Copper Hot Water Cyl - Heating how much

[utterlydiy]

I have a copper Hot water cyl approx. 36" x 16" which is some 30 years old, fitted in an upstairs airing cupboard.

12mths ago a new Worcester forced vented boiler was fitted in place of the original balanced flue.

The system was pressure flushed with additives added, new new pump with selectable flow rates, all four bedrooms and kitchen radiators with thermostatic valves and a magnetic filter near the pump. I have no problems with the operation of the hot water or central heating temperatures etc. Motor valves for both hot water and central heating are ok for full period of timed heating.

But with the hotwater cyl tank, how much of it should be hot after heating for approx. two hours.

Mine gets approx. two thirds hot from the top.

Right or wrong.

thanks

 

[hazetimesfive]

Wrong

I suspect you have a problem there

 

[utterlydiy]

thanks

Such as ??

thanks again

 

[Madrab]

Either a semi blocked/restricted cylinder coil or an old, very inefficient hot water cylinder would be the probable causes I would reckon. Are you in a hard water area? If so, the coil could be coated too.
Time to replace the cylinder would be my recommendation.

Recovery time of a standard 170ltr modern cylinder would be about 40mins. In saying that I now believe with the Part L amended building regs this requirement has been halved to 20 mins for new systems.

 

[jackthom]

Have a look at these gledhill cylinders for example and you'll see how the recovery time and insulation have improved since your original one was fitted.

http://www.plumbnation.co.uk/site/gledhill-condencyl-he-high-performance-vented-hot-water-cylinder/

We have something roughly the same and it can easily reheat to fill a bath in 20mins or less.

 

[utterlydiy]

Thanks both

The water from the taps, is hot that you can't put your hands under it.

The tank thermostat is at approx 65c and the boiler at approx. 75/80% rotated.

So how much of the tank should get hot, all of it or just part from the top.

thanks

 

[jackthom]

It could depend on both the position of the thermostat and the length/height of the coil inside.

Generally it will remain cool below the bottom coil connection, which is the return to the boiler.

Untitled

• jackthom
• 18 Nov 2013
• 2

 

[utterlydiy]

Ok thanks,

My thermostat is roughly just below half the height of the tank.

Could I move this lower to roughly three quarters of the height of the tank or would this be a bad move.

thanks again

 

[Galoka]

That could well be the problem.

Normally they are mounted 1/4 to 1/3 the way up the cylinder. I'd move it down a bit

 

[utterlydiy]

thanks

I'll give it a try.

 

[kbdiy]

I recently replaced my old copper cylinder (36"x18") about the same age as your's, as the foam insulation had blown and the boiler was continually trying to make up the temperature, in spite of the fact that I had added a loose jacket over the top. Plus I suspect it was well scaled up and the coil might have been near end of life.

I went for a stainless steel 1200mm x 450mm from Screwfix as I wanted to increase the capacity for pumped showers as well as improving efficiency.

What a difference! Reheats in next to no time and doesn't continually cycle the boiler. In total with pump and other plumbing parts total cost of £500 so well pleased with the result. Am hoping the bills will reflect some kind of saving in the long term.

 

[Madrab]

yup +1.... should be roughly 1/3 of the height from the floor which should be just above the bottom coil. Even then though you are getting 2/3rds of the tank heated though 2 hours to heat 2/3rds of the tank is still far too long IMO. Running the boiler more than double the amount of time it should be is a serious waste of any1's dosh i'd say

 

[jackthom]

Yes definitely another vote for a new cylinder. The older ones have small coils and insulation is poor to nonexistent.

My new boiler used to cycle ON for about 40 secs then OFF for a minute or two trying in vain to heat up the 30 year old one.

 

[JohnD]

also a 36"x16" cylinder is rather small, I doubt you can get a full bath out of it.

What colour is it?

Insulate the hot pipes with Climaflex or similar while you're about it.

 

[utterlydiy]

My new boiler used to cycle ON for about 40 secs then OFF for a minute or two trying in vain to heat up the 30 year old one.

The time mentioned earlier, is the time set for the system as awhole CentralHeating/HotWater in mornings. Not that it takes that long to heat the tank/hotwater.