am i missing something obvious??????

[boblydon]

Bit of advise/help required lads, here is the problem i have at home with the boiler.

I have a 35kw icos which used to feed my heating/hot water cylinder (valiant 300litre unvented solar twin coil), system controlled by honeywell s plan. 17 radiators the whole system has worked perfect for 5/6 years.

I have now altered the system, the icos now just just feeds the cylinder, cylinder stat is now not connected, cylinder temp is controlled by boiler stat only, pump is controlled with switched live from programmer, system is is sealed exp vessel is fitted.

I would expect the hot water heat recovery to be bloody quick with this set up (it was always good with the s plan setup), however it now takes ages (hours) for full recovery, pump is a new grundfos alpha 2, i have tried it on lowest and highest speeds, it runs all of the time when the programmer is on an on program.
The boiler stays off on stat for ages (always has switched live feed same as pump. The problem seems to be as if air is still in the system i.e. pipe only half full of water, you can kind of here it........the boiler and cylinder are only 3metres away from each other, honeywell auto air vents are fitted on flow and returns to both boiler and cylinder........these are working correctly and the system is fully vented and treated with x100.
Do you think i need some sort of micro bubble eliminator????, if so what make do you reckon as can't seem to find one on the spiro website.

Have you ever came across x100 frothing up it if a system is overdosed, there is no more 12m of 22mm pipe fitted to the flow and returns, and a full bottle of x100.

Heating is superb as i have installed a Remeha 18kw system boiler completey weather compensated.

Any ideas?????, BTW there are defiantly no partial blockages in cylinder or boiler heat exchanger, and the boiler stat is within correct tolerances, so deffo would appear to be a heat transfer issue.

 

[markfxy]

So theres no control over the water temperature apart from the boiler stat? why

 

[bob the plumber]

title : 'Am i missing something obvious??????'

answer:

yes! your unvented g3 ticket

 

[Kev the gas]

Boblydon, you must use the cylinder stat in the unvented cylinder.

I cant work out if you have taken the perm live to the boiler and the switched live to term 2?

Copied below from manufacturers instructions.

Wire a permanent live supply into the 5-way remote plug
terminals L3, N and .
IMPORTANT. A permanent live is ESSENTIAL in order for
the advanced diagnostic controls to function correctly.
3. Wire the switched live supply into L2 or connect L1 and L2
via external control switching, as shown in Frame 37. In
either case, remove the wire link fitted L1 to L2.
4. Secure the mains lead with the cable clamp.
5. Connect the mains lead connector. Ensure it is fully located

Also you may need a auto bypass to help flow rate through the cylinder, or maybe a small rad at the side of the tank to work as a heat dump.

Kev.

 

[mfgs]

As said you need a cylinder stat on unvented, its part of the required safety devices.

Also the amount of pipework you have is gonna get very hot, very quick and shut off on the boiler stat and then it will take a long time to cool down enough to for the boiler to kick in again.

 

[boblydon]

Thanks for the advice lads.

1/ Just to clarify a few things, i have my unvented and have had it since it was mandatory.

2/ Yes i am aware the regs say that a cylinder stat is required, it WILL be reconnected, however i am not after wiring advice, i have probably wired more control systems than 95% of people on the forum.

3/ This is NOT a wiring issue, thanks for the info Kev you are correct regarding the flow rates thats why i fitted an alpha 2 variable pump, i would have thought a 300 litre cylinder should have had enough heat transfer in the coil though.

4/ I am not new to the game i have been doing it for some 34 years and am gas safe qualified for every appliance both domestic and commercial in natural and LPG, commercial catering in natural gas and LPG, boats, caravans, catering trailers, laundry appliances etc.......i also have part "p" full scope...........so you may now have an an idea i have a clue what i am talking about.

Any way back to the question, the other thing i was thinking of doing is down rating the boiler output, the reason i have not done this as yet is simply because on the s plan the hot water worked fine, so the amount of pipe etc has stayed the same length and size etc, only difference is the motorised valve has been removed

 

[GQuigley67]

have you put a full bottle of x100 into the system ?? imho its a bit excessive, usually these bottles are enough to treat a 100 litre system, I would of only put in a 1/4 of the bottle if anything at all

 

[boblydon]

I agree about the dosing being rather excessive, however you have to bottle so you just add the lot, thats why i was thinking maybe the excessive amount is frothing up/foaming up.............as it worked perfectly beforehand this seems the common denominator.

Will give sentinel a ring and report back.

bob