Small Under Sink Heater v More hot water needed

[sturharv]

Need a little advice guys, I have a large capacity sink located in a utility room about 25-30m from the cylinder. There is currently a 10 litre mains pressure HW store under the sink (which is normally more than adequate for what you normally would use the sink for), but there is not enough hot water for what the sink is now wanting to be used for i.e. hand laundry washing, where there may need to be 2 or 3 sink fills at a time.

I have seen these electric 'instant' tankless units but I am of the understanding that the flow rates aren't that good, plus they need their own electric supply from the consumer unit, which is not to easy to get to. I know there are instant gas heaters out there but putting gas in that area would be difficult and costly.

When the new laundry was built there was a cold and hot supply brought from the main house (for the taps, washing machine etc. but due to the length of the pipe there would need to be a lot of HW drawn off and this would take a lot from the cylinder. Could you connect this 'capped off' hot supply which is currently under the sink onto the heater unit which would help the recovery of the hot water in the 10 litre unit, although I am aware that it will draw off from the main cylinder, but you wouldnt need to wait ages for the hot water

Any other suggestions please?

Cheers

 

[clf-gas]

How about an instantaneous gas water heater fired from LPG?.

Only needs cold feed which you have, external wall for the flue and a bank of two bottles outside connected via an auto change over.


Just a thought

 

[sturharv]

Cheers, although I think positioning it may be abit tricky, can it go under the sink?

Have you any models that you would recommend?

 

[Biggles..]

we use Red Rings electric instantanious heaters, 8.5 or 9.5KW models. they're about 300mm x 200mm and work fantastic.

 

[clf-gas]

Cheers, although I think positioning it may be abit tricky, can it go under the sink?

Have you any models that you would recommend?

Main medway or mersey, made by Baxi.

These are combi boiler sized so may not fit under sink, though they can give better delivery than electric, cost around the same (£300+), though cheaper running cost.

 

[sturharv]

we use Red Rings electric instantanious heaters, 8.5 or 9.5KW models. they're about 300mm x 200mm and work fantastic.

Thanks..... Maybe the wrong forum! but do you happen to know if these RedRing units require a dedicated electric supply circuit.

 

[JohnD]

anything over 3kW needs a dedicated radial circuit.
Any 3kW heater produces the same amount of hot water per time per electricity used.

You can dribble it out through an Instant heater, or you can accumulate it as in your 10 litre heater, but you can't get more of it any quicker.

 

[ChrisR]

Could you connect this 'capped off' hot supply which is currently under the sink onto the heater unit which would help the recovery of the hot water in the 10 litre unit, although I am aware that it will draw off from the main cylinder, but you wouldnt need to wait ages for the hot water

To my mind this is a fine idea, which I have considered for the eastern wing of ChrisR mansions. The heaters are "unvented" but since the water can expand back up the pipe, all they'd need is the pressure relief valve in case it got blocked.
You might need a second sink, or somewhere to dump any cold water coming from the pipeful of cold, which would come through unheated.

An idea I've just had would be to use a thermostatic mixing valve (£30), one input from the "unvented" store and one from the HW feed. If the store were at say 60 and the output at say 45, you would be using the pipeful of cold to mix, until the gravity tank water arrived. Needs some more thought.

 

[JohnD]

that long pipe is going to absorb a lot of heat from the water before it arrives. I hope it is well lagged.

Does anyone know if plastic is better than copper for not chilling the hot water on a long run like this?

 

[Biggles..]

Unfortunately yes 10mm normally.Just ripped half a dozen Supremes out and installed these in an office instead. Fits nicely in a cupboard and no PRV,tundish and associated items with unventeds.

 

[sturharv]

Could you connect this 'capped off' hot supply which is currently under the sink onto the heater unit which would help the recovery of the hot water in the 10 litre unit, although I am aware that it will draw off from the main cylinder, but you wouldnt need to wait ages for the hot water

To my mind this is a fine idea, which I have considered for the eastern wing of ChrisR mansions. The heaters are "unvented" but since the water can expand back up the pipe, all they'd need is the pressure relief valve in case it got blocked.
You might need a second sink, or somewhere to dump any cold water coming from the pipeful of cold, which would come through unheated.

An idea I've just had would be to use a thermostatic mixing valve (£30), one input from the "unvented" store and one from the HW feed. If the store were at say 60 and the output at say 45, you would be using the pipeful of cold to mix, until the gravity tank water arrived. Needs some more thought.

Thanks, would the mains pressure cold water be a problem linked into the TMV as the HW also linked to it will be gravity pressure?