Plumb a unvented hot water cylinder to gravity header tank

[BeefCube]

Hi,

I'm thinking of installing a point of use mini hot water cylinder into my laundry room.

Something like this: https://www.plumbnation.co.uk/site/...-sink-15l-3kw-electric-unvented-water-heater/

My question is, can I connect an unvented mini cylinder to the water supply from my loft header tank, not the water mains feed. Reason being we don't have mains. (catchment tank) To do this, maybe I cannot connect the pressure reducing valve?

However, I know you get vented ones but have to use a specific venting tap which are pretty sub standard in looks. If I cant use an unvented cylinder and get a vented mini one with vented tap could i hook up 2 taps from it, one for kitchen (standard tap) and one for laundry room (venting tap) but only have one use the venting tap or do they both need to be vented ?

Cheers

 

[Agile]

Although its not designed with that use in mind, you can still fit it from your gravity fed tank and don't need the pressure reducing valve.

However, think about the quality of the water in case it contains anything which will damage the water heater.

Tony

 

[BeefCube]

Well the water is not the best but okay.. But either way vented or unvented there will be same issues? Or is vented more robust?

Reason i don't want to go vented is that i have to use a ridiculous tap.

 

[Agile]

It will only work as unvented if you have a high mains supply pressure in excess of 1.0 bar for example.

You seem to be confusing vented and unvented.

If using it vented there should be no restriction between the inlet and to the gravity feed tank so that the water can expand up the pipe.



Tony

 

[BeefCube]

It will only work as unvented if you have a high mains supply pressure in excess of 1.0 bar for example.

You seem to be confusing vented and unvented.

If using it vented there should be no restriction between the inlet and to the gravity feed tank so that the water can expand up the pipe.



Tony

Hi Tony, i am not that confused . You didn't mention earlier that it will only work with 1 .0bar pressure this is the sort of info i was after.

With a point of use cylinder vented you have to use a venting tap. Like these ones: http://www.amazon.co.uk/Undersink-E...-Kitchen/dp/B0080RD48A/ref=pd_sxp_grid_pt_1_0

I don't want to use one of these venting drip taps that is why i am looking into unvented... If i could use any tap I would go for a vented setup!

 

[Agile]

You are confused!

You have just said "vented" when you meant "unvented"!

Its only when using it UNvented that you may need to use special taps.

It will work as an unvented with less than 1.0 bar but its normally expected that the supply pressure will be above the outlet pressure of the pressure reducing valve.

If the inlet pressure is too low, as in your case, then it may be insufficient to allow any water at all to flow through the pressure reducing valve.

Tony

 

[BeefCube]

Its vented through the tap!! In other words its VENTED! I don't want the hassle of having a pipe going back to the header tank to vent it do I!

Unvented does not require a special tap but rather an expansion vessel and outlet and mains pressure.

 

[Agile]

You are confusing the regulations for small ( under 15 litres ) unvented cylinders and larger ones.

It is still classed as an unvented cylinder if under 15 litres and fitted with a special tap.

The term unvented refers to the fact that they run at a pressure greater that atmospheric.

The special tap does not make the cylinder vented. It just opens slightly to relieve the pressure if that becomes too high.

Tony

 

[Biggles..]

Would you like a size 10 to keep digging Tony?

A point of use heater that requires a vented tap is referred to by the manufacturer as a "vented pointed of use heater", check out heatrae sadia, maybe look at the UTC99 as an example

those heaters that dont require a vented tap are refered to by the manufacturer as UNvented, maybe look at the hotflo,multipoint.

Maybe the manufacturers are also confused and don't know what they actually make, thank the Lord your here to straighten out all this confusion, eh Agile!

 

[BeefCube]

LOL, after all that, I have decided to go for just a simple instant water heater

http://www.dafi.co.uk/instant-tankless/in-line-73-kw-instant-dafi-under-sink-water-heater.html

 

[Biggles..]

Fitted hundreds of those last summer.
Bought into the country by Plusens in Nottingham.

They're ok, tend to split quite easily within the unit and the plastic bridge bar across the top ain't much cop.
They send a restrictir to go on your tap to alter flow rate.
we used the small 3kw (2.6kw if memory serves me right).

 

[Biggles..]

Just to clear up vented point of use and vented taps

"These products are variously known as 'Point of use', 'Open outlet', 'Displacement' or 'Non-pressure' water heaters. They have an open outlet and rely on the opening of a tap or valve on the inlet side to displace the hot water in the heater with incoming cold water. The open outlet ensures that any excess pressure in the heater is vented. During the warm-up cycle it is normal for expanded water to drip from the spout or tap."

 

[BeefCube]

Fitted hundreds of those last summer.
Bought into the country by Plusens in Nottingham.

They're ok, tend to split quite easily within the unit and the plastic bridge bar across the top ain't much cop.
They send a restrictir to go on your tap to alter flow rate.
we used the small 3kw (2.6kw if memory serves me right).

Looks like they sell parts to sort them , maybe they do fail quite a bit then but for the price worth it.