Combi boiler and HW tank

[XrayDave]

Hi folks

Further down the path of having our c/htg boiler replaced.

Latest thought is for a combi boiler - which can get rid of the F & E tank and the CW feed tank in the loft (something that I would like to do).

Also with a combi the HW tank can be removed from the airing cupboard.

OK, so four questions.

1) can we still have a HW storage tank together with a combi boiler?

2) if we get rid if the CW feed tank, can we still have a HW storage tank?

3) could we use the existing (vented) HW storage tank or would we need to replace the existing HW cylinder with an unvented one?

4) would a heat store be a better option than a HW storage tank (and is this the same as an unvented HW storage tank)?

Thanks in advance

Dave

 

[past3bar]

You probably need to decide between an unvented cylinder and heat only/system boiler or a combi boiler. Either way you can lose the tanks.

 

[XrayDave]

You probably need to decide between an unvented cylinder and heat only/system boiler or a combi boiler. Either way you can lose the tanks.

Thanks for the swift reply.

Wife is interested in a combi boiler but isn't too keen to lose the DHW cylinder.

Question is, could we retain the unvented (ie original) HW cylinder with a combi boiler (I think the answer is NO)?

Could we have an unvented hot water cylinder in place of the original HW cylinder with a combi boiler (I think the answer is YES)?

Can we lose the CW feed tank in the loft (for the HW cylinder)?

I know that a combi would get rid of the F & E CW tank in the loft and (ordinarily) you'd lose both the CW feed tank and HW tank as well.

Cheers

DAve

 

[Onetap]

Question is, could we retain the unvented (ie original) HW cylinder with a combi boiler (I think the answer is NO)?

You could use either a vented or unvented HWS storage cylinder with a combi. You would have a hot water supply from the combi which you could use for a shower.

If you had a vented cylinder, you'd need to retain a cold water storage tank in the loft. .

Could we have an unvented hot water cylinder in place of the original HW cylinder with a combi boiler (I think the answer is YES)?

Yes, done that.

Can we lose the CW feed tank in the loft (for the HW cylinder)?

Yes, but not if you have a vented cylinder.

The stored cold water is useful if the mains water supply ever fails; it rarely does though. If you have a combi, no stored water and the mains fails, you're up the creek with no paddle and nothing to wash the sh1t off with.

 

[XrayDave]

Thanks onetap

So, to make sure that I've got this straight:

My current (25-year-old) copper HW storage tank is vented 'cos it has a cold water feed tank in the loft?

I could get rid of this tank IF I change the HW storage tank to an UNVENTED type?

If I keep the vented HW storage tank, I need to keep the cold water feed tank in the loft?

Either way, I can lose the c/htg Feed & Expansion tank in the loft - the small one - if I go with a combi bolier?

If I retain the cold water feed tank in the loft & the HW storage tank, then should the mains fail, I'd still get hot water from the storage tank - but what happens as the cold water feed tank empties - there would come a point when the HW storage tank would become "empty" and then that would cause a problem?

Thanks

Dave

 

[Agile]

Its not possible to make any statement about what you can or cannot do until the dynamic mains flow rate has been checked.

Any installer who quotes for installing a combi or unvented should be regarded with extreme caution if he does not measure the water flow rate first.

They should also look at the gas supply pipework as that may well need upgrading.

Tony

 

[XrayDave]

Hi Tony

If it helps the mains water flow rate is between 16 & 20 litres per min and the gas supply was judged to be OK - he looked at them both.

Dave

 

[Agile]

If thats the open pipe water flow then its very marginal even just for a combi !

You need a minimum of 15 li/m @ > 0.5 Bar for a combi and 22 li/min @ 1 Bar for an unvented as an absolute minimum.

Tony