Telford Tempest - De-strat pump?

[GB1309]

When we put in the 150lts Horizontal Tempest Cylinder in 2013 no one mentioned anything about destrat pumps and I have yet to meet anyone who has fitted one.
The temp gradient from the bottom to top of the tank is about 10 degrees and the rubbish stat that Telford supplied is grossly insensitive. I change it for another 1:1 and its little better! In order for it to open when the water reaches 55 degrees I have to set it at 37! This gives me a temp of 65 degrees at the tank output port. All well and good.
I would be pleased to hear anyone's views on destrat pumps. I am hoping that the 55-65 degree range I have in the tank would be safe against any bacterial build up.
Cheers,

Graham.

PS I have a separate post on Viessmann Vitodens DHW control which I need advice on.

 

[Masood]

Ummm.... ???

What would you like us to say? I've fitted several Telford horizontal cylinders, the manufacturer doesn't specify that a destratification pump is required. However, as you've learned, horizontals are very prone to it. Either the user gets used to the differential between indicated temperature and actual temperature at the draw-off, or they fit a pump. Experience teaches us many things that aren't in books.

 

[GB1309]

Thanks Masood. Since first posting I have done further research and ordered a Digital Dual Cylinder Stat which should at least give me accurate feedback on what is going on. It will also give a boost to 60 degrees once a week.
I think I have also learned that my 3 x half hour water heating slots per day is a bad strategy. I talked to Viessmann Tech and they advised leaving it on continuous with the tank stat calling the shots. They reckon with a well insulated system this will also be more economic. I am content to live with the temperature differential.
Cheers,
Graham.

 

[Riley]

Please get a G3 registered engineer to carry out any works on your unvented cylinder it's illegal for you to do it

 

[GB1309]

Thanks. I have. It was the G3 ticketted engineer doing his annual service that spotted the issue leading to this replacement Stat being ordered.
The Viessmann trained boiler service engineer arrives tomorrow to do that annual service.
My involvement was prompted by the fact that neither of them had done the wiring and so could not be expected to know what the detailed layout out was. As an electronics engineer I have traced it out.
We do things properly in this house and have all the certificates and service records to prove it
Cheers,
GB.