Lukewarm radiators and a Glow Worm boiler

[jamiebrennan]

Hi all,

Great site, only noticed it the other day and am hoping it might be my saviour!

Hopefully some of you might be able to assist me with a problem that I’m having with my central heating. It seems to be really dodgy and is causing problems so would really appreciate some of your more professional advice.

My system is as follows:

Glow Worm 24 hxi boiler (3 years old?)
Sealed system (showing 1 bar pressure)
7 radiators (some new, all with TRV, except in hall)
System age (25 years approx)
Sealed system with a pressure of 1 bar showing

Having moved into a house earlier this year I’ve not had the opportunity to use the heating until 3 weeks ago, at that stage the radiators were only getting lukewarm, this was after the boiler was on for over 4 hours!

I called a gas engineer who diagnosed a faulty pump and this was replaced with a Grundfos pump, however this did not remedy the fault. Having called the guy back he then said it was more then likely that I had an issue with sludge and said he could powerflush it. Instead of paying the £280 I was quoted I hired a machine and spent yesterday doing it myself. I was amazed at the amount of sludge that was in the system and thought I had sussed it, however when all back together I’m no better off.

I’ve double checked everything from the pump to the expansion vessel but everything seems to be in order. Part of me is wishing I’d called BG and got their one off fee service but aren’t even sure they’d solve the problem as they say it’s no fix no fee!

I’m an engineer so have a basic understanding of how everything should work together, the instructions help too although they don’t really provide much information on what the problem I’m having is. What I’d like to know at this stage is whether or not it’s my system or the boiler that is the issue. I don’t want this one to get the better of me but this cold snap is zapping the missus!

Let me know if you need any further information

Jamie

 

[lightning]

Is the roomstat turned up,are rads cold on bottom and hot on top.
Is your 2 or 3 port heating valve working correctly and not letting by.

Put c/h on programmer only does this fire up the boiler???

 

[jamiebrennan]

Thanks for the speedy reply.

Should have told you that the water is heated by a range and immersion heater so these circuits are not connected. There are no signs of any two or three port valves.

The room stat is turned up to it's maximum temperature, when switched off the boiler doesn't fire so I don't think there are any problems there.

There is no external programmer, I use the built in one on the boiler which is set to be constantly on!

Jamie

p.s. the radiators are evenly heated all be it very poorly!

 

[jamiebrennan]

Just a bit of an update, worked out that by pressing the reset button on the boiler it seems to start up for about 30 seconds, the fan seems to run faster and you can see mre action at the vent.

Jamie

 

[watertight]

Did you replace the pump valves when you replaced the pump, maybe they're only semi open. I suspect that it is an issue with a blockage but if you've powerflushed it this should have removed most if not all of it (presuming it's a sludge build up) and not a mechanical problem.

I've heard these boilers can be tempremental but don't quote me on that.

 

[jamiebrennan]

Yeah the pump valves were changed at the time of the pump, these certainly open fully up as the flow through the powerflushing hoses was quite dramatic.

I'm starting to suspect it's the boiler! I hit a high of 36degrees tonight!

 

[jamiebrennan]

Having spent another cold evening in because of our Glowworm Ultracom I am now thinking that there must be a blockage somewhere that has been overlooked, could it be that the powerflushing did not actually remove the blockage casuing the issues I'm having?

Could it be that I have a fault on the boiler, I've got a day off tomorrow and intend to start to move and inspect the central heating pipework, however as some of this is really unaccessable I'm loathed to do it.

Jamie

 

[mickyg]

if you have the manual, read where it tells you to access d codes. Then access d codes 40 and 41 with the boiler running. Post back the figures especially just before it goes off.
Did you include the boiler in your flush? if so you may have filled it up with sludge. Its possible to flush the heat exchanger but it takes alot of know how, the right tools and right chemicals.

 

[jamiebrennan]

Hey thanks for the message, the results are

With boiler running at max (just before cutting in minimal effort)
D40 = 45
D41 = 34

After running minimal for a minute or so:
D40 = 38
D41 = 34

The boiler never fires to full unless I press the reset button.

Following the advice of the engineer I disconnected the boiler during the flush.

Does this help you diagnose anything???

Jamie

 

[jamiebrennan]

Guys,

Sorry to try and get this close to the top again, not sure if any of you more experienced guys can tell me where my problems might lie, I don't wanna waste too much time if I can pinpoint the problem

Jamie

 

[watertight]

From what I see the boiler should operate correctly under these conditions, this implies it might be one of the thermistors or the pcb, please don't quote me on that though but it might give you something to look at.

Mark

 

[jamiebrennan]

Thanks for the post,

I think I've discovered something of interest. From information on here and on the net I presume that the boiler cuts out when there is a large difference in the flow and return temperature, which is measured via the thermistors?

With this in mind I removed the thermistor off of the return pipe and attached it on the flow pipe (by the one already there). I assumed that the temperatures measured by both would be the same and the boiler should therefore heat at max, or near fax until it hit's the temperature set on the display.


Turning the boiler on it fired up and was on max but only lasted about 20 seconds before reducing itself to it minimal heating. I checked the d40/41 values as suggested earlier and found these to be identical (32oC).

Does this imply therefore that the problem is indeed with the boiler, maybe the control board????

Jamie

 

[Beerlover]

Go to D99 and see what the status of the boiler is. S.53 would suggest either a blocked pump impeller or a blocked heat exchanger.

Agree with mickyg, about flushing the boiler BTW

 

[jamiebrennan]

I assume that the pump won't be the problem seeing as it's new, I'll check when I finally get home, would ask the gf but she'll be watchiong Corrie no doubt!

Thanks guys, I might finally get there,

Jamie

 

[jamiebrennan]

Hey all,

Firstly apologies for the delay in updating you to my problem, I was hoping that I'd have had it sorted by now as I called British Gas hoping that they would come out and repair the problem for a fixed price.

To cut a long story short the engineer did come out and inspect the boiler and stupidly I mentioned I'd had the pump replaced thinking this would solve the problem. After telling me this he probed me further before discussing the job with the office. He came back and said that it wasn't likely they could repair the problem and left. Although I was not charged I was amazed that they would not tackle the problem.

I'm now back at square one. I have checked the status menu by doing into the diagnostics and selecting 99. The display returns F22 (no S code as such). I believe that this fault is as a result of me placing the thermistors side by side. I have checked the pressure in the system which lies perfectly at 1.5bar.

Given how far I've got (or not as may be the case) could there be something I've overlooked?

To recap this is what I've done so far:-

Powerflushed the system
Had the pump replaced
Placed flow and return thermostats side by side to check if it was an issue with a large temp difference.

Thanks in advance,

Jamie