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Thread: Evohome and OpenTherm boiler recommendations?

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  1. #1
    Automated Home Legend
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    Default Evohome and OpenTherm boiler recommendations?

    Hi All,

    I know the information on which boilers do and don't play well with Evohome OpenTherm is buried in this forum somewhere, and I've read quite a bit of it in the past (and forgotten more than I read) but a search is failing to turn up what I'm looking for as I suspect it's spread across many threads buried in the middle of threads with seemingly different topics...

    So can those of you actually using Evohome with OpenTherm let me know what boiler brand/series you're using, whether it works 100% or whether there are any caveats or workarounds required?

    My reason for asking is an interesting one - we've found out that we are eligible for a grant to cover (most of) the cost of a new boiler and system due to our circumstances, including the fact the existing system is not far off 30 years old now...

    While it has been fairly reliable, many of the radiators need replacing anyway, it's an open vented system with most radiators on 8mm microbore, a somewhat limescaled heat exchanger and the 74% (when new, probably not now!) efficiency of the boiler is really costing us a fortune in the winter...

    I have no idea how these kind of grants work - we're due for an onsite inspection on Friday to look at the old system and discuss the options, and I have no idea whether we would just be offered a certain model of boiler take it or leave it or whether there is some flexibility there or whether we could contribute a certain amount to for example upgrade to a model that supports OpenTherm, as I'd quite like my next boiler to at least be OpenTherm capable even if I don't use that right away.

    Hence the query about good OpenTherm compatible choices especially in the more budget ranges that they'd be likely to be offering on these kind of grants. I'm not completely wed to the idea of OpenTherm if its going to be too expensive or just not an option - I've never had it before after all... but if I can for minimal extra cost, why not.

    The current boiler is 23kW and is also running a 100 litre hot water cylinder however at 74% efficient that's only about 17kW out at best, and that seems to be enough to heat the house and hot water at the same time. (Just) The current cylinder is too small for the bath in the house now (just barely runs an adequate bath before running cold) and there is no more room for a larger cylinder in the boiler closet and to be honest I'd rather not have Evohome controlling hot water anymore after all the problems the CS92A has given me over the years!!

    So a replacement is almost certainly likely to be a combi-boiler which will simplify the system dramatically. No more cylinder, two open cisterns removed from the loft, two zone valves no longer needed, two BDR91's no longer needed and best of all, CS92A no longer needed. The shower is electric so the boiler is only used for bath and kitchen/bathroom hot taps.

    The boiler lives at floor level in a moderately large closet inside the back porch backing against one of the kitchen walls - a large enough closet that a 100 litre cylinder sits above it anyway. So the new boiler doesn't have to be super compact like one you might fit between kitchen cabinets, and it is out of sight and earshot so noise/looks aren't really an issue either.
    Last edited by DBMandrake; 2nd March 2021 at 01:35 PM.

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