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Thread: Adding Evohome to 25+ year old CH system...

  1. #1
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    Default Adding Evohome to 25+ year old CH system...

    My parents have been so impressed with my evohome system when they visited that they have decided they want it for themselves. #

    Currently they have a 25+ year old Oil Fired central heating system, no thermostat, no TRV's etc. DHW capability was added at a later date (approx 15yrs ago).

    I'm trying to visualise what amendments will need to be made to the plumbing in order to fit Evohome effectively. Would just be looking at fitting the base pack and hot water pack to start with, no TRV zoning yet.

    This is the current boiler and pipework setup (in the garage):

    IMG_1819.jpgHeat.jpg

    So, I was thinking a honeywell 3-port mid position valve, or two 2-port valves on the boiler outlet pipework. Would this work?

    What about a boiler bypass, as there currently isn't one (no need). Would one strictly be required, as any time the boiler is on (commanded by boiler relay), one or both of the zone valves would be open? There is no pump over run that I know of.

    Any advice appreciated

    Thanks,

    Gareth

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    Hi Gareth,

    Firstly I need more pics, especially of the airing cupboard and the pipework there. I assume there is no controls at all, not even on the cylinder? Also, where is the open safety vent pipe to the header tank for the boiler as it is not visible?

    OK, well once I have some more input I would suggest keeping the system as simple as possible - S Plan minus would be my suggestion. This would be the simplest system to install and would save you a motorised zone valve on the heating flow pipe - it does however require HR92's on all rads.

    So, Base Pack, Hot Water Kit, 22mm Motorised Zone Valve for cylinder, HR92's, V120-15A Radiator Valves and Automatic Bypass Valve is a basic spec list without further detail.

    Any questions at all, please ask.

    Richard

    P.S. I just noticed the oil de-airation device is fitted internally! Highly illegal, get it moved externally!!!

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    Hi Richard,

    There are no controls on the cylinder whatsoever. The system is very old (and useless IMO). All hot water is gravity fed (making showers great fun!) and the system will be an open vented system. The boiler is located in the garage some 40m from the airing cupboard.

    The only control the system has (apart from an on/off programmer) is the red hand-operated valve you see at the bottom of the photo. Closing this simply allows the hot water cylinder to be heated on its own, without the radiators. However the central heating can't be on exclusively - if the CH is on, the cylinder is being heated (which, considering it's not that well insulated, costs a lot! I believe they are paying 3k+ annually on kerosene.

    HR92's on all radiators is going to be impossible I'm afraid. It's a large house (40+ radiators, from memory) so even converting all radiators to TRV would be almost 500 in parts, let alone the 2k+ cost of HR92'ing them all. I was going to install Evohome base pack, hot water pack and gateway simply for its own thermostat ability, plus the added benefit of being able to control the system from afar using the Evohome iPhone app. Zoning of the most used rooms can be done at a later date.

    I will ask for more photos, but there really isn't anything to see in the airring cupboard. Regarding the open safety vent pipe - no idea. Would it usually go straight from the boiler?

    The Tiger Loop? Hmmm, been there for 15+ years, can't see them moving it now! It's in Ireland, perhaps the regs are different? lol

    Thanks

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    Tigerloop regs are same anywhere, but just bear in mind oxygen + oil vapour = combustion!

    More pics would be good, but don't see why evohome cannot be fitted. OK, so 3K+ per year on fuel so I would say a 1200 saving per year here could be achieved. A reasonable payback could be achieved, but as you said a large outlay. You can fit both motorised zone valves (heating and hot water) and add HR92's now and again, building the system up as and when it could be afforded. Maybe do the ground work, so do the Base Pack, Hot Water Kit, 2x motorised zone valves, ABV and change the rad valves so they are compatible?

    Open Safety Vent should go from top of boiler to the header tank, but there are many configurations for OSV's.

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    Ok great, thanks.

    So an automatic bypass valve needs to be fitted, yes? This would require extra pipework wouldn't it? (Was hoping it would be relatively simple to do this myself, without having to enlist a heating engineer/plumber).

    I only ask again as there's no way the boiler/pump can be on when both zone valves are closed, especially if I configure the relays to operate the zone valves, and they in turn operate the boiler (s-plan).

    Regarding the open safety vent, dad says there is definitely a vent pipe leading up from somewhere in the heating system into the loft and looping over into the central heating header tank - this be it? It's nowhere near the boiler though.
    Last edited by garmcqui; 17th March 2015 at 09:43 PM.

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    I suggested fitting an ABV as the likelihood is that the system would be drained and with it likely you will 'smart zone' in the long term, it would be a logical move to fit one (get all the wet system items done in the initial wave of works). It is literally a pipe from the positive side of the pump (before the motorised zone valves) to a return pipe - really not much work to do when the system is drained.

    I couldn't see from the photo if there was an OSV or not, hence the question.

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    Hi Richard,

    I received my Evohome base pack and hot water pack today - very fast shipment so thank you!

    However I'm becoming concerned that I won't be able to safely fit Evohome (more specifically, zone valves) to my parents badly designed heating system.

    Reason being I have done a little investigating. It seems there is no open vent to the f&e tank in loft, just a 22mm cold feed pipe (which I presume also serves as an expansion pipe). Someone has told me this may be classed as a "combined feed and vent"?

    This is a rough outline of the current system:

    Current.jpg

    As you can see, there is no vent as such and the cold feed pipe connects into the system between the pump and the hot water cylinder. The following diagram shows where I was going to place the zone valves for CH and DHW:

    Proposed.jpg

    Will this work? My worry is if the CH valve is open, but the DHW valve closed, the expansion/feed pipe is isolated. Can I get around this by moving the DHW zone valve further along the pipe, closer to the cylinder (so that it is "after" the cold feed connection)?

    Thanks, any help appreciated.

    Gareth

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    Anyone?

    Would this position be better, so the DHW zone valve (when closed) doesn't isolate the cold feed/expansion?

    Proposed2.jpg

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    Quote Originally Posted by garmcqui View Post
    Anyone?

    Would this position be better, so the DHW zone valve (when closed) doesn't isolate the cold feed/expansion?

    Proposed2.jpg
    take a look at the schematics in the appendix of the evohome installation guide
    I work for Resideo, posts are personal and my own views.

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    have done this, there isn't so much as a mention of an open vented system, let alone advice on where to site the zone valves.

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