Y-plan heating

[D-4-Y-v-V]

Hi all,

New member, recently qualified.

Went to a customer's to fault find their heating sometimes working, sometimes not following a brand new Worcester boiler being fitted. long story short found a bad termination.

Upon inspection however, I found that a cylinder stat had been tied to the pipe leaving the boiler just before the circulation pump. There's also a cylinder stat on the hot water cylinder itself.

The stat was wired to 'heating only' conductor from the 3-way valve so I wasn't sure if this was also tricking the system to think the water was hot enough, when infact it wasn't.

Just curious if this is common practise now, or if not, what up with that? Completely baffled by such an installation!

I was tempted to completely remove it but wanted to check if anyone's come across this before with a reasonable explanation.

Thanks,

 

[SPECIAL LOCATION]

Possibly could be a frost-stat rather than a cylinder stat..?

Detecting if the pipe gets too cold, to trigger the boiler to fire up and stop the whole lot freezing up, if property left unused for a while during winter cold weather..

Especially if the boiler is installed in an un-heated part of the house e.g. a garage.

e.g.
https://www.heatandplumb.com/acatal...17659219&utm_content=SH2 - Honeywell Shopping

 

[D-4-Y-v-V]

Possibly could be a frost-stat rather than a cylinder stat..?

Detecting if the pipe gets too cold, to trigger the boiler to fire up and stop the whole lot freezing up, if property left unused for a while during winter cold weather..

Especially if the boiler is installed in an un-heated part of the house e.g. a garage.

e.g.
https://www.heatandplumb.com/acatal...17659219&utm_content=SH2 - Honeywell Shopping

Deffinatly not. It was set to 50 degrees.

Boiler in the kitchen, just your average install.

 

[SPECIAL LOCATION]

Deffinatly not. It was set to 50 degrees.

Boiler in the kitchen, just your average install.

Well that has exhausted my Sunday night post beer suggestions....!!

Lets hope someone else can offer further ideas?

 

[Geoff1946]

Quote - Upon inspection however, I found that a cylinder stat had been tied to the pipe leaving the boiler just before the circulation pump. There's also a cylinder stat on the hot water cylinder itself.

Isn't the pump integral to the boiler, and on the return?

There are good manuals available on line from Worcester, including how they should be wired.

 

[NozSpark]

Without seeing it id go with what Spec Loc says,,,, if its on the return pipe for the radiator circuit it could be in series with a frost stat, so that when the pipework reaches a minimum temperature it sees the frost protection as satisfied

 

[D-4-Y-v-V]

Without seeing it id go with what Spec Loc says,,,, if its on the return pipe for the radiator circuit it could be in series with a frost stat, so that when the pipework reaches a minimum temperature it sees the frost protection as satisfied

Hi both,

It's on the pipe leaving the boiler just before the circulation pump, which is just before the 3 way valve.

 

[ProDave]

Hi all,

New member, recently qualified.

Went to a customer's to fault find their heating sometimes working, sometimes not following a brand new Worcester boiler being fitted. long story short found a bad termination.

Upon inspection however, I found that a cylinder stat had been tied to the pipe leaving the boiler just before the circulation pump. There's also a cylinder stat on the hot water cylinder itself.

The stat was wired to 'heating only' conductor from the 3-way valve so I wasn't sure if this was also tricking the system to think the water was hot enough, when infact it wasn't.

If it has just had a new boiler, why did they not get that installer back to fix their new install?

Has this mystery pipe stat always been there or was it something new fitted when the new boiler was installed? Again another question to be asking of whoever fitted the new boiler.

The fact they got someone else to fix the problems suggests they have an issue or don't trust the original installer for some reason, and there might be a lot more to this than they are telling you.

The sort of job I would turn down as there is likely a big can of worms waiting for you to open it.

A lot of problems with Y plan are the 3 port valve misbehaving. Was a new one fitted?

 

[D-4-Y-v-V]

If it has just had a new boiler, why did they not get that installer back to fix their new install?

Has this mystery pipe stat always been there or was it something new fitted when the new boiler was installed? Again another question to be asking of whoever fitted the new boiler.

The fact they got someone else to fix the problems suggests they have an issue or don't trust the original installer for some reason, and there might be a lot more to this than they are telling you.

The sort of job I would turn down as there is likely a big can of worms waiting for you to open it.

A lot of problems with Y plan are the 3 port valve misbehaving. Was a new one fitted?

No, no new valve fitted. That seems to be functioning just fine.

The owner of the home doesn't know when it was fitted, but it was very white and new looking so my assumption was rather recently.

They also left live conductors on the old room stat as they now also have a wireless one.

I don't know the ins and outs, all I know is I got their heating working as it wasn't working very well.

I wasn't really going to tamper with this mystery stat unless I found it to be causing the issue, just curious really if anyone had seen anything like it before.

 

[ProDave]

I have only seen pipe stats normally on hybrid systems with a stove with a back boiler, to make sure the circulating pump comes on when the stove is heating the water.

 

[binky]

I wasn't really going to tamper with this mystery stat unless I found it to be causing the issue, just curious really if anyone had seen anything like it before.

Lesson 1, don't change anything unless you really have to, especially odd wiring...

Lesson 2, there's all sorts of controls you can get these days, including such things as weather compensation controls connected to an external weather station. The days of a simple timer and room stat are long gone.

 

[Phoenix]

Are you sure the pipe stat was not on the return pipe from the coil in the cylinder? The rate of heat transfer from the coil to the stored water will depend on the temperature gradient across the two, so if the water is coming back at x deg C, we can usually assume that the water in the cylinder is within a few degrees of x, unless something improbable has occured such as:

* The flow is significantly in excess of x deg C, thus you can have a sizeable reduction across the coil and return still in excess of X (might occur for very hot flow temps and very low set points)

* The pumping speed is high enough that that the water can make it through the coil without time for energy transfer to take place

* The coil has become insulated with limescale such that effective heat transforer cannot occur

Its a bit of a dirty workaround when you can't get a cable to a cylinder stat, but you can to a place where there is a return pipe that only goes to the cylinder. Its less of thing these days when you can use an RF tank stats.