Glow worm 24c not sufficiently heating the house

[entrancehighrise]

The boiler is a newly installed Glowworm 24c ,

The problem is that the heating is only partially working in that the radiators are only just warm - and the house is cold.

From what I’ve observed of the boiler, it comes on for a few minutes before the CH temperature reaches the set maximum temperature (as indicated by the boiler LEDs). The boiler then ceases firing and the various temperature LEDs decrease until only the 30 degree LED is illuminated. It then stays in this state i.e. pump working and the boiler not firing for several minutes.

The boiler thermostat is set to max.
The heating thermostat is set to max.
The pump appears to be working ok.
It’s a sealed system and the pressure is 1.5 bar

To summarise:

1. When the boiler fires the boiler CH outflow pipe gets very hot - as one would expect.

2. The inflow pipe is always luke-warm - and doesn't really change in temp before the boiler stops firing.

3. When the boiler stops firing, the outflow pipe quickly cools to luke-warm again.

4. When the boiler is not firing, the in/out water pipes are therefore both barely luke-warm.

5. The same temperature change in pipework can be observed at the radiators.

Any ideas greatly appreciated.

 

[MIGEM]

The boiler is a newly installed Glowworm 24c ,

What has your gas registered installer said about it?
Was the existing system flushed prior to the boiler being installed?

 

[mickyg]

dirty sytem, blocked filter. I assume this is a betacom C, cowboys choice.

 

[entrancehighrise]

Cheers for the replies

The system is all brand new (installed into a house that did not have central heating beforehand), so I doubt its a blockage due to sludge or wear. When the boiler is heating the water the pipe work around the system is hot. Its just that it does not heat the water continuously.

My understanding is that combi-boilers should keep the circulating water up to temperature and not let it get to the point where outputted water is lukewarm. I'm wondering if its a fault with the temperature sensor that monitors the inflow :s

I've checked with Glow Worm that the boiler should be able to cope with the demand from my rads and they are happy it should. I am getting the installer back in to look at it, but obviously I want to be as informed as possible for when I speak to him about it.

 

[MIGEM]

What external controls did your installer fit?
If the room stat is above a radiator, it will be turning the boiler off before the house heats up.
TRV's on radiators?
Did he balance the system?

 

[mickyg]

told you the problem, up to you if you wanna fix it or not !

 

[entrancehighrise]

What external controls did your installer fit?
If the room stat is above a radiator, it will be turning the boiler off before the house heats up.
TRV's on radiators?
Did he balance the system?

Hi MIGEM,

Room stat was a standard honeywell which I have replaced with a digital stat. Both have been used whilst experiencing the same issue. The stat is placed downstairs in the lounge and is across the room from the radiator. The room can get up to a temp (according to the digital stat) of 16deg but cannot manage to get any hotter, the stat is still demanding heat from the boiler.

I have TRV's on all rads bar the towel rail in the bathroom. I suspected they may be stuck so have checked the pins on the downstairs RADs.

He claims to have balanced the system but I don't think much effort went into it. I have started balancing the rads which has helped a little, I have also only had one rad on at a time to check for trapped air. Each one I have bled has not had any air in it, no gurgling is heard around the system.

The boiler is in the attic, sitting up there you can see that the boiler fires on, heats the water for around a minute. Outflow pipe gets too hot to touch. The boiler gets up to the set temp of 80deg (as shown on front panel LEDS) , it then stops heating the water but continues to pump it around the system, the boiler then lets the water temp drop to 40deg before refiring. That to me seems wrong.

During this time the outflow pipe becomes lukewarm to touch, the inflow is always lukewarm. You can experience the same effect on any of the radiators inflow connections, so I feel that the flow around the system is good due to how quickly you feel the change in temperature, its just that the boiler is not providing the heat for long enough.

told you the problem, up to you if you wanna fix it or not !

Is this likely on a brand new system that's only been used for around a year? The system has inhibitor in it, water bled from it comes out clean.

 

[MIGEM]

Your lounge rad shouldnt have a trv on it, if the thermostat is in the same room. The trv stands a good chance of closing before the room stat is satisfied, but i wouldnt say that was your problem.
TRVs can close if the pipe below is long enough to get hot and the rising heat surrounds the trv head and closes it. Take them all off and try again with the heating on.
If its a new boiler, it may simply be a problem with the pump running slow, in which case it will be covered under a warranty, if thats at fault.
It could also be a pipe work installation problem, if the boiler is struggling to push the heat down from the roof, or if the pipe work is not correct, it may be pushing against itself not knowing where to go.
There seems to be a restriction in the flow, so it could also be that he may have fed too much solder into a joint and filled the tube.
Any system cleaners, such as a magnaclean? If so, are the isolation valves on it open?

 

[dcawkwell]

system badly balanced

 

[entrancehighrise]

Your lounge rad shouldn't have a trv on it, if the thermostat is in the same room. The trv stands a good chance of closing before the room stat is satisfied, but I wouldn't say that was your problem.
TRVs can close if the pipe below is long enough to get hot and the rising heat surrounds the trv head and closes it. Take them all off and try again with the heating on.
If its a new boiler, it may simply be a problem with the pump running slow, in which case it will be covered under a warranty, if that's at fault.
It could also be a pipe work installation problem, if the boiler is struggling to push the heat down from the roof, or if the pipe work is not correct, it may be pushing against itself not knowing where to go.
There seems to be a restriction in the flow, so it could also be that he may have fed too much solder into a joint and filled the tube.
Any system cleaners, such as a magnaclean? If so, are the isolation valves on it open?

Cheers, I'll remove that TRV.

No system cleaners to check.

I'm hoping that the overall install is sound (else gulp!), when the boiler does kick in it does reach both of the downstairs radiators inflow pipes quickly so I'm hoping that indicates a relatively good flow, but then the boiler cuts off. If anything I hope that its the pump as that should be straight forward to replace, although the hot water when its on does seem to shift around the system quickly.

Regarding blocked filters etc, I do get constant heat from the hot water taps, so I'd have thought that would be a good indicator that the heat exchanger can work effectively. I also tried running the taps at the same time as the heating to see if that helped move heat from boiler and keep it running the central heating for longer, but it still cut off the heat as before. Not sure if that was a valid experiment though Also tried running it on the lowest CH temperature setting on the boiler. Same outcome

system badly balanced

I really hope your right ! Although we have had the whole system wide open, I'd have expected the boiler to run okay in that situation with the radiators not necessary getting hot in certain rooms.