Y plan system. will only give HW or CH alternatively after powering off.

[armyash]

I hope that thread title makes sense.

Here's a bit more info.

We got a call a few days ago that there was no HW but CH was ok.

3 port got changed, Now HW and CH both working.

I got a call today to go back, no CH, I walk in and it's hot, turn room stat up and heating comes on fine and they had HW. Nobody home btw. So I report back that HW and CH both working so we assume that it was user error.

I continue with my day, then get a phone call saying when I have completed my next job can I go back to this address as they are home and they are saying that CH comes on when turned up by room stat and will go off with room stat but then won't turn on again with room stat.

Ok so arrive at the property and the tenant is home (croation, so has to explain things to me a couple of times)

He explains that the heating will work ok but has no HW unless he turns the room stat off and boiler off at the mains then back on again. and the same again to get the heating working.

Seems very strange but i'm thinking it's either the pump not activating when it should or the programmer needs replacing. (programmer would be my first try as if i turn CH off at programmer it goes off but doesn't come back on with programmer)

Tenant said this has just started happening since 3 port got changed but if HW wasn't working anyway could still have been the programmer. (3 port was screwed anyway though). New 3 port was wired correctly.

Hope that's clear enough 😀

Any ideas?

 

[albatross]

Faulty cylinder stat sticking one way or the other or inbetween.

It sounds to me like there is a problem around the grey (hw off) wire to the valve or the pcb inside the valve.

if there is no power to the grey when hw is off/cyl stat is satisfied then you won't get ch only.

Faulty cyl stat would give no hw on either.

A faulty 3 port valve will not give no hw so that maybe did not need changing anyway.

 

[Nostrum]

Did the entire 3 port get changed or just the actuator head?

 

[armyash]

The entire 3 port got changed. There was no HW at all before this but now there is HW but only when operated as described.

Thanks for the replies. It's pretty confusing, obviously my inexperience does not help but the fact that there was no HW and now there is makes it more confusing.

The cylinder stat issue sounds like something worth investigating. I was there tonight at gone 6 tonight and supposed to finish at half 4 boss called and said we will go back Monday.

 

[Whyme]

try flicking the cyl stat up and down with screwdriver to see if it kicks in or not. then start testing electrics, and a 3 port will give no hw if stuffed and no ch if stuffed. unless you've got a hw priority valve..

 

[Pelsey]

Could be the old valve was one that motored all the way round like a switch master or there is another make similar, I replaced one recently with a normal 3 port and had the same symptoms. Had to get the old type valve and change the lot again or re-wire it all as the wiring centre had relays in!

 

[tamz]

If it is an unvented cylinder it could be the cut out is fekd or dodgy

 

[armyash]

cheers guys.

Pelsey, it was a honeywell straight swap but thanks for the input.

tamz - it's vented but thanks for the reply.

 

[Killy Bing]

Having to turn off the mains?
I'll be different and say moneys on a dodgy programmer on this one.
What size fuse is fitted in the spur?

Link out the programmer if you can start and stop the demand then with the room stat and cylinder stat then you've found your answer 🙂

 

[tamz]

If the wiring is correct it is a dodgy valve.

Here is a really good easy to get your head round guide to how a y plan works
Central Heating

 

[tamz]

Checking out a programmer is simple. You don't need to take it off the wall.

 

[AMGasServices]

Link out the programmer if you can start and stop the demand then with the room stat and cylinder stat then you've found your answer 🙂

Loop the live to dhw on. As Killy bing said.

 

[neily01]

Sounds very much like i had the other day, another faulty honeywell programmer (st9400c). Which ever channel was energized first wouls send out switch live, but when the second channel came on the light came on but no feed. So the cust was goung through a sequence of turning it all off then on to get hw or htg.

 

[armyash]

Same programmer! 😀

 

[armourer]

Dodgy relays on the honeywells. They start off by working on which ever the first one is switched on but the second selected will turn on the light but no click.
Eventually they both will fail. The indicators light so you think its on but no click because the relays dont make.

 

[armyash]

Dodgy relays on the honeywells. They start off by working on which ever the first one is switched on but the second selected will turn on the light but no click.
Eventually they both will fail. The indicators light so you think its on but no click because the relays dont make.

i'm going to suggest new programmer. boss said im going to be rewiring on Monday but think it will be a waste of time. wont be my call though hopefully it is just the programmer.

 

[armyash]

Replaced the programmer. All good now.

It's an old system and the tenant said a few components have been changed over the last couple of years so I think it's all slowly packing up.

Thanks for the replies.