Radiator still hot when boiler off

[stuartmac]

Can anyone offer any thoughts

I have a customer who has been leaving the two glowworm combi boilers on but using the thermostat to turn on and off the heating as they don't know how to programme the timers but after they hve turned the thermostat to zero two of the radiators stay hot??

I am going to teach them to use the programmer tomorow but does just using the thermostat turn off the heating ? no TRV's fitted or is it still working to a lower temp? this ight explain why their monthly gas bill is £330

 

[tamz]

I gather since it has 2 boilers this is a big house¿
House may be split into zone/s and thermostat is controlling the zone valve/s. You will know when you look at it.

 

[stuartmac]

Thanks been a couple of times now to do other work they have just mentioned this one, had that in mind it is spit into two zones - but only ever seen one control pannel and one thermostat though can both be controlled by one or does it have to be two ??

I suppose if i turn off one bolier and heat up the rads on the other then by process of elimination by checking will find out what controls what.

 

[PlumbBobBob]

could the two rads be piped into flow and return before 3-way valve?

 

[stuartmac]

Forgive me but no cylinders so they wouldn't have one would they?

 

[dontknowitall]

Sometimes a bathroom radiator was plumbed in off the primary flow and return so whenever the hot water was on the bathroom radiator received heat as well irrespective of whether the heating was on or not.

 

[stuartmac]

Hi thanks - how does that work then ? do you mean it was on the hot water - and then heating return?

 

[dontknowitall]

It's a separate circuit just for that radiator - off the flow (to TRV), through radiator and lockshield back to return. Hot ....

It's a combi!! Doh!

I wonder if this wasn't spotted when the boiler was installed? Just a thought as these "circuits" are quite rare.

 

[stuartmac]

Hi is worth checking could have been teed off the hot water as flow and then back into return flow on heating? simple way to check I suppose would be to turn on the hot water i bathroom and see if rad heats up,

some combi boliers boilers i have heard can vent pressure fom constant hot water running into the rad system as a way of dumping

There are two rads stay on one in one of the many bathrooms d one on the third floor I thought it might be the fact that the zero on the thermo does not mean zero maybe 10 or 15 deg in reality and these rads giht be at the start of the flow runs so heat up?

 

[stuartmac]

To try to understand the circuit - teed of the heating flow or off the hot water flow? if off the heating flow how come none of the others get hot off the flow?

 

[dontknowitall]

I'm as puzzled as you are at the moment ... hopefully someone can come to the rescue soon.

 

[PlumbBobBob]

it is teed into the feed before the trv, i.e between boiler and connection to cylinder so if the heating isn't called for and trv to hot water only, the rad still gets hot. although don't know if that would remain after changing to a combi. unless always been a combi in which case ignore me lol.

 

[tamz]

It will be nothing to do with the hot water.
If it is split into more than one zone there will be a motorised valve or 2. You can control as many valves as you like with one stat. It is just a switch.
It may be the room stat closes the valve by just operating the motor and the programmer shuts down the boiler fully. It is badly designed and wired system if it does. It can be wired to as many zones as you like and shut of the boiler when the last zone closes. Might need to alter some pipes to get it to work properly.

 

[stuartmac]

thanks for that, I understand what you are saying in terms of the zones so it looks like chasing pipes around to try to see how it all fits together, if they are not zoned correctly and the themostat is switched to zero will they keep going till the bolier timer is off then

 

[tamz]

Sounds like that.
The valves need to be wired to the boiler via the orange and grey wires to work correctly.

 

[stuartmac]

Thanks, the more I think of it I do wonder if there are any zones!! one boiler off what heats up , swap what heat up, turn off heating turn on water what heat up?

The control pannel should indicate zones I would have thought?

 

[stuartmac]

Thanks for all your thoughts, i visited today and by process of elimination ensured that one controlled downstairs only and one upper floors, then programmed each boiler and turned on and off using programme not thermostats the rads went off. so even though the themostats said zero the bolier kept pushing heat into two rads. Combi boilers.