Radiators not heating , poor circulation?

[Olivias Grumpy]

Hi
My sons house has. Potterton profile 60e boiler
Total of 12 rads and 1 towel rail
Upstairs rads heat ok
It downstairs is poor
I suspected pump issue as I could turn off all upstairs rads and open up downstairs and heating does improve but not great
It seeems worse at far end of downstairs.

I suspected pump problem so Grundfos UPS 15-60 was replaced with alpha 2L

No great improvement really

Can anyone shed some light on best settings for this pump please?

Cheers

 

[JohnD]

Profile is very old. Have you given it at least a chemical clean and fitted a filter?

On my Alpha, there is a range of "automatic" speeds, but if you keep turning the knob, it hits "manual" speeds 1, 2 and 3 (you can feel the clicks). Manual 3 is highest you can get.

You should then balance the radiators to get equal temperature at all rads.

Profile 60 is about 18kW which is not a lot for a 12-room house.

You can calculate the heat requirement of the whole house with
http://calculators.baxiknowhow.co.uk/boiler-sizing/
(I find it calculates a bit on the low side, for a really cold night)

You can estimate the gross heat input of the boiler by running it for a known period and seeing how much gas it uses. One cubic metre is about 11.2kWh. It might be that the boiler is not running correctly. I used to have a Profile 100 that would kettle and clonk when it got hot, due to limescale and sediment deposits inside the heat exchanger, which reduce efficiency somewhat. There are chemicals that will loosen sediment, and a few that will slowly dissolve limescale (I don't recommend aggressive acid cleaners for DIY use).

I am a householder not a heating pro.

 

[Olivias Grumpy]

Thanks for reply
Should have said it has 12 rads none of them very big, and all have been there since the system was installed. Except for towel rail which was installed as an extra about 4 years ago
System has been regularly serviced, flushed etc by previous owners.
I’ve drained it again and filled with protector etc. When drained all water was clean no black crap
Everything is in good order, except for poor heat at building extreme

We know boiler will need replacing , but it isn’t in this years budget for renovation.
Ideally he wants to fit a combi in the future

 

[JohnD]

a plain water rinse doesn't dislodge scale or sediment, nor does inhibitor. If you put some X400 in the water may well turn black with loosened sludge, which can be drained out after a few weeks. After cleaning it, X200 will slowly reduce limescale.

I'd say start by balancing it. If you find the boiler return pipe is hotter than the radiators, some of the flow must be by passing them, possibly a bypass (which may have a control valve you can adjust) or possibly through the cylinder circuit.

The flow pipe should be "too hot to hold" and the return pipe should be "too hot to hold for long." This is a non-modulating boiler so it will stop firing when it reaches the preset temperature (or the overheat sensor if the thermostat fails).

What do you calculate the total heat demand of the house to be?

 

[Olivias Grumpy]

Thanks again
Perhaps a chemical clean is next to be done. Couldn’t have picked a better time of year

I’ll measure the rads to guesstimate load

 

[Olivias Grumpy]

Sorry should also have added
I’ve been trying to balance the system with limited improvement
Cheers

 

[JohnD]

clean out any mud from the F&E tank before you start, into a bucket, or it may get washed down into the system. I'd also sponge the inside, including the lid and ballcock float, with bleach, because fungus and bacteria sometimes take hold when clean fresh water is added.

The capacity of the radiators may differ from the heating requirement of the house, and both may differ from the power of the boiler.

 

[Doggit]

How are you balancing the system; you'd normally open each one by about half a turn, and then start from there. Turn all the rads off, and then start with the rad nearest the boiler and see how hot it gets; then add each rad in turn till the system falls over. It could be that the thermistor has failed, and the boilers not getting up to the required temperature in the first place. Do we assume that the system was working fine before things went wrong, but is there anything you can point to when he started getting issues. Can you test the temperature on the output flow pipe.

Changing the pump didn't do much, but what speed have you got the Aplha set to, and do the lights move across in sequence as it runs.

 

[Olivias Grumpy]

Hi Doggit
The pump is currently set on the 2nd of the variable settings , which if I’m correct , is recommended on a Grundfos webpage.

I’ve tried balancing , much as you suggest, at the moment I have 2 rads upstairs turned off and the others about one turn open on the lockshields.
Downstairs the first 2 are turned down the next couple are off. The next one is open and the next one is off. The final 2 are open and I can get heat there but not great
If I open any of the others the heat flow at the furthest end is reduced.
He’s only been in the house a year.
Last year no problem it seems

Can’t test temps of pipes but flow is fkin hot and return doesn’t hurt as much.

One thing I’ve noticed is that boiler doesn’t seem to stay on heat for very long and turns off on boiler temp I guess.

Boiler temp knob is set at 4-5
I tried it at max and it went into a shut down state until I found a reset button

If anything makes sense please let me know
Thanks for your interest

 

[Doggit]

First check the pipework along the flow and return with all the rads off, and see if you've got a decent flow around the system. Then start with 1 rad set at half a turn open, and then add each one in turn and see where it falls over. The furthest rads will always need to be opened up more than the nearer ones, so once you get near the final part of the balancing stage, you then start shutting down the near ones.

The boiler shutting down when you set it to maximum, could indicate that the heat exchanger needs cleaning, or the heat isn't being taken away fast enough. Do you know if there is inhibitor in the system, and if you draw a bit of water off, what colour is it. Try setting the pump at 1, and then see if you can get the boiler to maximum.

 

[Olivias Grumpy]

Some people never sleep

Thanks again
There was a sticker on the boiler saying that there was inhibitor in it. When drained it was reasonably clear , slightly yellowish?

As per a previous reply I decided to give it a clean and have now poured in some Fernox F3 and will leave it bubble for a few days

I’ll drain and flush and have another go with balancing.

I tried most of the 7 pump selections without any noticeable differences . All it has proved so far is that there wasn’t much wrong with original pump! minus £130.00 ouch!

 

[Hugh Jaleak]

Clear water, colour of weak urine, classic sign of inhibitor in the system. If there was no evidence of any black water or sediment, then I'd be surprised if muck was an issue, as seems system has been correctly protected in the past. Balancing may be part of the issue, but if it worked ok last year, again its unlikely to be muck, as this would result in a gradual deterioration in performance. What has been done over the last year that could have affected it, other than pump change?

As an aside, investigate the pros and cons of a combi, before committing in the future. Whilst they have their uses, they are not a 'one size fits all' solution.

 

[D_Hailsham]

First check the pipework along the flow and return with all the rads off, and see if you've got a decent flow around the system.

If you shut off all radiators, the only flow you will get is through any bypass valve. The flow and return pipes are not joined together at the far end of the system. It's like a ladder: the rungs are the radiators, the sides are the flow and return pipes.

It's not unknown for a system to have a bypass across the last radiator.

 

[Olivias Grumpy]

Hi Hugh
Thanks for response
Only work that has been done other than pump was to remove/replace 2 rads for decorating (these are furthest from boiler) and a Hall rad changed for new item.

I agree with comment re combi.
Doesn’t suit everyone.

Cheers

 

[Hugh Jaleak]

Possible if the 3 rads that have been removed were cranked wide open, then these could rob flow from the rest of the system, but balancing should solve that. Just a thought, have you got TRV's on any of the cold rads? If so, remove the heads and check pin is moving freely to allow valve to open fully.