Iceverge Posted March 8, 2023 Share Posted March 8, 2023 I just had a genius idea so did a quick sketch. 300l Cylinder. No problems 4 Link to comment Share on other sites More sharing options...
TerryE Posted March 8, 2023 Share Posted March 8, 2023 9 hours ago, Dave Jones said: I need to provide for 4 showers happening at the same time, the washing machine and dishwasher on at same time. The showers are decent 20L/min, so won't take long to empty a small tank. You could also just feed a HW tap direct into a drain and then you'd get through the HW a lot or you could ask what your objective are here and modify behaviours accordingly to minimise costs whilst maintaining those objectives. In terms of our DW and WM, these are both cold-fill and have timer functions in-built so 90+% of the these go on overnight to use cheap rate electricity. My aim in having a shower is to get clean, quickly and efficiently. All of this COVID focus on the "right way" to hand-wash reminded me that the three most effective components in removing microbes, dead skin, sweat and dirt are (i) soap solution on skin, (ii) contact time, and (iii) mechanical friction. A high-flow volume doesn't really help here, as this buggers up (i) and (ii). So my strategy is to do a quick wet down (say ~10s), then a full body lather and rub down for at least 60s, then a quick rinse and blade off to remove 99% of the soap and then a final rinse off. Our showers have a 8 L/min click-stop and I probably have under a min flow under this stop limit. We have ~2bar head at normal flow rates so unstopped we get maybe 15-20 L/min but I find I need maybe 30 sec final rinse-off to come out spotless and soap-free, so perhaps 15-20L in total for the shower. Maybe this might seem a bizarre behaviour to most members, but all I can suggest is that I come out of the shower cleaner than if I'd just stood under it for 3-5min @ 20L/min, so I view this latter as pouring money down the drain for no benefit. Or just call me boring old Mr Pompous. 🤣 2 Link to comment Share on other sites More sharing options...
Nickfromwales Posted March 8, 2023 Share Posted March 8, 2023 3 hours ago, JohnMo said: Yes a Combi boiler and a combi-nation of components Ok, then does the combi not fire DHW to all outlets via the buffer? Eg when any hot water tap is run, the combi diverts to DHW mode? Link to comment Share on other sites More sharing options...
Nickfromwales Posted March 8, 2023 Share Posted March 8, 2023 1 hour ago, Iceverge said: I just had a genius idea so did a quick sketch. 300l Cylinder. No problems You have WAY too much spare time on your hands! PMSL. Link to comment Share on other sites More sharing options...
Adrian Walker Posted March 8, 2023 Share Posted March 8, 2023 1 hour ago, TerryE said: Maybe this might seem a bizarre behaviour to most members, but all I can suggest is that I come out of the shower cleaner than if I'd just stood under it for 3-5min @ 20L/min, so I view this latter as pouring money down the drain for no benefit. I totally agree, allowing 4 people to shower @ 20L/min for 20+ mins is madness. I would install electric showers that are controlled via a coin-mech using £1 and £2 coins. That is your most efficient HW setup. 2 1 Link to comment Share on other sites More sharing options...
Onoff Posted March 8, 2023 Share Posted March 8, 2023 1 hour ago, Iceverge said: I just had a genius idea so did a quick sketch. 300l Cylinder. No problems Presumably you could do similar with WC pans and soil pipe runs? 1 Link to comment Share on other sites More sharing options...
JohnMo Posted March 8, 2023 Share Posted March 8, 2023 15 minutes ago, Nickfromwales said: 4 hours ago, JohnMo said: Yes a Combi boiler and a combi-nation of components Ok, then does the combi not fire DHW to all outlets via the buffer? Eg when any hot water tap is run, the combi diverts to DHW mode? The buffer is the combi thermal store. Cold water goes through the upper coil, all the time, if buffer is warm or hot, cold water is pre-heated, if above 43 degrees a diverter valve sends all preheated water to a mixer valve, if below 43 it all goes to combi boiler for heating then and gets mixed with cold via the mixer. Combi boiler water temp is set to 65, this gives the best gas usage overall. Multiple taps and showers at same are no issue. Link to comment Share on other sites More sharing options...
Dave Jones Posted March 9, 2023 Author Share Posted March 9, 2023 thanks for the useful replies. Doesn't look to be too difficult to accomplish. Using a single 500L unistor as a a start, even from completely depleted it would take 3.5 hours of pre-heat from the ASHP followed by 1.9 hours of immersion topup for a total of 33.1Kwh . That's assuming only 6kw of heat from the ASHP which is pretty low.More than feasible overnight on cheap rate or top up over the day from PV. Should capacity be an issue then can allways add another little smaller tank and still have plenty of spare capacity on the mains/heat pump. Now for the hard part, the controls...... Requirement 1. - need the above hot water to happen irresepective of time of year. Requirement 2. - Where house stat calls for heat it need to be supplied, low flow temp, no zones, 3 degree nightly fallback. Requirement 3. - cooling, still need req1 to happen but also need heatpump to reverse and put cold into ufh and supply mvhr chiller unit. As its likely to have an excess of solar heat the tanks to a much higher temp (90c?)with immersion only to give more useable and negate the need for heat pump to provide hot water? Asking the impossible for a control system to do all the above automatically ? Link to comment Share on other sites More sharing options...
JohnMo Posted March 9, 2023 Share Posted March 9, 2023 Unistor may not be the best choice, believe they need an anode and associated maintenance, the coil size is the minimum they could get away with. Others will give 3m2 + coil for better reheat times but more importantly a lower supply temp from HP to get same cylinder temp. 1 Link to comment Share on other sites More sharing options...
Dave Jones Posted March 9, 2023 Author Share Posted March 9, 2023 was looking at these yesterday and noticed the flow rate from them. it wont be enough. Will continue looking for tanks with larger flow but may make more sense to split the tanks so each supplies 2 of the showers. https://www.cylinders2go.co.uk/shop/renewable-energy/500-litre-telford-tempest-heat-pump-cylinder-twin-immersion/ Link to comment Share on other sites More sharing options...
JohnMo Posted March 9, 2023 Share Posted March 9, 2023 The Telford ones have a pretty big coil, about 3.2m2. You can also get the custom made to suit you. Extra insulation, 28mm inlet and outlet etc. 1 Link to comment Share on other sites More sharing options...
Dave Jones Posted March 9, 2023 Author Share Posted March 9, 2023 mixergy claim their plate heat exchanger is more efficient than a traditional coil. Not sure by how much ? As its external I guess it could be bolted onto a standard tank/used to heat two tanks with valves ? https://mixergy.co.uk/news-and-insights/mixergy-heat-pumps-faqs/ Link to comment Share on other sites More sharing options...
Dan F Posted March 9, 2023 Share Posted March 9, 2023 1 minute ago, Dave Jones said: mixergy claim their plate heat exchanger is more efficient than a traditional coil. Not sure by how much ? As its external I guess it could be bolted onto a standard tank/used to heat two tanks with valves ? https://mixergy.co.uk/news-and-insights/mixergy-heat-pumps-faqs/ They reckon 6-10% more efficient, but that's going to depend on the heat pump and the external PHE obviously has higher losses than an internal coil. What Mixergy claim is that the PHE means that i) the tank volume is more fully utilized ii) they can offer slimline tanks. If you want a PHE for a standard tank you could look at this one: https://mcdonaldwaterstorage.com/products/plateflow-plate-heat-exchanger/. I don't know where the Mixergy PHE is installed relative to the tank, but this one being at the top means that: "At times when less than the steady flow rate is required, all the hot water requirement is generated instantly by the PHE (A), with any excess recharging the buffer vessel (B). Only when demand exceeds the steady flow rate of the PHE, is water from the buffer vessel used (C). Even when the buffer vessel is depleted, the steady flow rate is always available." 1 Link to comment Share on other sites More sharing options...
markocosic Posted March 9, 2023 Share Posted March 9, 2023 Ask Telford for a tank with 28 mm or 35 mm inlets/outlets. And 2x 6 kW immersions for manual backup / stupid reheat when family of 9000 visits option. Allow the heat pump to reheat the water. The OEM controls allow time clocking should you wish. Using an immersion is dumb. Just let the heat pump do its job. It has nothing else to do in summer anyway. Don't do night setback in a newbuild. Waste of bloody time and leaves the heat pump working overtime when it's nasty cold first thing in the morning. Leave it at setpoint 24/7. No house stat. Again you let the heat pump's single zone stat manage it all. KISS. Cooling is perhaps the only one that needs any complexity. Chilling the UFH is straightforward enough again via the heat pump's standard controls. Adding the MVHR duct cooler in is a complication. I don't know how you would manage that. I would design it out if you don't need it. Less is more if the UFH is enough to cool. Running chilled plasterboard ceilings is also an option. More effective than chilled floors. Link to comment Share on other sites More sharing options...
JohnMo Posted March 9, 2023 Share Posted March 9, 2023 6 hours ago, Dan F said: They reckon 6-10% more efficient, but that's going to depend on the heat pump and the external PHE obviously has higher losses than an internal coil. Really depends on what is being compared and the size of the internal coil. You also add the cost of running a pump. PHE and controller is also additional extra on top of the cost of the cylinder, if want to divert PV that's another extra. Link to comment Share on other sites More sharing options...
Dave Jones Posted March 12, 2023 Author Share Posted March 12, 2023 (edited) struggling to find the COP or SCOP when running in cooling mode, doesn't seem to be listed on the data sheets ? https://midsummerwholesale.co.uk/pdfs/ht-quiet-datasheet.pdf Edited March 12, 2023 by Dave Jones Link to comment Share on other sites More sharing options...
JohnMo Posted March 12, 2023 Share Posted March 12, 2023 3 hours ago, Dave Jones said: struggling to find the COP or SCOP when running in cooling mode You need to find and download the technical manual for the heat pump, these are normally available but hard to find Link to comment Share on other sites More sharing options...
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