Radiators... Talk to me - Please
- Thread starter Gimpymoo
- Start date
Depending what you have your boiler set to for flow temp, your boiler might never go into condensing mode as the return temp will be too high.
As the water temp drops so does the ability of the radiator to do its job. But a condensing boiler works best with a return temp of around 55c or less.
For instance in doing my house based on t35. Which means you take the radiator rating and multiply by 0.63.
If you go to the radiator manufacturers store they will have the calculations and may even list the ratings for different deltas.
For instance a 2000w radiator suddenly becomes a 1260w.
As the water temp drops so does the ability of the radiator to do its job. But a condensing boiler works best with a return temp of around 55c or less.
For instance in doing my house based on t35. Which means you take the radiator rating and multiply by 0.63.
If you go to the radiator manufacturers store they will have the calculations and may even list the ratings for different deltas.
For instance a 2000w radiator suddenly becomes a 1260w.
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Well, most of the BTU calculators say around 7500 BTU for the back room, so taking into account inaccuracies and a cold house, I am getting a 9500 BTU rad. No harm in over speccing is there?
The thing is, I do not want to be removing pipes (concrete floor) so has to be a 2000mm rad anyway.
The thing is, I do not want to be removing pipes (concrete floor) so has to be a 2000mm rad anyway.
With a TRV you can regulate the room temp so with an over sized radiator it will heat up quickly and then stick to the temp where as undersize it and it will never get to temp and no way to sort it easily. Also, as Robj has pointed out, a radiator with a BTU of 9500 at DeltaT50 will be lower at a lower DeltaT figure. Most newer combis are most efficient at a return temp of 55 so the DeltaT is already below 50.
Soldato
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- 1 Jul 2003
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- There's a voice that keeps on calling me.
Sorry to jump in on the thread, but i could do with some advice.
I need to do my entire house, as the boiler is a Worcester 30kw condensing combi, but the house is old draughty and the rads are mega old, so probably filled with crud hence why its freezing. Im gessing my boiler will require a ret temp of 35c as its a condensing boiler??
My plan is to replace all the rads, flush the system, put in TRV's all round, and finally go round the whole house with a stonking great silicon sealant gun to plug in all the gaps!!
I need to do my entire house, as the boiler is a Worcester 30kw condensing combi, but the house is old draughty and the rads are mega old, so probably filled with crud hence why its freezing. Im gessing my boiler will require a ret temp of 35c as its a condensing boiler??
My plan is to replace all the rads, flush the system, put in TRV's all round, and finally go round the whole house with a stonking great silicon sealant gun to plug in all the gaps!!
Return temp around 55C> is fine. But generally the lower the better.
Just get a laser thermometer and measure the return pipe going into the boiler. If its 60c turn the boiler down a few degrees.
The reason new boilers struggle on old systems is old boilers didn't condense so the most efficient setting was the highest hence radiators didn't need to be as big.
Regards TRVs on all radiators, only do that if you know the system has a bypass valve fitted. If your not sure one radiator shouldn't have a TRV fitted, which if you have a thermostat in a room, you don't need a TRV on that one anyway.
Is that encase the boiler stays heating the water but all radiators could be closed?
The pump tends to overrun anyway so there isn't boiling water in the boiler. They're also designed with a minimum flow so having either a radiator with no TRV or a bypass is the best thing to do. Some new boilers can have an internal bypass, but it doesn't hurt to fit an external one if you aren't sure.
I prefer the radiator without a TRV though at least the heat goes somewhere useful that way.
I prefer the radiator without a TRV though at least the heat goes somewhere useful that way.
Right...
The old rad was imperial, 2150mm.
The pipes are buried in concrete so moving them is not an option.
So, the rad size choices are:
2000mm
This will need the pipes/tails returning in by 75mm each end.
I fear this will look ugly?
2200mm
This will need pipes/tails being extended by 25mm each end.
Is this an easy task?
I am not doing it, Plumber is booked for Wednesday
If so, is this any good:
https://www.columnrads.co.uk/revive-600h-x-2200l-double-premium-radiator
ooh, or this one:
http://www.screwfix.com/p/kudox-premium-double-convector-radiator-white-500-x-2200mm/50935
Does one go for a 500 or 600mm height? Aesthetically, does it make a big difference?
T21 vs T22 - The depth difference makes a T22 rather "chunky" in my opinion.
Perosnally, I would rather have the extra height but less depth.
The old rad was imperial, 2150mm.
The pipes are buried in concrete so moving them is not an option.
So, the rad size choices are:
2000mm
This will need the pipes/tails returning in by 75mm each end.
I fear this will look ugly?
2200mm
This will need pipes/tails being extended by 25mm each end.
Is this an easy task?
I am not doing it, Plumber is booked for Wednesday
If so, is this any good:
https://www.columnrads.co.uk/revive-600h-x-2200l-double-premium-radiator
ooh, or this one:
http://www.screwfix.com/p/kudox-premium-double-convector-radiator-white-500-x-2200mm/50935
Does one go for a 500 or 600mm height? Aesthetically, does it make a big difference?
T21 vs T22 - The depth difference makes a T22 rather "chunky" in my opinion.
Perosnally, I would rather have the extra height but less depth.
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Soldato
- Joined
- 1 Jan 2003
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- Derbyshire
Go for the larger radiator, its only a 2" dog-leg. And you can have a choice whether to do it even (1") at each end, or if one end of the rad is partially hidden (furniture etc) get it altered at that end, and leave the other alone.
Got a P+/K1/T1 radiator in the end (Double panel, single convector) for the back room, was fitted today.
Went with 2200mm in the end and luckily, it fitted where the imperial Rad was with no additional joints. The imperial rad was about 2150mm ish.
Turns out the old pipe work had some "play" to it so squeezed bits in and worked a treat which was lucky as looks much tidier.
Went with 2200mm in the end and luckily, it fitted where the imperial Rad was with no additional joints. The imperial rad was about 2150mm ish.
Turns out the old pipe work had some "play" to it so squeezed bits in and worked a treat which was lucky as looks much tidier.
Gimpymoo;30483622 said:
P+ and K1 are different, P+ is a Type 21, K1 is a Type 11. Always confuses me all the different terms, Type is the easiest i find, first number the number of panels, second number the number of convectors.
Bonus that it went on so easy. Why not go for a Type 22 though minimal extra cost for a decent increase in output.