Intermittent Boiler Issue
- Thread starter Iainmcr
- Start date
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It was on the earlier locked thread, entitled something like "15mm or 22mm".
Taken that as 50kW output, so input at ~ 96% eff, 52kW, gas flow 4.64m3/hr. Not sure what you mean by high loss fittings, so I assumed 90° elbows.
As the pressure loss most likely needs to be in the region of 1mb, I did 2 pipe sizes.
Nominal 22mm, 2.14mb
Nominal 28mm, 0.73mb
What do you get? I've shown you mine....
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Taken that as 50kW output, so input at ~ 96% eff, 52kW, gas flow 4.64m3/hr. Not sure what you mean by high loss fittings, so I assumed 90° elbows.
As the pressure loss most likely needs to be in the region of 1mb, I did 2 pipe sizes.
Nominal 22mm, 2.14mb
Nominal 28mm, 0.73mb
What do you get? I've shown you mine....
As we all know it’s 1mbr max loss. So 22mm won’t do! That’s not an ambiguous figure. It’s the basic requirement.
50kw needs to be 28mm minimum. That would give a loss of 0.760mbr
So there you go........
Edit: And as above max length @19m in 28mm
I think that proves you give gas advise without the proper knowledge?
What's the matter with you? I thought we were having a sensible discussion.
I gave pressure loss figures for 2 pipe sizes, one to give > 1mb loss, one to give less. Obviously if you have to work to not more than 1mb loss, you select the bigger pipe. Who said it's an ambiguous figure? You work out the pressure drop, and select the pipe accordingly.
Your 0.76mb vs my 0.73 are gratifyingly close, particularly as I don't know what you assumed for high loss fittings. Unsurprisingly, 19m pipe gives close to 1mb loss.
Your standard of "proof" leaves a lot to be desired. My recommendation is the same as yours in this situation. And it's advice, not advise.
That's right, I mentioned it and showed it was too small. Shall we leave it at that?
Yeah, we’ve formed our opinions.
Aye me too! I've learned a fair bit about the capacity of gas pipes but very little about my own boiler problem.
What I'm trying to find out is what I (as a maintenance electrician) can do before I have to call out a heating engineer, for instance can I rule out the 3 port valve? Or is the consensus that it's either the PCB or one of the gas valves? If it's the gas valves I'm taking it that it's more likely to be the valve mechanism that's sticking rather than the solenoid actuator not energising, If it's the PCB (and this was changed in the last 4 years) is that possible to change without going near the gas side of things (which I wouldn't).
if it is the pcb and i am not saying that it is, nothing to stop you changing it yourself on that boiler, when your system fails check to see if you are getting 240v to the gas valve , if you are and the boiler isnt on, then im sure as an electrician you can work out what the fault is, if you arent then work your way back
We changed our Potterton Profile 60e last year after 25 years of service as it was starting to kettle. I had similar problems as the OP three times during its lifetime and each time it was the PCB. Fitted the last two myself - really easy to change. Annoying thing was I only changed it a few months before it was replaced and as I needed one on the quick, I think I paid around £180 for a genuine one from a heating supply shop on Christmas Eve. Mind you, I removed it and got £45 back for it on eBay when the boiler was changed. I think you can get reconditioned or pattern ones for a lot less than the OE retail price.
I think you can get reconditioned or pattern ones for a lot less than the OE retail price.I had just that problem - 240volt to the gas valve (SIT as here) but it wasn't firing. Turned out one of the solenoids (of 2) was open circuit. I got one from Solenoids UK for £12 which worked OK, but the connector was in the wrong place so needed a temporary wiring fix. The replacement from Italy was £37 after various outfits had taken a cut.
But the fault was not intermittent like the OP's problem.
Agree they normally fail to OC but have seen the valves sticking intermittently, not common but can happen
3 ports are fairly easy to check on a basic system. Just set both CH and HW stats to max, then enable CH or HW at the time clock. The actuator should move the valve to CH or HW positions, then boiler and pump should start. Sometimes the boiler itself controls the pump, to allow for pump over run.
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