majority of the winter months. The only problem would be sizing a hp to suit the max demand in the morning if all 5 zones called for heat. My 15kw pellet stove just about keeps up at the moment. But a 15kw hp would be expensive. 17kw ASHP for change of £2500.... Link to comment Share on other sites More sharing options...
Declan52 Posted November 30, 2018 Share Posted November 30, 2018 15 minutes ago, PeterW said: 17kw ASHP for change of £2500.... Cheaper than I thought but not the nice sub £1k bargains mentioned above. Link to comment Share on other sites More sharing options...
PeterW Posted November 30, 2018 Share Posted November 30, 2018 True but still a bargain. Those IVT ones are bizarre though as 18 months ago they were less than £600... Link to comment Share on other sites More sharing options...
ProDave Posted November 30, 2018 Share Posted November 30, 2018 Well my 5KW HP is doing a fine job of keeping the house warm, running at a very low duty cycle. I cannot imagine anyone needing a 17Kw version. In my ideal world, I would not even try heating the DHW until mid day. I am a "shower at night" person, I just can't see the logic in getting into bed dirty and waiting until the morning to get clean, so I just need a bit of warm water in the morning for a face wash. But the girls seem to want a piping hot shower at the crack of dawn which forces a DHW top up early in the morning, when the day has not had chance to warm up, and (thinking of the future) not even any sun for the PV Link to comment Share on other sites More sharing options...
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