I am aware that better quality geysers are available which retain heat better. However I cannot find a list of these. Anybody??
Regulation requires all new geysers to be at least class B. When I shopped around a while ago the “name brands” were all class B, and I couldn’t find anything better than that. (However, there were still some class E geysers being sold so watch out.)
I ended up going for a couple of these:
If I heat it up during the day to 55C it is still 50C the next morning, so the standing losses are in the ballpark of what one would expect from a class B geyser.
When I read things like this I cant wait for my geyser to give up the ghost and get a new one. Not that I have any idea what my losses are, but it is most definitely not as good as this.
I have done what I could though in terms of putting it in an enclosure (its outside), wrapping it with a thermal blanket and filling up the remainder of the cavity with roof insulation material.
Class B seems to be a fairly high bar that has been set. The outside of the geyser is cool to the touch, even when the water inside is at 60C, so I have not bothered with a geyser blanket.
When I first got the geyser I heated it up and measured the drop in temperature over time before and after completing all the piping. The losses in the copper piping seemed to be a significant factor, even with lagging in place and no actual water drawn off - just natural convection. I realised that further improvement in the geyser standing losses would probably not gain much in the real world, as the losses in the piping would overtake it.
Yes, it is amazing how much heat leaks out that way!
You can calculate how much it should be. A geyser typically has a standing loss of around 2kWh over 24 hours, slightly less for 150 liters, slightly more for 200 liters. If we assume 150 liters, and 1.16Wh per liter per °C, then it will lose about 12°C on average over 24 hours, most of it in the first half (because the rate of cooling is proportional to the temperature delta, ie faster at the start). So I would say a 7°C drop overnight (on average, top of the tank is always warmer than the bottom) is completely normal.
No doubt this is my biggest issue. But I have no way of insulating them as it is a double storey house with geyser basically on the 3rd floor/roof. Getting hot water in the kitchen on ground level is a 1-2 minute exercise.
Strangely enough, the bath on the 2nd floor has hot water within 5 seconds, but the shower 2 meters away but on the other wall takes 2-3 minutes to give hot water.
The piping to the shower thus was routed another km or so through a very cold house’s walls.
Get yourself one of those 15-liter local water heaters. It is worth the water savings.
A bit of a story, since we are talking about hot water and how far it has to travel:
About two weeks ago (after living in this house 4.5 years) I finally worked out what that one last valve on the wall next to my geyser does. It was closed when we moved in, and I kept it closed, not knowing what it does. It seems silly, a homeowner really should know his house, but it was just one of those things to be dealt with later.
Well… the gas geyser feeding the outside “AirBnBs” packed up again. Only produces lukewarm water. And for a while now, I’ve been thinking that closed valve was probably installed the day the systems were split into two gas-heated segments. So I carefully closed the tap on the gas geyser, and opened that mysterious valve. No water spraying anywhere… phew… and now those outside buildings actually have hot water. Also, it only takes about 45 seconds to get there, which is much faster than I would have thought.
Also, the kitchen (which has a little 15-liter Prism jobbie) is on that same segment. I suddenly understood why they installed that water heater. They didn’t want the kitchen to run from the gas geyser for the flats, and that was way easier than messing with more pipework. Now that those segments are re-unified, the kitchen (being right below the geyser) is actually close enough that I no longer need that little unit. But… that is a problem for yet another day
We REALLY have to redo our sculary so when this happens, I will definitely add that to the expense bill.
Marvelous news!
I want to do a test of fitting an isolation valve on the hot water outlet. Then to check the system overnight with this open and closed.
Watch this space…
According to my crude understanding would mean that there will be no residual water in the pipes to cool the piping even further if the valve is closed?
Well it will prevent heat transfer (or reduce it)
The valve will not transfer heat as well as water does
But another issue is preventing any hot water flowing out of the geyser even if it’s only a leak…
Should this turn out to be a significant improvement, does one get valves that can be opened electronically/remotely - wifi enabled type contactor device thingamabob?
Because to walk to my geyser on the roof (even with stairs to do it) would be a major schlep for me.
To get back to this unanswered topic I visited my connection at Geyserwise to hear what his opinion is.
He reckons that fibreglass geyser has good insulation but complications wrt fitting a specific element.
The best one he reckons is Tecron. The main reason is corrosion resistance and that it’s well made.
Clearly a big issue for dedicated solar water heating is the drama that you encounter when the geyser is replaced. This is an issue with the market leader Kwikot that has a limited lifespan compared to better made geysers.
I wanted to buy a tecron, but they don’t make anything Class B…
I’m finding that my Class B Kwikot geyser isn’t retaining heat very well. I have still to get to the bottom of why but my guess is their measurement procedure. I would like to do a head to head comparison…
Disgree about the second part. The elements are readily available, and I’ve swapped them myself without issue.
They’ve been promising to upgrade to class B for years. I waited for them for a long time before I gave up and bought fibreglass geysers.
My bad: I’m referring to the PTC elements that Geyserwise use on their dedicated PV hot water systems (which is what I have)
Yeah, they told me they were busy developing one about 5 years ago when I last replaced my geyser. I’m probably going to have to do a replacement again soon because the kwikot has a 5 year warranty and they seem to have perfected planned obsolescence.
Can one not mitigate against this by getting the anode changed every 2 or 3 years?