Replacing radiators

vikkimcd

I know, it sounds awful, but it isn't that bad really!

How do I find the flow temperature? The temp on the display goes up and down depending on what is happening (i.e. heating on, taps running etc.)

QrizB

How do I find the flow temperature?

Do you know what make/model of boiler you have? Somebody here will know how, or we can find you instructions.

Aternatively, when you've got space heating only (not water heating), there will be a temperature above which the boiler turns off and waits for it to fall. That'sd the temperature we're interested in.

Just as an example, my boiler is a Vailant and my flow temperature is set to 50C. When the heatin starts the temperature on the display might be 20C, but it rises until it reaches 50C before the boiler turns off while the pump still runs to circulate the water. Once it falls to 45C the boiler turns back on and the cycle repeats.

(Your flow temperature is probably higher than 50C!)

Ildhund

@QrizB wrote:

… the pup still runs to circulate the water …

Is that better than using a hamster?

QrizB

😂 Fixed it!

Ectophile

https://forums.moneysavingexpert.com/discussion/comment/81902499#Comment_81902499

The hot water for taps can be set different to the heating on many boilers, so don't worry about that.

Check the temperature once the heating has been on for some time. Maybe an hour or two. That way it will be up to full working temperature. For the boiler to do its condensing thing properly, that temperature shouldn't be more than about 60 to 65C. Lower is better. But with old fashioned radiators, it may take hours to warm up the house at a lower flow temperature.

luci

I'm pretty sure our flow rate is 60C. The boiler's in the loft, so awkward to check. I haven't noticed the radiators taking a long time to heat up.

Scot_39

The heat output to the room is the more important issue - that would vary with the flow and hence radiator temperature.

A radiator has a nominal power rating - just as say an electric heater or a kettle - which is often quoted at a fixed temperature difference - delta T - typically now maybe 50 degrees C.

Older radiators - may well even have been rated for 60 degrees - when say older boilers ran hotter.

As a guide - if run a 60 rated at boiler 50 delta T - maybe 80% rated power, or a 50 rated at 60 delta T - 125% rated power.

One site quotes an example - 20C room, 50 delta T requiring 75C flow temp - at a 10C temperature drop ( delta T = (flow + return)/2 - room - so 50 = (75+65)/2 - 20.

See one example rating change with delta T (the first one on google)

https://www.radiatorsdirect.co.uk/delta-t-conversion/

[off topic

When it tends to really matter is when make a big drop - say if upgrading and so dropping to ASHP flow levels - and say a delta T 30 (flow temp c45-50) on a modern delta T 50 radiator - maybe an effective power as low as 50% rated power. 51% in that linked table. Like running 1 bar rather than 2 on an old electric fire. Which is why many upgrades need radiator changes and / or efficiency improvements.]

I doubt few time say their boiler activation so close that a smaller flow change would be that critical - bit if noticed a change - over a few days - bringing start time forward 10/15 min - would likely quickly fix.

During the energy crisis many were advised to drop flow temps to 60C - as many were set higher

Other users like post above - at 50C - run lower than that.

https://cleanenergy.campaign.gov.uk/save-energy-in-your-home/

The issue would then be the radiators effective power would drop - and so the room itself would take longer to heat up. And so some found still fine for needs - others maybe activated a little earlier in the morning or late afternoon if "off" or on low "overnight" / "midday" if out all day etc.

Needing same amount of energy(E) to heat / maintain - using a lower power (P)= more time(T). (E=PxT therefor, Treq = E req / Peff)

(In the dT 30 ASHP example - in simplest terms - twice as long)

vikkimcd

The boiler has been idle for some time and the temp shows 61.9. I notice that when I turn the heating on it drops dramatically to around 30, but I guess that's normal.

vikkimcd

Just wondering - I know someone mentioned the thing on the end of the radiator that isn't heating up as much (on opposite side to thermostat) - this is stuck solid. Should I be moving able to adjust it? I am not sure why the guy would have set it so static.

Ectophile

https://forums.moneysavingexpert.com/discussion/comment/81904895#Comment_81904895

The lock shield valve should turn without too much difficulty. There's usually no handle fitted. Pull off the dust cap and find a tool in the box that will fit it, eg. An adjustable spanner.

If set correctly, it should be somewhere between fully off and fully on. Once you have a suitable tool, it should turn on and off like any other tap.

Maybe someone over tightened it in the off position when taking the radiator off, and forgot to turn it on again.