System only get Warm at best!

[s3dbw]

OK folks,

I am really struggling with this one and it would seem my plumber is as well, so here goes the catalogue of events to date:

1. Back in the summer I upgraded my ancient boiler to a modern worcester greenstar, no obvious problems at the time as I was only running the hot water. At that time the system was power flushed and after 20 years there was a lot of sludge removed.

2. Fast forward to Winter when I start to use the heating I notice that at best the radiators are only warm even after all the usual bleeding etc

3. Plumber notices that the "on" light for the burner is no on as often as it should and reckons there might be a circulation problem, ie the hot water is not getting away from the boiler and the stat in the boiler is causing it to shut off, so the as the circulating pump is also ancient we replace that.

4. Still no significant improvement and I notice that the hot water isn't really as hot as it should be either, so the system is powerflushed again, more sludge removed, though obviously not as much as first time.

5. I fit a magnaclean to the system to keep taking out any residual sludge

6. Still not getting the temps, so plumber converts the system from an open (header tank) to a closed pressurised system.

7. Now with the new boiler, new pump, 2 X Powerflushed system and closed system, the radiators should be able to get so hot that you cant touch them, but even with the boiler stat turned up full they are best only warm and hot water could be hotter.

Suffice to say, I am starting to despair, so any thoughts would be appreciated

regards

 

[quality]

Where do you live as some one will need to look at this to sort your problems
That is some one who knows what they are doing (no offense)

 

[ferret]

does boiler get up to temp itself ie between 70 and 82 degrees , if so check bypass , could be open too far causing short circuit , if so it needs shutting then resetting

 

[s3dbw]

Hi Guys,

Thanks for replies, in order

1. I live in the North of Scotland
2. I dont have a thermocouple to measure actual temps, but when running, the outlet water pipe on the boiler gets to the sort of temps, I would expect the radiators to be sitting at

Cheers

 

[mikegas]

do any rads at all get up to temp?

 

[s3dbw]

The ones at one end of the house do a get a bitter hotter, though not so hot as you cant your hold your hand on them, ones furthest away only luke warm. If the "hotter" ones were really hot, I would figure on a bit of balancing being the problem, but even the ones at the hot I would only classify as warm.

Its almost as if there was still a blockage in the system, but after 2 power flushes, i would have thought that would have been sufficient to clear most of the sludge out. Incidentally there only 10 radiators in the system.

 

[gasmarc]

it sounds like a circulation problem if the boiler is getting up to temperature , I would follow the pipe and see where it turns cold and check these is no isolation valve part closed

 

[s3dbw]

The pipes appear to be quite hot after they leave the pump and go down under the floor and there are no isolation valves under the floor, so unless there is some sludge/blockage that the power flushing did not remove?

 

[gasmarc]

i have seen a one way valve partially blocked before ,it was a right nightmare ,i suppose you could try turning the pump around you could also have a problem on the diverter valve not opening fully

 

[s3dbw]

Downstream of the control valves also appears to be very hot, but for whatever reason. just not seeing same level of heat in radiators

 

[mikegas]

you could try flushing them out manually

 

[s3dbw]

May have to resort to this, was hoping to avoid if possible. Anyone any experience with vibraclean as an alternative to pulling the radiators?

 

[gasmarc]

rubber mallet does the job , might be worth changing the oldest and worse rad,or as above

 

[JimH]

I had a similar problem - I found that the plumber had fitted an ordinary valve between supply & return pipes, instead of directional PRV... it was opened very slightly, which resulted in hot water supply instantly going to return pipe & back into the boiler - virtually no heat anywhere else.
Feel your return pipe (close to the boiler - be careful you don't burn yourself), if very hot - get the plumber back to replace valve.

referring to a directional PRV (if fitted), could be stuck open.

 

[s3dbw]

Hi JimH,

Definitely got a PRV fitted as opposed to standard valve and retun pipe to particularly warm, so I dont believe its passing. I still think its some crap stuck somewhere in the system, but finding it is the problem!

 

[s3dbw]

Out of curiosity, is there an internal thermostat on the greenstar boilers that a plumber could adjust as opposed to the external control knob for the consumer?

 

[SafeGasInstall]

what jimH mean is called auto bypass not a prv ,it just looks like one !

is it a combi or is it system/regular one ???

 

[s3dbw]

Hi there,

If its the crossover pressure valve after the pump that links the supply and return circuits, then we are talking about the same thing. Its a regular system not a combi.

Just been checking the outlet on the boiler again and while hot I can hold my hand on it! Would this point to a problem with the boiler stat as I wouldn't have thought I should be able to hold my hand fully on the outlet pipe immediately after the boiler!

 

[mikegas]

Could be under gassed

 

[s3dbw]

System is running at 1.5bar

 

[mikegas]

If thats a response to my last post thats your system pressure not gas

 

[s3dbw]

Sorry, misunderstood

 

[mikegas]

no prob wasnt sure whether it was or not

 

[quality]

Could be this could be that just needs someone with knowledge / experience who knows what they are doin

 

[dontknowitall]

Did you change the programmer when you had the boiler installed? I'm wondering if there are two programmers "fighting" each other (or thermostats) as I'm assuming the boiler is the correct size.

 

[s3dbw]

Had a new wall controller stat and potterton controller fitted at the same time as the boiler. As to the correct size, I can only assume that they fitted one appropriate for the size of house/No. of radiators. The wall stat is set high and the room temp is not reaching the preset so unless its faulty i dont think its competing

 

[gasmarc]

might be worth checking gas meter handle is in on position

 

[Blackcatgas]

Flow and return connected the wrong way round, autobypass stuck open, or a bypass pipe fitted somwhere near the boiler. Although possible i doubt that its muck in the system.

 

[stevetheplumber]

first step lets go back to basics was the replacement boiler of similar size did the system get hot with the previous boiler ? what size is the existing boiler is it burning the correct amount of gas

 

[gasmarc]

agree with above, has it ever worked correctly ? feel a bit like Mystic Meg lol

 

[s3dbw]

Having had a bit of investigative work done on the system I thought I would update with findings such that it may be useful for anyone else with a similar issue. Despite having had my system powerflushed twice, it appears that the culprit is still sludge, only this time it found its way into the heat exchanger of the relatively new boiler unit, so while the boiler was working, the low heat transfer to the circulating water due to the fouling had two effects. Firstly it wasn't heating the water very high, hence the initial problem with lack of heat, but secondly, as the boiler input heat was OK, but it was not transferring this heat fully to the water, the boiler flue gas temp would rise and cause the unit to shut off, thereby causing an on/off duty cycle which of course would not put any heat in when it was off.

Present Magnaclean filter is on the outlet side of the boiler, so this is being switched to the inlet side to protect the boiler and of the course with the heat exchanger cleaned out, I am now getting the heat into the system.

Thanks for all the responses and help, as a result of your input it was useful in tracking down the real cause.

Cheers and a good New Year with trouble free plumbing to you all!

 

[tipintim]

Im a fan of magna clean, yet it only takes out metalic particles.
What you may need is the magnaclean twin tech that takes out metalic and non metalic partcles.

You need to have it flushed with a magnacleans power flush unit.
As for a quick solution of your traditional powerflush, the minuite the guy goes, your system starts to deteriate.
With the magna , its continualey working and collecting sgite from your system.
Like a dialisis machine