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We moved into our current home in June. The heating is supplied by a 10 year old WB Greenstar CDi 37kkW combi boiler. I had the boiler checked by a local 'Registered Professional Gas Engineer' engineer who has serviced my son's boiler for many years. He said it was working correctly.

So far it has worked OK, getting the house up to temperature each morning. A few days ago, however, when it began to get much colder outside, we noticed that the room temperature was much lower, even though the room stat was still set to 21C. I turned the stat right up to 24C but the room temperature only rose half a degree.

I decided to watch the boiler and found that it was heating up to about 55C (set to approx 75C) then switching off. Pump overrun would start and the temperature would drop to about 35C before restarting. So the cycle continued. I checked parameter 9C (heat output) and it was only getting up to 50%.

Why is this happening and what's the solution?
 
We moved into our current home in June. The heating is supplied by a 10 year old WB Greenstar CDi 37kkW combi boiler. I had the boiler checked by a local 'Registered Professional Gas Engineer' engineer who has serviced my son's boiler for many years. He said it was working correctly.

So far it has worked OK, getting the house up to temperature each morning. A few days ago, however, when it began to get much colder outside, we noticed that the room temperature was much lower, even though the room stat was still set to 21C. I turned the stat right up to 24C but the room temperature only rose half a degree.

I decided to watch the boiler and found that it was heating up to about 55C (set to approx 75C) then switching off. Pump overrun would start and the temperature would drop to about 35C before restarting. So the cycle continued. I checked parameter 9C (heat output) and it was only getting up to 50%.

Why is this happening and what's the solution?
I have a heat only Gloworm which is very complex re the Boiler thermostat operation and the condensing boilers as will the combies be similar in their technicalities re water temp control. These condensing boilers have a similar PCB to a computer which does not work properly sometimes. The PCB through the inputs from the sensing stats /devices instruct the gas valve and the associated controls to put the appropriate heat into circulation. Many sense the return temp and do not put out the heat that is required for the system to operate properly. Mine in my static caravan has a 'mind of it's own! sometimes it will get right up to the 'target' temperature sometimes it does not. It does not especially when I want it to! When it should 'call for heat' it does not. I have the benefit of fitting the same brand new boiler in a mates house that was seen to behave absolutely perfectly and did not stop once and never has done in about 4 years. When it does start playing up I would wager it will be the PCB that is not behaving as it should but I could be wrong. I have a PCB that has not been fitted 'yet' because while our caravan is satisfactorily warm I'll leave it on top of the boiler in it's packet. Renovated PCB's can be got from International Boiler spares Tyne & Wear for about £50 with a years guarantee. If you are not an expert I would be careful though to check all incoming devices that supply the board with info as that is essential before replacing anything. It may well be the board though but then again it could be the gas valve or even a tuppeny hapeny sensor. Luck does not and never will come into that equation.
I was once asked donkey's years ago what are these new fangled combies like = I said they are all right till they go wrong... Mark my words though in respect that they will go wrong and if you are unlucky enough they stop on Christmas eve!
 
We moved into our current home in June. The heating is supplied by a 10 year old WB Greenstar CDi 37kkW combi boiler. I had the boiler checked by a local 'Registered Professional Gas Engineer' engineer who has serviced my son's boiler for many years. He said it was working correctly.

So far it has worked OK, getting the house up to temperature each morning. A few days ago, however, when it began to get much colder outside, we noticed that the room temperature was much lower, even though the room stat was still set to 21C. I turned the stat right up to 24C but the room temperature only rose half a degree.

I decided to watch the boiler and found that it was heating up to about 55C (set to approx 75C) then switching off. Pump overrun would start and the temperature would drop to about 35C before restarting. So the cycle continued. I checked parameter 9C (heat output) and it was only getting up to 50%.

Why is this happening and what's the solution?
doitmyself...repost your post has got mucked up, its very unusual
centralheatking
 
WB DT10RF version 2. It;'s the 7 day version with Optimization, which is turned on. The HW preheat is turned off.
Post automatically merged:


There's nothing wrong with my post; it's what I wrote.
Did you read my post about how complex the target temperature is on the modern Combies and Heat only Boilers? The PCB is a computer and evaluates the return temp the water temp within the boiler and even with a 'clean' boiler the PCB and associated sensing devices can put out or rather limit the temperature even though the target temperature is set higher than the boiler stops heating the water within the boiler. Some very good engineers are finding htis symptom is a nightmare to rectify because on many occasions it is intermittent. All the sensing devices are checked OK with a good meter & yet the older boards do not get to the target temperature. This subject hjas been discussed by quite a few on the heating forums. It seems to be the most frustrating symptom of all (the mother of all symptoms) You could as I said get a refurbished board from International Boiler spares (they do all boards) £50 approx + £8 next day post. Years guarantee You've got to start somewhere? For starters have you checked the value of each and every sensing device as per the installation manual?
 

oz-plumber

Esteemed
Plumber
Done that, They are all on the default setting.
The reason I said this is because some boiler brands use the same PCB throughout their range.
You sometimes have to alter a parameter to adjust the PCB for the output of the boiler it is being installed into.
Sometimes you have to alter a few parameters to suit the boiler model/ configuration and type of installation.

It may be why the heat parameter is only getting to 50%

The previous owners may have had a board replaced and not adjusted to suit.
 
The reason I said this is because some boiler brands use the same PCB throughout their range.
You sometimes have to alter a parameter to adjust the PCB for the output of the boiler it is being installed into.
Sometimes you have to alter a few parameters to suit the boiler model/ configuration and type of installation.

It may be why the heat parameter is only getting to 50%

The previous owners may have had a board replaced and not adjusted to suit.
You may well be right in your thoughts.... but.... Please see my post re our condensing heat only Gloworm HXi boiler
( because I would not have a combi for a gift with free gas) which is in our static caravan? I firmly believe it is not down to the setting of parimeters in the fault that I have experienced with this particular boiler because the fault is not a continuous fault by any means, it is most definitely intermittent. So I believe that if it was settings of the various inputs it would be a permanent symptom but as said it is not. I have checked and adjusted all the settings as per the instructions & yet the damn boiler still persists in shutting down especially when the burner should continue to its target temp. But most of the time the target and even a few degrees above the target temp is achieved which is acceptable. I bought our boiler from Ebay for £5.50 but had to go to Oxford from Nottingham for it. I often ponder was it because of this frustrating fault the previous owner outed it?
I have played with this boiler for 4 years and have as I said got last year a renovated PCB from the reputable folks at Tyne & Wear. Due to us using the boiler outside of the winter season I have not condescended to fit the renovated PCB. It does produce in minutes 22 gallons of hot water due to my cylinder being two stainless beer barrels welded together. I know the heat exchanger is as new because I always acid every used boiler I lay my hands on. The pump is very adequate and the return arrives back to the boiler well within the 11 c 'drop'. I've cured many a fault on all sorts of brands of boiler and I note that even the experts who work only on certain brands of boiler are into the' change that because I've got one in the van
syndrome'! however that method of approach can and sometimes does save a lot of time and of course saves taking a lot of librium!
 
Did you read my post about how complex the target temperature is on the modern Combies and Heat only Boilers? The PCB is a computer and evaluates the return temp .
I just skimmed over it and decided it was not relevant. My boiler does not have a return temperature sensor, only a flow sensor. So the only control available is to monitor the flow temperature and modulate the boiler down when the flow temperature exceeds the set value by a certain amount. If the boiler has modulated to minimum output and the flow temperature still rises above the set value, it goes into on/off mode with anti-cycling.
 

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