Why is my CH so rubbish? (Potterton Puma 100e Combi Boiler)

[adamtw]

Ok, just moved house, its an older property (1926), 4 beds, 1 bathroom, 1 shower/WC (but with an electric shower). House is double glazed too, however......

House has a Potterton Puma Combi boiler (can't recall the model number off by heart but it looks big!)

Hot water generally seems ok, gets hot immediately but then seem to taper off which is annoying. I thought combi's gave you instant and never ending scalding hot water?

Central heating is pathetic. A couple of rooms get warmish, most are cold, some are freezing. I can have the heating on ALL day and some radiators are still stone cold. I have cheched they didn't need bleeding etc.

What I find odd is there is no separate thermostat in the house, only the 2 dials on the boiler itself (for water and heating) . Both are set to MAX, all rads have thermo valves, also set to max. There is an old digital/lcd timer unit downstairs, but this only seems to control what times the boiler comes on or not, it has no separation for heating or water. Is this normal for a combi boiler?

Is this is general issue with combi boilers or is it something more involved such as a knackered pump or just a nearly dead boiler?

If it IS a dead unit and needs replacing, anyone got recommendations for a large house that will keep us toasty for the next 10-15 years?

 

[JohnD]

1) tell us about the insulation of the house

2) tell us how much gas and sludge there is in your system

 

[bengasman]

No general issue with combis.

The problem you have is a combination of several factors, being:
1 a poor quality boiler with various known issues
2 installed by a cowboy
3 suffering from lack of maintenance

the good news, do a search on the forum for --new boiler-- or better, --boiler replacement – and you will find all the info you need

 

[adamtw]

I believe the house has brick cavity walls although I'm unsure so far, roof was replaced in the past 15 years so has felt liner etc. I also don't know if there is loft insulation.

I have no idea how much sludge there is in the system, I have a boiler engineer coming out today to do an inspection/service. I guess he will find out. I will wait and see what his diagnosis is.

If Potterton boilers are low quality, which brands should I look at IF I need a new boiler?

Thanks chaps.

 

[gas4you]

I would get someone in to check the DV and possibly replace the wax capsule in it.

 

[DP]

I would go say there are no rubbish boilers (maybe an odd one or two made by Ideal perhaps), only that the boiler has to be fitted to a clean system (rarely happens), combi has to have an adequate size gas line (often not), boiler has to be serviced regularly (seldom is, if it is then more often than not an operational check is carried out which the client believes to be a service.

As suggested by Gas4you, get someone to check the system out and rectify the problems. Fitting a new boiler to the system you have might give you temperory heat, but a dirty system will kill the new boiler before long. So why spend good money on a singing dancing modern day plastic steamer, when good controls fitted to present boiler after malfunctions have been corrected, will give you better return.

Above assumption is based on cost of parts for condensing boilers, frequency of breakdowns, complexity of internal components requiring special equipment all collectively amounting to greater repair costs.

 

[gas4you]

I would go say there are no rubbish boilers (maybe an odd one or two made by Ideal perhaps)

The odd one or two that work ok maybe

 

[JohnD]

... I also don't know if there is loft insulation...

use one of these (two if you have them)

 

[adamtw]

OK, had the plumber chappie out, seemed a good egg and not a BS merchant. His observations were that the circuit board has been replaced at some point and pointed out the scorch marks in the top left corner behind the current one. Large amount of dead spiders indicated lack of servicing apparently.

Basically his diagnosis was that yes it is a crap boiler, but it is still working, heating does come through (some of) the rads eventually and hot water does come out. However the circulation is clearly crap too. his suggestion is to have the entire system chemically flushed, then see if the circulation improves. If it does then we can live with the current boiler for a while longer.

If it doesn't then he says the issue may be that the pipes are running huge loops round the house and therefore completely inefficiently placed. The kitchen for example is the room below the boiler however the rad in there NEVER gets warm. It would seem the supply pipe runs down the wall and does a full circuit of the room first.

Renewing the pipes sounds like major upheaval, floorboards will be coming up, carpets and floor coverings ruined most likely, adding to the cost.

Then the next stage might be to replace the boiler itself with something more efficient. At the moment, the heating needs to be on for 5 hours minimum before the house feels warm, thats just a crazy amount of gas being burnt. Just what we need when we have a huge mortgage on our recent purchase, massive gas bills too!

In your opinions, does the chemical flush make much difference and is it worth doing? By the way, they quoted £395 for the flush, about right?

 

[gas4you]

Obviously he's ignored all the points raised previously on here

£395 is an average powerflush price, but tell him you will have it done on the assumption that you only pay if it fixes it.

Powerflushing is the easiest diagnosis if he hasn't drained any water out to test it first

 

[Nige F]

OK, had the plumber chappie out, seemed a good egg
Pipes..... running huge loops round the house and therefore completely inefficiently placed. The kitchen for example is the room below the boiler however the rad in there NEVER gets warm. It would seem the supply pipe runs down the wall and does a full circuit of the room first.

You`ve got a one pipe system...probably almost as old as the house...I`d get a second opinion as you plumber may be excellent , but not old enough to have seen /worked on those old setups........I personally would remove each rad and manually clean rather then "powerflushing"..I`ll let the tradesmen explain why ............if you`re near Sussex I`ll have a look...............won`t cost you much , because I don`t need to work .....I like to keep my hand in , and like the old systems.....bit more of a challenge

 

[adamtw]

OK, its not a Powerflush they have quoted for, its the chemical flush. I rang another local plumber and they quoted £400 too and said they did not do the Powerflush as they feel the soft flush is better for your pipes etc...(how would I know?)

Here's some more symptoms:

If heating is on all day the house does get nice and warm eventually, even the coldest radiators show signs of heat, however, the 'stat on the boiler for the CH is set on Maximum. Anything lower that Max and the rads dont get hot. When the Stat is on Max and the heating has been on all day the pressure gauge reads about 3 bar. As soon as you turn the stat down a smidgeon, it drops back to about 1.5 bar after about 30mins. Can it be very bad to have such high pressure on a combi?

Here's the best bit!

The boiler has had a separate pressure vessel (previous owner called it a diaphram) fitted. The boilers internal one broke and instead of taking the boiler out and apart they added in this big red round thing with a flexi hose with an inlet tap on to increase the pressure when it gets low. I'm no expert, but when you have to resort to such things, you are on rocky ground.

The last thing we want or need is to have to renew the pipes in the house just because of the disruption, ripping up floors and the added expense. Perversely I could cope with a new boiler cost.

From a completely no plumber knowledge aspect, I can see sense in flushing the system, if it is a success, we might have better heating circulation. If it doesn't help, we at least have a clean system prior to a potential new boiler.

In response to the last reply, the plumber who came here was in his mid to late 40's. (are there lots of elderly plumbers out there?!!!)

Sadly we're in Leicestershire so your kind offer won't work out!

Oddly, I went to a local post office and got chatting with the post lady, it turns out she lived in our house as a child and left in 1971. She said there was no central heating then. Would we therefore still have a single pipe system do you think?

 

[Gasguru]

Nothing wrong with having the external expansion vessel, taking the boiler off the wall is often not practical.

The pressure should normally be about 1 Bar with the system COLD and ideally no more than 2 Bar when hot (2.5 Bar absolute maximum). Either the vessel is low on air pressure (see FAQ section on re-charging the vessel) or it is undersized for the size of the heating system.

Has the boiler been range rated? ie is the heating output adjustment on the board correctly set and the output measured, is the bypass valve correctly set, does the diverter valve operate correctly - have you tried turning off the cold water feed to the boiler to see if the heating improves? Did the plumber check the board for poor joints? Is the system balanced. All these must be answered first - cleaning is a last resort and rarely required...it's nearly always the more basic solutions.


The average age of heating installers was about 52 when the last survey was carried out

 

[adamtw]

OK, thanks for the replies, I really wish we had a friendly plumber nearby but we don't so we'll have to do what most people do, pay someone to bugger about until its fixed.

To answer the most recent points:

The system was balanced by the chap who came to service the boiler but its no better. In fact today, the heating has been on for 6 hours so far and most of the rads are still cold. The fact that it is SO inconsistent puzzles me.

The boiler has not been range tested (I don't know what it means)
No idea if the bypass valve is correctly set
No idea if the diverter valve operates correctly
I've not tried turning off the cold feed (How would this improve the heating?)
The board was not checked for dry joints but he did notice it had been replaced as there were scorch marks on the upper left back plate.

My viewpoint is this: If there IS sludge build up in the system, surely that would explain why some rads get hot and some don't, then why on some days its worse than others as perhaps the sludge has moved around a bit?
Am I being too simplistic?

 

[JohnD]

An old system is very likely to have a lot of sludge in it. Removing this will do nothing but good.

A chemical clean and flush will help but will not get out 100% of the muck.

If you can afford an extra £100, it is worthwhile having a Magnaclean fitted on a vertical 22mm return pipe. You will be surprised and gratified at how much black sediment it captures and traps, and it carries on working indefinitely. Once fitted, it needs no plumbing skills to take the top off and remove the trapped sediment. It will also prevent any new accumulations building up.

You have to do the clean and flush as well because not all the dirt will be the black sediment which can be trapped by a magnet.