Remeha - one radiator since service

[D_Hailsham]

If you have only one rad turned on, the boiler will need to cycle as it can only modulate down to 6kw. This makes fault finding difficult. Remove all TRVs(*) and open any wheel valves (not lockshields). Set the display to show nF/0 (it will go back to just dots after a short time) then turn on CH. It's now a case of monitoring t1, t2, and nF (lots of button pressing) Keep a note of the readings. You may have to do this for some minutes until a pattern appears, e.g boiler cycling on/off every few minutes. Post the info.

Have you set the display (P6) to 1? Doing this will give useful info on the boiler status.

Do you have hard or soft water?

I am wondering if the diverter valve has got seized up, partly open, due to a build up of limescale. If so, the water would be circulating all the time through the DHW plate heat exchanger as well as through the rads. The hex will be the easier path, so more water will flow that way. This would account for the very high DHW temperature and the rads not heating up.

(*) TRVs can sometimes be stuck shut, even though the pin is up. This is because the pin is not attached to the part which shuts off the flow (think of an upside down mushroom with stalk separated from head.) You can often free these TRVs by tapping the valve body with a hammer.

 

[chriselevate]

Perfect, thanks. That makes sense. Fault finding with only one radiator switched on will make it hard find as I'll find the boiler is cycling as it can't modulate down to 6kw.

I'll give your advice about removing all TRVs and opening up wheel valves (not lockshields) a try tonight and make a note of the t1, t2 and nF readings.

Yes, I have taken your advice and set the display (P6) to 1 last night. It looks like pressing the "R" button returns you to this display. What readings would you like from this and and what points?

So it sounds like this could be the issue...
"I am wondering if the diverter valve has got seized up, partly open, due to a build up of limescale. If so, the water would be circulating all the time through the DHW plate heat exchanger as well as through the rads. The hex will be the easier path, so more water will flow that way. This would account for the very high DHW temperature and the rads not heating up."

Is there a way to test if this is the case? Does this mean it's a new diverter value to be fitted? I'm guessing this is a qualified plumber (GasSafe) only job?
Would this be linked to the service I had done in any way or is it just coincidence that it's happened following that service?

The water is pretty soft. Not like it was when I lived in East Sussex where the limescale buildup was really high!!

Thanks again for all the help.

 

[D_Hailsham]

Yes, pressing the R key takes you back to the status codes. Here they are:

0 - standby
1 - prepurge
2 - ignition
3 - running for CH
4 - running for DHW
5 - waiting-time; 3 to 10 minutes (only when flow temperature has already been reached and heating demand is still existing)
6 or 7 - pump run-on after CH or DHW satisfied
8 - controlled stop. When the boiler is at it’s at minimum output and the flow temperature still continues to rise, once the flow set point

is exceeded by 5°C the boiler will shut down​

9 - 10 minute block. An insufficient water flow, however caused, - indicated by a flow/return DeltaT > 45°C or a rate of rise in the flow temperature

> 1°C/sec. This can lead to a E7 if no water or faulty pump.​

Normally you should just see a cycle of 0, 1, 2, 3/4, 6/7, 0.

5 is self explanatory, 8 only occur when the boiler is at minimum (nF=13) and 9 indicates a potential problem.,

It might be best to get the diverter valve looked at first as it could be the cause of all your problems. Yes, it's a Gassafe man you need as it means delving inside the boiler. It may be just the age of the boiler, nothing to do with limescale.

I have never found E Sussex water hard, though it could be where I live (username!).

​

 

[chriselevate]

Thanks Nige,

I've had the CH on for 40 minutes I'm getting the following....

Time 0 . 10sec . 3min . 5 . 8 . 10 . 15 20 . 35 . 40
t1 43 . 51 . 68 . 71 . 75 . 75 . 75 . 89 . 68 . 59
t2 . 43 . 47 . 62 . 65 . 69 . 68 . 69 . 89 . 64 . 55
nF . 0 . 13 . 27 . 19 . 20 . 21 . 19 . 0 . 13 . 13

I've had most radiators slightly (and I mean slightly) warmer than cold at the top. One radiator, at the top of my stairs was very hot, rest weren't. I can't figure it out!

Plumber update....
Rang the plumber who serviced it and he fobbed me off saying he'd phone me back later or tomorrow morning (heard that before) and I mentioned the divertor value to him and he said, yes it could be but there's also a "cartridge" it could be too.

 

[ianmcd]

It is possible that it is the diverter valve cartridge, that would explain the excessively hot water

 

[chriselevate]

Yes, the other thing I got to stress on that post is that the DHW is INCREDIBLY hot. The hottest I've ever felt it.
So the divertor valve and divertor cartridge cartridge are two separate things?

Is it looking certian it is one of them from what we've seen so far?
Is there a way to tell which one it is and be sure it's that part as I don't want him to start replacing parts that are fine.

Thanks.

 

[ianmcd]

the diverter valve is just a lump of brass, there is a motor called an actuator that moves the diverter cartridge in and out depending if you require HW or CH, the divertor valve doesnt actually do anything, common for the cartridge to become faulty, less common for the actuator motor to become faulty unless there is a water leak.

 

[chriselevate]

Thanks ianmcd.

So from that I'm guessing you're point your finger towards the diverter cartridge?

 

[ianmcd]

yes but I havent seen it but your plumber has so he knows a lot more than I do about it, but that is where I would be looking

 

[chriselevate]

sorry I was just asking. not sure if he'll be able to see it's broken or what he's looking for. I'm just trying to get a handle on what's going on as I don't really have a good local plumber that I feel I can trust at the moment as I'm new to the area and haven't managed to find any good recommendations yet.

 

[ianmcd]

here is your boiler manufacturer, give them a call and see who they recommend for your post code

http://www.remeha.com/products/domestic-boilers/

 

[chriselevate]

Ok, thanks and thanks for your help ianmcd.

 

[D_Hailsham]

here is your boiler manufacturer, give them a call and see who they recommend for your post code

http://www.remeha.com/products/domestic-boilers/

That link is for Remeha commercial boilers. Domestic repairs are now handled by Heateam, tel 0344 335 2266.

 

[chriselevate]

I was hoping that I could find a local plumber to do the work or at least work out an idea of the issue before calling in someone who I didn't know whether they were replacing parts for the sake of it or not. Thanks for you help guys. Sorry we couldn't get to the bottom of it.

 

[D_Hailsham]

I have had a look at the boiler data you posted - here it is:

The first thing I noticed was the small difference between flow and return temperatures - 4C to 7C - which should be between 11C and 20C. The boiler starts off at nF =13, which is OK. The boiler then ramps up to raise the flow temperature to 75C (standard setting in the parameters). At 15mins the boiler output reduces as the return temperature is increasing even though the flow temp is constant. Its a pity there is no data between 15 and 20 mins, but it is obvious that the flow temp has continued to rise to 89C, which is unusual as the boiler software should not let it go above 80C.

The boiler is behaving properly, i.e reacting correctly to what is happening. However it should not be getting up to 89C under any circumstances and the differential is much too small. This could all be due to the hot water circulating through the DHW heat exchanger, due to a faulty diverter valve.

Was the person who serviced the boiler knowledgable about Remeha boilers?

Here is an alternative number for Heateam: 0344 871 1545

It might be worth trying them as they may offer a fixed price repair.