Nest to control direct hot water tank

[locoloic]

Hi all! so, current setup is this:

-oil fired central heating. Boiler is still serviceable and ok.
- gravity fed water system. Insulated copper hot water tank, with immersion heater and boiler in Aga in kitchen.
- water comes from borehole, pumped up to tank in loft.
-Nest controlling central heating system only. Timed spur for immersion heater in summer when aga is off.

We have the opportunity to get onto mains water, which presents some opportunity.

I want to pull out the hot and cold water tanks. Remove boiler in Aga (pretty grim having the hot water go through it) and have an unvented, direct heated hot water tank in the loft, freeing up space in the airing cupboard.

So, I was thinking I could control the timing of the hot water using the nest, wiring up a chunky relay to power the immersion heater in the hot water tank, something like this:

https://www.heatingsave.co.uk/product/immersion-heater-relay/

however, does a direct hot water tank need more current than just a normal immersion heater? I was thinking I might need to run a new dedicated high current circuit for the new hot water system, which wouldn’t be too difficult.

Any other suggestions?
Thanks in advance.

 

[EFLImpudence]

You seem to be confusing several issues.

Anyway, if you want an unvented system then you must get a suitably qualified installer - so it would be better to ask him.

 

[SimonH2]

Just replace the direct cylinder with a thermal store - simpler than an unvented cylinder. You get mains pressure hot water, stored heat, and no mixing of the DHW with the stored hot water - and it can safely take heat from all of your existing heat sources.

 

[ericmark]

With this the tank is not pressurised and the multi hot coils allow many heat sources to join together my bother-in-law had it with his last house, I would agree heating water with solid fuel does present some problems note the white towel rail shown on this system to sink excess heat, but bother-in-law would spend months away from home and his solar panels were enough to keep house warm, his solar panels were electric and put heat into system using an immersion heater.

As to Nest Gen 3, mine runs DHW as well as central heating with an old oil boiler and no motorised valve or thermostat on DHW in summer I have it set at 1/2 hour a day, winter I turn it off as it is auto heater when ever central heating runs.