Aqualisa showers and Expansion tank

diz79

Ive moved into a new house which is old, ive chanced it to see if an aqualisa shower will work that was given to me by a family member, who then bought a new one, its all fully setup but only cold water comes out, the hot doesent seem to work. I assume its the expansion tank or whatever its called is the problem, but could I be mssing something else? When pressing the power button cold water comes out for about 20 seconds, then stops. Hot water not working. So I think its most probably the expansion tank or something ive missed?(The expansion tank has an outlet pipe, not ssure if this effects anything?) Thats where im at, Ive tried to list as much info as possible any help would be greatly apprecaited. Ive also included pics below.

ThisIsWeird

Hi Diz.
If you look at the Aqualisa's info plate, you'll see it says 'min 1bar pressure'. That means it needs to be supplied from a 'high' pressure system, such as an unvented cylinder or combi boiler.
The same info on your cylinder suggests it's a 'combination' cylinder, so has its cold supply tank literally sitting on top of the hot cylinder. That means it'll be very low delivery pressure - a fraction of a bar - so sadly not suitable if so.
You'd need to find a method of boosting your hot supply to at least 1bar. I'm assuming your cold supply to the Aqua is from the mains, so there's also an imbalance there; the cold is 'high', but the hot 'low'. 
I'm not sure what the answer is - whether you can simply pump-boost the hot to the Aqua so it gets close to the cold?

FreeBear

ThisIsWeird said: I'm not sure what the answer is - whether you can simply pump-boost the hot to the Aqua so it gets close to the cold?

A booster pump would be about the only way to get the shower to work. Something like the SP2B would do the job. If plumbed in beside the tank, it would boost hot water delivery to all the taps as well. And being low voltage (12V) and outside the bathroom, it can be DIY installed without too much difficulty.

Albermarle

The same info on your cylinder suggests it's a 'combination' cylinder, so has its cold supply tank literally sitting on top of the hot cylinder.

I was wondering why there was no insulation around the top part of the tank !

FreeBear

Albermarle said:

The same info on your cylinder suggests it's a 'combination' cylinder, so has its cold supply tank literally sitting on top of the hot cylinder.

I was wondering why there was no insulation around the top part of the tank !

It wouldn't hurt to add some insulation on the upper part.

The stored cold water will get some preheat from the main cylinder, so it makes sense (in my mind) to keep that heat in. Reduces the amount of energy required to heat the water once it enters the main tank - OK, the saving is likely to only be a few watts, but it is still a saving.

Another advantage of insulating the header tank (and the cold water feed pipes) is that it reduces condensation forming.

diz79

Thanks for  informative and quick responses. I think I will go for this one unless anyone knows any better ones? The only other thing I thought about was moving the black box lower, but as you have pointed out, its less than 1 bar so probably wouodnt make a difference?

Kind regards

diz79

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ThisIsWeird

diz79 said:

Thanks for  informative and quick responses. I think I will go for this one unless anyone knows any better ones? The only other thing I thought about was moving the black box lower, but as you have pointed out, its less than 1 bar so probably wouodnt make a difference?

Your 'head' - the height the stored water is at, compared to the outlet you are running - is set by the top of that cylinder. So, if you raise your shower handset to the same height as that cylinder, no water will flow. If your shower was located on a downstairs floor, then you'd likely have a decent enough hot flow, but it would still be overpowered by the mains cold.

I have a horrible feeling that the pipe showing there going through the wall is for the shower, in which case it's on the same floor level? No way was hot water going to come out of this - it would be defying gravity.

Fitting that control box at a higher level is also bad news, as it adds friction to the hot water path, as well as the risk of air locks, so if you could lower it down to the rough height of where the outlet passes through the wall, that might help a bit - the idea being for the hot water to always be 'falling'.

But, it was never going to work without a pump, and FreeBear's suggestion there has got to be worth a punt.

You have isolating valves on the pipes supplying the control box, so - once the pump is fitted and running - you may need to tweak down the cold mains one so that the flow matches that of the pumped hot (ie 9lpm max). Ie, if the cold is still overpowering the hot, then half-shut-or-more that valve, and see if it helps. Play around with it. 

diz79

Thanks its on the same floor and downstairs in a bungalow. Someone else suggested that

the problem I have is that water is supplied to the hot water cylinder from a small header tank with a very small capacity. If I put a pump in the system, I will rapidly drain the cold water tank and the hot water will stop flowing. This will result in a cold shower and probably a knackered pump.
The standard Aqualisa processor I have is designed to work on balanced mains pressure hot and cold. The pumped version is designed to work on balanced tank fed hot and cold. Unfortunately I have neither of these setups.

diz79

Im now thinking to change the cylinder to unvented as its quite old now, 

Ive been loooking at water pressure and it isnt really great this is what I have


Water pressure
10 secs 60secs
Kitchen 1.3ltrs x6 7.8ltrs

Outside tap 1.5ltrs x6 9ltrs

Bathroom 2.1ltrs x6 12.6ltrs

15ltrs p/ minute good water pressure

10-15ltrrs p/m acceptable

Anything below is poor

I think the reason the water pressure is highest in the bathroom is because thats where it comes in, its an old house.

Is the pressure good enough for the bathroom do you think? Also it seems the property has always had vented, so how do I know if I can go with unvented and does unvented help with the water pressure at all?

ThisIsWeird

diz79 said:

Thanks its on the same floor and downstairs in a bungalow. Someone else suggested that

the problem I have is that water is supplied to the hot water cylinder from a small header tank with a very small capacity. If I put a pump in the system, I will rapidly drain the cold water tank and the hot water will stop flowing. This will result in a cold shower and probably a knackered pump.
The standard Aqualisa processor I have is designed to work on balanced mains pressure hot and cold. The pumped version is designed to work on balanced tank fed hot and cold. Unfortunately I have neither of these setups.

If you read about that pump, you'll see that one of its useful scenarios is to balance H&C when the C is from the mains, and the H from gravity (vented) like wot you have. I have no experience of them, but assume they would therefore work in your situation.

However, as you point out, your mains supply is pitiful, so would likely struggle to keep the wee CWS topped up and provide cold to the shower at the same time. But but, the 12.6lpm at the bathroom is 'ok', so perhaps it would work. It all depends on how long your showers are, and how much flow you have it on at. In theory, it should work.