Sunvic valve and heating/hot water issue

keystone

If the mid position valve is faulty (whether the head or the valve itself) then its highly likely that it will allow CH to operate with only DHW selected or vice versa. Nothing at all to do with the way that the system is wired or plumbed. What is your programmer make/model?

Cheers

ValHaller

keystone wrote: »

If the mid position valve is faulty (whether the head or the valve itself) then its highly likely that it will allow CH to operate with only DHW selected or vice versa. Nothing at all to do with the way that the system is wired or plumbed. What is your programmer make/model?

Cheers

We have no evidence that the system is indeed correct. OP has moved in to discover the situation as is - the system has never been observed to work any other way. Really, to ignore these issues invites sending OP on a wild goose chase or doing damage. OP has already forced something with a screw driver when I think you and I both would be checking much less agressively

Calleja wrote: »

Thanks ValHaller. Looking at the programmer manual, it seems to support use of CH/HW independently. The plumbing, on the other hand, I wouldn't have a clue.....any quick way of telling by looking? Apologies if its a stupid question!

If I do need a new one of these valves, can it be fitted by a plumber or does it need to be a gas safe engineer?

Thanks all!

It is not a stupid question and I feared you would ask .... Basically you need to either get a book on Central Heating from the library or spend half an evening googling and find some explanations of dometic CH. Your system should be plumbed as a 'fully pumped' system - but you may want to look at 'gravity system' too for comparison.

I would not put money on the plumbing being wrong, but it would be no surprise. The effort you put in on understanding this will be worthwhile regardless of what the problem is

Calleja

Thanks, the programmer is a Sunvic select 207XL. But its just a programmer, there isn't a thermostat (its quite an old system).

I appreciate all your help and patience! I will attempt all your advice when I get back - at least the heating works and thats the important thing for my house sitter!

keystone

ValHaller wrote: »

We have no evidence that the system is indeed correct. OP has moved in to discover the situation as is - the system has never been observed to work any other way.

With all due respect equally we have no evidence that it isn't correct. Its a classic failure mode of a faulty mid position valve that it doesn't settle in a position that shuts off either one port or the other allowing both to appear to be operating when only one is selected. OPs recent statement that there is no roomstat to control CH might also have something to do with it.

Really, to ignore these issues invites sending OP on a wild goose chase or doing damage.

I'm not ignoring any issues but equally I'm not dreaming up other potential issues either on the off chance that they may or may not exist. That is potentially the path to wild goose chases. I prefer to fault find one step at a time TBH else there is enormous scope for confusion.

OP has already forced something with a screw driver when I think you and I both would be checking much less aggressively

Concur.

Cheers

keystone

Calleja wrote: »

Thanks, the programmer is a Sunvic select 207XL. But its just a programmer, there isn't a thermostat (its quite an old system).

Ok thanks. Some old programmers have a mechanical interlock that prevents CH being on if DHW is also not on. Yours doesn't. Just checking and eliminating.

Cheers

ValHaller

keystone wrote: »

I prefer to fault find one step at a time TBH else there is enormous scope for confusion.

Which is precisely the argument for establishing what the system is - ie what you can expect it to do - BEFORE you pick on some likely component (3 port valve) and start fault finding on it for not doing something the system might not support.

OP may not waste too much time if he tackles it your way, provided he realises that on the available information, the system has not been shown to support the mode of operation he expects.

keystone

ValHaller wrote: »

Which is precisely the argument for establishing what the system is - ie what you can expect it to do - BEFORE you pick on some likely component (3 port valve) and start fault finding on it for not doing something the system might not support.

You do realise this paragraph is pure gobbledegook don't you old son? It was fairly clear from your previous posts that your expectation is the same as mine. Thats its a conventional Y plan system otherwise why would you be looking for evidence that it is a) plumbed incorrectly and/or b) wired incorrectly. There is no evidence to suggest either. Methinks you might have forgotten the First Rule Of Holes.

OP may not waste too much time if he tackles it your way, provided he realises that on the available information, the system has not been shown to support the mode of operation he expects.

Thats mainly because nine times out of ten the problem he reports is down to the three port valve and you are wrong in one respect - it wasn't me that fingered the valve in the first place. Eliminate the most obvious first rather than - what was it you said Oh yes - a wild goose chase looking for something obscure and extremely unlikely and which is TBH clearly confusing the OP.

Cheers

ValHaller

keystone wrote: »

You do realise this paragraph is pure gobbledegook don't you old son? It was fairly clear from your previous posts that your expectation is the same as mine. Thats its a conventional Y plan system otherwise why would you be looking for evidence that it is a) plumbed incorrectly and/or b) wired incorrectly. There is no evidence to suggest either. Methinks you might have forgotten the First Rule Of Holes.

If you think what I wrote is gobbledegook, then I think your tag line is quite apposite in capturing our differences:

The difference between genius and stupidity is that genius has it's limits. - Einstein

I am afraid I have recognised my limitations in communicating the point to you.

keystone

ValHaller wrote: »

If you think what I wrote is gobbledegook, then I think your tag line is quite apposite in capturing our differences:

Ahh if all else fails resort to the ad hominem approach. I'd thought better of you than that.

I am afraid I have recognised my limitations in communicating the point to you.

Theres nothing wrong with your point in principal. It is its application in the context of this thread with an OP who is looking for help and guidance being told to go and look up operation of central heating systems thats inappropriate.

chopper1985

Hi, just hoping for some help. I have a sunvic 207 xl and every time i put the hot water on the heating comes on as well. Bit of a pain when its hot out. Any help would be appreciated. Thanks.