Warm radiators when CH not on

[Yorkie]

Hi - hoping someone can help me pinpoint the issue here!

I’ve got an Ideal Isar (yup, I’m aware they’re crap boilers). My radiators get warm even when I don’t have the central heating on.

I switched the boiler off to let everything cool down and then switched it on to document what happens. I had CH off at programmer and dial on boiler for CH right down:

• Ignition sequence commenced - boiler displays “d” - manual says this is code for DHW. This sequence lasts about 1 min 20
• Felt radiators - not warm but can tell there’s some hot water being supplied to them. Pipe from valve is warm
• 2.5 mins later, boiler fires and displays “t” - manual says this is code for preheat to keep water at temperature, which I believe kicks in when the termistor detects certain level of temperature drop. This preheat lasts about 1.5 min
• Felt radiators - gotten a bit warmer
• 3.5 mins later, boiler fires and displays “t” again
• Radiators a bit warmer again
• Turn hot tap on - boiler fires and displays “d”. Have hot water, boiler continues for about 30 secs after closing tap and then stops
• Put CH on at programmer - boiler fires and displays “c” - manual says this is when central heating is on
• Turn hot tap on - displays changes to “d” and back to “c” when turned off

Also, when I run a bath or shower, the radiators heat up and stay warm for the duration.

So problem seems to be:

• Preheat kicking in too frequently - manual says it will fire periodically and is depending on ambient temperature, but my kitchen isn’t cold so the water can’t have cooled that quick
• Hot water is going to my radiators when not required

From various threads I’ve read, I’m suspecting that the diverter valve is knackered, allowing the hot water to leak off into the CH system, so the termistor detects a temperature drop and kicks in frequently to reheat the water again. When I’m calling for hot water, water is also leaking off into the CH system.

It’s one of those things I’ve been able to live with over the past year by turning the radiator valves off in summer so that the house doesn’t overheat when showering, and turning the boiler off when heating and hot water not needed to prevent near constant firing of the boiler and unnecessary energy consumption. I have a smart meter and noticed that on days when I’ve left the boiler on doing nothing it uses somewhere in the region of about 4p an hour. Doesn’t sound much but 24/7 that’s £30 a month extra! Problem is the cold weather is coming and if the boiler is switched off, I can’t use my programmer to get the house toasty for when I wake up or come home from work - so I have to get it sorted.

I took the cover off my boiler to watch the actuator, and the little switch in the side moves right back when the CH is on. When the CH is off, it moves forward but there is still some slack on it (i.e. I can pull it forwards). So wondering if that might be the fault? I don’t know how these parts are made up and whether you have to replace the value and actuator together, or if they are separate.

Any advice?

 

[ShaunCorbs]

Time to get a gas safe engy out also put the boiler cover back on

 

[Rob Foster]

Hi - hoping someone can help me pinpoint the issue here!

I’ve got an Ideal Isar (yup, I’m aware they’re crap boilers). My radiators get warm even when I don’t have the central heating on.

I switched the boiler off to let everything cool down and then switched it on to document what happens. I had CH off at programmer and dial on boiler for CH right down:

• Ignition sequence commenced - boiler displays “d” - manual says this is code for DHW. This sequence lasts about 1 min 20
• Felt radiators - not warm but can tell there’s some hot water being supplied to them. Pipe from valve is warm
• 2.5 mins later, boiler fires and displays “t” - manual says this is code for preheat to keep water at temperature, which I believe kicks in when the termistor detects certain level of temperature drop. This preheat lasts about 1.5 min
• Felt radiators - gotten a bit warmer
• 3.5 mins later, boiler fires and displays “t” again
• Radiators a bit warmer again
• Turn hot tap on - boiler fires and displays “d”. Have hot water, boiler continues for about 30 secs after closing tap and then stops
• Put CH on at programmer - boiler fires and displays “c” - manual says this is when central heating is on
• Turn hot tap on - displays changes to “d” and back to “c” when turned off

Also, when I run a bath or shower, the radiators heat up and stay warm for the duration.

So problem seems to be:

• Preheat kicking in too frequently - manual says it will fire periodically and is depending on ambient temperature, but my kitchen isn’t cold so the water can’t have cooled that quick
• Hot water is going to my radiators when not required

From various threads I’ve read, I’m suspecting that the diverter valve is knackered, allowing the hot water to leak off into the CH system, so the termistor detects a temperature drop and kicks in frequently to reheat the water again. When I’m calling for hot water, water is also leaking off into the CH system.

It’s one of those things I’ve been able to live with over the past year by turning the radiator valves off in summer so that the house doesn’t overheat when showering, and turning the boiler off when heating and hot water not needed to prevent near constant firing of the boiler and unnecessary energy consumption. I have a smart meter and noticed that on days when I’ve left the boiler on doing nothing it uses somewhere in the region of about 4p an hour. Doesn’t sound much but 24/7 that’s £30 a month extra! Problem is the cold weather is coming and if the boiler is switched off, I can’t use my programmer to get the house toasty for when I wake up or come home from work - so I have to get it sorted.

I took the cover off my boiler to watch the actuator, and the little switch in the side moves right back when the CH is on. When the CH is off, it moves forward but there is still some slack on it (i.e. I can pull it forwards). So wondering if that might be the fault? I don’t know how these parts are made up and whether you have to replace the value and actuator together, or if they are separate.

Any advice?

I was taught by British Army how to blow things up nicely, and properly. If you have no knowledge put the cover back on your boiler right now and call a gas safe expert for your families sake and your neighbours as well, autumn is the season for big bangs, I have seen the results of a gas bang all over the face of a fully qualified gas engineer years ago...severe case of sun burn 4 10weeks his son and I had to clear up afterwards ....do not go there
Rob Foster aka centralheatking

 

[Harvest Fields]

Time to get a gas safe engy out also put the boiler cover back on

I had agreed with you on this today already. Any idea where my green tick went?

 

[Rob Foster]

I had agreed with you on this today already. Any idea where my green tick went?

Can I have a green tick as well please ? Or even 2 green ticks

 

[Yorkie]

I didn’t take the sealed panel off, it was the front panel. There’s never been a bottom panel on it since the boiler was installed when the house was built (which no gas engineer has ever commented on or been concerned about, and the house hasn’t blown up), so I could have actually seen what I saw if I could have gotten under the boiler with a torch. I didn’t expose anything not already exposed.

Rob Foster - a simple friendly “put the cover back on” like Shaun Corbs would have sufficed. No need for the story and condescending tone

 

[dan_the_plumber]

Sounds like a broken motorised valve to me, nothing to do with the boiler

 

[dancinplumba]

Sounds like a broken motorised valve to me, nothing to do with the boiler

combi, its inside boiler

 

[dan_the_plumber]

combi, its inside boiler

Oh sorry 🙂