under sink heater

[Tomswan]

As back up for when my oil boiler packs up I am thinking of putting in an electric under sink water heater in the kitchen.

Obviously at the moment the hot tap is fed from the boiler. It would be simpler to connect that feed from the boiler to the heater rather than use the cold main.

Any reason I can't do that? I can't think of one but all the advice is to use the cold water main.

 

[cross thread]

Read the instructions depending on the model you may need a none return valve and expansion vessel

 

[Tomswan]

Read the instructions depending on the model you may need a none return valve and expansion vessel

Ok, cheers. It's a combi boiler, and would be off whenever the electric heater was on, so maybe the boiler's expansion vessel would be good enough.
Must be a reason they don't mention it though. Unless I haven't looked enough.

 

[cross thread]

No the boiler expansion is a completely different thing

 

[Tomswan]

No the boiler expansion is a completely different thing

Ok thanks. I will do some more research

 

[Madrab]

The electric instantaneous heater will restrict the flow to the hot tap. They normally have internal flow restrictors to slow the cold water down, it's the only way they are able to heat the cold water up to any significant degree.

 

[Schrayder]

If its instant you may need a spark to run in a new cable. If its storage, I believe you need a g3 qualification to install (but dont need building regs sign off / self cert if under 15 litre)

 

[ianmcd]

you would be better leaving it as it is, if you want a back up, use an over the sink water heater supplied from the cold main