180L v 300L tank ?

blast06

Hi,

The air to water pump system i am going with in a new build comes with a 180L 'hot-water' tank. It costs quite a bit to upgrade to a 300L tank. Just wondering what the typical hot water needs would be for a family of 5 (parents and 3 kids) and whether i would need the 300L tank?? Anyone any experience on this ??
Kids get bathed a couple of times a week and in years to come (teenage years) i expect kids will be showers rather than baths - same as Mammy and Daddy ! DOn't know if there are any other considerations ?
Cheers.

daver123

You will need a 300 ltr tank as each person usually needs 50 litres of water per day

ccsolar

daver123 wrote: »

You will need a 300 ltr tank as each person usually needs 50 litres of water per day

+1

shane0007

daver123 wrote: »

You will need a 300 ltr tank as each person usually needs 50 litres of water per day

That rate is only used for solar as solar does not have a re-heat time as such. A heat pump does.
If solar is being used in conjunction with the heat pump then a larger cylinder is useful.

The price difference between a 180L cylinder & a 300L cylinder would only be about €100.

daver123

shane0007 wrote: »

That rate is only used for solar as solar does not have a re-heat time as such. A heat pump does.
If solar is being used in conjunction with the heat pump then a larger cylinder is useful.

The price difference between a 180L cylinder & a 300L cylinder would only be about €100.

What rate would you suggest for non solar

Outkast_IRE

Are we to assume your showers arent electric ?

Also OP a thing to consider is this. In most standard systems the hot water is heated to at least 60 degrees in the cylinder. The higher you tell the Air to water system to heat the hot water to , the less the COP of the unit will be, costing you more money to run. I see alot of manufacturers COP is for water heated to 35 degrees.

shane0007

daver123 wrote: »

What rate would you suggest for non solar

It really depends on what is heating it & the recovery time.
Heat pumps generally do not work well with large volumes as they take a very long time to reach the desired temperature.

daver123

shane0007 wrote: »

It really depends on what is heating it & the recovery time.
Heat pumps generally do not work well with large volumes as they take a very long time to reach the desired temperature.

I live in a house at the moment with a 200 litre tank which is heated by gas condensing boiler and is also backed up by solar ( kingspan thermomax 20 tube system ) which really only makes a good contribution from april - october, there are 2 people in the house and i put the gas boiler on for about 1 - 2 hours a day to heat the hot water in the winter and 1 hour a day from apr - oct as the solar gives a boost

shane0007

20 tubes is probably on the low side for 200L. I always find solar in Ireland needs to be a bit over-sized to perform well.
Saying that, the last 2 years has been absolutely crap for solar.

daver123

shane0007 wrote: »

20 tubes is probably on the low side for 200L. I always find solar in Ireland needs to be a bit over-sized to perform well.
Saying that, the last 2 years has been absolutely crap for solar.

Totally agree i suppose the return on the investment will happen over time as energy costs increase, it is also nice to be able to come home in the summer months and have real hot hot water which was supplied by a renewable resource

blast06

Thanks for the comments.

My heating source will be a air to water heat pump .... to get the water from 40-45 from the heat pump up to ~60 will mostly be done by electricity on night-saver rate as much as possible. I will have no electric showers.

The cost of going for 300 instead of 180 is quite significant for me cos the 180 tank is sold as part of the overall heat pump, UFH packages by the supplier and is pre-configured, wired etc so i was quote €700 to change this to a 300L tank.

Partly based on this I am veering towards staying at 180L. Yes, the average usage per person will be 50L (and 5 of us in the house) but saying that demands a 300L tank presumes the tank does not re-fill and re-heat in a 24 hour cycle ?!?! My concern was more that on a particularly busy morning where we also have other family staying that the usage would be such that the re-fill and re-heat of the water would not be able to keep up with the demand.
Any other thoughts ?!

brophis

blast06 wrote: »

Partly based on this I am veering towards staying at 180L. Yes, the average usage per person will be 50L (and 5 of us in the house) but saying that demands a 300L tank presumes the tank does not re-fill and re-heat in a 24 hour cycle ?!?! My concern was more that on a particularly busy morning where we also have other family staying that the usage would be such that the re-fill and re-heat of the water would not be able to keep up with the demand.
Any other thoughts ?!

Does the cylinder have an immersion as a backup for such a scenario?

blast06

blast06 wrote: »

Thanks for the comments.

My heating source will be a air to water heat pump .... to get the water from 40-45 from the heat pump up to ~60 will mostly be done by electricity on night-saver rate as much as possible. I will have no electric showers.

The cost of going for 300 instead of 180 is quite significant for me cos the 180 tank is sold as part of the overall heat pump, UFH packages by the supplier and is pre-configured, wired etc so i was quote €700 to change this to a 300L tank.

Partly based on this I am veering towards staying at 180L. Yes, the average usage per person will be 50L (and 5 of us in the house) but saying that demands a 300L tank presumes the tank does not re-fill and re-heat in a 24 hour cycle ?!?! My concern was more that on a particularly busy morning where we also have other family staying that the usage would be such that the re-fill and re-heat of the water would not be able to keep up with the demand.
Any other thoughts ?!

Without the ability to easily or quickly reheat the cylinder 180lt of hot water can become a issue, daily usage and visits will need to be well planned.

With 300lt you are less likely to notice any issuess and your hot water will just work.

Although 300lt will cost you more you will have less heartache, 180lt can be adapted too but it's a pain when you have no hot water and a hot water system that can't respond.

shane0007

gary71 wrote: »

Without the ability to easily or quickly reheat the cylinder 180lt of hot water can become a issue, daily usage and visits will need to be well planned.

With 300lt you are less likely to notice any issuess and your hot water will just work.

Although 300lt will cost you more you will have less heartache, 180lt can be adapted too but it's a pain when you have no hot water and a hot water system that can't respond.

Yes but remember its been heated by a heat pump which is also serving the space heating system. I would be seriously looking at the reheat times before decisions are made.

Tommyboy08

blast06 wrote: »

Hi,

The air to water pump system i am going with in a new build comes with a 180L 'hot-water' tank. It costs quite a bit to upgrade to a 300L tank. Just wondering what the typical hot water needs would be for a family of 5 (parents and 3 kids) and whether i would need the 300L tank?? Anyone any experience on this ??
Kids get bathed a couple of times a week and in years to come (teenage years) i expect kids will be showers rather than baths - same as Mammy and Daddy ! DOn't know if there are any other considerations ?
Cheers.

What make of air to water have you decided on, with integrated tank I'm guessing thermia

blast06

It's a Danfoss.
Sticking with the 180L .... I think!

Tommyboy08

blast06 wrote: »

It's a Danfoss.
Sticking with the 180L .... I think!

Which model is it, DHP-AQ Maxi?
Or the DHP-A Opti?