So the first job is to check if the valve works as it should:-)
I would first test the continuity between the orange and grey with the power off, then I would stick 230V across the brown and blue and see if the orange wire becomes live when the motor operates.
I would treat this as a "It used to work until a 4 wire valve was fitted and then a pro messed it up job".
First job is to get the thermostat wired properly, (Live, Neutral, and Load, for a start) and controlling the pump, that will give a working system better than it is now. If it stops there, that's ok.
Then to check the valve actuator. Something certainly isn't right, and I can only see what by taking it off the valve. And that's where the contortionist part comes in...
When I was last there, with the programmer pulled out, I could only find any sort of continuity, a couple of hundred ohms, I think, between one of the motor terminals and one of the valve terminals, and that could have been backfeed through the pump, looking at the Actual Wiring Diagram. There was no change at any terminal pair when I moved the manual operator to 'ON', and it felt as though it was moving the valve against the spring. What position the valve was in, I have no idea. This relates to my un-answered question earlier about the arrangement of the tongue flats of a CH valve.
I am not even sure if it ever worked as a 'C' Plan system should have done. But when I'm finished, I intend it to do so. A pro did mess it up, though, the wiring could never have been this bad when it was first installed. I hope. Even if the pro didn't mess it up, he left it in a mess, and it certainly doesn't control the radiators.
Watch this space, next visit is tentatively set for Tuesday.
In message , Davey writes
After being shut down last summer, my Sister's heating system would not bring on the boiler. The diverter valve had been replaced the previous year so I was not expecting any wiring or actuator faults.
With the cover off, poking the gear wheel with a screwdriver allowed the valve to close further, operate the microswitch and start the boiler. It has been OK since then.
IANAP:-)
Thanks for that.
All in all, a successful afternoon, apart from the DMM. It was very cheap, so no great loss.
I don't think it matches any Honeywell's letter plan definition - B for bastardized perhaps?!
In concept, it's similar to the old (pre "plan") gravity HW and pumped CH system - where you couldn't have just CH without HW, and where the room stat controlled the pump when CH was required. Yours is a variation of that, with boiler *and* pump running for HW, and then a zone valve for CH.
Sounds like it wouldn't be too difficult to convert to an 'S' plan - you'd just need another 2-port zone valve in the HW circuit, plus a cylinder stat (if there isn't one already) and then re-jig the wiring to suit.
As good as any.
But why bother? It's a functional system right now, and space is very limited. If it ain't broke......
Quite. The only possible improvement I can see (without getting very OTT for a historic system) is separate circuit temps to improve efficiency slightly.
NT
Very slightly, for a system that costs very little to run as it is. There are flats above and below, so no point in even thinking about it.
The job is done!
That is the bit I don't get. If the tank stat is saying I'm hot enough but the room wants some heat, hot water is still circulated to the tank regardless?
If the tank is hot enough, then the pump and boiler both shut off, which means that the radiators do not get any hot water. Not perfect, but it's never been a problem. The boiler 'stat is set very high, so the boiler is effectively controlled by the room 'stat and its own thermostat, the tank is always asking for heat, and the pump runs all the time that the programmer asks for heat. It's not a perfect system, but there are effectively no problems, certainly nothing to worry about changing pipework for. I wouldn't have designed it that way if it had been me, but it wasn't.
it's harmless. When DHW temp = primary temp, no heat transfers to the DHW. In practice just enough transfers to deal with standing loss.
The other simple control option is to have all primary water go through the cylinder coil, then either through the rads or straight back to the boiler.
NT
Just spotted this due to the change of the subject.
No name AFAIK but I have seen it before and I know how it works and why it is used. It's due to the lack of gravity on the HW side of the system. I like the name "B Plan" as suggested by Roger and his description on the setup you have is very good. The tank stat BTW has no purpose at all IMHO.
I did try to warn you about that. However it seems I pressed "reply" and instead of "reply group"................Sorry about that as I did also say in that "post" that my email was valid and feel free to email me whilst you were there if you needed any help.
Yep a simple 2521 actuator would do the job. And the programmer is operating correctly for the "B plan".
Not sure on that. But you fixed it so who cares?
Whoops:-) We have all done it.
May I recomend a
or similar tester?
Well done fella.
Thank you!
How about "for the pleasure derived from having created a thing of beauty from an abomination"?
Seriously, whether it's functional depends on how you define "functional". OK, the boiler and pump both work, and provide hot water and space heating after a fashion.
*But*, from what I can make out, you can't have space heating without the possibility of heating the DHW up to boiler temperature. The water coming out of the taps could thus be dangerously hot unless you turn down the boiler stat to a level which will probably not make the radiators hot enough in cold weather. In addition, the boiler is cycling on its own stat and wasting energy even when there's no demand. It would be so easy to convert it into an S-Plan system where you would have independent control over DHW and CH and with boiler interlock so that the boiler will shut down when there's no demand from either circuit.
That sounds just like a gravity fed system:-)
especially if this is a "Let" I would be worried about this and a possible case of negligence, if anyone was injured by scalding hot water out of a tap.
Well, it behaves in a similar way, despite being fully pumped - yes.
When I installed a gravity HW/pumped CH system in my previous house way back in the 1960's I did at least put a Cyltrol valve in the HW return - which stopped the DHW getting too hot. Davey's system doesn't even have anything which does that.
I have thought a bit about this. In answer to Fredxx, it is not a let, in fact, the lease expressly forbids this. But it is still a valid thought, so:
My own experience working in industry tells me that holding metal in a
150 F. atmosphere (industrial car body paint ovens) is perfectly acceptable, whereas 160 F. becomes unsustainable after more than a few minutes. This would indicate that air at 150 F. is ok. For water, I can find various tables that indicate that 150 F. water should not be kept in contact with skin for more than about 1.5-2 seconds, risking burns if kept there longer. This sounds fair, considering the difference in thermal properties between air and water, and provides adequate time to snatch a hand away from a hot stream of water from a tap. So for safety, 140 F. would seem to be a target maximum hot water temperature, which is what I have seen other tank thermostats set to.For the system described, the now so-called 'B' system (!), the first consideration is that the tank 'stat needs to be set higher than the boiler 'stat, to keep the valve open and water circulating through the radiators if needed. If it were the other way round, it could create the perverse condition where the circulation was shut down due to high tank temperature, but the lack of circulation would mean that there was no way for the heat to be lost. So we will put the tank 'stat 10 F. higher than the boiler 'stat. If we then set the boiler 'stat at 130 F., the circulated water can never exceed this temperature, as this is where its heat comes from. The tank 'stat would be set at this plus 10, ie 140 F., ensuring continued circulation (according to the programmer), and so even if the boiler 'ran away' for some reason, the tank 'stat would shut down the circulation and Domestic Hot Water supply at 140 F, a full 10 F. below the 150 calculated earlier. This would still be the undesirable no-circulation condition described earlier, but would at least shut off the pump and boiler, as the boiler is powered through this 'stat. If both radiator control and Hot Water proved fine, then both thermostats could be set 10 F. lower, maybe even twice.
So the next time I go there, I will set the tank 'stat at 140 F., and the boiler 'stat at 130 F. And although I have no way to check the finite accuracy of them, I will operate them and compare them to each other, to confirm an agreement or not of their settings, and testing of the hot water to check that it is not scalding.
I believe you need a rethink of the setup.
Let's start with a clean sheet.
Which of these are true?
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