Water Not staying hot for long with Tempest Cylinder 250L

neilmcl

chris1012 wrote: »

Apologies for my novice description and info.

So I have had a look at the manual and it is a Telford Tempest 250l indirect cylinder.
We have a combi boiler (Potterton Titanium) but has been modded to work as a system boiler and we have one of our three downstairs toilers using hot water directly from the combi boiler so the 'diverter valve' is used regularly.

According to the manual it states 'Time to re-hear from cylinder from 75% draw off boiler is 25mins or time to re-heat from cold 35mins'.
This is what I understood as the water being drawn off the combi boiler.

The combi is used for scheduled downstairs underdloor heating, feeding one bathroom with hot water and all the rads in the house.

The Cylinder provides hot water to 2 bathrooms and the kitchen sink.

The "draw off" from the cylinder is the hot water from the taps/showers in your upstairs bathrooms. If you only have it on for an hour early in the morning and not again after you've drawn water for your showers/baths etc in the morning then no wonder there's little left in the evening for another shower.

Are you sure it's a combi you've got and not the Potterton Titanium Heat boiler?

chris1012

100% it is a combi, as we have had it for 7 years and only the cylinder for the past 1 year.
Could you elaborate on the draw off from the taps/showers in the bathroom?
What is the draw off in relation to the 25minutes they mention in the manual?

As mentioned during the summer, we had plenty of hot water left during the evening.
Pretty sure when I spoke to Tempest last year, they advised 45mins-1hr using the boiler draw off was sufficient to heat the cylinder up.

southcoastrgi

chris1012 wrote: »

As mentioned during the summer, we had plenty of hot water left during the evening.

Did you read my post :cool:

southcoastrgi

thorganby wrote: »

I believe that you are confused how your hot water system actually works.

Think of your 250 L tempest unvented cylinder as a water heater, not a hot water storage cylinder that stores water for you to use.

Mains pressure cold water flows though a heat exchanger in the cylinder which needs to be kept very hot to heat up the cold water as it passes though.

I think it's you that are confused, you are describing a thermal store not an unvented cylinder

ComicGeek

chris1012 wrote: »

Could you elaborate on the draw off from the taps/showers in the bathroom?
What is the draw off in relation to the 25minutes they mention in the manual?

As mentioned during the summer, we had plenty of hot water left during the evening.
Pretty sure when I spoke to Tempest last year, they advised 45mins-1hr using the boiler draw off was sufficient to heat the cylinder up.

So you've already used 75% of the 250 litres of hot water - the 25 minutes relates to how quickly the boiler will reheat the cylinder (now with 75% cold water inside) to 100% hot water.

Assuming a typical shower/tap usage of 6 litres/min of hot water, your daily usage equates to 210 litres per day plus kitchen usage - no surprise that you're running out of hot water in winter, when the cold water pipe into your house is much colder.

Easy answer is to set your programmer to both 5am-6am and 4pm-5pm - that will reheat the cylinder in the afternoon. Modern cylinders are very well insulated, but you'll still lose some heat if the room is really cold.

Have you got insulation on the primary pipework from the boiler to cylinder? If not, you may find that your cylinder is not getting hot enough in the winter - coupled with the colder intake water temperature, this will reduce the storage temperature of the cylinder, but not be an issue in summer.

thorganby

southcoastrgi wrote: »

I think it's you that are confused, you are describing a thermal store not an unvented cylinder

Agreed the the Tempest unvented cylinder is available in both direct and indirect versions and the OP did state previously that a direct cylinder was their preferred option.

chris1012 wrote: »

Direct cylinder just to loft bathroom or Indirect Cylinder to whole house?

We are having a loft conversion start in two weeks and are still struggling to find the best solution for getting a well pressured hot water supply to the loft when other bathrooms/ water outlets are in use.

The loft bathroom will be used for occasionally for guests for now and in the future most probably for two of our children.

If we go for an unvented indirect cylinder setup, we would have to cause some considerable damage to our current kitchen flooring and hallway, for the pipes to get to our current combi (33kw), main supply pipe, water softener (under kitchen sink that supplies softened water to all bathrooms and boiler) and then up to the loft.

However if we went for a small direct unvented cylinder to supply the loft bathroom only, we would not need to disrupt the kitchen and could t-off the mains supply in the cellar and run the one 22mm cold feed straight up in the wall to the direct unvented cylinder in the loft. We would have to purchase a separate water softener for the loft but this setup would be for the one bathroom only.

From my understanding the cost of running a direct unvented cylinder is considerably more expensive than an indirect one, however as it will be supplying just the one bathroom, we are thinking this may be the best route to avoid the big disruption if we went for the indirect setup.

Just wanted to ask you all what your thoughts were on the above, if my understanding is correct and if there is any other better way of achieving our required setup?

This is a badly compromised set up not helped by the OP believing that they can override the cylinder stat by restricting the boiler on time, presumably choosing cost saving over comfort and convenience.

chris1012 wrote: »

Apologies for my novice description and info.

So I have had a look at the manual and it is a Telford Tempest 250l indirect cylinder.
We have a combi boiler (Potterton Titanium) but has been modded to work as a system boiler and we have one of our three downstairs toilers using hot water directly from the combi boiler so the 'diverter valve' is used regularly.

According to the manual it states 'Time to re-hear from cylinder from 75% draw off boiler is 25mins or time to re-heat from cold 35mins'.
This is what I understood as the water being drawn off the combi boiler.

The combi is used for scheduled downstairs underfloor heating, feeding one bathroom with hot water and all the rads in the house.

The Cylinder provides hot water to 2 bathrooms and the kitchen sink.

A 250 L cylinder is not sufficient to supply two bathrooms and a kitchen with piping hot water when the boiler is only allowed to fire for one hour and at the same time the boiler is supplying heat to downstairs underfloor heating, another bathroom and heating all of the radiators in the property!

The boiler on time should be determined by the cylinder stat not a timeswitch and you are obviously not allowing sufficient water to be heated for your needs

What is the boiler output temperature set to? The cylinder requires 75 - 85 C whereas underfloor heating is normally much lower at 35 - 45 C.

During the time that the boiler is working as a combi supplying hot water to the bathroom, this takes priority over supplying the downstairs underfloor heating, radiators and heating the cylinder.

Forget what the manual says as it does not apply to your non standard set up, that is what the cylinder stat is for.

What a mess!

southcoastrgi

thorganby wrote: »

Agreed the the Tempest unvented cylinder is available in both direct and indirect versions and the OP did state previously that a direct cylinder was their preferred option.



This is a badly compromised set up not helped by the OP believing that they can override the cylinder stat by restricting the boiler on time, presumably choosing cost saving over comfort and convenience.



A 250 L cylinder is not sufficient to supply two bathrooms and a kitchen with piping hot water when the boiler is only allowed to fire for one hour and at the same time the boiler is supplying heat to downstairs underfloor heating, another bathroom and heating all of the radiators in the property!

The boiler on time should be determined by the cylinder stat not a timeswitch and you are obviously not allowing sufficient water to be heated for your needs

What is the boiler output temperature set to? The cylinder requires 75 - 85 C whereas underfloor heating is normally much lower at 35 - 45 C.

During the time that the boiler is working as a combi supplying hot water to the bathroom, this takes priority over supplying the downstairs underfloor heating, radiators and heating the cylinder.

Forget what the manual says as it does not apply to your non standard set up, that is what the cylinder stat is for.

What a mess!

Again you are totally confused, a direct cylinder will be heated via one or more immersion heaters, an indirect cylinder will be heated via a boiler although it may have immersion back up.

A unvented cylinder DOES NOT require heating to 85° however a thermal store will require this temperature, both cylinders will give you mains pressure hot water but are totally different things