Ravenheat CSI85 - Stronger Earth???

Was that a Lord Woolf by any chance? Has he had problems with his plumbing then? Perhaps he's in another thread...Or do you mean Boeu, Timber, Virginia, or Were (the last two are interchangeable, incidentally) lol.

Tony, the writer can intend all he wants, but he can't tell the reader how to interpret. It's a raging (literary) debate - but believe me, the reader is in charge these days. If you want a headache, Google 'Death of the Author' Barthes for more on the subject (unfortunately Barthes never uses 1 word where 100 will do). But I like the Humpty Dumpty example - for future reference, I will note what the writer has in mind, whether it's scrambled or soft boiled... ;)

...and I'm sure my 'stronger earth' engineer would appreciate that, cowboyplumber. If I ever have the misfortune to see him again, I'll tell him, thank you. ;)

Getting back to my Ravenheat CSI85 for a sec.. I was interested in what ChrisR said about opening the bypass valve. The boiler hasn't cut out again, but it sure is getting hot around the time we cook, despite the fact that it's on a very low heat setting. The drop-down hinged plastic door which usually shuts over the 3 controls (CH/DHW/Reset; Water Heat; CH Heat), falls open and won't close around this time - presumably because the boiler is hot and the plastic expands. This boiler has a feature whereby residual heat from the domestic hot water is dumped into the central heating system when the hot water tap is switched off, overriding all radiator thermostats - we get heat whether we want it or not (as long as the Central Heating is on). I guess we use our DHW fairly intermittently at this time, so I'd imagine that it transfers a lot of heat into the system too.

Could someone explain simply what this bypass valve does, please? On the manual diagram it looks (to a layman) as though it diverts hot water back into the boiler? Our bypass valve is situated right under the boiler - is this too close? Could the boiler problem have anything to do with the dumping of heat into the central heating system, which we have no control over (and the radiators can get quite hot when it happens)?

I can't help feeling that in censuring me for turning down the radiator thermostats in the late afternoon (and remember, I don't turn them all off - I just turn some of them down) the manufacturer is copping out of this issue. We had the same model boiler which worked without a hitch for 3 years - we haven't changed our routine or kitchen layout - but the old boiler didn't have the 'heat dumping' feature.

Since the last repair, the DHW comes on with a devil of a CLUNK which can be heard throughout the house. Sometimes it manages two smaller clunks instead.. It sounds like something from a seedy 1960's kitchen sink drama - you know the type, in black and white, where the rain is running down the window and the boiler is rattling off the wall... :(

I'm beginning to think that it's time to ask for a refund, and time to invest in a reliable boiler. This one isn't six months old yet. :(
 
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Could someone explain simply what this bypass valve does, please? On the manual diagram it looks (to a layman) as though it diverts hot water back into the boiler?

I thought I said enough a week ago when I gave a list of things to be checked out

Is there a bypass fitted? There should be and it should be set to 3 if its a honeywell one, otherwise just enough for the pump to force it open should all the TRVs close off the rest of the circuit.

Ok I didn't go to the finer end of a fart about it but I would call that layman's terms and I certainly didn't expect the spanish inquisition now you have been warm for a week!
 
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Could someone explain simply what this bypass valve does, please? On the manual diagram it looks (to a layman) as though it diverts hot water back into the boiler? Our bypass valve is situated right under the boiler - is this too close?


To quote from the Installation Manual:

The water through the appliance heat exchanger circuit must exceed the min. 2.38 gals/min. (650 It/h) when the burner is firing. It is important to ensure that this rate is achieved when sections of the system are shut off either manually or by automatic controls.
Therefore a by-pass must be fitted to the system (15 mm min.) (Fig. 6A).
If the volume of circulating water is too low, the boiler water temperature will rise too rapidly. This could cause noise in the system or even cause the safety thermostat to trip.


The pump is set so that it will circulate the water at the desired rate, taking into account the head (friction in layman's terms) of the pipes and radiators. When TRVs shut down the friction increases so the pump is unable to push the water round fast enough. This is where the automatic bypass (ABV) comes in. The valve is set so that, when all TRVs are open, the ABV is closed. As the TRVs close down, and the pressure increases, the ABV opens to provide an alternative path back to the boiler, thus keeping the water flowing through the boiler at the correct rate.

Instructions for setting ABVs can be found on the manufacturers web-site.
 
I thought I said enough a week ago when I gave a list of things to be checked out

Ok I didn't go to the finer end of a fart about it but I would call that layman's terms and I certainly didn't expect the spanish inquisition now you have been warm for a week!

:LOL:
That was before the note of alarm mate! You and the SI make a great team, though: who'd think that you lived thousands of miles apart! :rolleyes: I confess to allowing an offending boiler onto my property, I won't say what I think of the engineer...

What happened to Confucius?

Thanks for your explanation D Hailsham. So when the bypass operates, hot water intended for the radiators does in fact go straight back into the boiler, where it's presumably heated again in a never ending loop??? Is this the 'short circuit' effect that was mentioned?
 
Thanks for your explanation D Hailsham. So when the bypass operates, hot water intended for the radiators does in fact go straight back into the boiler, where it's presumably heated again in a never ending loop??? Is this the 'short circuit' effect that was mentioned?

Is this what you are referring to?

Woolf said:
Yesterday though, I spoke to someone who suggested that the problem may occur because when our house gets too warm, we turn down the radiator thermostats. Aaahhh - so the overheat cut out could kick in because of low flow pressure (or something along those lines)??? To test this, today I left all radiator thermostats on full and controlled room temperature by turning down the heat on the boiler instead

The purpose of the ABV is just to ensure that the water is flowing through the boiler's heat exchanger at the designed rate. If it flows too slowly, the boiler will overheat. Of course if the ABV is too close to the boiler there will not be enough of a temp drop over the bypass circuit for it to be effective and the boiler will still overheat. As the Ravenheat is a modulating boiler, this is also taken care of by reducing the gas rate.

Instructions for adjusting ABVs are on the manufacturers' web-sites.
 
Hi D Hailsham,

Thanks for your reply. No this is the reference I meant - sorry - I should have posted it with the last message:

One note of alarm -
So it's been opened fully (the abv). This seems like a fairly simple solution and as a layman I wonder why it's taken so many engineer visits and so much hassle to reach this conclusion.

Opening it fully means that you have much less pressure available to pump water round the system. It's like a shot-circuit. Much better if it's set correctly, by looking at the flow requirement, pump curve and pressure drop in the boiler.

The ABV is situated directly under my boiler - it's two inches away from it. I'm fairly convinced now that the ABV is ineffective in these circumstances and that it contributes to the overheating by directing water straight back into the boiler. The last 'repair' involved opening the ABV fully (whatever the correct setting is supposed to be!)

Today I phoned the new boiler installer and the original plumber who installed the system (and first boiler), to discuss the ABV issues. I didn't get through to either… but I will keep trying…
 
ABV should be at least 3m away from the boiler. The he going after 3 years sounds like the minimum burner setting has not been set correctly, which would aslo cause overheat as the boiler will never modulate down to a proper minimum.

This along with your lack of controls appears, I think, to be your problem.
 
ABV should be at least 3m away from the boiler. The he going after 3 years sounds like the minimum burner setting has not been set correctly, which would aslo cause overheat as the boiler will never modulate down to a proper minimum.

Now would you have said that on Thursday?

Anyway nice to have the opportunity to meet you at Leeds yesterday!

Tony
 
ABV should be at least 3m away from the boiler. The he going after 3 years sounds like the minimum burner setting has not been set correctly, which would aslo cause overheat as the boiler will never modulate down to a proper minimum.

Now would you have said that on Thursday?

Anyway nice to have the opportunity to meet you at Leeds yesterday!

Tony

NO :oops:

Just proves the worth of taking the time for proper training I think.

Always good to put faces to names Tony. I assume you arrived home without incident ;)
 
The Ravenheat CSI 85 Installation Manual can be read/downloaded from HERE

I has a Fault Finding chart, which may be useful
 
ABV should be at least 3m away from the boiler. The he going after 3 years sounds like the minimum burner setting has not been set correctly, which would aslo cause overheat as the boiler will never modulate down to a proper minimum.

Now would you have said that on Thursday?

Anyway nice to have the opportunity to meet you at Leeds yesterday!

Tony

NO :oops:

Just proves the worth of taking the time for proper training I think.

Always good to put faces to names Tony. I assume you arrived home without incident ;)

I'm paying another pilgrimage to Leeds on the 14th. Is anyone else going to that one?
 
Best manufacturers course I've ever attended. You will have a good day Slug.
 
Thanks all for your replies and thanks D Hailsham for your link too.

I've now spoken to the plumber who installed the new boiler and we discussed some of the issues raised here. He says that the ABV is in the correct place and he's done lots of installations like that! I've searched my manufacturer's Instruction Manual and it doesn't recommend any minimum distance of ABV from boiler. According to the Manual p.12 the subject seems to be covered by BS6798:1987/5449:1990 which I haven't accessed yet - but the installer has agreed to re-site the ABV if it's found to be incorrectly placed according to Regs. I also asked him about the Benchmark/Log tick boxes which we discussed a while ago D Hailsham, and he says that 1) Time and Temperature Control to Heating which is ticked Room Stat & Programmer/Timer is covered by the boiler controls, (it all comes down to that forward slash, I think!). Also (referring back to earlier in the thread): I found the Building Certificate which I thought we hadn't been given! :oops:

I also found the Benchmark/Log for the old boiler (same model). Referring to the same tick boxes above, they've both been left unticked. :eek: In the same Control section, 5) Automatic Bypass to the System the 'not required' box has been ticked! So I guess that answers my question there! I think that all this shows that Joe Public should try to acquaint himself with what's going on if he can, so that this sort of detail can be checked or queried at the time of installation. :confused:

So, I have a six months old boiler which is now working after much hassle. I don't think that it's working as it should (it's very noisy now and that 'aesthetically pleasing' (p.3) panel lid persists in dropping open - presumably through overheat?). But I've learned a lot about relevant issues and I'm certainly going to pursue some of them: I think I could ask for a refund on the grounds of non mercantile quality at purchase; or I could try to get (what I consider to be) the outstanding problems fixed…oh no…..zzzzzzzz…..

I've had some brilliant answers over the course of this thread and thanks again to everyone who has joined in for your help: this is a great site and highly recommended. Hope to let you know how I get on over coming weeks. ;) Bye for now.
 

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