Thoughts on use of a "Ring main" with a new Solar Hot Water system?

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Thoughts on use of a "Ring main" with a new Solar Hot Water system?

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Started 11 years ago by bundy
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bundy
Member

Hi all,

Just looking for some feedback as to the Pro's and Cons of putting in a ring main on a hot water service (Evac Tube Solar with Electric boost)

We are renovating our house and intend to install an Evac tube Solar HWS with Electric boost. While the renovation is underway we have moved into a rental and one thing I find most annoying is the length of time it takes to get hot water to the main shower. This house the Run is maybe 10 metres where in our house the longest run form the storage tank to the Ensuite shower is about 25 metres.

So it got me thinking the Hot water run on our renovation will be 2 - 3 times as long as it is in the rental and we will be running and wasting a lot of water every day. Not to mention the inconvenience factor

So it got me thinking are these Ring mains worth considering?

Upside I see are
- Saves a lot of water and possibly even saves hot water as it sends it back to the tank to reheat via Solar input instead of letting it cool in the pipes.
- Convenience
- Maximise use of "Free" Solar heating

Downsides -
Pumps hot water around unnecessarily
Loss of heat through pipes (Can be minimised with good insulation)
Another component to "break"

Appreciate any input or real life experiences

Posted Monday 22 Aug 2011 @ 12:27:35 pm from IP #
sun2steam
Member

The downside can be minimized by having a timer switch for the circulation pump. You push the switch to turn on the pump and after a predetermined time it turns itself off again.

There are a few other aspects to it:
Cost: there is probably no way to ever recover the cost of the installation by saving on water consumption.

CO2 output: more energy consumption by running the pump is minimal as the pumps are maybe 50 W and run for just minutes a day. However the embedded energy in water pipes and other stuff is significant.

Posted Monday 22 Aug 2011 @ 10:22:53 pm from IP #
bundy
Member

Thanks I understood the pumps use a Thermal switch to decide when to pump water and only run once the water in the pipe falls below a certain temp and needs to get "topped up " again.

Maybe though it is probably a good idea to have a timer so that it only runs from say 5am to 10pm and closes down overnight

How well the pipes can be insulated though I guess is the main thing as if you are constantly losing heat at a quick rate I will end up having to boost more than I would otherwise, which does concern me.

As for initial cost, Yes agree but if it is feasible I feel the convenience over the 20 years we expect to live in the house will far outway the initial cost. Being a new build I am thinking maybe $600 - $800 extra on my plumbers bill, which in the scheme of it isn't too bad

Thanks again

Posted Monday 22 Aug 2011 @ 10:34:54 pm from IP #
sun2steam
Member

I meant a different timer. Similar to a timer for a light switch.
You push it once and it turns itself off after a minute or so.

Having a temperature switch would be even better. But not in the way you mentioned, that it switches itself on as well.

It would be much more energy efficient, if you have to push a button which starts the pump. Once the pump sensor feels the heat it switches the pump off.
--> But the system must NOT switch itself on again. That would be a waste of energy.
The system should only be started by pressing the button.

Posted Tuesday 23 Aug 2011 @ 1:52:02 am from IP #
Benny
Member

bundy - have you checked your local building regulations ? I'm pretty sure here in WA its illegal for new buildings to have a run of over 20m of pipe from heater to usage point - or the length of pipe that would waste 2litres of water.
As sunsteam suggests, I'd strongly recommend against the use of a constantly circulating system - even running say 5-10pm - and suggest you use an "on-demand" pre-circulator. For a shower, you could start the pump as you undress and the hot water would be there by the time you get in and turn the taps on.
Ballpark figures I have seen for heat loss are 50W/metre for uninsulated 13mm pipe, 5W/metre for insulated. If you insulate 20m of pipe and have a 50W circulating pump, thats a total loss/use of 150W - running for 5 hrs it would be 0.75units. And remember if its circulating water at 5-10pm it won't get "solar reheated" as the sun will be gone.

Posted Wednesday 24 Aug 2011 @ 12:17:44 am from IP #
Thongdam
Member

I'm surprised no-one has mentioned the Ecoverta for which there is a link on this very website. Looks to be a much simpler solution to me. I'm looking at these.

http://www.ata.org.au/join-us/ata-member-discounts/

Posted Wednesday 24 Aug 2011 @ 1:55:43 am from IP #
bundy
Member

Thanks all for your input. I emailed my plumber also this week and he tells me he has a lot of previous experience with Ring mains and advises I do NOT do it at my place.

We haven't caught up as to exactly why not but looks like I will just be wait for the HW to arrive.

Benny re the 20m pipe length - I cant find any reference to that regulation, (Maybe looking in the wrong places) but as I have 3.5 metre ceiling height there's near on 7 metres gone before I move sideways so it won't take long to eat up 20 metres.

As for the Ecoverta nice way to not waste water down the drain but does nothing to get my Hot water to the outlet quicker. From what it looks like you sit there with the tap on waiting with no water flowing out, be it hot or cold. That would drive me crazy.

Posted Friday 26 Aug 2011 @ 10:09:35 pm from IP #
Russell Moore
Member

I have mentioned this here before.

At our household, as we get undressed for a shower we turn on the hot water tap for the bath, and run the cold water in the hot water pipe into the bath. When the bath is almost full (it takes about two weeks) we syphon it out onto the garden. Costs nothing, and we get hot water in the shower straight away.

Posted Saturday 27 Aug 2011 @ 7:30:37 am from IP #
Johnnojack
Member

Agree with Sun2. have a switch which you press to turn on the pump, and it switches off itself after a minute. Can't understand why you wouldn't do it (Bundys plumber) If you use a magnetically driven pump there is nowhere water can leak out if joints and piping are up to standard. I have a pump already (Grundfos model N2042) and intend to install it with 2 intakes to the pump, one from the shower and one from below the kitchen sink. I figure that with the excess of hot water we have from this time of the year on it will pay off in not heating cold water with the kettle let alone the dishwasher. About 3 -4 litres needs to be run down the sink to get hot water so we usually don't bother. We do what Russell does with the shower except with a big bucket in the bath. The water from the bucket keeps the front garden going over summer but I am so over lugging that bucket and would prefer to use the hose. Now to find a plumber willing to do it, Hmmm.

Posted Wednesday 5 Oct 2011 @ 6:04:11 am from IP #
Johnnojack
Member

Friend of mine found this
http://www.reece.com.au/plumbing/products/9502995
Don't need return pipe as it pumps into cold tap and then turns off when it detects hot water. Bit pricey though, about $450

Thing is it could be installed under a sink quite easily

Posted Tuesday 1 Nov 2011 @ 6:08:45 am from IP #
sun2steam
Member

It is strange that they claim the pump does not need a return line, when the schematic inside the manual clearly shows a return line.

Returning the cooled down hot water into the cold water mains is most likely not acceptable because of health standards. This means that only in cases where the cold water to the shower comes from the cold water supply to the hot water tank would be OK. This could probably be done in a house which is just being built, but for an existing house the installation of a return line will be necessary.

Posted Tuesday 1 Nov 2011 @ 6:47:19 am from IP #
Inspector
Member

I investigated a high consumption complaint for a McMansion that had one of these systems. The customer was told that he had gas boosted solar hot water, with two collectors on the roof. The tank was in the basement (two storey dwelling) and had recirculating hot water system ("ring main" as indicated by the thread title). You can only imagine the lengths of pipe involved for such a size premises. Add to that, most of the piping I could see in the basement had no lagging (the green sheathing for insulation), so the heat loss from this system would've been enormous. I forget exact consumption figures, but it was ridiculously high - something like 60kwh/day and they didn't use under-floor heating or airconditioning in the previous billing quarter. It turned out the hot water tank had an electric element (which the circuit breaker was turned on!) and the gas boost was a separate instantaneous unit which had been plumbed-in (and the power outlet for the igniter was turned off!). It was immediately apparent the element must've been heating 24/7 in an attempt to maintain temperature (customer complained it was luke-warm most of the time) and the heat collectors on the roof would've done little to heat the water with such a large surface area of pipe throughout the premises dissipating the heat. A simple flick of two switches and advice to the customer to keep an eye on the meter (I didn't hear back, so I presume my solution worked).

I too loathe the 45-second delay before I get hot water in the bathroom - my next house will be designed to have the hot water closer to the bathroom, or mid-way between kitchen and bathroom to help alleviate this problem.

Posted Thursday 3 Nov 2011 @ 10:16:16 am from IP #
peter69_56
Member

I just spent $50 and insulated all my roof mounted plastic hot water lines to all outlets with armorflex insulation. What a difference. Water now comes out hot, little loss and if I come back in a few minutes the water in the line is still hot, before it would be cold from line losses. Had to retro fit it by splitting the 2m lengths and slipping it over. Pity it wasnt done when the house was built. So much for the plumbers comment when I complained about pipes badly insulated on my solar HWS "it doesnt make much difference and not worth it". Just goes to show how many of the people with the certifications seem not to care and/or understand. It doesnt recirculate but insulating does help and make the effort of recirculating via a ring main less of an issue (for me anyway)

Posted Thursday 3 Nov 2011 @ 11:19:23 am from IP #
Diver
Member

peter69-56

Re insulating your 'plastic' hot water pipes, the Vic PIC and BCA requirement for hot water services is that they must be lagged for the first metre and insulated after that and my understanding is that this also applies to solar.

This quote: "All circulating heated water piping on solar hot water heating systems must be insulated with appropriate insulation" is from the PIC Technical Solution 6.04 "Installation Of Tempering Valves And Heat Retention For Hot Water Piping".

http://www.pic.vic.gov.au/resources/documents/6.04_installation_of_tempering_valves_and_heat_retention_for_hot_water_piping2.pdf

If insulation is a requirement, then the installation was not compliant and you are yet another who has paid good money for a useless Certificate of Compliance (amongst other issues).

I think the requirement for insulation on hot water service piping would encompass all hot water piping on solar heaters but the reference to "circulating" is ambiguous and confusing. Such ambiguity is not uncommon. Will look up the BCA regs when I get time.

Posted Thursday 3 Nov 2011 @ 1:29:45 pm from IP #
peter69_56
Member

Diver, my system isnt circulating so I guess it probably met code when installed 11 years ago. However now that I have spent th measly sum of $50, I find it a vast improvement. I do however take your point in that I bet if you looked into the roof of many new houses now, you would find they are either not insulated at all, or have that crap green plastic covering which imitates insulation. All hot water lines should be insulated regardless of whether it recirculates or not.

I also take your point about solar pipework having the requirement to be insulated as well. Mine was but was badly done, especially close to the HW tank which is a good point of continual heat loss if not done well.

Is there anyone here who has just had a new home built, and can they tell us if the hot water lines inside the roof space are insulated?

Posted Friday 4 Nov 2011 @ 1:10:24 am from IP #
Diver
Member

The BCA, for several years now as per AS3500, has required insulation on:

“All pipes conveying hot water, including all vent or exhaust pipes to the working water level of the hot water system.”

I would think that this has to include solar systems. I don't know why there is a reference to "All circulating heated water piping on solar hot water heating systems" in the document I previously posted. It seems strange.

The Vic new home standard is now 6 star but the old 5 star standard had a high incidence of varying non compliance. Even with the new houses that were compliant, the high incidence of eaveless homes and trendy black driveways and rooves with huge evaporative air conditioners mounted atop tells me that something is wrong somewhere. The heat signature off some properties must surely be greater than some deserts. The Urban Heat Island Effect is alive and thriving.

For details about massive non compliance, just send a PM if you are interested.

Posted Friday 4 Nov 2011 @ 3:30:10 am from IP #
bundy
Member

peter69_56 said:

Is there anyone here who has just had a new home built, and can they tell us if the hot water lines inside the roof space are insulated?

Yes - Just had a new home built for my Mum by a builder and it is only 3 months old. It is in Perth and the only Insulation is outside for 6 inches from the HWS to the Wall. Other than that there is no insulation on any of the pipes in the roof space (Plastic Pex pipes) I was told by a plumber if it is outside they must insulate it but inside the building ie the Roof it is not required under the BCA so that's how they get around not doing it

Posted Saturday 5 Nov 2011 @ 9:06:10 am from IP #
peter69_56
Member

That so sucks. For $50 you can have the pipework insulated fully within the roof and it makes a big difference. When I now wash at the sink, previously if I waited 5 min the water was again cold and a long wait period, now its still hotenough for most jobs. So much for 6 or 7 star efficiency. Once again governments making grand statements and not supporting it with detail.

If I were you I would retro fit armorflex. it comes in 2 m lengths, I just slit mine down the centre with a sharp knife, this way you can slip it over the plastic pipe up to any joins or clips. Whilst it isnt 100% due to the small slit, it does make a big difference for the small cost. $3.73 per length. I have a 4 bed home and I bought about 13 lengths. You have to do the tempered line in to the bathrooms and the hot water line to sink and laundry. I also made sure that when they insulated the tank pipework, it was insulated right to the tank and not stopping some 5-7 cm short of the tank on all pipework. The greatest heat loss is in the first few inches.

I do so hate how we regulate everything here and then never look at the detail or ensure that the correct work has been done. My home will specify that all hot water lines are fully insulated. it will also specify what and how the solar HWS will be fitted and on what section of roof (or they then put it on the roof closest to the HWS tank, which may be a west or east roof just to save copper pipe).

Posted Saturday 5 Nov 2011 @ 10:06:58 am from IP #
Diver
Member

AS3500.4 is the applicable standard to reference hot water pipe insulation. My information was that the BCA now requires insulation on all hot water piping but I cannot find any reference to this online but there are plenty of references to insulating the first 500 mm of piping. Websites are notoriously slow to update and so I will reserve judgement for now. To purchase the standard costs nearly $150.

The plumbing stardards in the various States are rarely in unison and often do not match the BCA. WA also has a standard that requires hot water piping to be no more than 20 metres in length and not hold more than 2 litres. A recipe for more non compliance?

Given the small cost and ease of installation at the time of building, it would be a gross oversight if hot water pipe insulation was now not mandatory.

Posted Saturday 5 Nov 2011 @ 11:53:03 am from IP #
bundy
Member

Yes agree it is just builders looking to squeeze out every cent of profit and as a result quality suffers and the old addage "What you dont see" I guess that's why governments have to regulate them otherwise if they had their choice 2 pieces of tin would be a saleable house. If Ceiling insulation was not mandatory I guarantee builders would not put it in

As for insulating HWS pipes I agree 100%. I am Owner building my own place at the moment and all pipe work (even that run in the Cavity wall and under slab) is being insulated for the HWS. It doesn't cost a lot as you say and is just a but of planning to ensure it is all done at the right times. It's not so easy to retrofit up the wall cavity so you only get one chance sometimes

As for retrofitting my Mums place it is on the To do list, but with the OB work is down the track for me. Good to know it has made a big difference to your place though. Gives me more incentive to get it completed sooner rather than later.

Posted Sunday 6 Nov 2011 @ 12:29:53 am from IP #

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