Halstead Quattro Gold getting too hot & no CH circulation

[weseeyou]

I have had ongoing problems with my boiler and no heat or hot water for 10 days now. I am a full time carer for my 90 year old disabled Father who is a dementia sufferer so things are getting a little dire and quite smelly too.
HISTORY

Local GS Engineer replaced gas valve and igniter pcb and reset gas pressure and it worked for 2-3 days gradually getting hotter and hotter with kettling and increasingly frequent tripping of the overheat stat


Boiler fires up on both CH and DHW demand.

Burner goes into immediate full pressure burn on CH ?!

After 8-10 seconds boiler starts to kettle and primary heat exchanger (PHE) pipes and pump too hot to touch.

PHE flow is red-hot to the inlet of Diverter valve but heat goes no further.

If DHW demand then boiler bangs violently as cold mains goes through DHW exchanger.


Switch off ... then seconds later overheat stat trips . Heat confined to PHE pipes and pump . No heat evident in CH flow from diverter valve but some heat creeps through diverter valve and the bypass pipe to DHW exchanger .

As far as I can tell the pump is working and the system is at approx 1Bar and air fully vented.

I’m thinking either pump not working , or diverter valve jammed open to DHW exchanger giving short loop or primary heat exchanger blocked or CH flow blocked.?

I’d appreciate your thoughts on this before I strip it down again and fit a new diverter valve and pump and flush the system and boiler yet again!

ps Engineer refuses to attend again saying new boiler required. Well she wants to fit a new boiler I guess

 

[aggis]

Sounds like pump, is there 240v to it & is it spinning?

 

[GerrythePlumber]

pump may been running but with broken impeller

 

[weseeyou]

Its difficult to hear anything over the burner and kettling to be honest and the fan is a bit squeaky too.
I checked the pump impellor spun and cleaned and flushed the pump before putting it back.It has 240v supply yes
I'm sure I have heard the occasional bit of air rushing through the pump but to be honest I have to turn it off after 10 seconds because its getting so hot and the kettling.

I have a replacement pump and new diverter valve to fit and I need to flush the primary heat exchanger so I guess I'll have to drain it down again tomorrow. I think I might be able to pressure flush the PHE without removing it hopefully.

 

[weseeyou]

pump may been running but with broken impeller

mmmmm hadn't thought of that!.... If there were isolating valves I'd swop the pumps over but unfortunately there is no way to isolate the pump or the boiler so its a complete draindown.

I suppose the increased heat has probably lifted a load of scale which has circulated and jammed both pump and diverter. As the CH flow is split GF and FF I can't believe both could be completely blocked. Whats the likelihood of the primary heat exchanger being blocked causing this ?

 

[GerrythePlumber]

You obviously live in a hard water area like me. Being a Scotsman, I couldn't believe the limescale problem could be so bad. Kettling is usually a sure sign scale in the heat exchanger. Looks like you need to descale or replace it. Iv'e fitted a combi-mate on the incoming cold main. It doesn't take the scale problem away, but it makes it soft instead of hard thus preventing it from sticking to hot surfaces. I tried to investigate this when I first came to England and am still finding unbelievable sutuations with this stuff. Hope you manage to solve it.

 

[weseeyou]

You obviously live in a hard water area like me. Being a Scotsman, I couldn't believe the limescale problem could be so bad. Kettling is usually a sure sign scale in the heat exchanger. Looks like you need to descale or replace it. Iv'e fitted a combi-mate on the incoming cold main. It doesn't take the scale problem away, but it makes it soft instead of hard thus preventing it from sticking to hot surfaces. I tried to investigate this when I first came to England and am still finding unbelievable sutuations with this stuff. Hope you manage to solve it.

thanks .
Talking about how hard the water is I have a picture somewhere of a huge lump of limescale picked off my cat's tooth .!