de stratifying DHW tank

[ALAN/ALAN D]

To comply with
Legionnaires' disease compliance I have used a standard central heating bronze circulating pump. Still working after 18 years.

In Essex where the water can be a bit hard.


There are various systems available to supply hot and cold water services that range in size, scale and complexity. All can present foreseeable risk of exposure to legionella. Temperature control is the traditional strategy for reducing the risk of legionella in hot and cold water systems. Cold water systems should be maintained, where possible, at a temperature below 20°C. Hot water should be stored at least at 60°C and distributed so that it reaches a temperature of 50°C (55°C in healthcare premises) within one minute at the outlets.

Just need a timer to run it for a few minuets every hour.

[openspaceman]

As the water is constantly refreshed rather than stored and reheated I do not think legionella is an issue and I expect to heat the tank over 60C regularly anyway.

Stinsy I have ordered a willis jacket less element and insulation as I shall fit a 1.5kW immersion.

Now need to bend some copper and that will be a first too.

[AE-NMidlands]

Now need to bend some copper and that will be a first too.

It is fun - and very satisfying when it works!
40 years ago I found that, using internal springs, 15mm was ok, but for 22mm I had to have a good length of pipe each side of the bend. Adjusting a bend near the end of a pipe was impossible, and I didn't manage to work out how to use a compression fitting to lengthen it without complications either...
28 mm and bigger was all Yorkshire fittings back then (now I mostly use endfeed on the smaller stuff.)
Good luck!
A

[openspaceman]

Thanks, I think I shall use compression fittings to Tee the 15mm into the 22mm cold feed and hot take off.

[Sim_C]

Just logically thinking about the plumbing in of a Willis heater effectively in parallel with a hot water tank.

So the Willis heater has 15 mm pipes terminated in 22-15-22 tees fitted in the cold water inlet pipe (bottom of the tank) and the hot water feed to the taps (top of the tank).

When there is a large draw off, say to fill a bath, will there not be some flow from cold to hot pipe via the Willis heater that may not be powered by solar at that instant in time? This cold water will then mix with the hot off the top of the tank, so reducing the temperature fed to the taps.

I guess it depends on the relative values of flow rate, through the tank and 22 mm pipes compared with the the 15 mm pipes and Willis heater.

Has anyone any experience of the real world effect of this?

Also does the Willis heater need the the full electrical power in order to generate the required thermal water flow from cold inlet to hot outlet?
The only Willis heaters I have found have a 3 kW element, which could be de-rated using a solar diverter such as the MyEnergi Eddi.

Here is a warning on correct installation of Willis heaters.
https://forum.buildhub.org.uk/topic/130 ... s-heaters/

[Countrypaul]

Just logically thinking about the plumbing in of a Willis heater effectively in parallel with a hot water tank.

So the Willis heater has 15 mm pipes terminated in 22-15-22 tees fitted in the cold water inlet pipe (bottom of the tank) and the hot water feed to the taps (top of the tank).

When there is a large draw off, say to fill a bath, will there not be some flow from cold to hot pipe via the Willis heater that may not be powered by solar at that instant in time? This cold water will then mix with the hot off the top of the tank, so reducing the temperature fed to the taps.

I guess it depends on the relative values of flow rate, through the tank and 22 mm pipes compared with the the 15 mm pipes and Willis heater.

Has anyone any experience of the real world effect of this?

Also does the Willis heater need the the full electrical power in order to generate the required thermal water flow from cold inlet to hot outlet?
The only Willis heaters I have found have a 3 kW element, which could be de-rated using a solar diverter such as the MyEnergi Eddi.

Here is a warning on correct installation of Willis heaters.
https://forum.buildhub.org.uk/topic/130 ... s-heaters/

Thinking logically ( ), the flow of water generated through the Willis when the IH is on is determined by the water density so if the heater was only running at say 100W it would take much longer to lower the density of the water in the Willis resulting in a much reduced flow compared to the full 3kW. So, imho, using an Eddi should be no problem at all with a Willis - but make sure it is the right way up - as per your link.

Given the water in the tank and the Willis will be at the same temperature at the same level (when no cooling or heating taking place) if there is some hot water drawn off then there will be a change in the level of water at a given temperature in both the Willis and the Tank. For example, if the temp was 50C at 1m high and 40C at 0.9m high then if 10cm of water was drawn off both should be at 40C 1M high. If the draw off flow is limited by the 22mm pipe size (both to the tank/Willis and to the bath), there should be no reason I can see that the flow through the Willis will be such that cold water will bypass the tank. This assumes the pluming is similar to the diagram you have linked to, of the Willis is directly in the flow and the tank is on the branches of a tee there could be ncreased flow through the Willis.

[openspaceman]

It takes me a while to start on a project; in this case I am waiting for warmer weather and I shall attempt to replace a rusty old galvanised cold water cistern at the same time.

I have the Willis jacket and have bought a 1.5kW immersion element for it but cannot comment on how it will work.

I intend to trigger the immersion switch by the voltage on the battery and hold it for a minimum of 15 minutes but haven't decided whether I can make use of the relay on the Smartsolar charger yet as ideally I would switch on the immersion for 15 minutes once the charger tries to move from bulk to absorption or float. So the water will be heated in 1/3kWh spurts until the panels are in full sunshine.

These Willis heaters are not recommended for hard water areas like mine so I do need to plan it so I can occasionally take it out of the system and descale it, because the element is inserted from the bottom I can see scale could fall and build up at the base of the element.

It may be a good time to reconsider filling the cold water cistern from my well which should have reverted to being soft water by now (long story revolving around low water pressure on an un metered supply being caused by chronic leaking, I should have twigged it much earlier when I was surprised the well tested hard yet we are on sand).

[Stinsy]

Possibly a good idea to fit "pump style" isolation valves top and bottom so the Willis can be removed for maintenance without draining down...

[openspaceman]

Possibly a good idea to fit "pump style" isolation valves top and bottom so the Willis can be removed for maintenance without draining down...

Too risky IMO as that creates a closed vessel with a heating element

[Fintray]

Here is a warning on correct installation of Willis heaters.
https://forum.buildhub.org.uk/topic/130 ... s-heaters/

That's OGB's post.