Pulsacoil 2000 - Blown fuse and burnt out P.S.C board

[JPM1981]

I have had many problems with my pulsacoil 2000 hot water system over the years. The latest problem I had appeared to be the same as before, where the Heat Exchange got clogged up with limescale - slowly reducing the flow from hot water supply (to all taps and shower), until no hot water at all.

As I had seen this repair done a few times I decided to order a new heat exchange and install it myself - I drained the tank, took off the old heat exchange (which did show signs of limescale build up) and then installed the new one.. This all seemed to go well and the flow rate from the hot taps has returned to full power (although at this point still cold, as the system hand not be powered up or the tank re-filled).

I refilled the tank, turned the power back on and waited for the tank to re-heat (after pressing the boost button).  The tank heated up fine and the heat exchange became hot, but when I ran the hot tap it initially came out hot at first, but then became cold again after 15-30secs and the heat exchange was then cold to touch.

I left it for a while (while I had to go out) and then when i came back and looked again, i noticed that the fuse on the PSC board had blown.  I proceeded to replace the fuse and when i turned it back on there was a spark and the fuse blew again.

Then I realised that when I had replaced the heat exchange, I had left a rag at the bottom of the unit (under the pump) to soak up any spilled water, which was on top of an earth cable coming from the feed pipe under the pump to the metal casing of the boiler. I guess that this may have been what made the fuse blow (my fault!), so I removed it and made sure it was all dry before trying it again with a new fuse. When I put the new fuse in it blew again and also sparked in the isolating terminal connectors (to the left of the main psc board).  I also then noticed that the top left corner of the psc board has burnt around the black chip type thing which leads to the pump controls.

I then unscrewed the top casing of the pump, which showed a small sign of burning, which i could also smell.

I have now ordered a new psc board and am planning to order a new pump head.

basically my questions are;

1. Is the fact I had covered the earth cable at the bottom with a damp cloth likely to be the cause for the fuse / psc blowing problem (or perhaps because a fair amount of water poured over the pump head when I removed the old heat exchange)?

2. Now that I have moved the cloth and dried the area, should it work if i replace the psc board and pump head?

3. Can I replace the pump head only, without having to remove the whole thing and drain the tank again?

4. Will the isolating terminal connectors require replacing due to the spark, although there doesn't appear to be any sign of damage?

I hope the above makes sense, please let me know if you have any questions or any other advise / suggestions.

I'm a little concerned that after I install a new psc board it will blow again and I will have to fork out for another one.. I think I may have made matters worse - again! - by putting in a 2A fuse in rather than 1A.. Perhaps if there is still a fault after I replace the parts, it will just blow the fuse and not the board, if I have the right fuse installed??

Thanks in advance for any help

[Mario.S]

Hi
you have probably spilled a bit of water over the pump wiles draining or disconnecting the exchanger ( I guess). This has shortened the pump and with this of course also the pcb.
Change the Pump head ( this will do, you do not need the pump body change) by isolating the pump on both sites with the fitted pump valves. Also change the burned out connectors and if the pcb has any sins of blown components also the PSB .You would be better off to cover the pump electric with a plastic back or so, wiles draining out or working on the exchanger.
Regarding the hard water and regularly change of exchanger, try a water softener or water conditioner to fit ( like an Aquadial Combi Care System) . This will help.
kind regards Mario at Mario's Boiler Service

[JPM1981]

Hi Mario,

Thanks very much for your helpful advise, which has helped confirm what I need to do..

I have ordered a new pump now, hopefully I will be able to get it back in working order once all the parts arrive!

Do you know what reference / part number the isolating terminals are and where I might be able to order them?

Thanks again!

Jon

[Mario.S]

Hi
just in for lunch,
First , the connectors on the PCB ( PSB) coming with a new board, so no need to order them, if you talking about the main connector block where all external cable are connected to, Just go in any DIY shop, this is only a 16 Amp rated cable connector block , screwed on the panel.( we talking about £1 to £3 pounds). The connectors on the Relay comes with the new relay base as well. any future questions ( course I have to dash) contact me on 07513 50 55 55
kind regards Mario

[JPM1981]

What I was referring to when I said isolating terminals is shown in the attached photo, fitted on a din rail.. there doesn't appear to be anything wrong with them, I just thought I might have to replace them because they sparked.. are they the same thing you are talking about that I can get from any diy shop? I have seen many different types online, but haven't managed to find any that look exactly the same.. although, it might help if I look for a make / spec on the ones currently installed!

The parts that I'm referring to are also shown in the user manual as item 6 on page 6

Thanks for your help again Mario, I'll have a look at the terminals later when I get back from work..

[Mario.S]

Hi
I recognised now, yours is a later model, the old ones had a relay fitted on this position. If you like to be on the save site and save some money you could use 2 of the CP B16 ( 16 amp MCB from Contactum online or in a shop near you from TLC for about £2.20 each). This could be easy fitted on the din rail and is doing the same job as the dry fire protectors (16 amp fuses !!) , original fitted and are also resettable. Just weir them the way the original was fitted. http://www.tlc-direct.co.uk/Products/CPB16.html
kind regards Mario

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