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Author: Subject: House rads - why are they wrong?
Mr Whippy

posted on 3/9/18 at 11:47 AM Reply With Quote
House rads - why are they wrong?

So here's the thing, we all know how to plumb in a car rad, the hot hose at the top, the cold at the bottom so the hot water flows through the radiator core and not by-passing it if say some numpty designed a car radiator with both the inlet and outlet on the bottom....

Well then why oh why when house radiators which have the same basic internal layout of passages, do people keep putting the inlet and outlet on the bottom???? it's no wonder the bottom is like super hot and the top barely warm

what's going on? it looks totally stupid, like people just keep copying the same mistake without question....







[Edited on 3/9/18 by Mr Whippy]

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Mash

posted on 3/9/18 at 11:51 AM Reply With Quote
I'm guessing it's a combination of ease of plumbing, and relying on the fact that heat rises.

Shouldn't be a massive issue though if the rads are properly bled.

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cliftyhanger

posted on 3/9/18 at 11:58 AM Reply With Quote
The rads get hot at the top first, or should. If not it needs bleeding!
The system does work just fine. Probably not optimal, but they are cheap and effective, and you can normally plumb them top or bottom if you wish, but not very attractive if top plumbed.

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Mr Whippy

posted on 3/9/18 at 12:06 PM Reply With Quote
possibly a bit of both but really, it's still plain wrong

Reason I'm asking is I'm installing a solid fuel boiler, one of the requirements is that for safety there should be one rad and the water tank heater coil not on the loop for the pump in case the power goes off. They should work by convection circulating the water, however they'll be no real circulation from the rad if both the inlet and outlet are on the bottom, how does the water know which pipe to chose when they are both the same temp and the only temp difference is the top of the radiator??

Hence I was (am) going to be plumbing it correctly regardless of the "normal way" however I can't think off any reason not to do all the other ones the same way so water is flowing through the radiator and not trying to heat the carpet.

Not bothered about looks as I'm putting them in decorative radiator cabinets so the kids don't burn themselves

[Edited on 3/9/18 by Mr Whippy]

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Charlie C

posted on 3/9/18 at 01:44 PM Reply With Quote
Unlike a car cooling system where heat is lost as quickly as possible, a domestic heating system has to exchange heat from multiple radiators to heat an entire house more or less evenly whilst trying use as little energy as possible.

This is how a domestic renewables scientist explained to me why the in and out let are on the bottom
Hot water rises in the radiator when the water temperature in the radiator is equal or nearly equal the water can take the shortest route through the radiator because its not raising and back into the heating system therefore reducing heat loss in the heating circuit water/liquid. This is one way to increase the efficiency of the system only very marginally but it all helps.

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hughpinder

posted on 3/9/18 at 02:39 PM Reply With Quote
Don't forget the flow side goes to the thermostatic valve if you are having them - the plumber that did my house got this wrong and it was ages before I got the water hammer noises sorted.
Regards
Hugh

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big-vee-twin

posted on 3/9/18 at 03:24 PM Reply With Quote
linky





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chris

posted on 3/9/18 at 03:56 PM Reply With Quote
fitting the decorative rad covers will reduce radiator output by as much as 50%
from my experience

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wylliezx9r

posted on 3/9/18 at 04:15 PM Reply With Quote
....as other have already said they are not designed wrong, they serve a completely different purpose to the type used in a car.





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sdh2903

posted on 3/9/18 at 04:43 PM Reply With Quote
Agreed it makes no difference. We've got some fancy vertical dad's that are plumbed how you want to do yours and they are no better than the standard layout of the rest.

The radiator covers whilst looking good are terrible for heating. Lose so much heat.

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Mash

posted on 3/9/18 at 05:18 PM Reply With Quote
quote:
Originally posted by sdh2903
Agreed it makes no difference. We've got some fancy vertical dad's that are plumbed how you want to do yours and they are no better than the standard layout of the rest.

The radiator covers whilst looking good are terrible for heating. Lose so much heat.


My Dad's 94, and whilst he's not fancy, he does manage to be vertical at least half of the day

I'll get my coat

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adam1985

posted on 3/9/18 at 06:06 PM Reply With Quote
TBOE is actually slightly more efficient the only problem is it doesnt look as tidy. Its normally seen more commonly in commercial building and schools
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sdh2903

posted on 3/9/18 at 08:35 PM Reply With Quote
quote:
Originally posted by Mash
quote:
Originally posted by sdh2903
Agreed it makes no difference. We've got some fancy vertical dad's that are plumbed how you want to do yours and they are no better than the standard layout of the rest.

The radiator covers whilst looking good are terrible for heating. Lose so much heat.


My Dad's 94, and whilst he's not fancy, he does manage to be vertical at least half of the day

I'll get my coat


bloody predictive text.

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Mr Whippy

posted on 4/9/18 at 06:00 AM Reply With Quote
quote:
Originally posted by big-vee-twin
linky


interesting however, would require a pump. I do wonder if that is the desired flow vs the actual flow, it would have been better if they had used a clear plastic rad and some die inside. For the rad that is to serve as the failsafe for if the pump fails I'll pump it to the top and bottom.

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cliftyhanger

posted on 4/9/18 at 06:14 AM Reply With Quote
Every rad I have ever fitted (OK, only about 60 over the years, I don't do it every day) gets hot at the top first, with the middle bottom bit warming last. When the system fires up, put you hand against the rad and feel it.

Gravity should keep circulation going adequately....

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Bluemoon

posted on 4/9/18 at 07:26 AM Reply With Quote
quote:
Originally posted by cliftyhanger
Every rad I have ever fitted (OK, only about 60 over the years, I don't do it every day) gets hot at the top first, with the middle bottom bit warming last. When the system fires up, put your hand against the rad and feel it.

Gravity should keep circulation going adequately....


This is the point, it's gravity doing the circulation in the rad, (hot water is lower density so rises). Not the same as a heat exchanger with a pump forcing the water around a core.

Also, Rads are designed to pass the water some 12C cooler back into the circulation to the other rads...

Dan

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907

posted on 4/9/18 at 08:43 AM Reply With Quote
quote:
Originally posted by Mr Whippy
possibly a bit of both but really, it's still plain wrong

Reason I'm asking is I'm installing a solid fuel boiler, one of the requirements is that for safety there should be one rad and the water tank heater coil not on the loop for the pump in case the power goes off. They should work by convection circulating the water, however they'll be no real circulation from the rad if both the inlet and outlet are on the bottom, how does the water know which pipe to chose when they are both the same temp and the only temp difference is the top of the radiator??


[Edited on 3/9/18 by Mr Whippy]






If you have hot water into the bottom and the outlet at the top the water will flow all the time because heat rises.

This is how your safety rad should be plumbed.
( From top of boiler to bottom of safety rad and back to bottom of boiler via the top of the rad. )


The remaining rads are plumbed in at the bottom and out at the bottom.

These then work with a pump.


Paul G





Member of the Suttol Owners Club, the MX5 Owners Club and the BMMC

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Mr Whippy

posted on 4/9/18 at 11:28 AM Reply With Quote
^ yip this is how I shall do it, ta
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garyo

posted on 4/9/18 at 04:44 PM Reply With Quote
quote:
Originally posted by 907


If you have hot water into the bottom and the outlet at the top the water will flow all the time because heat rises.

This is how your safety rad should be plumbed.
( From top of boiler to bottom of safety rad and back to bottom of boiler via the top of the rad. )


The remaining rads are plumbed in at the bottom and out at the bottom.

These then work with a pump.


Paul G


Mine aren't plumbed like that, presumably because the water loses heat as it goes through the rad, becomes more dense, then flows out the bottom back to the log burner.

So for mine : Top of boiler -> top of rads -> bottom of rads -> bottom of boiler.

Both of my rads are higher than the boiler.

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r1_pete

posted on 4/9/18 at 06:04 PM Reply With Quote
The none pumped thermo syphonic requirement you speak of is generated by the boiler not the rads.

The hot output from the boiler will be at the top, and the return at the bottom, as the boiler heats the water it rises and generates the circulation. Pre combis, the bypass you describe was a must to prevent overheating in the boiler.

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Mr Whippy

posted on 5/9/18 at 06:27 AM Reply With Quote
Paul G


Mine aren't plumbed like that, presumably because the water loses heat as it goes through the rad, becomes more dense, then flows out the bottom back to the log burner.

So for mine : Top of boiler -> top of rads -> bottom of rads -> bottom of boiler.

Both of my rads are higher than the boiler.


interesting, to here some have been plumbed like that so not wrong, just depends on whether it is a pump or convection is the motive force for the water. So sounds like you could run you boiler with no pump.

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garyo

posted on 5/9/18 at 07:52 AM Reply With Quote
quote:
quote:

Mine aren't plumbed like that, presumably because the water loses heat as it goes through the rad, becomes more dense, then flows out the bottom back to the log burner.

So for mine : Top of boiler -> top of rads -> bottom of rads -> bottom of boiler.

Both of my rads are higher than the boiler.


interesting, to here some have been plumbed like that so not wrong, just depends on whether it is a pump or convection is the motive force for the water. So sounds like you could run you boiler with no pump.


Mine doesn't have a pump - it's just a log burner boiler (horizontal plate boiler on a slight skew so that the hot output is an inch higher than the cold input. The hot pipe immediately rises from the boiler, and the cold inlet immediately falls by a foot before heading up, further exaggerating the gravity pumping.

Other than there's just the two rads and a dirty great 28mm piping, plus an F+E tank in the loft.

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