Not all my radiators are hot..... Help

[dazeybear]

Hi all,
I had a cd35c Alpha combi boiler fitted about 18 months ago when I had a new extension, had new rads fitted in the new part with old on the system as well, all worked fine just old rads were unsightly and not very efficient so recently had them updated for new one's....

Here's the problem since this has happened we have different radiators not getting hot, some too hot and others warm.... Balancing I hear you say.... My plumber has been back and forth a thousand times adjusting this and that but to no avail. We have had the system drained several time along with inhibitor being put in to give it a flush (having had a problem using old pipework) some of the rads are hot at the top and cold at the bottom but cannot have sludge build up due to the cleaning and they are new,

I am at my wits end as I am sure is my plumber, getting weekly calls to come and have another look... I have done everything from shutting down the hot so that the cold ones will get hot but as soon as you regulate it again they go cold if not that one another one will do it upstairs or down.

Please help if you can.

 

[JohnD]

close the hot ones on the lockshield and let then get cold

turn the lockshield open by 1/8th turn and feel if the flow starts to get warm. If not, open another 1.8th turn. Yiu need hardly any movement to go from "closed" to "open"

As soon as you have got the flow getting warm, stop.

Wait 10 mins and see if it is reasonably warm all over.
If so, go and do the same with the next "Hot" rad.

You do not want it to be uniformly hot all over, it is quite correct for the flow to be "too hot to hold" and the return to be "hot." For todays purposes, even "warm" will be enough. Do not open it any more until you have done this with all the "hot" ones, and then see how the "cold" ones feel. It is OK to spend 10 mins on a single radiator. It must be cold before you start. If you let it get fully hot all over you will have to close it and wait till it gets cold to start again. It is important to work with the lockshield and put the cap back later so that neither you, nor anyone else in the house, alters the setting later. Write how many 1/8ths of a turn you gave it in your notebook.


A lot of people try to balance rads using too much turn, so try this and see if that is what teh prob was.

So as not to annoy your plumber, count exactly how many turns it took to go to fully closed, so that if necessary you can put them back to how he left them.

p.s. you say you have recently had new rads fitted. Whaty type, shape and size are they? Did the fault arise after the new rads went on? Have they got TRVs?

 

[Rico99]

I'm sorry to say this, but this does sound like the system is still not properly balanced.

Have any of the rads got TRVs on them.

Rico

 

[Bahco]

Bet it is microbore pipe.

 

[dazeybear]

Thanks JonD god the rads are all doubles and white various sizes not a lot of help but neither am I which is why I am in this mess they all have trv's I have even taken these off to see if it makes a difference... Today I left the house with two radiators downstairs that were cold, I have come home this afternoon to find they are now hot and 3 of the upstairs ones are luke warm, it moves around without anyone touching it...

Oh and yes the problem only started when we put the new rads on the old, but didn't happen when we had the new with the old system

 

[dazeybear]

can I ask what is microbore pipe and why the sad face does this make it bad?? how will I know

 

[D_Hailsham]

JohnD

I agree that you only need to make very small adjustments at a time. However I think you need to go through the radiators in a logical order, starting with the one nearest the pump.

Drayton have very good instructions which can be downloaded from http://www.draytoncontrols.co.uk/WorkArea/DownloadAsset.aspx?id=10306

Also see How to Balance a CH System

 

[Goldspoon]

can I ask what is microbore pipe and why the sad face does this make it bad?? how will I know

10mm bad rather than 15mm good. Then again it's fitted all over the country...

 

[JohnD]

Thanks JonD god

you overestimate me

... Today I left the house with two radiators downstairs that were cold, I have come home this afternoon to find they are now hot and 3 of the upstairs ones are luke warm, it moves around without anyone touching it...

you say all rads have TRVs.

If the upstairs rooms got warmer during the day, those TRVs might have closed down the upstairs rads, forcing more heat to the downstairs ones.

 

[D_Hailsham]

Balancing I hear you say.... My plumber has been back and forth a thousand times adjusting this and that but to no avail.

It certainly has all the hallmarks of poor balancing. But it could be that the boiler is not up to the job of supplying all the rads.

Which boiler do you have - make and exact model? Forget that! Just read your first poet again!

What is the total output of your rads? If you don't know, use the Stelrad Elite Catalogue to get an approximate answer.

Post boiler and rad info.

 

[dazeybear]

Hi, right I got the total watts (am assuming that is what you mean) female!!
total watts is 20671 also got the BTU/PH which is 70563


that is 15 Rads

also a small towel rail but I don't know what that is

make is Alpha CD35C

 

[dazeybear]

also I lied not all have trv's 2 in living room don't 1 on landing, 1 in downstairs loo and towel rail doesn't sorry forgot that

 

[JohnD]

this one? http://www.alpha-innovation.co.uk/products/?id=1003

looks like it has 30kW of CH which should be ample (will be less if boiler temp is set low)

A combi so no heat going to cylinder

Do the new rads in the extension seem hotter or colder than the older ones? Are you sure that none of the rads seem particularly hotter than the others?

 

[D_Hailsham]

looks like it has 30kW of CH which should be ample (will be less if boiler temp is set low).

So you have a 30kW boiler heating up 20kW of rads. That's a 50% oversize! OK, the boiler will modulate down so the temperatures are correct, but each time it ignites it will start at full whack and then reduce output.

Setting the boiler temp low reduces the radiator output, which may not be a good idea in very cold weather.

The basic cause of the OP's problem is incorrect balancing.

 

[dazeybear]

Yes that's the one! we did have it on 6 but now up to 7 on thermo on boiler. the rads in the whole of the house are now new which is where the problem started once we replaced the old ones on the system, the new rads are not all hotter in the new part compared to the old part of the house, it changes daily as the boiler kicks in again once the temp drops. some of the rads are extremely hot and some hot but not burning, others luke warm and some warm at top and cold at bottom, (can't be down to sludge as they are new, no dirty water coming out when bled not to mention the half dozen times he has put cleaner in. ie every time he drains it down) also we have a magnaclean with filter on system and some are warm one side and cold the other end... I think I am going to have to some how get the plumber to shut the system down, close all the valves and open and adjust each one as he fires up the boiler taking his time..... Not the easeist job trying to tell someone how to do there job... Would do it myself but keep seeing when searching the problems with leaks if you keep playing with the flow

Thanks so much for your help, your a star