Indirect Thermal Store pre heating to Combi?

[dilalio]

If you are keen on an Intergas, then you could get in touch with @Razor900 and ask him to recommend an installer near you, to come and give you an appraisal. He works for Intergas.

 

[Dan Robinson]

Erp is a load of pap. But horizontal cylinders are a MAJOR compromise. Better to have two smaller vertical Unvented cylinders if you can.

 

[muggles]

Where in the country are you? I agree that an Intergas and a Joule are a great combination, but horizontal cylinders never work as well as vertical ones. The cost difference between an A-rated and C-rated cylinder is too large to justify as it's unlikely to pay for itself

 

[Elliotpea]

I'm just outside of Southampton.

Happy to go with 2 x 150l vertical.

Understand what you're saying about A vs C rating and paying for itself, i wondered the same myself.

I've also run some online calculators for boiler size, most are coming in at about 14kw based on my house size, windows, insulation etc, so perhaps an Intergas SB 18 and 2 x 150l Joule Indirect Unvented? C rated, or A rated if the price isn't massively different?

 

[muggles]

Sounds good, although the smallest standard Joule Solar cylinder is 170L rather than 150. What are your size restrictions? Is it possible for you to post a diagram, or max height and width? I appreciate that if you're going into the apex of a roof then width reduces with height, but Joule make shorter fatter cylinders which might turn out to be appropriate for you

 

[Elliotpea]

I'll get up on the loft tonight and get some measurements. Looking at http://www.jouleuk.co.uk/wp-content/uploads/2015/09/ErP-Fiche-Indirect-Technical-Data2.pdf the short cylinder at 300L is 1600mm high. No idea if this would fit or not, but i'll take a look and post up some dimensions.

I don't think i need a specific solar cylinder? As i'm only going to run the immersion from the solar pv, i can use a standard indirect cylinder i think?

 

[bernardgreen]

Understand what you're saying about A vs C rating and paying for itself, i wondered the same myself.

A low rated cylinder in a well insulated cupboard can have less over all heat loss than a high rated cylinder in an open space.

 

[Agile]

I don't think i need a specific solar cylinder? As i'm only going to run the immersion from the solar pv, i can use a standard indirect cylinder i think?

There are many different designs of hot water cylinder.

But many sold specifically for solar have a boiler fed heating coil half way up which can be used to raise the temperature of the top half only on cloudy days.

That avoids heating all the cylinder with the gas when you hope that the lower half will eventually or partially get heated by the solar energy.

Tony

 

[muggles]

I don't think i need a specific solar cylinder? As i'm only going to run the immersion from the solar pv, i can use a standard indirect cylinder i think?

Yes, quite right, sorry - saw solar and assumed thermal rather than PV. A single coil will be fine

 

[Agile]

A few words of warning relating to the thread title of preheating combi DHW inlet water.

Legionella: storing water at 20C to 40C is the ideal breeding temperature for Legionella. A totally fit young person is not greatly at risk. But my boss at the BBC caught the disease while walking near Broadcasting House. It came from untreated cooling water on the roof. Another pedestrian died and the person responsible committed suicide I gather. My boss was unable to drink any alcohol at all for several years and even now only to a much lesser extent.

Boiler temperature control: a basic combi uses 24 kW to raise the water from say 10 C to 50 C. But the minimum heat output of a boiler can be as high as 8 kW. So if the incoming water exceeds about 27 C then the boiler will be unable to modulate any lower and will be forced to turn the burner on and off. That will cause fluctuations in the output temperature!

Many boilers include a flow rate limiter so that the flow rate can not exceed what the boiler is capable of heating. For a basic 24 kW combi that can be at 10 li/min. So to achieve a higher flow rate that part would need to be removed. That would technically be an unapproved modification to the appliance.

Tony

 

[Tipper]

I'd also question putting a tank or two of hot water in the loft. There have been cylinder failures in the past, one, to my knowledge, scalded a child to death...

 

[Dan Robinson]

my knowledge, scalded a child to death...

That was a cold water cistern connected to a open vented cylinder .

 

[Echo the husky]

I'd also question putting a tank or two of hot water in the loft. There have been cylinder failures in the past...

Looks like it would be safer having it in the loft!

 

[Dan Robinson]

I was thinking of something else. .


http://www.getsurrey.co.uk/news/surrey-news/mums-horror-boiling-water-poured-11250864

 

[Echo the husky]

Don't forget that woman that died too. All of these deaths were from directly heated cylinders though. I was doing some work recently in a house where the unvented cylinder had popped and the side split open, emptying it's contents through the ceiling of the dining room. From what the customer was saying, the 2 port valve actuator broke and stuck open, and the pressure relief valve was jammed due to corrosion. Cylinder had never been serviced in the 9 years it had been installed...