Any reason why they are all working 'perfectly'?
Help with Evohome / Opentherm / Intergas
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Originally posted by The EVOHOME Shop View PostThis is not entirely true.
G3 regulations don't actually state you need a 2 port valve. What the regs say is that the heat demand to the coil needs to be removed when there is a high limit situation. This can actually be achieved by rotating a 3 port valve 180 degrees so the closed port is on the hot water side instead of heating. It is loosely called 'D-Plan' after Dan from Jennings Heating who came up with the idea (although others claim they were doing it earlier).
I actually prefer hot water priority with a 'inverted' 3 port diverter valve - works much better with OpenTherm and evohome.
As for OpenTherm, evohome and Intergas... I have all 3 things working just perfect in our training facility! ����
The fact that you are advising people to do this is quite frankly worrying. If you want HW Priority just wire the system accordingly with the 2 Port valves.
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Originally posted by mtmcgavock View PostSorry I have to disagree with that, I think you'll find that every Unvented cylinder comes supplied with a 2 Port valve, along with clearly stating in the instructions that the valve must be fitted. As you state that regulations say that the heat demand needs to be removed, by fitting a 3 port or even diverter valve cannot guarantee this. Many 3 port valves pass on the HW side not providing a full shut off, along with the fact that in case of power loss to the 3 port valve it will fall to it's naturally open position which is HW. This then isn't closing the circuit, where as that a 2 port valve would close. Should power continue to a heat source (Such as the Boiler relay) it could prove quite deadly.
The fact that you are advising people to do this is quite frankly worrying. If you want HW Priority just wire the system accordingly with the 2 Port valves.
I have stated that the 3 port valve would have to be reversed 180 degrees so the 'open' port 'B' is on the heating side and therefore when the power is cut to the valve it closes the hot water port - absolutely no different to a 2 port. I have seen many cases where 2 port valves have failed open and the fact most 3 port valves are made with the very same mechanism as most 2 port valves (I have only ever fit Honeywell valves) makes what I have described no different. It is just an intelligent way of looking at the problem and finding an engineering solution.
People like to make their own regulations up in the heating industry and there is nothing wrong with what I have suggested. As for unvented cylinders, unless you have completely bypassed the T&P valve by capping it off and also removed the high limit thermostat on the boiler, I can't really see how a 'deadly' situation would occur? More likely an immersion heater to cause issues with unvented cylinders than a gas boiler ever would.
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Originally posted by The EVOHOME Shop View PostI'm sorry but this is showing a lack in your knowledge not mine.
I have stated that the 3 port valve would have to be reversed 180 degrees so the 'open' port 'B' is on the heating side and therefore when the power is cut to the valve it closes the hot water port - absolutely no different to a 2 port. I have seen many cases where 2 port valves have failed open and the fact most 3 port valves are made with the very same mechanism as most 2 port valves (I have only ever fit Honeywell valves) makes what I have described no different. It is just an intelligent way of looking at the problem and finding an engineering solution.
People like to make their own regulations up in the heating industry and there is nothing wrong with what I have suggested. As for unvented cylinders, unless you have completely bypassed the T&P valve by capping it off and also removed the high limit thermostat on the boiler, I can't really see how a 'deadly' situation would occur? More likely an immersion heater to cause issues with unvented cylinders than a gas boiler ever would.
I've seen many situations where a 3 port valve has been fitted to a unvented cylinder where the high limit stat has cut out and heat still being transferred. On one particular occasion where a Worcester had been fitted with a pump over run and no bypass so it was pumping the heat round the cylinder. On this one it was discharging at a considerable rate, should that T&P failed it could have lead to a serious problem.
Another occasion where a Viessmann boiler with internal diverter had been fitted, the temperature sensor had fallen out and the HW left on constant. Resulted in the cylinder overheating with no thermal cut off. Had a 2 port valve been fitted following the manufacturers instructions it would have prevented this.
Whilst I agree it is very unlikely a deadly situation could occur as a number of components in the chain would have to fail, starting to deviate from the manufactures instructions shouldn't occur. The regulations are there, but the manufactures instructions should be followed. If you had an issue down the line they'd be very quick to say it wasn't fitted correctly. As gas safe always state with gas appliances, always follow the manufactures instructions.
Use a 3 port valve, but put a 2 port valve before the cylinder. At least then should anything change on the installation that's out of your control you've always got the fail safe of the 2 port valve.
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How exactly would an unvented cylinder overheat to the point of dangerous pressure release when heated by a closed loop to a boiler ? It can't get any hotter than the flow temperature of the boiler - which unless the boiler is faulty, is going to be under 90 degrees. (So now you have two separate devices failing at once to cause a problem, and that's pretty hard to protect against)
From an electric element its possible, yes, because the electric element can reach several hundred degrees...
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Originally posted by DBMandrake View PostHow exactly would an unvented cylinder overheat to the point of dangerous pressure release when heated by a closed loop to a boiler ? It can't get any hotter than the flow temperature of the boiler - which unless the boiler is faulty, is going to be under 90 degrees. (So now you have two separate devices failing at once to cause a problem, and that's pretty hard to protect against)
From an electric element its possible, yes, because the electric element can reach several hundred degrees...
The above particular situations, the Viessmann one hadn't discharged. The one with the 3 port valve I'm not quite sure what had happened in that situation regarding the discharge - but it had been discharging.
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Originally posted by mtmcgavock View PostSo when you've fitted the reserved 3 port, what happens when someone else, who isn't the original installer comes along when the valve has failed and says this hasn't been fitted correctly (Not aware of the situation). He then puts it on the right way round and leaves it - your are opening a can of worms.
Originally posted by mtmcgavock View PostI've seen many situations where a 3 port valve has been fitted to a unvented cylinder where the high limit stat has cut out and heat still being transferred. On one particular occasion where a Worcester had been fitted with a pump over run and no bypass so it was pumping the heat round the cylinder. On this one it was discharging at a considerable rate, should that T&P failed it could have lead to a serious problem.
Originally posted by mtmcgavock View PostAnother occasion where a Viessmann boiler with internal diverter had been fitted, the temperature sensor had fallen out and the HW left on constant. Resulted in the cylinder overheating with no thermal cut off. Had a 2 port valve been fitted following the manufacturers instructions it would have prevented this.
Originally posted by mtmcgavock View PostWhilst I agree it is very unlikely a deadly situation could occur as a number of components in the chain would have to fail, starting to deviate from the manufactures instructions shouldn't occur. The regulations are there, but the manufactures instructions should be followed. If you had an issue down the line they'd be very quick to say it wasn't fitted correctly. As gas safe always state with gas appliances, always follow the manufactures instructions.
Originally posted by mtmcgavock View PostUse a 3 port valve, but put a 2 port valve before the cylinder. At least then should anything change on the installation that's out of your control you've always got the fail safe of the 2 port valve.
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Originally posted by The EVOHOME Shop View PostCustomers are more intelligent than you give them credit for (or certainly that's my experience of being in the trade and dealing with 1000's of customers through our multiple businesses) - tell them this is what you have done and that they can contact the installer if they need any further information. I personally have always left plans of my heating system design with the customer and this removes possible conflicts in the future.
Originally posted by The EVOHOME Shop View PostThis is nonsense. A 3 port valve fitted 'correctly' as you say would pass water to the unvented cylinder without a 2 port valve... Things naturally fail that's why there are multiple safety systems that should be checked annually.
Originally posted by The EVOHOME Shop View PostAbove 88 degrees from the boiler? I would imagine it was hot but still not dangerous - you are making excuses now.
Originally posted by The EVOHOME Shop View PostMost manufacturers would be happy using a 3 port valve in the method I have described - I know Joule have no issues with this.
I'd like to see Heatrae or one of the other big manufactures put it in writing that it's fine to do what you are saying. Also why would they send a 2 port valve with every cylinder if it wasn't necessary? They could save themselves a fortune.
Originally posted by The EVOHOME Shop View PostWhy? This would be like fitting a 2 port valve and then fitting a second 2 port valve behind it (and seems ridiculous from an engineering perspective).
Whilst I quite respect where you are coming from, I think we'll have to agree to disagree on this one.
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Whilst customers may be intelligent, the same cannot be said for all installers. Recently, I had an issue with the Combination Valve on my Oso cylinder. I called out 2 G3 engineers to look at the problem. One failed to comment on the fact that the valve had been installed at the bottom of the cylinder - below the Tundish - and he couldn't tell me why the cylinder was failing to hold an air gap. The second engineer took one look at the valve and then went outside to check the outflow pipe which he could see was dripping water from it. He explained to me why it was important that the Combination Valve was positioned above the Tundish. Obvious when one thinks about it. The other engineer came back with a quote just to replace the old valve with no change to the pipework! Had I not asked for two quotes, I suspect that I would have been none the wiser.
FWiW, I had a new boiler installed earlier this year. The installer has left the original HW (2-port) valve in place wired as per OSO's installation manual. The CH 2-port valve was replaced with an inline valve to give HW priority (it closes when the HW valve opens).
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Interesting.
The Megaflow we are having installed will have two motorised valves on the hot water feed, one controlled by the tank, set at the tank maximum, one controlled by the Evohome cylinder kit.
Overkill? Probabably, but since we paid for both valves we may as well use them.
As an interested, and very experienced amateur I am constantly amazed that you require a certificate to install a non-vented cylinder, yet there seems to be disagreement in the trade about how to do it. Makes me wonder if certification is just another way of persuading those of us who are totally competent, but lacking the certificate, to part with our cash.
Far better if we were able to carry out the work and have it signed of by building control.
Grenfell Tower reminds us all that experts are often that in name only, and that you should take even expert advice with a pinch of salt. Caveat emptor for services and goods.
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Originally posted by the crooner View PostInteresting.
The Megaflow we are having installed will have two motorised valves on the hot water feed, one controlled by the tank, set at the tank maximum, one controlled by the Evohome cylinder kit.
Overkill? Probabably, but since we paid for both valves we may as well use them.
As an interested, and very experienced amateur I am constantly amazed that you require a certificate to install a non-vented cylinder, yet there seems to be disagreement in the trade about how to do it. Makes me wonder if certification is just another way of persuading those of us who are totally competent, but lacking the certificate, to part with our cash.
Far better if we were able to carry out the work and have it signed of by building control.
Grenfell Tower reminds us all that experts are often that in name only, and that you should take even expert advice with a pinch of salt. Caveat emptor for services and goods.
However, as a second generation heating installer, do I think the G3 regulations are out of date? YES I do!
Unfortunately installers have stopped thinking about heating systems and just follow the 'rules' without question, as per the conversation above. Many installers don't even understand basic heating system design.
It is not the fault of installers that they have stopped thinking, as it is easier to just throw systems in as you are told to. However, this may mean that the best engineering solution for the customer is missed, especially with OpenTherm and energy saving minded people like me (an extra 22mm 2 port valve on a system is a waste of money and energy in my opinion). We are going into times where energy waste must be minimised.
I am currently working on the evohome and the Intergas modulation 'issue'. Some installers have stopped fitting evohome with Intergas boilers because of this issue. On initial assessment there seems to be a lack understanding from installers about evohome and OpenTherm. The good news is that I now have 3 evohome and Intergas ECO RF systems working and fully modulating on OpenTherm (and a robust way of getting it to work).
There will be more news to this to follow soon, but it's really good news for us as we specialise in the sale of both products online! 👍🏻
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i still don't understand what the issue is/was with OT and Intergas. I never quite understood the "won't work with multiple zones" issue. i know that Viesmann and Ideal had the issue of the boiler ignoring its own set max and heating till it's physical max. But has anyone actually articulated the issue with the Intergas?
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Originally posted by bruce_miranda View Posti still don't understand what the issue is/was with OT and Intergas. I never quite understood the "won't work with multiple zones" issue. i know that Viesmann and Ideal had the issue of the boiler ignoring its own set max and heating till it's physical max. But has anyone actually articulated the issue with the Intergas?
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Originally posted by fergie View PostSo what was at fault and how was it resolved?
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