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Evening all,

My sister is having a bit of trouble with her CHS at her new house at the moment. She informs me that when it gets to temperature it's knocking off the heating as well as the hot water.

I've not worked on any heating system personally but I said I'd go over and check out the general electrical condition - sounds to me like a thermostat problem or maybe at a push a problem with the controller.

As I'm going over tomorrow, I thought it would make sense to see if anyone has encountered similar problems, or have an idea of certain things to look out for while going over the system?

Many thanks
 
You need to start by identifying the system she has first of all,
e.g. S plan, Y plan and so on etc.
Once you've found that out you should know what is supposed to happen, in what order and that in turn will start you in the right place for testing components.
 
You need to start by identifying the system she has first of all,
e.g. S plan, Y plan and so on etc.
Once you've found that out you should know what is supposed to happen, in what order and that in turn will start you in the right place for testing components.

It's a Y plan system. When calling for heating from the programmer without H/W it doesn't seem to contact the boiler.

Has anything recently changed on the heating system? boiler?

Only radiators but the problem was there before these were changed.

So how does she 're-set' the system to start it heating again?

Unsure, will try to find this out.
 
Check the programmer it should be on 16 programmes and there should be a wire on the DHW off terminal at the programmer.
Check that before anything else.

Quite often, the DHW off is left out if it's been wired by someone who doesn't understand Heating wiring. As a get out of jail card, they change the programmer to 10 programs so it kind of works in a fashion and people get used to it.
This issue normally presents itself after a new programmer or boiler has been installed, when you realise that the system won't do what it's supposed to do.

It can be a bit random as the cylinder temp can alter how it behaves and circumstances dictate when it throws a wobbler.
 
Check the programmer it should be on 16 programmes and there should be a wire on the DHW off terminal at the programmer.
Check that before anything else.

Quite often, the DHW off is left out if it's been wired by someone who doesn't understand Heating wiring. As a get out of jail card, they change the programmer to 10 programs so it kind of works in a fashion and people get used to it.
This issue normally presents itself after a new programmer or boiler has been installed, when you realise that the system won't do what it's supposed to do.

It can be a bit random as the cylinder temp can alter how it behaves and circumstances dictate when it throws a wobbler.

Much appreciated! I'll begin with that.
 
Not much joy I'm afraid. The programmer is quite old which I don't think helps, and can only be either 2/3 ON/OFF modes. The plumber is going to try changing the three-port valve today and see how he gets on with that as he's been advised that's where the problem could lie if not in the wiring.
 
Not much joy I'm afraid. The programmer is quite old which I don't think helps, and can only be either 2/3 ON/OFF modes. The plumber is going to try changing the three-port valve today and see how he gets on with that as he's been advised that's where the problem could lie if not in the wiring.

Did you look at the wiring in the programmer?
Did you look if it had a DHW off connection ?
Is it definitely a Y plan ?
Trying something is not good enough. You need to find out the answer before you start paying for parts and labour from a plumber.
It won't be cheap !
What if he guessed wrong ?
There is always a way of testing component parts of a heating system.
 
Did you look at the wiring in the programmer?
Did you look if it had a DHW off connection ?
Is it definitely a Y plan ?
Trying something is not good enough. You need to find out the answer before you start paying for parts and labour from a plumber.
It won't be cheap !
What if he guessed wrong ?
There is always a way of testing component parts of a heating system.

I did, programmer worked fine from what I could tell. It had a DHW off connection and it's definitely a Y-plan.

As for the trying being not good enough part - that's probably true however she was clearly informed that I don't know a lot about CHS heating systems and would just be able to check the general state of the wiring to see if anything was amiss. He isn't ordering anything however, he has got one that can be tried out and returned to stock if it doesn't fix the problem.

I suggested if that doesn't fix the problem, getting in a heating engineer to find out the problem although she does want to upgrade to a combi-boiler sooner rather than later anyway.
 
Ok, I get where you're coming from. If you're a trainee and you've never dealt with heating systems before, it could be a bit daunting.

I do think it's a missed opportunity to learn something that may be valuable to you in future though.

I've never been one for guesswork.
It could be a valve problem but like I said before, that can be tested and proved like most things.

have a look at the Honeywell Y plan diagrams on google images
 
Ok, I get where you're coming from. If you're a trainee and you've never dealt with heating systems before, it could be a bit daunting.

I do think it's a missed opportunity to learn something that may be valuable to you in future though.

I've never been one for guesswork.
It could be a valve problem but like I said before, that can be tested and proved like most things.

have a look at the Honeywell Y plan diagrams on google images
 
Am with the last plumber you should have powered up the valve both ways and seen if the the switch made turned the pump on and a tip is to disconnected the feed in the boiler to the controller pcb so your not turning the boiler off and on. You can tell if the water getting around the system as well. Let you know that the DHW is going round the tank and not the rads. Also make sure the earth isn't used as a live conductor, I've been to loads of these that have been wired up wrong.
 
So I was looking through a picture that I took of the connector blocks and noticed that a neutral looks like it's dropped out of the three-way connection along with the supply neutral & boiler/pump neutral.

This makes sense to me as when the H/W is active, the pump is a closed circuit and therefore the cyl stat has a neutral path. When the water reaches temperature, the pump shuts off and the heating loses its neutral path.

I'm going to take another look over the weekend, but figured this actually makes a lot of sense given the scenario.
 
So I was looking through a picture that I took of the connector blocks and noticed that a neutral looks like it's dropped out of the three-way connection along with the supply neutral & boiler/pump neutral.

This makes sense to me as when the H/W is active, the pump is a closed circuit and therefore the cyl stat has a neutral path. When the water reaches temperature, the pump shuts off and the heating loses its neutral path.

I'm going to take another look over the weekend, but figured this actually makes a lot of sense given the scenario.
 
So I was looking through a picture that I took of the connector blocks and noticed that a neutral looks like it's dropped out of the three-way connection along with the supply neutral & boiler/pump neutral.

This makes sense to me as when the H/W is active, the pump is a closed circuit and therefore the cyl stat has a neutral path. When the water reaches temperature, the pump shuts off and the heating loses its neutral path.

I'm going to take another look over the weekend, but figured this actually makes a lot of sense given the scenario.

You've looked at that wrong, unless it's wired wrong !
There should be no switched neutrals ( unless I've misunderstood your point) ?
If you look at the wiring diagram I mentioned before, you'll see how it's meant to be. The only difference should be that the pump should be wired from the boiler, due to the pump over run. ( if boiler needs one and most modern ones do).
 

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