Browse Forums Heating, Cooling & Insulation Re: Recirculating Hot Water Service 7Nov 23, 2016 9:17 am In my experience I have found that recirculating hot water systems for domestic dwellings are very inefficient. You lose a lot of heat energy from heat loss in the pipes, so the system is constantly circulating hot water around the house, that then loses the heat, and so the cycle goes. I have monitored energy usage in this situation and then monitored it with the circulating pump switched off, and it was a significant difference in energy consumption (about 30-40% higher with the circulation pump system operating). With that said, you could operate the circulating pump on a 7 day timer so that it is only circulating during the hours that you are likely to be using hot water (for example, for a typical family household, operate in the mornings and evenings during the week, and from day 5am - 10pm on weekends). It would be much lower cost to design the house and the plumbing system so that hot water pipe runs are minimised (i.e. locate the hot water system as central as possible to the hot water fixtures and to insulate the hot water lines with armaflex or similar. Our house is single level and quite a "sprawling" U-shaped layout. The solar hot water system is directly above the kitchen, laundry and the two other bathrooms, but the hot water pipe run from the solar hot water system to our ensuite is about 30 metres. It takes 40-50 seconds to get hot water to the ensuite. What I did was have a small Steibel Eltron instantaneous electric system installed in series with the hot water line in the ensuite, so that it heats the "dead leg" of cold water until the hot water from the central system gets to that point, then the instantaneous unit switches off. Building Services Engineer Renovating our 1960's modernist home in Brisbane https://forum.homeone.com.au/viewtopic.php?f=53&t=82091 Re: Recirculating Hot Water Service 8Nov 23, 2016 6:24 pm Reticulated hot water systems are only inefficient energy wise in domestic dwellings if the pump is constantly running. You can increase the overall efficiency with the use of timers to cycle the pump on and off and like you suggest, timeclocks to only run the system at certain time periods. I've monitored my own gas consumption over the last 12 months with my instantaneous hot water with circulating pump system compared to a 12 month period prior to my reno where I had an old storage hot water service and my consumption now is less and costs less. Considering the tariff and service charge has gone up since then, this is considerable. I'm sure I'll get better savings when I find where I misplaced that timeclock I am intending to install to only allow the pump to run during certain time periods where it will still only cycle for 3 minutes every 15 minutes to maintain the temperature of the ring main. You can't stop heat loss out of the pipes but you can reduce it by insulating all the pipework. If you go into the decision to get a reticulated as an afterthought then that's where you'd run into issues with heat losses from the pipework, increased energy consumption, etc. This should be something to be planned from the beginning and discussed with the plumber installing it who should advise and recommend things such as insulating the pipework, keeping branches as short as possible, etc. There's nothing wrong with how you've setup your hot water though I probably wouldn't do it that way myself. Like anything, horses for courses. Re: Recirculating Hot Water Service 9Nov 24, 2016 12:50 pm Yeah it's a bit unorthodox, but the layout of the house and the fact that it's 50 years old with nowhere to run new pipes was not really conducive to any other viable solution. The ensuite is miles away from the other bathrooms, kitchen and laundry. The setup works really well and only costs a few cents per day in electricity. The stiebel eltron units are variable power, so they only use as much energy as required to get the temperature rise required (e.g. from 25 degrees C to 60 degrees C), once the hot water from the solar HWS tank gets to the unit (usually within 30-40 seconds and well over 60 degrees C), it switches off completely. If it has not been long since hot water was last used, the water in the lines might be at 35-40 degrees, so it only needs to use enough energy to get the water to rise 20-25 degrees, so with insulated pipes the instantaneous heater doesn't have to do much work at all. Building Services Engineer Renovating our 1960's modernist home in Brisbane https://forum.homeone.com.au/viewtopic.php?f=53&t=82091 Re: Recirculating Hot Water Service 10Dec 03, 2016 10:10 am Bels Reticulated hot water systems are only inefficient energy wise in domestic dwellings if the pump is constantly running. You can increase the overall efficiency with the use of timers to cycle the pump on and off and like you suggest, timeclocks to only run the system at certain time periods. I've monitored my own gas consumption over the last 12 months with my instantaneous hot water with circulating pump system compared to a 12 month period prior to my reno where I had an old storage hot water service and my consumption now is less and costs less. Considering the tariff and service charge has gone up since then, this is considerable. I'm sure I'll get better savings when I find where I misplaced that timeclock I am intending to install to only allow the pump to run during certain time periods where it will still only cycle for 3 minutes every 15 minutes to maintain the temperature of the ring main. You can't stop heat loss out of the pipes but you can reduce it by insulating all the pipework. If you go into the decision to get a reticulated as an afterthought then that's where you'd run into issues with heat losses from the pipework, increased energy consumption, etc. This should be something to be planned from the beginning and discussed with the plumber installing it who should advise and recommend things such as insulating the pipework, keeping branches as short as possible, etc. There's nothing wrong with how you've setup your hot water though I probably wouldn't do it that way myself. Like anything, horses for courses. Hi, our builder advised us that heat pump will not work on solar hot water, we might have to use normal hot water storage without gas boaster. the storage Hot water service HWS which was originally to service the ground floor has been re-purposed to serve the 1st floor. The proposed heat pump HWS will now service 1st floor. Both HWS will be fitted to recirculating pumps. What do you think this setup? otherwise, builder said that will be costly. I also heard the timer could damage the heat pump if switch on and off; but it shouldn't be cause too much problem as it only use timber twice in morning and night daily. Thanks, Gary Re: Recirculating Hot Water Service 11Dec 03, 2016 8:33 pm I don't think the heat pump HWS is going to be too flash when used with a circulation pump. If you disregard the recycle timer I'm using and use purely a time clock, when it's running in the morning and at night only, the circulated water will still call the heat pump on and run the compressor if the return water is below its setpoint. I'll try to detail an example below if that helps to explain what I mean. Time clock allows operation between 5am - 8am so the circulation pump is running constantly during that time. Heat pump starts at 5am and switches off at 5.20am when the hot water is 65 degrees. With heat losses, the return water temperature drops to 50 degrees at 5.45am and the heat pump starts again Heat pump switches off at 5.50am when the hot water is 65 degrees At 6.15am the return water temperature drops to 50 degrees and heat pump switches on At 6.20am heat pump switches off again At 6.50am heat pump switches on At 7.05am heat pump switches off And so will continue until 8am when the time clock stops the circulation pump from operating. That's the sort of starting and stopping I was referring to in my original reply. Maybe contact the manufacturer of the heat pump HWS you intend of using and check if their system is compatible with a reticulated hot water system. hth Re: Recirculating Hot Water Service 12Dec 04, 2016 4:47 pm Bels I don't think the heat pump HWS is going to be too flash when used with a circulation pump. If you disregard the recycle timer I'm using and use purely a time clock, when it's running in the morning and at night only, the circulated water will still call the heat pump on and run the compressor if the return water is below its setpoint. I'll try to detail an example below if that helps to explain what I mean. Time clock allows operation between 5am - 8am so the circulation pump is running constantly during that time. Heat pump starts at 5am and switches off at 5.20am when the hot water is 65 degrees. With heat losses, the return water temperature drops to 50 degrees at 5.45am and the heat pump starts again Heat pump switches off at 5.50am when the hot water is 65 degrees At 6.15am the return water temperature drops to 50 degrees and heat pump switches on At 6.20am heat pump switches off again At 6.50am heat pump switches on At 7.05am heat pump switches off And so will continue until 8am when the time clock stops the circulation pump from operating. That's the sort of starting and stopping I was referring to in my original reply. Maybe contact the manufacturer of the heat pump HWS you intend of using and check if their system is compatible with a reticulated hot water system. hth Thanks, I should find out more about the heat pump. Re: Recirculating Hot Water Service 13Dec 06, 2016 10:48 am The builder suggested us to replace solar hot water with heat pump system, it also fit with recirculating pumps. However, I read some articles that suggested the unit is only work well in warm, humi climate; does it mean the performance in Melbourne winter will be halved? Any thought? I sent your set up system to the builder, but seems they reckon that we are different. Re: Recirculating Hot Water Service 14Dec 06, 2016 10:54 pm Yeah usually in low ambient temperatures (dead of winter in Melbourne) heat pumps will struggle to draw heat out of the air and ice forms on the outdoor coil after prolonged operation. I've had a quick look and Sanden, Rinnai, Rheem, Chromagen and Dux heat pumps all don't recommend installation in Melbourne/Victoria in general as you'll likely be using the booster element a fair bit which defeats the purpose of getting a heat pump. Solahart works down to 3-5 degrees and utilizes the booster element after that so also not that flash. The Stiebel Eltron heat pump is equipped with active defrost so would be my recommendation though I'd still check with them on compatibility with circulation pumps. My experience with finding builders was that most did not want to do anything that was out of the norm for them. Re: Recirculating Hot Water Service 15Dec 07, 2016 6:08 am Yeah builders often don't really know what they're talking about with electrical/mechanical stuff and don't like departing from their usual setup. Building Services Engineer Renovating our 1960's modernist home in Brisbane https://forum.homeone.com.au/viewtopic.php?f=53&t=82091 the sun master is the solar heating to "warm" the water in the tank the S26 is your hot water system which will heat the water (25 degrees?) so with both turned on you… 2 12390 I want to build a decking to the drawn shape outlined in black. The problem is how close can I build to the gas hot water unit? 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