resettable immersion heater thermostat

"never seen one that did not have that 'overheat' bi-metal disc cut-out mounted"

The old-type BS immersion heater thermostats didn't have an ?overheat' cut-out device. The reason for this lies in the design of the hot water systems.

Until 1987, the UK Water Regulations only permitted the mains water to be connected to the kitchen tap and to a cold water storage tank in the loft. Hot water was usually supplied from an indirect heater (cylinder), usually on the floor below the loft, with the cold water feed pipe from the loft tank and with an open vent pipe from the top of the heater discharging back over the tank. If the electric heater's thermostat failed, as described here, the worst that might happen was that steam and boiling water would blow out of the open vent pipe into the tank. The old tanks were usually galvanized steel, so they could survive boiling water.

It is a fairly foolproof system and accounts for our renowned ?English drizzle' feeble low-pressure showers. On the positive side, the traditional system made contamination of the water mains by back-siphonage very unlikely and the tanks served to minimize the effect of peak-demand flow rates reducing the mains pressure. The loft tanks might fill up more slowly, but there'd be no difference in the water flow at the outlets. The water suppliers' pumps could be smaller and demand was more uniform.

The accident in Cornwall mentioned above happened because, although the plastic cold water storage tank could have tolerated boiling water, it was not adequately supported. The plastic tank's sides softened, distorted and collapsed.

formatting link
Your hot water tanks are connected to the mains water supply, maybe via a non-return valve & PRV. A water storage tank in a draughty loft would not be a good idea, given your winter conditions. I've never encountered pumped well systems here, although there are some in rural areas.

Since 1987 unvented mains-pressurized water heaters have been permitted here, to bring us into line with the EEC. The majority of houses still have traditional open-vented systems. The newer unvented systems are much the same as your tanks. They rely on three safety devices on the electric heater (primary thermostat, secondary resettable cut-out and the temperature & pressure & relief valve) to prevent the tank over-heating and bursting explosively. The primary thermostat and secondary cut-out are usually both built into the immersion heater thermostat. This resettable-type of thermostat has always been specified for the electric immersion heaters installed in unvented systems. Some unvented systems have non-standard immersion heater bosses, to prevent the cheaper, non-resettable type of thermostat being fitted as a replacement.

"Deteriorated tanks and corroded heater elements have been something of a problem here"

You could try posting any query on the US discussion forum at Heatinghelp.com, ?The Wall'. There are some very knowledgeable people there & they seem to have the answers to most such things. In particular, Larry Weingarten, who posts there occasionally, knows most things about your water heaters.

We still have the bayonet type bulbs. I think they're OK, but I don't know any different. Maybe they've improved since you last saw them.

"And yet cars over here use some bayonet (and wire-ended) lamps!" Maybe Lucas electrics weren't so bad after all then?

Reply to
Aidan
Loading thread data ...

No it doesn't make sense at all. A someone else has posted, the tank collapsed because it was inadequately supported, not because it had boiling water in it. The new legislation should have address the tank installation, not the thermostat.

It's exactly this kind of kneejerk reaction to a *very* small number of fatalities that leads to stupid laws which people will flout at every opportunity. Take the new building regs that will effectively outlaw DIY wiring. How many lives do you think that will really save? Even if the MP's daughter's kitchen (see todays papers) had been wired "properly" it wouldn't neccesarily have prevented her husband putting a screw through the cable leading to a utensil hook being live. Would buried electrical trunking stop an SDS going full whack?

MBQ

Reply to
MBQ

Maybe an upgrade to the new thermostat, with the cut-out device would be a sound idea for many existing immersion heaters. It shouldn't involve draining and removing the immersion heater. About £4.13 plus Vat & delivery from BES.ltd.uk (for example) , Part No. 1665.

Their blurb says; "Universal type, conform to the new standard EN

60335.2.73, for use within all heaters. Can be fitted into 'old type' heaters to upgrade to the latest standard. 16 A 240 V thermostat. BEAB approved."
Reply to
Aidan

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.