over sizing radiators

flea.rider

flea.rider

flea.rider

Permabanned
Joined
7 Aug 2017
Posts
2,141
Location
by the tower the one up north ..
so i'm going to start oversizing my radiators .. the ones i have are from the 80's (well i think) so i'm starting with the bathroom .. then bedroom .. i'm going to install the most btu for the size thats there .. some are a little taller ..
my thoughts are .. i've turned my boiler right down 60 deg c but it's not warming the house thru .. so i should have better results with new rads .. ??
am i on the right or wrong track ?
 
Spec them correctly. Your boiler needs a drop in return temp in order for it to run efficiently .
Spec them too big and you'll pull too much heat out of them and some rads wont get as warm.
Too small and your boiler wont run efficiently.
 
Have you tried getting a quote for a heat pump from Octopus? We’ve seen a few on the forum get quotes for under £2,000 which include any necessary radiator replacements.

Your logic is right but I agree with the post above - you need to keep them in balance, otherwise you’ll have other problems with some rooms too hot or too cold.
 
Coran said:
Have you tried getting a quote for a heat pump from Octopus? We’ve seen a few on the forum get quotes for under £2,000 which include any necessary radiator replacements.

Your logic is right but I agree with the post above - you need to keep them in balance, otherwise you’ll have other problems with some rooms too hot or too cold.
Click to expand...
mattyg said:
Spec them correctly. Your boiler needs a drop in return temp in order for it to run efficiently .
Spec them too big and you'll pull too much heat out of them and some rads wont get as warm.
Too small and your boiler wont run efficiently.
Click to expand...
understand what your saying .. only time the rads come on is at night .. we use a wood burner while we are in .. and just let them run at 12c when we are not .. dogs have coats and beds to keep warm it's a Worchester 24i .. where would i find out how to resize the rads ?
 
we did exactly this, oversized ours - roughly doubled the BTU of each, has worked a dream, we run the boiler at 60 and the radiators all get warm (as does the house), though did have to balance them as one went to double height. a small change like that can make a big difference to the flow.

We are EPC B though, and I think that is also important, I suspect in our old place which was like a fridge it would not have worked as well.
 
Last edited:
mickyflinn said:
There are radiator calculator's online the will give you the correct size rad for the room size . Then add some to oversize but as long as your fitting thermostatic rad valves you can control the temp in each room.
Click to expand...
yeah thinking on going wifi to the rads as strange as it seems for me .. tapo or something like it ..
 
You don’t need to yolo it, most calculators will ask what flow temperature you’re going for, DeltaT, and give you sizing appropriate for the room at that flow temperature
 
If your rads are from the 80s, replacing them like for like will make a huge difference. I have a 1990s 800mm double panel rad in the front office and its garbage compared to the double panel 600mm in the bathroom.
 
dirtychinchilla said:
Also, if you're replacing the TRVs as well then automatic balancing TRVs are the best things you can get. Smart heads I suppose might make things even better for you.
Click to expand...
Do these go on the flow or return side? I guess if the former you just fully open the return?
 
Something fun to do. Replace your central heating pump with a modern variable one.
There are a number of reasons, but the main one is that they self adjust to ensure that the circulation is at the correct rate, to maintain efficiency of the system. An old static pump can't compete. Also, installers tend to just set the old pumps to maximum, which is the worst thing you can do. As a result, the system works but is not running efficiently at all.
An old pump can use up to 120W continuously, whereas a new one will throttle itself down and may use as little as 10W or less. When you consider how many hours the heating is on, it soon adds up.
It will also automatically adjust itself if you have thermostatic valves on the radiators, an old style pump won't.
 
Last edited:
mattyg said:
Spec them too big and you'll pull too much heat out of them and some rads wont get as warm.
Click to expand...
This is simplistic and wrong.

You can significantly oversize your radiators (after calculating the correct fabric/ventiliation heat loss).

What it allows you to do is put out the correct heat output whilst dropping the flow temp of the boiler down so it runs at peak efficiency and is almost always in condensing mode.

Most importantly, radiators and the overall system needs balancing properly for the heat loss of the house/rooms.

Heat Geek website has loads of great info and youtube videos.

flea.rider said:
so i'm going to start oversizing my radiators .. the ones i have are from the 80's (well i think) so i'm starting with the bathroom .. then bedroom .. i'm going to install the most btu for the size thats there .. some are a little taller ..
my thoughts are .. i've turned my boiler right down 60 deg c but it's not warming the house thru .. so i should have better results with new rads .. ??
am i on the right or wrong track ?
Click to expand...
Don't just throw anything in, you need to do heat loss calcs for each room and size radiators accordingly.

But when looking at radiators you need to look at their output for various Delta T levels. Most list output according to Delta T50, so for a 20 degC room your boiler flow temp will be 70 degC. For a Delta T30 radiator output your boiler flow temp will be 50 DegC and you'll see the lower output (hence then oversizing).

Spending thousands on rads won't actually pay back quickly and is an inefficient way to spend money.

Firstly you should look at the fabric, aka drafts around doors, windows, missing insulation in the loft. Can you add more insulation in the loft, or get under the floor to insulate (if you have a suspended timber floor). I used a Topdon thermal camera (£240 Amazon) and it really helped with locating ill-fitting windows/doors, drafts under skirting boards the could be sealed up etc.

Also, what's your boiler, if you have the option on it, then running weather compensation (WC) mode would be ideal. For example, I have a 2014 Gloworm where you can play with the pump overrun settings to reduce short cycling, then I added a wireless external temperature sensor for it to enable WC. I will be putting some 20mm PIR insulation boards behind my rads which will make a huge difference then will be putting 170mm of insualtion quilt between the joists on the ground floor (from underneath).

If you have a solid walled house, then it would be efficient to get some insulation behind your radiators, less effective if you have a cavity or insualted cavity.
 
Last edited:
SpellowHouse said:
Something fun to do. Replace your central heating pump with a modern variable one.
There are a number of reasons, but the main one is that they self adjust to ensure that the circulation is at the correct rate, to maintain efficiency of the system. An old static pump can't compete. Also, installers tend to just set the old pumps to maximum, which is the worst thing you can do. As a result, the system works but is not running efficiently at all.
An old pump can use up to 120W continuously, whereas a new one will throttle itself down and may use as little as 10W or less. When you consider how many hours the heating is on, it soon adds up.
It will also automatically adjust itself if you have thermostatic valves on the radiators, an old style pump won't.
Click to expand...

bLjT2pz.png


Relevant graph from a CPD I deliver.
 
-Ad- said:
This is simplistic and wrong.

You can significantly oversize your radiators (after calculating the correct fabric/ventiliation heat loss).

What it allows you to do is put out the correct heat output whilst dropping the flow temp of the boiler down so it runs at peak efficiency and is almost always in condensing mode.

Most importantly, radiators and the overall system needs balancing properly for the heat loss of the house/rooms.

Heat Geek website has loads of great info and youtube videos.


Don't just throw anything in, you need to do heat loss calcs for each room and size radiators accordingly.

But when looking at radiators you need to look at their output for various Delta T levels. Most list output according to Delta T50, so for a 20 degC room your boiler flow temp will be 70 degC. For a Delta T30 radiator output your boiler flow temp will be 50 DegC and you'll see the lower output (hence then oversizing).

Spending thousands on rads won't actually pay back quickly and is an inefficient way to spend money.

Firstly you should look at the fabric, aka drafts around doors, windows, missing insulation in the loft. Can you add more insulation in the loft, or get under the floor to insulate (if you have a suspended timber floor). I used a Topdon thermal camera (£240 Amazon) and it really helped with locating ill-fitting windows/doors, drafts under skirting boards the could be sealed up etc.

Also, what's your boiler, if you have the option on it, then running weather compensation (WC) mode would be ideal. For example, I have a 2014 Gloworm where you can play with the pump overrun settings to reduce short cycling, then I added a wireless external temperature sensor for it to enable WC. I will be putting some 20mm PIR insulation boards behind my rads which will make a huge difference then will be putting 170mm of insualtion quilt between the joists on the ground floor (from underneath).

If you have a solid walled house, then it would be efficient to get some insulation behind your radiators, less effective if you have a cavity or insualted cavity.
Click to expand...
So.... Was i right or wrong..... I've highlighted your contradictions.

mattyg said:
Spec them correctly. Your boiler needs a drop in return temp in order for it to run efficiently .
Spec them too big and you'll pull too much heat out of them and some rads wont get as warm.
Too small and your boiler wont run efficiently.
Click to expand...
 
-Ad- said:
This is simplistic and wrong.

You can significantly oversize your radiators (after calculating the correct fabric/ventiliation heat loss).

What it allows you to do is put out the correct heat output whilst dropping the flow temp of the boiler down so it runs at peak efficiency and is almost always in condensing mode.

Most importantly, radiators and the overall system needs balancing properly for the heat loss of the house/rooms.

Heat Geek website has loads of great info and youtube videos.


Don't just throw anything in, you need to do heat loss calcs for each room and size radiators accordingly.

But when looking at radiators you need to look at their output for various Delta T levels. Most list output according to Delta T50, so for a 20 degC room your boiler flow temp will be 70 degC. For a Delta T30 radiator output your boiler flow temp will be 50 DegC and you'll see the lower output (hence then oversizing).

Spending thousands on rads won't actually pay back quickly and is an inefficient way to spend money.

Firstly you should look at the fabric, aka drafts around doors, windows, missing insulation in the loft. Can you add more insulation in the loft, or get under the floor to insulate (if you have a suspended timber floor). I used a Topdon thermal camera (£240 Amazon) and it really helped with locating ill-fitting windows/doors, drafts under skirting boards the could be sealed up etc.

Also, what's your boiler, if you have the option on it, then running weather compensation (WC) mode would be ideal. For example, I have a 2014 Gloworm where you can play with the pump overrun settings to reduce short cycling, then I added a wireless external temperature sensor for it to enable WC. I will be putting some 20mm PIR insulation boards behind my rads which will make a huge difference then will be putting 170mm of insualtion quilt between the joists on the ground floor (from underneath).

If you have a solid walled house, then it would be efficient to get some insulation behind your radiators, less effective if you have a cavity or insualted cavity.
Click to expand...
Worchester 24i it's nearly 10 ys old attic has 2ft of insulation right to the walls .. no draughts to speak of .. i'll keep in mind what your saying replaced the bathroom rad today ..with a towel rail £66 .. put it on for 10 mins far better than the old one .. thx
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom