Rad getting hot with hotwater

[Dan Robinson]

I went to one training centre my mates use and found I was a square peg and they a round hole! Nice guys there and they suggested I meet with Centre manager when he returned from leave, to see if he could tailormake a route for me. Haven't had a chance to meet him yet as too bloody busy!
I'd love to get it - still trying to work out the logistics

Have a chat with Uncle Kevin at GES in Welwyn .

 

[dilalio]

Have a chat with Uncle Kevin at GES in Welwyn .

That sounds interesting! I'll text you mate

 

[unclebob1]

Unclebob, look at the link posted

http://www.hertsboilers.co.uk/tech/Back Flow.pdf

This is reverse circulation
I asked if the direction of water through the rads reverses when CH is on then off while HW is being heated
You said the direction of flow in the rads is the same when CH is off and when CH is on during water heating

In the diagram note the flow through the rads is reversed when only HW is on
If CH valve opens while HW is on, flow through the rads will be reversed

Clearly I cannot see what Tony is thinking of with TRVs- no relevance to reverse circulation

It would appear your CH motorised valve is passing if flow direction remains the same with CH valve on or off, otherwise a plumbing issue

I think the NRV may be the easiest option, but i need to correctly identify the pipework for the HWT first, cant see why i would have 5 sets of 22mm for rad circuit, unless it is plumbed in to the rads somewhere. Could be that the return for the upstairs rads could be via the tank to take up any extra heat, but nothing to say that the water coming from the rads, isnt cooler so a bit pointless without a diverter valve setup!

Mirror and selfie stick time i think to see whats going on with the pipework behind...

I suspect I may end up getting someone in to remove the tank and re pipe the area correctly...

 

[DP]

You need to understand the system
The cylinder will have several connections.
Two lower ones are from the boiler (primary flow and return)
T+P valve
Cold water in
Hot water out

At the boiler you will have flow and return pair
The flow pipe will have, after safety connects to header cistern (if applicable) have three motorised valves for three zones
The return will have three tees with connections in correct order else you could have reverse circulation

TRVs on radiators will only effect radiator operation if that zone is active

 

[unclebob1]

Thanks DP:
My tank has a total of 8 connections.

At the top, i have cold in, hot out, and a white expansion tank.

At the back i have 2 22mm connections (They go towards a section of the tank i can not see).
At the front i have 3 22mm connections (again they go towards a section of the tank i can not see).

At the boiler side, i can see:
flow which has 3 tee's + bypass

First T goes to zonevalve for UFH.
Second T goes to zonevalve for DHW
Third T goes to zonevalve for upstairs rad.
end of loop goes to bypass back to return.


On the return, i can see the T for bypass,
then UFH,
Then the pipe goes behind the HWT and i haven't been able to accurately follow it

Behind the tank is where the 22mm feed and return are for upstairs rads, as well as HW and CW for upstairs... but all in a location which is difficult to get to by sight or hand so hard to follow!

 

[DP]

Behind the tank is where the 22mm feed and return are for upstairs rads, as well as HW and CW for upstairs... but all in a location which is difficult to get to by sight or hand so hard to follow!

That is the area I would be looking at.
Visualise the pipes in your statement above and then extrapolate the information in the link I posted.

I would check the direction of flow in radiators again with heating on and then heating off with HW demand on

 

[unclebob1]

thanks dp - need to get decent view of what pipes are going where to try and see whats happening. I suspect that the flow or return for rads is passing though the HWT for some reason, but once ive got a camera on a stick or wife's compact mirror on a stick i can see which pipes at the back correspond to what i see on the front, and what goes into the wall... then i'll get my labeler out and mark up everything!

 

[unclebob1]

So I turned on Ch only for upstairs noted what pipes got hot and in what order.


So zone valve opened and pipe got hot, followed it and it led to the hot water tank bottom connection(middle of three)

The back of the tank has two outputs, of which the top of the pipe got hot, which then went into the wall.

There is another 22mm in the wall just behind which appears to be return but didn't get hot. Meanwhile return to boiler is hot, as is the bottom output from he


So I'm getting the feeling that the feed for Ch upstairs is through the HW tank... Though not traced return yet but suspect it is the bottom pipe at the back, and flowing to the front return (ie mixing with the boiler side of hot water tank)... Suspect I'm gonna have to get someone in to take the tank out and replumb behind it... Not sure I want the original installer back!

 

[DP]

thanks dp - need to get decent view of what pipes are going where to try and see whats happening. I suspect that the flow or return for rads is passing though the HWT for some reason, but once ive got a camera on a stick or wife's compact mirror on a stick i can see which pipes at the back correspond to what i see on the front, and what goes into the wall... then i'll get my labeler out and mark up everything!

Why not pick a radiator that is heating during HW ON. Is the left pipe or the right pipe hotter?
Now switch CH on, is the same pipe on that radiator heating or is the opposite pipe getting hotter.

 

[unclebob1]

Images of the front, back and pic of manual...

I'm guessing he's done as image shows, but instead of ufh manifold he's done rads.

Manifold would not heat if zone doesn't need water, but rads will if no thermostatic valves!

 

[DP]

Last picture would suggest only two zones i.e. radiator zone and cylinder zone
Underfloor would be taking heat from the cylinder. I would imagine if cylinder temperature drops, cylinder would then run the boiler. Could be wrong as I am just imagining how it might work.

Looks like you need professional help here to get to bottom of the problem

 

[unclebob1]

Got this sorted eventually, ufh now goes via tank, actuators on manifold don't heat up floor unless they are open, do no heating when water is on.


Also got wiring swapped so hot water is wired seperatly, as hot water priority... Well sort of! My dial channel programmer doesn't allow for a separate common for each Chanel. Tempted to put hotwater on thermostat only, and put a single Chanel wireless programmable thermostat upstairs.

Only question I have is on the intergas can I wire hot water, open therm and normal relay connection for three zones? (Maybe one for Dan?)

 

[Dan Robinson]

Relay connection?

 

[unclebob1]

Sorry ment normal thermostat (ufh) and a second opentherm stat for 1st floor