Intermittent central heating problem over past 12months

Waesfjord

Could anyone shed any light on what may the problem I am having with heating system.

I've a gas boiler (Glow Worm 18Si) with the following problem.

After running for a while (i.e. number of weeks) with plenty of immersion hot water and piping hot cylinders, the performance just tends to tail off, with raditaor temperature not nearly as hot, even with boiler switched on for long periods. I've bled the radiators so that's not the problem.

I've had a plumber in, will break the system at various piints, find nothing really wrong, however the the rad temps are red hot again for a number of weeks, before tailing off again. In next visit, was told it is the heat exchanger. Tried to change that, hwoever issue with spare HC, so installed the original one again, with performance improving again for a few weeks before falling off. This happened throughout last winter, now starting again, so want to sort it permenantly.

Other symptoms of boiler system is sometimes rapid heat up of circulation water.

More recently I can here the gas blowing out and being relit frequently. This last problem I think is possibly the air/gas setting is incorrect, so intend to get a boiler service to hopefully sort this out.

With regard to the cycle of falling temp of rads, plumber visit etc, anyone any ideas of the gradual fall off in performance and return after crack open the system - I'm guessing an intermittent issue with circulation, so possibly air being pulled into system or something like that.

Any plumbing experts out there willing to advise?

Egass13

I'd say circulating pump . The reason I'm suggesting it is I've had a similar experience twice before , albeit on a different boiler . Pump would stop intermittently when hot and cause the boiler temp to shoot up, then would kick back in when cool.
Not saying this is definatly your problem but it does sound similar based on your description

With high levels of system water contamination(chloride) you can find the pump sticks at high system water temperatures and restarts as it cools.

So you may want to look at the quality of your system water.

Egass13

gary71 wrote: »

With high levels of system water contamination(chloride) you can find the pump sticks at high system water temperatures and restarts as it cools.

So you may want to look at the quality of your system water.

Makes sense Gary . That's what I find I lack most of the time , the reasons WHY these things happen . I know they happen and I know how to fix them but I'm often at a loss for an explanation for it !

Egass13

Egass13 wrote: »

Makes sense Gary . That's what I find I lack most of the time , the reasons WHY these things happen . I know they happen and I know how to fix them but I'm often at a loss for an explanation for it !

I think knowing how to fix it is the important thing, the rest is just chit chat;)

Waesfjord

gary71 wrote: »

With high levels of system water contamination(chloride) you can find the pump sticks at high system water temperatures and restarts as it cools.

So you may want to look at the quality of your system water.

Thanks for the reply Gary.

I know the water in area (D15) has high limescale. Regarding high chlorides, who knows. Is this something that can build up on closed water loops?

If so, is it a matter of ust flushing out the water?

Waesfjord

Egass13 wrote: »

I'd say circulating pump . The reason I'm suggesting it is I've had a similar experience twice before , albeit on a different boiler . Pump would stop intermittently when hot and cause the boiler temp to shoot up, then would kick back in when cool.
Not saying this is definatly your problem but it does sound similar based on your description

I had suggesting something similar to plumber (i.e. some sort of circulation problem) however he was convinced it was a HX blockage, however that couldn't explain the intermittent nature of problem, becasue if blocking HX, the radiators would similar remain warm all the time.

Is there any way to figure out if the pump is definitely the problem, or is it something that is cheap enough to simply change out.

By the way, cam across this lin when checking for price of replacement pump. Sounds familiar...

http://www.diynot.com/forums/viewtopic.php?t=203348

brian1976

brian1976 wrote: »

Thanks for the reply Gary.

I know the water in area (D15) has high limescale. Regarding high chlorides, who knows. Is this something that can build up on closed water loops?

If so, is it a matter of ust flushing out the water?

The first step would be to have your system water checked to determine water quality and chloride levels.

High chloride levels are indicative of flux(part of pipe installation process) contamination of heating system water, which should be flushed and the chloride level then re-checked.

Waesfjord

gary71 wrote: »

The first step would be to have your system water checked to determine water quility and chloride levels.

High chloride levels are indicative of flux(part of pipe installation process) contamination of heating system water, which should be flushed and the chloride level then re-checked.

I'll get that done on monday as my wife can ge that tested in QC lab at work. Cheers.

Waesfjord

Found a cheap new pump housing spare (without motor) on fleabay, maybe worth consiering picking up at that price?

http://www.ebay.co.uk/itm/glow-worm-boiler-pump-block-assembly-2000801901-/301020937910?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item46163efeb6

Egass13

Is be more considering the motor rather than the housing

Waesfjord

Egass13 wrote: »

Is be more considering the motor rather than the housing

sorry I don't follow, do you mean I may need to replace the motor also, so something like this needed?

http://www.ebay.co.uk/itm/Glowworm-Boiler-Part-No-2000801896-801896-Pump-Spare-Boiler-/220530602392?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item3358a5f198

Waesfjord

Hi everyone, in need of more help as boiler is now shut down!!

I've not yet taken a sample of water for chloride content from boiler as wife not back to work till tomorrow, however will get that done anyway.

When boiler was running today, I heard an awful sound from boiler, like loud crunching or something, the boiler also raised a F9 fault (water pressure sensor fault), so guessing the sound is the pump running dry. I (stupidly) pulled the drain valve on boiler, to confirm water was in boiler, however sounded like I drained what little water was in system as could hear a flow only for a few seconds then slowed down, now boiler saying 0.4barg pressure, so obviously too low.

To top up system, I went to hot press upstairs. From what I see, the mains water inlet to system in hot press has a gate valve for isolation, then passes through a pressure reducing valve which has a small pressure gauge (reading ~0.4barg). This line then feeds into a t-piece to adjoin it with the exit from base of immersion coil (which has its own local gate valve), for the return line to boiler downstairs. The other line in hot pressure is the feed line from boiler which has high point air bleed, then a small diaphram explansion tank (the one above boiler is collapsed and cannot be accessed), TCV at immersion coil inlet.

I can hear what seems a trickle flow through mains piping. I've fully closed the gate valve on mains inlet and reopened, with no change noted on PI. The pressure reducing valve has a lock nut and adjustment nut facing out, with plastic handle facing back The plastic handle just keeps turning so guess the threads are gone on it. I loosened the locking nut, then adjusted the adjustment nut clockwise (to increase pressure) and anti-clockwise, however no change in PI reading.

So I guess I know that there is some problem with the water supply. As mains to kitchen tap okay, then problem must be with in immersion with either the mains gate valve or PRV sticking closed I guess - does the above make sense or am I missing something obvious?

If this is problem, I'll get a plumber in to check/replace ASAP.

Waesfjord

Struggling trying to get a plumber out in Dublin 15 to fix the gas boiler - problem as previously described - can anyone recommend anyone suitable as house is freezing.

Cheers