Tuning up an old system

[jezsherwood]

Hello guys,

A question of best practice if I may?

My 25 year old heat only Glow-worm space saver 60BR mkII supplies a fully pumped open vented system plus indirect cylinder.

My questions are, what should the flow temp be set at roughly when the cylinder stat is set to 60 to heat it the most efficient ish?

The boiler manual says the max output is 82c and I have it set no where near that.
I know the boiler is if off the chart as being inefficient but I need to tune the heating side up but want to know what flow temp I will be working with.

The boiler manual says the pump speed should give an 11c split between flow and return when set to max 82c. I take it that's after all the rads / cylinder have had their take and rad balancing is to 11c diff approx?

I've got some rads to change/move so thought it a good time to learn about the system.

Thanks

 

[Agile]

The boiler flow should be the lowest that gives enough heat from the rads.

BUT the flow also has to be a minimum of 10° C above the setting on the cylinder!

Why is 55° C not adequate for your hot water?

Tony

 

[jezsherwood]

Only because I believed the recommendation for the cylinder should be 60c to prevent bacteria growing.
Also if you only need a little hot to a lot of cold then less cold is going into the cylinder.
Otherwise, colder hot water meaning drawing more off so more cold in the cylinder meaning more heat to warm it back up again.

Nothing wrong with 55c, just curiosity

Thanks

 

[Agile]

55 C is adequate for killing bacteria.

Its also an adequate temperature for storing and using hot water!

You seem to be trying to make arguments for saving money on hot water somehow without realising that its only 15 % of the fuel bill and the potential savings from reducing your bill is with the 85% which is heating and reducing the flow temp is likely to give you way more savings!

Tony

 

[Madrab]

Afraid I have to disagree -

WRAS state - "any domestic hot water storage should be kept at no less than 60°C to minimise the risk of legionnaires and delivered to the point of use - outlet or TMV - at no less than 55°C"

According to latest research it's the difference of :-

60°C - 3-30 mins @ 90% bacteria destruction
55°C - 1.5 to 5 hrs @ 90% destruction, dependent on strain.

Scalding and energy consumption factors not withstanding.

 

[Agile]

That's quite true!

But 90% killing is still achieved but a bit later.

However, hot water is less likely to be used immediately after it has been used for a shower. So in most cases it will have been stored for some while.

The risk from legionella is often over stated. Its all around us! Its also present in hot supply pipes and taps so when water is first run off it can be quite concentrated. It only gets into you by breathing an aerosol spray and not by just touching the water.

Water should not be delivered to taps above 55° C so a small conflict here!

Old or infirm people are most at risk. They are also the ones likely to be scalded by too hot water, hence the recommendation that water to taps is limited to 45° C.

 

[jezsherwood]

You seem to be trying to make arguments for saving money on hot water somehow without realising that its only 15 % of the fuel bill and the potential savings from reducing your bill is with the 85% which is heating and reducing the flow temp is likely to give you way more savings!

That is not how I ment it to come across.

What I was trying to achieve was knowing what to have the flow temp at to manage the cylinder temp effectively.
then I can balance the heating system from there as the flow temp won't change being such an old boiler whether its heating water or heating.

I understand the heating is the greatest saving but didn't want to drop the boiler temp down too much and find it takes all day to get hot water because the differential is not high enough.

Many thanks

 

[Agile]

The balancing stays set regardless of the flow temp if its about about 60° C.

All you need to do is decide on the cylinder temp, 60° if you re old or infirm or 55° if younger and stronger ( like me ). The set the boiler flow temp to at least 10° above your chosen value.

Be aware scales on cyl stats are often quite inaccurate!

Tony

 

[jezsherwood]

Thanks Tony,

None of that applies but I do have little people so lower temp rads and water is not a bad thing.

Cheers

Jez