WB Heatslave 15/17 Oil Boiler & Wireless Programmer / St

[jjon]

Hi,

We've got a 20 year old or so Worcester Heatslave 15/19 non condensing oil fired boiler, however the internal battery in the programmer is packing up - the shortest power dip now causes the clock to reset, so the blooming thing needs reprogramming. As the installer helpfully installed it at right angles underneath a worktop (before we moved in), it's not the easiest thing to redo, so I'm looking at swapping the programmer out for a wireless one, and adding a wireless 'stat to the system as currently there isn't one at all.

Any recommendations as to a wireless stat and programmer package - I've seen a few people mention Honeywell and Siemens ones on here when searching, but it doesn't look like they do heating as well

Secondly - should this boiler be able to run hot water flat out for long enough to do something like run a bath? It'll run the first few inches roasting hot, then it gets colder - drives the missus up the wall. If you don't turn the hot tap fully on it copes a lot better, but I'd have thought it should be OK to run a hot bath without having to worry?

Worcester have serviced / fixed it a few times since we've lived here and it all appears to check out OK (and is better than it was)... We mentioned about replacing it with a newer condensing one, and the guy didn't seem to think it would get us much, and they are a lot more complex so tend to go wrong more...

Lastly - any recommendations for what to replace it with, should we decide to? Obvious replacement would be the newer condensing WB, but ideally we'd want to rotate it so it faced front under the worktop, so it'd need to have a side exit flue. Anything better out there?

Cheers

Jon

 

[Tibbot]

Check the power from the programmer is on for hot water. If not you'll only get energy from what's stored and it won't fire up to begin recovery when you turn on the tap. The boiler is designed to have hot water permanently programmed on but off overnight so it doesn't keep firing. Stored hot water will be enough for washing hands etc through off period.

If you don't want to waste money, only consider replacement when beyond economical repair.

 

[jjon]

Check the power from the programmer is on for hot water. If not you'll only get energy from what's stored and it won't fire up to begin recovery when you turn on the tap. The boiler is designed to have hot water permanently programmed on but off overnight so it doesn't keep firing. Stored hot water will be enough for washing hands etc through off period.

The boiler fires when you turn the hot tap on (assuming it's in it's 'on' period) - however it's like the boiler can't keep up with demand for hot water, so after a while it goes cold - which suggests to me that something isn't right somewhere, as the flow isn't that high. It'll run a shower fine though, but not the bath hot tap on full whack

 

[Tibbot]

Check the hot water thermostat is turned up and heatbank reaches temperature. If ok the run hot tap, pump should start, burner fire and diverter valve pass water from heatbank through plate heat exchanger. Check if any of these are not passing heat. When heatbank is exhausted you should still get enough hot for a tap or small shower.

 

[jjon]

Thanks for the suggestions. How can you tell which way the diverter is passing?

The heat bank seems to fill up OK from cold, it'll fire when you turn the hot tap on, but then it goes cold after a bit. Leave it for a few mins and it'll run hot (for a bit) again. Should the flow drop off as the heatbank runs out of hot water, and it's heating it on the fly?

(sorry for all the stupid questions )

 

[Tibbot]

Sorry, I meant the diverter pass heat from the pipe from pump though pipe to heatbank. Hot water will only be as hot as the heatbank. The burner serves it. Not heat in the heatbank = none at the tap. You could have a defective pump, diverter, or plate heat exchanger. Check again the burner continues to fire with tap off to pre-heat heatbank. If it doesn't you've no demand from programmer or store stat.

 

[jjon]

OK - thanks. Will have a look later on and report back

 

[oilhead]

Replacing the programmer with any 2 channel is easily done and is covered in the installation instructions. The builtin unit is connected by a plug into connector blocks. Thermostat connections are made into one of the PCB's and again is covered in the installation instructions. Choice of manufacturer is down to your personal choice, but I prefer Siemens units as they have a 6 amp switching capacity whereas the Honeywell only switches 3 amps. On start up, the combined rating of a circulator, a burner motor, and an ignition transformer can exceed this especially if the components are getting on a bit.
If your heat store is up to temperature, then poor performance is likely down to scaled up heat exchanger, although something nags me that I can't check at the minute that on older models, the DHW heat exchanger is now a unit with more plates, hence more output, than originally fitted.

 

[jjon]

Had a quick look last night - when the hot tap goes on, the burner fires up nearly instantly, and carries on running after the hot tap goes off (to replenish the heat bank I guess).

Didn't get a chance to try with the bath tap, but the tap in the utility room would get cooler as it kept running, so from suggestions on here it looks like the heat exchanger isn't exchanging enough. Is it possible to descale them, should it be scaled up? I'm guessing it's a reasonably sealed unit?