Another boiler problem

caveat_emptor

paul_pockets wrote:

sorry I misunderstood the DHW flow and DHW temp. The flow of water from the hot tap is good, just cold, as you said.
I'll check this when I go home tonight.
If the burner is modulating all the time, what is the solution?
thanks
paul

Suspect that DHW thermostat is either set too low or is stuck in modulation mode and needs replacing.

paul_pockets

Morning all,

the boiler has a switch fot hot water and heating or hot water only, not a central heating only setting. So not sure if i'm able to test this correctly?

Regardless of that the heating was on full with the flame burning full. I turned the hot tap on and the flame stayed constant. The water was warm/hot to the tuch, but not as hot as it should be.

Does that help your modulation theory?

thanks
paul

robowen

I've got the same boiler as you Paul, and I gotta be honest...its pants
My boiler is not as old as yours and we have always had to reduce the flow rate to increase the hot water temperature. We have good water pressure here as I dug in a new water supply at he time of fitting this boiler.
More recently the water temperature increased drastically causing the pilot flame to trip out.
We enjoyed the increase in temperature filling a bath for a while by ensuring that we didn't stop start the hot taps, a constant flow prevented the pilot tripping. Working in the kitchen meant the hot was on and off all the time. We got tired of resetting the pilot after a while and eventually I replaced the DHW thermostat and we were back to the poor hot water temp on maximum flow.
I'll be honest...I've not bothered checking gas rates for this heap of junk....I made my mind up it's coming out in the summer...we're just plodding on till then.
If I get chance I'll gas rate the hot water for you to compare....If I get time I'll do it tomorrow, if not it'll be next week.

rob

paul_pockets

Hello,

I spoke to a very helpful man at Ravenheat today. After listening to my story, he asked me to test something for him. I popped home at lunch and switched the heating on and turned the hot tap on. the boiler has 2x 22mm pipes one CH flow the other CH return. He said that if the CH flow pipe got hot with the heating on and the HW running the diveror value is faulty, as it's job is to stop water flowing into the CH system once a HW tap is on. This makes sense to me as a man with no idea.

How about you guys?

paul

robowen

Thats right.
The divertor valve gives priority to the hot water. If you put the hot taps on and switch the heating on at the same time, the heating wont get warm till you turn the taps off.

rob

paul_pockets

I'm not really loving the boiler either at the moment. I've had it tuen off for apparently no reason, I now suspect this is over heating like yours robowen.

I'm not sure what the max flow rate is for this boiler, but it's never been amazing and you need to plan the a day ahead if you want a bath!

I inherited the boiler when I bought the flat 2 years ago. Ideally I'd like to change it when I redo the kitchen, but that isn't going to happen for a couple of years. So I'd rather fix it.

thanks for the gas offer, it'll be interesting.

paul

robowen

DHW flow rate 30 dg rise 11.3 l/min
DHW flow rate 35 dg rise 9.7 l/m
DHW flow rate 40 dg rise 8.5 l/m

DHW min flow ate 3 l/m
DHW pressure max 10 bar
DHW pressure min 0.8 bar

rob

moneysavingplumber

If you have a gas meter with a dial, make sure all your appliances are turned off, then mark with a removable marker the position of where on the dial the pointer is pointing to. Get a stop watch and open the hot tap, wait until the burner lights and start timing. Leave the tap running, go back to the meter and wait until the pointer has completed one full revolution on the dial and then stop the stopwatch. Post the time here in seconds and either Rob or myself will be able to tell you the gas rate the burner is running at (assuming the dial is 1 cubic foot per revolution which it should say on the badge).

If the meter is more modern with a digital counter display then the procedure is slightly different. Make a note of the last three digits, then turn the hot tap on and when the burner lights, start the stopwatch. Time for two minutes and then turn the tap off. Go to the meter and note the last three digits again, then subtract the first set from the second and post the result here and one of us can check it against what it ought to be.

paul_pockets

Thanks for the flow info rob. I'm definately not getting anything like that!

moneysavingplumber: I'll check that tonight and post my results tomorrow. Do you think it could be the valve now based on my earlier post about the CH flow pipe?

many thanks
paul

moneysavingplumber

paul_pockets wrote:

Thanks for the flow info rob. I'm definately not getting anything like that!

moneysavingplumber: I'll check that tonight and post my results tomorrow. Do you think it could be the valve now based on my earlier post about the CH flow pipe?

many thanks
paul

I think it will depend on the result of the gas rate test. If it turns out the burner is running at CH modulation then your best course would be to phone Ravenheat technical again and ask further guidance. We all use manufacturer's technical helplines, as all boilers have their own quirks and it's usually the best way to positively diagnose a fault if you are unsure.