what size tank

[tally100]

I am due a new boiler and ultrasteel tank to be fitted. What size tank would you reccomend for a 4 bed detached 1 bath and en-suite and i have 3 children. i,ve had quotes for 210ltr and 120 ltr is the 120ltr going to be too small as the 210ltr quote was a lot dearer

 

[gas4you]

I would have thought a 170 or 180 litre cylinder. it depends on the cylinder recovery time. If the 120 is a fast recovery cylinder then it should re-heat from cold in about 12 mins there giving you nearly constant hot water without having to store a lrge wasteful amount of hot water

 

[tally100]

It is going to be an Ultrasteel cylinder with a Vaillant 418 boiler, how do i find out the recovery rate
Thanks

 

[gas4you]

manufacturers technical instructions should specify this.

Good choice of boiler, but why not fit a vaillant Unistor cylinder. The two of them can then 'talk' to each other via ebus for greater efficiency

 

[tally100]

installer said it would be a lot more money to put in a unistor.I dont want to be penny pinching but do you have an idea of difference between an ultrasteel and a unistor 155. Would it be worth the difference to put a unistor in

Thanks

 

[Paul Barker]

Does it modulate the burner and pump speed directly from dhw conditions Gas4u?

 

[gas4you]

When using the Unistor via a VR65 the ecotec plus then controls the water temp. This is why the DHW temp knob is left on the front of a system/open vent ecotec plus boiler.

I cannot answer your question 100% positively but my understanding is that when unistor calls for heat the boiler will modulate to the appropriate level to heat the water quickly.

Depending on the timer used and assuming it is a Vaillant plug in one on the front of the boiler, then you also have the choice of an anti-legionnaire setting for the unistor, where every Wednesday morning the system will fire up to heat the unistor to 70C to prevent/kill off any bacteria present. Ideal for nursing homes etc and the health and safety requirements etc.

 

[Paul Barker]

What will they think of next?

 

[gas4you]

Paul, yes the boiler/unistor will select the optimum burner rate to heat up cylinder quickly whilst giving the most efficiency