Also in the middle pic of the left side of the boiler there are two 22mm pipes entering the boiler. The rads and cylinder seem to return to the bottom one. The flow comes out of the right side. What's the top left.pipe?
Getting HW when only CH is on and it's not the valve???
- Thread starter ragj195
- Start date
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Exactly.
Your system was originally a "pumped heating, gravity hot water" type. It has now been converted to a fully pumped system. I suspect that this has not been done correctly.
Solve one problem and you have solved the other.
As for the mystery pipe, it looks like a 28mm one so it was probably the original feed to the cylinder. It is now probably the vent pipe.
Is the pump in the flow or return?
Which boiler do you have?
It's Potterton Kingfisher RS60 GC No. 41 601 37. I can't find the manual anywhere online. The pump is on the flow on the pipe that comes straight out of the right of the boiler. This was always the case. Really the only thing that was done recently was the CH MV replaced and a HW MV added between the pump and the cylinder. The problem with HW only heating rads isn't since this recent work. It's been like this since got the house 7 years ago. I just thought it was the MV hence why I got it replaced. I've drained it down and put an isolating valve on the 15mm pipe to what effect closing it has. Now it's refilling. In the meantime I did this diag. The rad near the boiler looks like it was added after the original install.
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Now that it's filled up I did some testing with the isolator valve on the 15mm pipe.
It looks like the 15mm pipe is 100% to the right valve of the towel rail. What I can't work is where the return from the rail goes. If this return goes into the CH return network would that explain why rads on getting warm when HW only is on?
Could I just cut the 15mm pipe and connect it to the top part to the 22mm CH Flow pipe with a 22x15x22 T? and put an end cap on the bottom part. I'm fine with the towel rail being part of the CH and not the HW zone if it means the in the summer when I have HW on only none of the rads get warm.
It looks like the 15mm pipe is 100% to the right valve of the towel rail. What I can't work is where the return from the rail goes. If this return goes into the CH return network would that explain why rads on getting warm when HW only is on?
Could I just cut the 15mm pipe and connect it to the top part to the 22mm CH Flow pipe with a 22x15x22 T? and put an end cap on the bottom part. I'm fine with the towel rail being part of the CH and not the HW zone if it means the in the summer when I have HW on only none of the rads get warm.
But you said it came out of the boiler on the left top - as in your pic.
Ahh sorry, I thought you meant the 15mm pipe that feeds the towel rail.
The 22mm one that I wasn't sure about in the photo isn't in the drawing but it does come out of the top left of the boiler and head straight up into the ceiling with nothing else connecting to it. As the other two 22mm pipes going up seem to to be CHF and CHR it must be the vent? There is a 22mm pipe with a U bend over the feeder tank in the loft.
The 22mm one that I wasn't sure about in the photo isn't in the drawing but it does come out of the top left of the boiler and head straight up into the ceiling with nothing else connecting to it. As the other two 22mm pipes going up seem to to be CHF and CHR it must be the vent? There is a 22mm pipe with a U bend over the feeder tank in the loft.
I've added it to your drawing.
It now raises another question: where is the feed from the feeder tank?
One possible answer is that you have a "combined vent and feed". If so there will be a 15mm pipe from the bottom of the tank which will join the 22mm vent pipe between the tank and boiler.
You don't appear to have answered my earlier question;
Which valve gets hot first (left or right) on each rad:
(a) when HW only is turned on; and
(b) when CH only is turned on?
I've managed to get hold of the manual at it does show that the vent can be out of the top left of the boiler.
I've done the test on a couple of radiators downstairs.
With HW only left valve heats up first
With CH only left valve heats up first.
Weird because I thought the return from the bathroom rad may have been heating up the other rads but if that was the case then wouldn't it be the right valve that heats up.
I'm just now doing a test on the rad in the diag next to the boiler as I have a feeling HW return is going through the rad return and into the CH flow on the left of the CH MV valve. The would explain why the other rads are heating up. If I close the rad valve and the CH flow or the other rads don't get hot then that's the cause!
I've done the test on a couple of radiators downstairs.
With HW only left valve heats up first
With CH only left valve heats up first.
Weird because I thought the return from the bathroom rad may have been heating up the other rads but if that was the case then wouldn't it be the right valve that heats up.
I'm just now doing a test on the rad in the diag next to the boiler as I have a feeling HW return is going through the rad return and into the CH flow on the left of the CH MV valve. The would explain why the other rads are heating up. If I close the rad valve and the CH flow or the other rads don't get hot then that's the cause!
As you say - weird.
I agree that if the return from bathroom rad is commoned with the return from the other rads, there could be reverse circulation, so the opposite valve would heat up first.
I think you need to repeat my experiment on all rads to confirm if reverse circulation is occurring.
I assume you haven't been able to confirm where the bathroom return is connected.
No the bathroom return is under a tiled floor and hacking away at the plasterboard ceiling the kitchen would be a last resort.
My latest test has confirmed this. With HW only on the HW return seems to be pushing HW through the rad return next to the boiler which goes all the way through to the left of the CH MV valve which leads on to all the other rads! This was done with the islolater valve on the 15mm pipe to the bathroom rad closed.
If I close the lockshield valve on the rad then do another test, it should prove this. I will then open the isolater valve to the bathroom rad and keep the lockshield on the rad closed. Hopefully the other rads will stay cold proving that it was all about the rad next to the boiler.
My latest test has confirmed this. With HW only on the HW return seems to be pushing HW through the rad return next to the boiler which goes all the way through to the left of the CH MV valve which leads on to all the other rads! This was done with the islolater valve on the 15mm pipe to the bathroom rad closed.
If I close the lockshield valve on the rad then do another test, it should prove this. I will then open the isolater valve to the bathroom rad and keep the lockshield on the rad closed. Hopefully the other rads will stay cold proving that it was all about the rad next to the boiler.
Update, there is reverse flow in the rad next to the boiler which heats the CH flow pipe up and a little of the first rad in the room above the boiler but not enough to really present the problem of all the rads heating up.I did the test on other rads. I can't find one rad where the opposite valve heats up when HW or CH is selected. Do you think the return from the bathroom rad could be plumbed into the CH flow rather than the return?
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