ravenheat RSF 84et- Hot water cycling hot cold hot cold

[daveinblackpool]

I have a problem with a ravenheat rsf 84et, firstly the diverter valve was
leaking and needed to be replaced. A genuine one was sourced and replaced (including microswitch). Now the hot water is cycling hot then cold
every 20 s or so, also the water in the boiler seems to be boiling so i looked up a similar problem and it said replace the dhw sensor. This has had no affect and i could do with some help please

I am going on holiday for 4 weeks and the others in the house will only have limited hot water ( 1 power shower via cylinder on central heating) circuit.

Any help will be most helpful
Dave

 

[kevplumb]

look HERE

 

[wizbongre]

I have a problem with a ravenheat rsf 84et, firstly the diverter valve was
leaking and needed to be replaced. A genuine one was sourced and replaced (including microswitch). Now the hot water is cycling hot then cold
every 20 s or so, also the water in the boiler seems to be boiling so i looked up a similar problem and it said replace the dhw sensor. This has had no affect and i could do with some help please

I am going on holiday for 4 weeks and the others in the house will only have limited hot water ( 1 power shower via cylinder on central heating) circuit.

Any help will be most helpful
Dave

Hi Dave,

I have the exact same problem with mine - see this post from a while ago //www.diynot.com/forums/viewtopic.php?t=65081

I have made some progress but can't understand the results... I started to try and check the DHW temp sensor with my multimeter as it was pretty obvious that this control loop didn't appear to be working - the DHW would start heating and instead of the boiler reaching the desired temperature and then modulating the gas flow to maintain that temperature it would keep on burning on full gas until it hit what I assume is it's internal overtemp sensor and the gas completely cuts out. After a short time it starts again - this gives the hot/cold/hot/cold cycle you are experiencing and may also explain why the water is boiling.

Anyway, I've discovered that if I set the DHW temp control to about half, the modulation control works and we get lovely constant hot water. This kind of implies the DHW temp sensor can only cope up to a certain point and then gives up the ghost - does this sound correct to anyone? As soon as I turn it up any more it starts cycling again as the modulation stops working.

As you've already replaced the DHW temp sensor it sounds like you have a different problem. Can you hear the relay switch "switching" if you turn the DHW temp control up and down? It may be the temp control isn't working so whilst your temp sensor is sending the correct signal the other half of the control loop isn't working.

Sorry I can't help any more but hopefully between us with the knowledgable people on here we can sort both our hot water!

 

[Agile]

Gareth, its a strange fact that some boiler manufacturers design their boilers so that they will not work properly if the controls are set to maximum.

In the trade we know that all tenants and many owners always operate their knobs on maximum.

Turning the knobs to a middle position will often cure many apparent faults.

A prime example is the Potty Profile boiler. This has a temperature scale from 1-5 and needs to be operated between 2-3. If its set any higher the manually reset overheat stat is likely to trip. This is not helped because they are usually over rated for the property and not connected with sufficient flow or pump over run.

If there really is any fault with Dave's boiler it could well be the gas valve is not set up properly.

Tony

 

[daveinblackpool]

I am happy to say the boiler is now working perfectly, have run 3 full baths and filled the sink for 5 minutes all were very hot and water temp was constant.

I have to say a great thanks to both Tony and Gareth for pointing me in
the right direction.

The DHW temp control had been moved to nearly full on, when repositioned to about 3/5ths it worked fine no more faults with cycling
hot water.

Happy New year to both of you.
now i can go on holiday without feeling guilty

Thanks Dave

 

[wizbongre]

Sounds like a result

And I'm glad it's not just my boiler that doesn't like being run at full whack!

For reference, mine will only work properly if the water temp is set no higher than in line with the little black marker on the back plate next to where it says water (about 1 o'clock on the dial.) At this point and lower with the front cover off I can see the gas modulating as I turn the dial up and down. As soon as I go past this point the gas just stays on full whack and then it overheats. As the temp sensor and potentiometer are quite cheap I'm still tempted to replace them in the hope it may give it a bit more range!

Oh well...

 

[Agile]

Dont bother.

It makes no difference at which point on the dial is the maximum.

If you have to run it on maximum that leave it at whatever point is still modulates at!

Tony

 

[wizbongre]

Dont bother.

It makes no difference at which point on the dial is the maximum.

If you have to run it on maximum that leave it at whatever point is still modulates at!

Tony

Ok - thanks Tony!