Rad getting hot with hotwater

[unclebob1]

Good Morning,

With the recent heatwave we are experiencing, i've come to realise that the radiators on my 1st floor (seperate zone), are warm/hot even when the heating side of the system is set to off via programmer.

I think i've pinned it down to the rads are getting warm when the HWT is demanding and getting heat.

The setup is:

Boiler - Intergas HRE24
three zones off it - 1: HWT
2: Upstairs rads
3: ground floor UFH manifold.

I've made sure both zones 2 and 3 are not open (zone valves not energized) while the hot water is on, but still getting warm on the rads.

My thinking is that the pump in the boiler is pushing the water through fast enough/with enough force to push the mechanical ball on valves 2 and 3. the manifold being closed is then not allowing any water to flow in the underfloor so its all being diverted to upstairs heaters.

Anyway to test this without getting someone out?

 

[DP]

Reverse circulation perhaps
I would be looking at the valves first, then check which side of said radiators starts heating during HW and check if opposite is the case when ch zone goes active

 

[unclebob1]

I know the flow/returns on the rads are mixed in the sense of TRV's on 2 are on the return, one is on the flow, and one has two lock shields so there is a plan later in the summer to change all out, was thinking if i need to make any adjustments at the zone valve ends i can do it at the same time when i drain the system down.

Will check what heats up first with HW when i get home tonight, though if the zone valve is closed, there shouldn't be a complete circuit for flow should there?

 

[DP]

TRV location, provided it is bidirectional, will not effect operation

Because you have got a circuit open for circulation during HW demand, that is why rads, perhaps not all, are heating up. Likely direction of circulation will be reverse to when CH is on

 

[Agile]

Reverse circulation occurs when the returns to the boiler are not connected in the right order and results in usually only some, often upstairs, getting hot.

Can sometimes be tricky to prevent if significant repiping is not possible.

 

[unclebob1]

I checked the rads that are coming on with hw on, so will try ch this weekend (dont really want to make the room any hotter then it already is!).

Agile, any guidance on what order?

The other thought i've had is my HWT has ability to plumb the output from the tank into a feed for UFH/other output source... i wander if this has any part to play? Pipe investigations must take place...

 

[DP]

I checked the rads that are coming on with hw on, so will try ch this weekend (dont really want to make the room any hotter then it already is!).

Agile, any guidance on what order?

The other thought i've had is my HWT has ability to plumb the output from the tank into a feed for UFH/other output source... i wander if this has any part to play? Pipe investigations must take place...

Unclebob, why don't you read my post again to check what I have written.
The heating does NOT need to start overheating the house so tomatoes can be grown, but for a few moments to check a scenario. your rads are already heating the space when they should be cold.
If the rads are heating as you say, all you need to do is check which rads are heating and which not, and also on each rad which pipe is hotter. Take note. You may find not all rads heat up to the same degree

Now select ch as well and check if direction of flow is reversed

You do not need to think me or anybody, after all this advice is given for free by someone who does this kind of work for a living and is offered for free to assist those in need.

Will let Agile hold your hand and guide you in your quest.

 

[unclebob1]

dp, thats exactly what i am doing, except i don't get enough time to wait for the pipes to cool back down before i could test the CH side yesterday, and the room was well over 28 at about 7pm without the HW heating the rad, and trying to get my kids to sleep isn't easy with that heat... I've marked the flow/return as i understand it from the hot water, and will double check this weekend with the CH (it seems to MATCH the HW flow/return rather then oppose).

I appreciate the help that you guys give, buy as doing it in between other stuff, rather then as part of a full time job, its harder to find time to do it!

 

[DP]

Why not switch off the programmer, and when you have some spare time, run HW zone and check which radiators are heating by checking the pipes connected to each radiator, take note of rads which are taking heated water when only HW zone is on. It will be several minutes before radiator will be evacuated of all the cold water in it

Once you have checked the rads, should take perhaps a minute, switch off the HW zone

Now switch on the relevant CH zone and check the rads again and see if the water flow is same as your notes

Easiest way of sorting this problem would be to fit Honeywell Evohome

 

[Terry lambert]

Reverse circulation occurs when the returns to the boiler are not connected in the right order and results in usually only some, often upstairs, getting hot.

Can sometimes be tricky to prevent if significant repiping is not possible.

Most times it is very easy to correct, did one just the other day and have another to correct next week, no extensive piping

Quite simple for an engineer unless critical fittings are completely inaccessible as in under finished floors

 

[Agile]

One I am asked to sort out has all the pipework totally hidden under engineered floors and panelling.

But I have cured the effect by finding that the TRV pins were rather stiff and not allowing the heads to fully turn off the valves.

That was a big feeling of success as the tenant was very bothered as she cannot open the windows because they are a door onto a balcony and she is frightened of kids going out and falling off!

 

[Terry lambert]

Whoop whoop !

Well done

 

[AGAS]

ffs's

 

[ericmark]

All I can say is what I found with daughters house, the micro switch in the motorised valve had failed, and some one to get central heating running had latched to valve to bleed setting, son-in-law cleaning airing cupboard caught the lever on the valve, and this stopped central heating working.

It also resulted in hot water in summer causing radiators to heat, but so little they had not noticed it.

Pins sticking on TRV now free may seem to cure the problem, but it still could be some one has latched the level on the motorised valve.

 

[oilboffin]

I'll bet that the last connection to the return isn't the dhw like it should be.Bob