July 18, 20197 yr 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.
July 18, 20197 yr 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.
July 18, 20197 yr 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.
July 18, 20197 yr 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, 20197 yr by gravelld
July 18, 20197 yr 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
July 18, 20197 yr 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.
July 18, 20197 yr 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
July 18, 20197 yr Author 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.
July 18, 20197 yr 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.
July 19, 20197 yr Author Can you get a flow switch fittted somewhere that kicks the pump in when it detects flow.
July 19, 20197 yr 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.
July 19, 20197 yr 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
July 19, 20197 yr 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. ???
July 19, 20197 yr 8 minutes ago, Patrick said: Now the big question is, how would one come across such an item. ??? Google ....!!
July 19, 20197 yr 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!
July 19, 20197 yr 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.
July 19, 20197 yr 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.
July 19, 20197 yr We have our hot re-circulation pump on PIR sensors in bathrooms and on the light switches also - same circuit activates the MVHR boost
July 19, 20197 yr 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?
July 19, 20197 yr 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.
July 19, 20197 yr 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?
July 19, 20197 yr 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.
July 19, 20197 yr 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.
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