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Paul C

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Paul C last won the day on October 16 2016

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  1. Agreed, with the right type of plastic it should be entirely possible. And with suitable bracing, the tendency to balloon will be mitigated if its too thin to retain its own shape. Loads of components in engines are now made of plastic - you've probably heard of plastic inlet manifold etc. I believe some cars now also have plastic sump. It will be a ramp function of temperature and time. Not massively dissimilar to pasteurisation.
  2. The main problem is that even if you have member(s) on ignore, they can continue their involvement in a thread (and obviously influence the path it takes, responses to their messages etc).
  3. Just for clarity my post was a quote from stegra's link. I think www.gasapplianceguide.co.uk simply assumed the water would be heated to >60degC, hence the tank shapes they prefer to offer. He voluntarily left the forum and gave up narrowboating.
  4. I think the main reason hot water systems are designed to raise the temperature ~60degC or above, then its later mixed with cold water, is to counteract microbial growth which can occur (and is the pathway for legionaires disease). However I'm not an expert on it and don't know all the details. Once you are talking about hot water, possibly under some pressure, then it determines the material/shape of any hot water storage vessel(s).
  5. They can't avoid moving altogether, because doing so would be in breach of their agreed-to licence conditions. They could minimise it though.
  6. I think you're making progress! Its probably worth asking "why is everyone installing a £500 calorifier instead of an £84 plastic rectangular tank?" If you can counteract those answers accurately, then it sounds like a good plan.
  7. Well yes it comes down to cost, but a side effect of your novel rectangular unpressurised tank is that it will bulge and if installed eg snugly underneath a bed, break the furniture around it. I know we're talking about low pressures but still, with thinnish plastic, it will distort. Ask any balloon artist who makes more intricate pieces than simple sausage dogs, etc. If you went for a much thicker tank, and/or some kind of metal framework to suppress this, then fine - but then its going to get more costly. The key aspect is the pressure - I know you've said its vented, therefore completely unpressurised, but I think if its well ventilated then there will be a horrendous inefficiency due to losses as it gets warmer. So, you want a little pressure, just a few psi would be okay. That could be achieved without a PRV, simply by having the vented outlet up a narrow tube, around roof height on the boat. Its certainly possible to do it. I'd focus more on the heating source - do you already have a gas or diesel water (and/or space) heater? They're quite expensive, around £2k but it tends to be a once-off install and a piece of equipment which is very useful (in siuations where you don't, or don't want to, run the engine as in a traditional single coil calorifier). I'd spend a little more and go for bigger rather than smaller, if you've not bought one of these yet. ETA - just reviewed the OP, I see you have a Webasto, that should be fine but obviously it will take some amount of time to heat up a bath-full of water.
  8. "be aware, water is more often than not stored in a cylindrical vessel for good reason."
  9. I'm not sure you're thinking outside the box; you just want someone to agree that your idea of an unvented plastic tank, raised to tepid temperature, will be okay.
  10. PRVs tend to fail safe, ie they open at a lower pressure than design. Dirt builds up around the valve opening and prevents a reliable seal. To fail closed, the spring would need to become jammed or some other moving part seize. I can't see that happening if its regularly used. But if it does, normally a plastic pipe would either split or a joint would fail, so it would leak and drop the pressure. There may be a bit of steam/condensation, and an amount of hot water, but nothing more dangerous than that. I'd not worry about safety aspects of a calorifier failing, just the inconvenience/cleanup factor. I think we're on the same page re: likely pressures though. Typically a PRV is 3 bar; and a 12V water pump typically has a 25-30psi cutout. 14psi = 1bar (approx)
  11. A simple back of the envelope calculation: 2x 75l calorifiers they can happily operate up to 85 deg C mixed with water at 10 deg C, this would mean 200l @ 66 deg C 1x 75l calorifier operating at 85 deg C mixed with water at 10 deg C, this would mean 200l @ 38 deg C So it shows its definitely possible, if you part-filled the bath to less than 200l and was happy with ~40 deg C (I think I'd prefer a touch more) then you don't even need to worry about a second calorifier. But it may be inefficient if its a horizontal, and for "normal" use on a boat given that you'd need a gas or diesel (or immersion) heater which you'd pay for the energy, rather than using the available excess heat from cruising and running the engine. A calorifier isn't "really" pressurised either, at least not to a great amount. Its only pressurised to the normal pressure the water pump operates at, to physically be able to flow the water out of the taps at a given flowrate. Its not, say, 10 bars or so, the pressure rise due to heating of water is relieved and vented by the PRV.
  12. Without delving too deeply into the effectiveness of insulation or the type (well.....heat handling capability) of the plastic tank, I'd have thought a purpose-designed calorifier would be better performing. Also, I had in mind you'd heat (a smaller amount of water) to what you might consider normal domestic hot water temperature, then mix during filling the bath to comfort. Of course, the energy demand would be the same.
  13. I think the sensible thing to do would be to double- or triple- up on components, eg have 3 calorifiers and 3 water heaters. You'd need to do the sums on sizes, heat input etc to size things properly and/or make sure the temperature is okay. The reason for doing so, is that when its NOT needed to heat up water for the bath, there isn't a large calorifier/heater running at very low setting, instead you could manually shut off the other leaving one "normal" duty bunch of components operating. Obviously you'd need to consider hot water expansion/(cold contraction) when designing how things are shut off etc.
  14. That's bad, to not understand its whatever comes first.
  15. Aaah, didn't spot that. Then, no. Definitely worth doing the oil change now rather than delaying. And in 40-50h time, not worth doing another merely for winter layup. Apologies for not spotting the info!
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