Is my pipe/rad layout poorly designed?

[b175c15t110]

Hi.

Hoping someone can advise.

My downstairs CH system is on 3 loops.
First loop 3 rads,
Second loop 7 rads,
Third loop 3 rads.
All loops return via the main 22mm pipe to the boiler.

However, the second loop also feeds 6 upstairs rads, making a total of 13 rads on that loop. The upstairs rads do get quite hot, but never as hot as the downstairs ones, and they are also very slow to heat up. Maybe 1 to 2 hours, but even then I can still keep my hands on them without burning.

Is the amount of rads on the second loop a problem?
I should say that balancing has improved things, but certainly not cured anything.

It would be quite easy for me to change the upstairs feed onto loop one, which would result in loop one being 9 rads, loop two 7 rads and loop three 3 rads, but I don't want to do this if I'm wasting my time.

The boiler is a recent Baxi platinum 40kw, and the system had a chemical flush when fitted, but not a power flush.

Maybe a solid blockage in the upstairs feed is the cause? Who knows?!

Thanks in advance for any advice.

Cheers,
Gary.

 

[JohnD]

The upstairs rads do get quite hot, but never as hot as the downstairs ones, and they are also very slow to heat up.

Thanks in advance for any advice.

Carry on with the balancing.

 

[Terrywookfit]

Is this a one pipe system

 

[b175c15t110]

"Carry on with the balancing."
All downstairs rads are set between 1/8 and 1/4 turn on the lockshields. Hard to turn them down much more!

"Is this a one pipe system"
No, all radiators are on a feed and return system, so there are 2 pipes going around the whole system.

I'm now looking into the possibility that some of the lockshields are not working, as the downstairs rads are still getting very hot, and quite quickly, despite the lockshields being set on 1/8 to 1/4 turn. The water just doesn't seem to want to go upstairs very quickly!

What do you think about my original question?
Is 13 rads (7 down and 6 up) too many rads on one loop, or does this make no difference?

Is there a limit?

The pipe runs are also quite long as it's quite a large house. Approx 40' X 35' floorpan and the same upstairs.

 

[JohnD]

Turn them down a bit more.

 

[Andy165]

How many rads in total ? May need an additional expansion vessel. Do you have a magnaclean filter on the ch return ? To help keep boiler clean. I think also that boiler has a mesh filter in the return valve. May need cleaning. Check mi ,s to see if there is one there.

 

[b175c15t110]

19 rads in total.

Boiler brand new.

Yes, large magna clean filter on return. Filter is clean.

Not sure about a mesh filter. Will check tomorrow.

Thanks.

 

[Bod ...]

19 rads in total.

Boiler brand new.

Yes, large magna clean filter on return. Filter is clean.

Not sure about a mesh filter. Will check tomorrow.

Thanks.

Was the system powerflushed when the boiler was replaced?

 

[b175c15t110]

From original post:
"The boiler is a recent Baxi platinum 40kw, and the system had a chemical flush when fitted, but not a power flush."

It's not the balancing. I shut all downstairs rads off completely, and the rads were still very slow (45 mins) to get hot upstairs, and they were already warm before I did this. This implies some sort of restriction in the feed going upstairs.

So maybe nothing to do with 13 rads on one loop?

Maybe the system needs flushing upstairs?

I've booked a plumber for this morning to see if he can sort it.

 

[JohnD]

How hot is the Return pipe at the boiler?

 

[b175c15t110]

I don't know the actual temperature, but after 15 to 30 mins of running, the return pipe is hot enough that the boiler either slows down or turns off. I don't know if the boiler modulates at this point, or just turns off for a while. Not sure how "clever" it is.

At this point, the downstairs rads are piping hot, and stay hot, but the upstairs rads are just warm and if anything, they start cooling a little.

 

[JohnD]

I had in mind that when you turn off all the hot downstairs radiators, but the cold upstairs ones do not heat up, the hot water is either cycling back to the boiler, without having given up any heat (so is still hot); or has given up all its heat in some un-noticed way (such as UFH or a cylinder), so will be cold.

The first result suggests there is a bypass, which might be deliberate or accidental.

The second result suggests there is a heating load you need to balance down.

 

[b175c15t110]

Not sure what ufh is, but possibly under floor heating? If so, I don't have that. Although all of the downstairs piping does run under the floor in a well ventilated void, and no insulation on the pipes. I would assume a decent loss there. A mammoth and destructive task to retrofit insulation!

When I bought the property, it was a bungalow with a flat roof, so no upstairs.
I have a suspicion that there may be a bypass under the lounge radiator which is the last in the original run, but I cannot be certain. I feel I might be lifting floorboards soon to take a look.

I now have a second story, so if there is indeed a bypass in the lounge, I assume the bypass would need to be placed upstairs instead to allow an easier flow?

The plumber that came this morning said the return temperature at the boiler was "normal".

 

[old duffer]

If you really want to know the answer then you have to measure...pressure at different rads, temp, flow, heat order, heat loss per room vs rad size.
Tiny pressure differentials can make a huge difference.
Use the power of maths..big undertaking but unless you have the specific answers, its all a guess.
There is no magic plumber method...

 

[b175c15t110]

I'll be looking into that bypass asap, as that could easily be the answer.