Horizontal Unvented Cylinder

coffeehound

ComicGeek said:

The circulating pump is on the hot water pipework to the showers, taps etc. It pumps the hot water around the house in a loop and then back to the cylinder - the idea is that in very large houses/buildings it means that it doesn't take long to get hot water from any tap, and also helps to maintain water temperature for legionella protection etc. Technically it's called domestic hot water secondary return.

The unused hot water then comes back into the cylinder (in between the heating coil and cold water inlet) - the benefit in terms of stratification is that it constantly keeps the water moving within the cylinder so helps with mixing. The downside is that you always lose some heat from the water loop while pumping around the house and it is more expensive to install. Not normally required for most houses, it's just trying to get around the key design flaw of horizontal cylinders.

It looks that Telford are recommending something a lot less complicated than a full circulating loop, so maybe more doable:

330d

coffeehound said:

ComicGeek said:

The circulating pump is on the hot water pipework to the showers, taps etc. It pumps the hot water around the house in a loop and then back to the cylinder - the idea is that in very large houses/buildings it means that it doesn't take long to get hot water from any tap, and also helps to maintain water temperature for legionella protection etc. Technically it's called domestic hot water secondary return.

The unused hot water then comes back into the cylinder (in between the heating coil and cold water inlet) - the benefit in terms of stratification is that it constantly keeps the water moving within the cylinder so helps with mixing. The downside is that you always lose some heat from the water loop while pumping around the house and it is more expensive to install. Not normally required for most houses, it's just trying to get around the key design flaw of horizontal cylinders.

It looks that Telford are recommending something a lot less complicated than a full circulating loop, so maybe more doable:

Yes I did see that. It does looks simpler but a pump is still required.

coffeehound

I would think losses and electricity to run it would be pretty minor.  One issue might just be noise if it made the pipes hum and it was above a bedroom.  Otherwise it looks a neat solution.

330d

coffeehound said:

I would think losses and electricity to run it would be pretty minor.  One issue might just be noise if it made the pipes hum and it was above a bedroom.  Otherwise it looks a neat solution.

Do you know if a specific Telford pump is required or a generic circulating?

coffeehound

They quote Wilo brand there.  Best speak to Telford CS to ask what model.

330d

330d said:

ComicGeek said:

The circulating pump is on the hot water pipework to the showers, taps etc. It pumps the hot water around the house in a loop and then back to the cylinder - the idea is that in very large houses/buildings it means that it doesn't take long to get hot water from any tap, and also helps to maintain water temperature for legionella protection etc. Technically it's called domestic hot water secondary return.

The unused hot water then comes back into the cylinder (in between the heating coil and cold water inlet) - the benefit in terms of stratification is that it constantly keeps the water moving within the cylinder so helps with mixing. The downside is that you always lose some heat from the water loop while pumping around the house and it is more expensive to install. Not normally required for most houses, it's just trying to get around the key design flaw of horizontal cylinders.

We put a lot of vertical cylinders in lofts, and they fit most times - I would really check that you can't get them to fit first, I would put in a standard 200l vertical tank instead of a 300l horizontal tank if it fitted.

Horizontal tanks are also normally made to order, whereas vertical tanks are off shelf items - so lead-in times at the moment are probably quite long.

Thank you, great reply and very good info. 

So by the sounds of it a pump can be used to help but then again the pump has its own disadvantages as you mentioned. 

Interesting point about having a 200l vertical vs 300 horizontal. The horizontals must be bad!

I have not measured the height I have available in the loft but do have a photo of it which I have attached. As you can see, the gable wall is roughly 6 blocks high. So if easy block has a height of 200mm, I have around 1.2m height to play with.

Looking at online retailers, even the 200l tanks have a height of around 1.4-1.5m. 

The 'best' I found was this 250l cylinder which only has a height of 1.33m which is short for a 250l cylinder - https://www.plumbnation.co.uk/site/telford-tempest-stainless-steel-indirect-250l-unvented-cylinder/

But even then I am not sure if that will fit.

Any suggestions please?

Any thoughts on this?

Ectophile

330d said:

Ectophile said:

If you have a circulating pump, you won't have any stratification.  If you use half a tank of how water, you'll then have a whole tank of warm water until you heat it up again.

Sorry I'm not quite with you, apologies for the confusion.

So a circulating pump will or will not solve the issue with stratification?

It depends on what you mean by "solve the issue"!  With a traditional vertical tank, if you are a light user of hot water then you only need to turn on the boiler once or twice a day.  Then you rely on the stratification to keep the top of the tank hot, even as you use hot water during the day.

A de-stratification pump prevents stratification, mixing the water up.  So as you use hot water, the remaining water will get cooler and cooler.  So you have to set the heater to come on more often.  That said, it may not end up taking more energy overall, as you're just heating the tank up from warm, rather than from cold.

coffeehound

That's interesting, Ecto.  I was assuming the de-strat was required only while heating the tank since there would otherwise be insufficient churn to heat the whole tank.  Then once heated, the tank would be allowed to stratify to get the best of the hot water, albeit less efficiently than with a vertical. (?)

coffeehound

The manufacturer confirms that the destratification pump is only run while the tank is being heated.

Ectophile

coffeehound said:

The manufacturer confirms that the destratification pump is only run while the tank is being heated.

That makes sense.  It ensures that the tank is heated up evenly.