Sime Friendly Format 80E - Diverter Valve vs. Heat Exchanger

[Sangers]

Hi there,

I have a Sime Friendly Format 80E boiler (or possibly a Friendly Format Technyl judging by part numbers) which is <5 years old, and have a classic problem...

The CH works absolutely fine, but we're experiencing problems with the DHW only being lukewarm AND low pressure - typical symptoms of a faulty Diverter Valve. However the plot thickens...

When turning a DHW tap on, the boiler fires up correctly and watching the Diverter Valve in operation shows that the diapragm is still working, as the pin extends and depresses the microswitch (not sure what this microswitch does). So I'm not 100% convinced its the Diverter Valve (possibly the Heat Exchanger?).

Despite the Diapragm looking like it works in terms of depressing the microswitch, the DHW only warms a little, and the CH flow pipe gets a lot hotter - as do the radiators. So, from my limited knowledge, I think its either the "valve" part (not the microswitch triggerring part) of the Diverter valve not fully diverting water to the DHW Heat Exchanger, or its the DHW Heat Exchanger itself.

Now, upon examining the DHW Heat Exchanger by touching the back, the left half gets warm and sometimes very hot, but the right half is always very cold, so I'm wondering if this is indicative of a clogged up or faulty DHW Heat Exchanger?

What I need to establish is which of the two parts (hopefully not both) is actually at fault here - is it the Diverter Valve or the DHW Heat Exchanger that I need to replace?

Had the system recently serviced, and the plumber said striaght away that I need to replace the Diverter Valve as the radiators heat up when the hot taps are open, but he also said he's not that familiar with the Sime boilers (lucky him), so what should I do?

Any advice would be VERY handy, and my intention is to replace the part myself, and then get the boiler and system re-serviced to get those nice warm showers in the morning again!

Thanks in advance for your help.


Sangers.

 

[Agile]

The fault lies in the lower part of the diverter ( called the manifold ) which is spring loaded and has become jammed and is not following the top diaphragm part.

This can happen to any boiler but for some reason seems particularly common on Sime boilers.

Its easier to change the whole diverter but it could be cleaned. Its a result of a slightly dirty system, particularly copper oxide deposits.

The plate heat exchanger may also be blocked and is easily checked and washed out when dealing with the diverter.

I would first try using chemicals to clean the boiler out myself but DIYers usually prefer to take things apart.

Tony

 

[Sangers]

Thanks for your quick response Tony.

We suffer from particularly hard water, so I wouldn`t be surprised if its a build-up of limescale too. All the pipes are copper, and we have 3 TRV rads downstairs, and upstairs we have 3 TRV rads and a non TRV rad.

Based on the above info, are there any particular chemicals which would be more suitable for this type of job? And can I get them at DIY stores such as Wickes, etc?

I'm tempted to strip down the manifold and clean it and the same with the exchanger, as I think the problem is getting progressively worse, and I can't see chemicals being able to do as effective a job as actually cleaning out the component itself. Although I may well use chemicals afterwards to give the whole system a flush through.

Incidentally, I have noticed that balancing the system to 1.0 to 1.2 bar (when boiler is off) makes a dramatic difference to the temperature - anything outside of this range seems to impact the DHW temperature quite dramatically.

If I manage to resolve the issue that way, the money saved is going towards a water softner!

Thanks once again for your help. I`ll keep everyone posted on the outcome...


Sangers.

 

[croydoncorgi]

Incidentally, I have noticed that balancing the system to 1.0 to 1.2 bar (when boiler is off) makes a dramatic difference to the temperature

What do you mean by this? Pressure should have no effect on whether the water comes out hot or not. Only on whether the boiler fires at all.

 

[Sangers]

OK Following the advice of Tony above, I drained down the system and added some sludge and scale removing chemicals. Then started to re-fill and balance the system again, but struggled...

The pressure kept rapidly dropping to 0 as though I have a leak, and then I narrowed the fault down to a faulty 3 bar safety valve - with water (and wasted chemicals) pouring out of the overflow pipe outside, so this explains the issue in croydoncorgi's reply.

I've ordered a replacement safety valve, and in the meantime, attached a closed tap to the pipe outside (dangerous I know - but it really is only a temporary measure to allow the use of the boiler whilst the safety valve is en route).

So now the tap is in place, I rebalanced the system, bled the rads, re balanced to 1 bar, bled again after running for a while, and voila - we have warmer water with slightly better pressure than before...

After running the water for a while, I felt the back of the DHW Heat Exchanger - and, once again only part of it has warmed up, and the other part is stone cold. Seems like there is a blockage in the DHW Heat Exchanger as mentioned by Tony.

When I drained down the system to add the chemicals, there was a lot of large black flaky residue in the water, and I was wondering where this came from, then I realised what the culprit may be...

Last year, we added a new TRV rad downstairs to some existing stopped-off CH pipes. When we un-stopped the pipes, there was a lot of dirt and sludge collected in them, which we simply let flow out. We made the mistake of not cleaning out the system and just attached the new rad, poured in some inhibitor, and refilled the system. I suspect this sludge and residue has now circulated through the system, and gotten lodged in either the Diverter Valve and / or the DHW Heat Exchanger - hence the overall problems I'm facing now.

I do think the DHW Heat Exchanger is definitely at fault (due to part of it being cold), but also the Diverter Valve (due to rads getting warmer when DHW tap is on). The new question is, and following on from Tony's post, is it easy enough to clean out the DHW Heat Exchanger, or should I replace it?

Thanks again for all your help, I just wish I'd found this site when we moved into the house a year ago...


Sangers.

 

[ChrisR]

Take that bloody tap off the pressure relief valve, it's giving us all the willies!

While you're playing, check the expansion vessel pressure - see "boiler pressure problems" in the "for reference" section.

You can expect the black stuff in the main (primary) heat exchanger, and on the primary side of the secondary heat exchanger.
Also it sounds like your water is so hard it has caused a build up of limescale in the secondary (tap water) side of the hw heat exchanger.

If you take the hw h/e out, you'll be able to get a good idea by looking into the holes. Sulphamic acid (eg Fernox DS-3) is best for the tap side, and for the primary Citric acid is the safest recommendation, or Kamco FX-2, or Fernox DS-40. Warm citric acid will have a good go at both sides.

You MAY not get it all out; even with a poweflusher connected to the h/e, the flow can bypass blocked bits.