Potterton Puma 80e lukewarm tap water.

5 Dec 2003
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United Kingdom
Recently bought a flat, and as expected the boiler causes problems within a few weeks! The problem is that the hot tap water comes out lukewarm from any tap that gets turned on. Central heating is working fine - very hot, no problems there. I don't think the problem is to do with the cold weather, as a few days ago it was all working fine and outside temperatures were not that different. This happens even with one single tap on (so i don't think it is due to excess demand of hot water). Am i missing something obvious?! I'd be grateful for any ideas. :?:
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With the heating off and cold pipes, turn the hot water on. Look up under the boiler for the "flow" pipe. Does it get warm? If so the diverter valve isletting the heat go where it shouldn't, and needs replacing. They usually fail the other way though, so your hot water would work and not the heating!

Otherwise, faulty water rtemp sensor , pcb, .....
After messing around a bit, I think it is my PCB. Looked up a couple of component dealers, and they quote £90-100. Anyone know if these can be bought second hand at salvage centres? :?: it seems silly to spend that amount on an old boiler.
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Maybe some of the answers, some of the time.
Poor HW isn't usually a pcb problem. More likely scale, sensor dud, or diverter not doing its thing properly.

Check for the "wrong" pipe being warm as described above. Also with all hot taps full on time the gas usage at the meter.
Assuming it's imperial measure time for one cubic foot of gas, which will be a full or half rev of the dial withthe pointer. Call that time T.

(3600 / T ) * 1035 gives btu/hr so if T= 60, usage = 103,500 btu/hr
If you have a metric meter I'll leave you to do the sums.

If you get less than about 75000 Btu/hr You aren't burning enough gas so it isn't just a diverter problem, say.

HW sensor should measure about 1MR cold and 100K hot iirc.

If you do need a board I've got somew "surplus" ones - email me (go up a level and click on my name to see profile)
After doing ChrisR's check on hot water passing the DV with CH off, which an ESSENTIAL test for a malfunctioning DV, and if the gas consumption is shown to be too low with a hot tap running, then it might be worth checking for the specific PCB fault that I had (which was finally found when all others were fixed).

The Puma 80 has two gas valves, with the second one operating to raise from 3.5mbar to 15mbar when DHW is called for. If you switch on the CH first, and watch through the spyglass while someone else opens a hot tap, then you should:

a) see the red DHW LED come on (if you have the front case cover off);
b) see the burner flames at least double in height.

In my case, (a) happened but (b) didn't. On inspection of the PCB the component R1 was disconnected and the leftmost relay was blackened. Reconnecting the resistance was (as any Borg engineer would tell you) was futile.
Thanks guys,

I actually gave up long ago. I had this problem in 2003, and after many cold showers and failing to find a part for less than £100 I gave in and had a new boiler installed.

Good luck with your one!

Hi stetanos

Oops! I didn't notice that your posting was a year ago. Coincidence about the date...


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