Heating sort of OK but no HW

[jsimpson]

Hi

Hopefully someone can help me with this.

I have an Icos M3080 condensing boiler with S Plan open vented configuration and gate valve in the bypass circuit.

My problem is when I require just HW (HW valve open and CH valve closed) the boiler fires and quickly (within 30secs) cuts off on temperature, both flow and return pipes to boiler are very hot. The boiler then stays at temp for about 7 minutes before cutting back in again for another 30secs and its just keeps doing this with little or no heat going in to the hot water tank.

Have tried it with the bypass gate valve fully closed to make sure no hot water is returning through this way, but still have the same problem.

With the CH valve and HW valve open the boiler stays on all the time and the hot water tank is heated. I have changed the times for my HW being on to coincide with the CH being on. This is sort of ok for the moment but come the summer (if we ever have one!) when the CH is switched off, I'm going to have a problem.

With just the CH on all the radiators do get hot, but they seem to be taking longer to get hot.

I had an engineer out from Ideal who says the system needs a Power Flush before he can diagnose any further. There is definitely a thin layer of sludge in the bottom of the F&E tank, but I don't want to go to the expense of the Power Flush if it's something less costly such as the pump.

Another question for any one that knows. Does the boiler switch off because the flow temperature is high or does it work on the return temperature?

Any help or ideas would be greatly appreciated.

 

[powell30]

One problem at a time i think......it sounds like a faulty valve not opening. Check by forcing open the HW 2 port and see if the pipes warm up. It may also be a blockage on that side of the pipework......do this and repost.

 

[jsimpson]

One problem at a time i think......it sounds like a faulty valve not opening. Check by forcing open the HW 2 port and see if the pipes warm up. It may also be a blockage on that side of the pipework......do this and repost.

Thanks for the reply powell30. I manually opened the HW 2 port valve, the boiler fires up, pump runs and both sides of HW 2 port valve get hot. After 30 seconds the boiler reaches temperature and cuts off. After approx 7 minutes the boiler fires up again and cuts off after 30 seconds. It just keeps repating like this.

 

[gavinda]

check if theres a high level bleed point near your cylinder... failing that ill jumo straight for the nasty and say the coil may be blocked... had 3 last week like that.

 

[jsimpson]

check if theres a high level bleed point near your cylinder... failing that ill jumo straight for the nasty and say the coil may be blocked... had 3 last week like that.

It's a horizontal tank in the loft. There's no high level bleed point that I can see. Is it easy to unblock the coil?

 

[gavinda]

hmmm the sould be something up there... any chance of a photo?

clearing the coil is something ive only seen donw with a powerflush machine and is costly. maybe one of the ancient guys here could offer a suggestion