Understanding this cylinder and the electrical requirements?

HappyHippyDad · Jul 21, 2019

I have a water cylinder to get power to.

The product is a gledhill stainless lite 'indirect'. The manufacturers data sheet says for use with gas or oil boilers. The sheet says the 'direct' model has 2 x 3kW immersions. However from the plate on the side of the tank (see pic) and the tank itself you can see that this model the 'indirect' has 2 x 3kW immersions as well. Even though the data sheet says it has an internal primary coil designed for use with gas or oil.

My questions:

1. How can it have 2 x 3kW immersions requiring an electrical supply and only be used by gas or oil?
2. Will both immersions be used at the same time?
3. Does the electrical supply to the immersions need to incorporate a timer switch or are they just fed from a FCU?
4. If they do need a timer switch would it be one timer for both immersions or one for each?

I'll be chatting to the plumber tomorrow but I just wanted to have a little more knowledge beforehand.

[ElectriciansForums.net] Understanding this cylinder and the electrical requirements?

Deleted account · Jul 21, 2019

One for daytime tariff. One fo4 night time tariff?

Or

One for normal use the other fed direct from solar panels?

Or

A spare in case the other breaks?

I’ve asked this question of plumbers. Never got an adequate response yet.

davesparks · Jul 21, 2019

Normally if its an indirect cylinder the immersion is only there as a backup for when the boiler breaks down.
So normally just supply the bottom immersion via a DP switch, don't do anything with the top one.

It's more normal to see a blanking plug in the top immersion hole when it's being used indirect. I think they are all supplied with two immersion positions regardless because it's cheaper to manufacture everything identical than make two variants.

Lucien Nunes · Jul 21, 2019

Agreed, lower element is the main deal if used as backup. But if flexibility is wanted, the upper element gets you hot water faster because it mainly heats the water above it. Traditionally there was a selector switch marked 'Sink' and 'Bath', only one element was used at a time. But there's no reason not to use both for speed if the supply allows. Or, cheap leccy on the bottom element used only at night to provide a full cylinder by morning.

GBDamo · Jul 21, 2019

If the inditect coil is being used from a heat pump, they can only achieve a temp of 45-50C which will require weekly boosting to 65C to avoid bacteria build up.

If there are solar panels at the property it is really worthwhile looking at putting the lower element on a "Solar iBoost" or similar.

If on site, it may be worth getting the plumber to pull the top element, plug it and keep as spare.

As has been said they are made en masse to a similar spect so not all ports/elements are needed.

HappyHippyDad · Jul 21, 2019

davesparks said:
Normally if its an indirect cylinder the immersion is only there as a backup for when the boiler breaks down.
So normally just supply the bottom immersion via a DP switch, don't do anything with the top one.

It's more normal to see a blanking plug in the top immersion hole when it's being used indirect. I think they are all supplied with two immersion positions regardless because it's cheaper to manufacture everything identical than make two variants.

Thanks for the answer Dave.
The Direct model has the bottom immersion in a lower position than the indirect. I'll check with the plumber tomorrow if he wants a supply to both or just the one.
If it is fitted with 2, would it not be better to have a supply to both so as to heat the water more quickly? There must be a reason why it has 2.

GBDamo · Jul 21, 2019

happyhippydad said:
Thanks for the answer Dave.
The Direct model has the bottom immersion in a lower position than the indirect. I'll check with the plumber tomorrow if he wants a supply to both or just the one.
If it is fitted with 2, would it not be better to have a supply to both so as to heat the water more quickly? There must be a reason why it has 2.

As has been said, its to allow flexibility of application without having to manufacture tens of variants.

The positioning of the elements Vs the indirect will be influenced by the internal coil location.

When wiring these up in the past, for use with heat pumps, we only used the lower element.

If you ask the plumber he'll go for the belt amd braces option, but if its his call let him make it.

HappyHippyDad · Jul 21, 2019

Many thanks for the replies as usual guys.

ruston · Jul 21, 2019

Historically in the days of night storage heating I have seen tanks have two elements , the bottom one being used at night on the off peak tariff.

davesparks · Jul 21, 2019

happyhippydad said:
Thanks for the answer Dave.
The Direct model has the bottom immersion in a lower position than the indirect. I'll check with the plumber tomorrow if he wants a supply to both or just the one.
If it is fitted with 2, would it not be better to have a supply to both so as to heat the water more quickly? There must be a reason why it has 2.

Wiring two supplies is just a waste of the customers money in my opinion, its a backup in case the main heating system fails.
If it is ever actually needed it's unlikely to be used for more than a few days, and modern tanks like that only tak ehalf an hour to heat up on one immersion anyway.

Plus if the heating system is properly installed and maintained the immersions will probably have developed faults from being stuck in water that long before they are ever used.

You can ask the plumber if you like, but ultimately its up to the customer how much money they want to spend on a non essential circuit theyay never use.

ferg · Jul 21, 2019

As others have said.

The 2 elements are for either a Bath / Sink switch or a dual tarrif set up.

For Dual Tariff the bottom element is connected to cheap rate and the top element to 24hr.

The top element then provides a top up to last until the cheap rate kicks in at night.

Bath sink is either the whole tank, bath, or just the top section, sink.

davesparks · Jul 21, 2019

ferg said:
As others have said.

The 2 elements are for either a Bath / Sink switch or a dual tarrif set up.

For Dual Tariff the bottom element is connected to cheap rate and the top element to 24hr.

The top element then provides a top up to last until the cheap rate kicks in at night.

Bath sink is either the whole tank, bath, or just the top section, sink.

If it was a direct cylinder then yes, but it's not, it's an indirect cylinder so the main source of heat is the boiler, the immersions are purely a backup should the primary heat source fail.

ferg · Jul 21, 2019

That is the most likely scenario granted.

Sometimes the indirect part of the cylinder is connected to a stove not as the primary source of heat but as supplementary heating.

I have also come across customers who switch off their external oil boiler in the summer and just use the immersion.

I'm not sure whether it makes economic sense or not but it's what they do.

Understanding this cylinder and the electrical requirements?

HappyHippyDad

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