Russell griffiths Posted July 18, 2019 Share Posted July 18, 2019 I’m starting to look into designs for our hw. One method is a recirculating system where a pump is fitted to the hot and fires up when needed. What are the pros and cons to this type of system, how have you got your pump wired, when does it kick in, timer, light switch, do you use the FORCE and just stare at it. Come on I need answers, the more I look on the forum and pretend I’m doing something the less she insists I help with the washing up. Ta very much. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted July 18, 2019 Share Posted July 18, 2019 A recirculation system is a massive waste of energy in a home when you will only draw HW a few times a day. For the rest of the day you will be keeping the pipes warm, and associated spaces, for no reason. In a hotel such systems work well as HW is in constant demand and pipe runs are long so delays getting to HW are not acceptable but in houses these runs can be short. I suppose you could mitigate the waste issue by just running the system at high demand periods, as in early morning / bed time or whenever else you bathe. Link to comment Share on other sites More sharing options...
ToughButterCup Posted July 18, 2019 Share Posted July 18, 2019 56 minutes ago, Russell griffiths said: [...] Come on I need answers, the more I look on the forum and pretend I’m doing something the less she insists I help with the washing up. [...] Shame on you : MTFU. Buy a dishwasher. 1 1 Link to comment Share on other sites More sharing options...
gravelld Posted July 18, 2019 Share Posted July 18, 2019 (edited) I've actually just had ours fixed (the pump was broken since we brought the house). It's not actually for recirculation to the taps though - for us it's actually used to circulate the hot water out of the top of the HWC, where the water is heated by an immersion coil powered by PV, and into the bottom. Otherwise, we only get 1/3 of a tank heated by the PV. I just run it for ten minutes as soon as the immersion coil hits 60C. If we didn't have such a silly design to begin with, I wouldn't bother, for the reasons @MikeSharp01 explained. You can do the calcs to work out the volume of water in the pipes. Another concern is overheating in a high spec house (the pipes become radiators). Naturally, all pipes must be lagged, and then ideally lagged/insulated again! Edited July 18, 2019 by gravelld Link to comment Share on other sites More sharing options...
PeterW Posted July 18, 2019 Share Posted July 18, 2019 You need around 2min/hour run time on these, and they need to be lagged. Constant is a waste of money, as are proximity sensors per room. Simple rotary timer on a bronze pump Link to comment Share on other sites More sharing options...
gravelld Posted July 18, 2019 Share Posted July 18, 2019 I actually wired mine to a smart plug so it can be automated with other things, but again that's because of my use case. Link to comment Share on other sites More sharing options...
joth Posted July 18, 2019 Share Posted July 18, 2019 14 minutes ago, PeterW said: Constant is a waste of money, as are proximity sensors per room. I'm planning motion sensors in bathrooms anyway as they could potentially do a lot more in due course -- MVHR boost mode, power up the towel rads, low level "night light", (turn on radio 2, crank up the UFH......). Installing them just for secondary return seems overkill Link to comment Share on other sites More sharing options...
Russell griffiths Posted July 18, 2019 Author Share Posted July 18, 2019 1 hour ago, PeterW said: You need around 2min/hour run time on these, and they need to be lagged. Constant is a waste of money, as are proximity sensors per room. Simple rotary timer on a bronze pump Thanks @PeterW do you have this timer running 24hours or do you get it to do it’s first 2minute spin at say 5 in the morning ready for morning showers, and say it turns off at 11 at night. Link to comment Share on other sites More sharing options...
PeterW Posted July 18, 2019 Share Posted July 18, 2019 It’s on a commercial building and it runs 6am - 11pm, and is one of the rotary ones so actually runs 15mins/hr as that’s the minimum you can set. It took about £350 off the electricity bill in its first year as it used to empty the hot water tank if you weren’t careful when on permanently. Link to comment Share on other sites More sharing options...
CC45 Posted July 18, 2019 Share Posted July 18, 2019 ours is wired into a single channel programmer. Link to comment Share on other sites More sharing options...
Russell griffiths Posted July 19, 2019 Author Share Posted July 19, 2019 Can you get a flow switch fittted somewhere that kicks the pump in when it detects flow. Link to comment Share on other sites More sharing options...
PeterW Posted July 19, 2019 Share Posted July 19, 2019 Yes however which pipe do you put it in ..?? By the time it’s kicked in as someone has opened a tap, the water will nearly be there anyway. Link to comment Share on other sites More sharing options...
PeterW Posted July 19, 2019 Share Posted July 19, 2019 If you want down to 2mins/hour then you probably need something like this - usually used on hydroponics of all things ..!! The heat loss from a lagged 22mm pipe is negligible, it’s all a matter of cost vs convenience 1 Link to comment Share on other sites More sharing options...
Patrick Posted July 19, 2019 Share Posted July 19, 2019 8 minutes ago, PeterW said: If you want down to 2mins/hour then you probably need something like this - usually used on hydroponics of all things ..!! Now the big question is, how would one come across such an item. ??? Link to comment Share on other sites More sharing options...
PeterW Posted July 19, 2019 Share Posted July 19, 2019 8 minutes ago, Patrick said: Now the big question is, how would one come across such an item. ??? Google ....!! 1 Link to comment Share on other sites More sharing options...
Jenni Posted July 19, 2019 Share Posted July 19, 2019 I'm mulling over having a hot water loop. My tank is adjacent to the bathroom but approx 15m from the kitchen + utility. I don't mind waiting a few moments for hot water, just hate watching it go down the plughole until hot arrives. So I'm thinking about having a button I press to run the pump, and a light and/or buzzer that tells me when the hot has arrived so I can use the tap. No idea yet how to achieve this tho! Link to comment Share on other sites More sharing options...
CC45 Posted July 19, 2019 Share Posted July 19, 2019 single channel programmer - most have a 1hr boost button. Not quite what you're after but just set it to run during busy water use periods. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted July 19, 2019 Share Posted July 19, 2019 An alternative is to just use small bore pipe for the feeds to basins and sinks. 10mm pipe is usually fine for these, if you have a decent mains pressure, and the hot water will run a lot quicker due to the smaller volume in the pipe. It's also easy to increase the size of the insulation on 10mm pipes without things getting too bulky in confined spaces, and the heat loss will generally be lower overall, due to the lower volume of hot water in the pipes and the smaller pipe surface area. Link to comment Share on other sites More sharing options...
Bitpipe Posted July 19, 2019 Share Posted July 19, 2019 We have our hot re-circulation pump on PIR sensors in bathrooms and on the light switches also - same circuit activates the MVHR boost Link to comment Share on other sites More sharing options...
Jenni Posted July 19, 2019 Share Posted July 19, 2019 Possibly a button like this will get the pump running hot through the loop - http://www.archiexpo.com/prod/cp-electronics/product-53932-1184141.html But haven't found a way to be notified that hot water is at the tap. I'm picturing an inline sensor, linked to led/buzzer. Smaller bore pipe is an interesting idea @JSHarris, are there any disadvantages to this for hot runs to kitchen and utility? Can the cold run be bigger or should it match? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted July 19, 2019 Share Posted July 19, 2019 23 hours ago, Jenni said: Smaller bore pipe is an interesting idea @JSHarris, are there any disadvantages to this for hot runs to kitchen and utility? Can the cold run be bigger or should it match? Smaller bore pipes seem fine for sinks, basins, washing machines, dishwashers etc, and for a mains pressure hot and cold system (which is pretty universal now, both pipes can be the same bore. They've been using smaller bore pipes in countries like France for decades now, and they seem to be OK. In general, a tap on a sink or basin doesn't need to flow at more than about 4 to 6 litres per minute, and the lower flow rate seems to reduce splashing a lot and make taps more controllable. The only caution I'd have is if you had a particularly low pressure mains water supply, as then the flow rates might be a bit low with smaller bore pipes. Also, it's best to run showers and baths from larger pipes in order to get them to flow at a reasonable rate. Link to comment Share on other sites More sharing options...
Jenni Posted July 19, 2019 Share Posted July 19, 2019 I happened to be filling an UFH manifold from tap / hosepipe this week, it was 3 bar. Not sure how that relates to litres per minute, but pretty sure it's OK? Link to comment Share on other sites More sharing options...
Bitpipe Posted July 19, 2019 Share Posted July 19, 2019 4 hours ago, Jenni said: But haven't found a way to be notified that hot water is at the tap. I'm picturing an inline sensor, linked to led/buzzer. The hot water won't make it to the tap unless it's running, it will be available at the junction/ manifold in the return loop that the tap supply connects to, so there will always be a small dead leg to draw off. Link to comment Share on other sites More sharing options...
Jenni Posted July 19, 2019 Share Posted July 19, 2019 Yes, thanks @Bitpipe, that's in my mind too, the loop junction can be less than 3m from the tap, rather than the 15m from the tank. Still need to figure out some kind of notification that the hot has arrived at that junction though. Link to comment Share on other sites More sharing options...
CC45 Posted July 19, 2019 Share Posted July 19, 2019 our recirculation system brings hot water to within 300mm of the taps. 1 Link to comment Share on other sites More sharing options...
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