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Hi everyone,
I'm a (somewhat, I hope...) competent DIYer and just want to get some advice if my suspicion on a problem we're having is correct. We had a Megaflo and boiler professionally installed as part of a renovation a couple of years ago. I will add all of the pipework was done by this plumber, not me! It took a couple of years for me to add the various rads on the downstairs and upstairs circuits (lockdown torpedoed progress a bit) and so we are only really noticing this issue this summer.
Basically, when the central heating is off, but the Megaflo calls for hot water, the upstairs rads begin to get warm (not hot usually, but warm). The following is a checklist of what I've done so far to narrow down the problem to what I think is reverse circulation:
1. The motorised valve for the central heating is functioning correctly - i.e. it does not let hot water through it to the flow for the central heating circuit. When the megaflo calls for hot water, the CH flow pipe is clearly cold and hot water is not entering the system this way. However the return pipe is hot;
2. Checked for crossover by isolating the hot water to the upstairs, and making sure that none of the hot water inlets had accidentally been connected to a flow for any rad (chances slim and I know the pressure differential may have exposed this earlier but just wanted to make sure). Problem still occurred which means the hot water was being introduced from either the flow/return rather than a (different) major cockup of plumbing;
3. Only the upstairs rads/circuit starts warming up when the hot water is being boosted by the system - reason this is relevant will be clear from the diagram;
4. The good old 'hands on pipes' test - I turned on the hot water boost manually, and followed the water flowing from the Megaflo return as it travelled along the pipe towards the boiler, but then started diverting up the return for the upstairs circuit (the first T point).
Here are a couple of photos of the setup in the utility room downstairs. The first shows the overall. The megaflo tank is just out of shot on the left. The second photo shows the tank.
The photo below I think is the most relevant and is a zoomed in one where I have annotated the pipes for ease and what I think is happening:
The annotations:
1=The return from the Megaflo to the boiler;
2=The return from the upstairs heating circuit;
3=Return from a single rad in adjacent room 1;
4=Return from a single rad in adjacent room 2;
5=Return from the rest of the downstairs central heating circuit;
6=Central heating flow pipe. The bit under the annotation is the downstairs element of the flow and if you track the pipe up it splits from upstairs to downstairs at the horizontal at the top of the picture (pipe with the drain cock on the end of it).
The arrows just show the 'direction' of the return pipe from the megaflo back to the boiler. Sorry for being so prescriptive but just want to make sure I'm getting everything in here.
My understanding is that ALL of the return pipes (i.e. 2,3,4,5) should fix to a common point before the return from the megaflow joins this return pipe to the boiler. And the reason the upstairs rads are heating up and not the downstairs when this problem occurs is because the T to the upstairs return is the first point at which the water on its way from the Megaflo return to the boiler is able to T off somewhere else.
Am I on the right track here? Is the solution to this to decouple the joins on 2/3/4/5 and connect them to one juncture, and then hook this in to the return on a straight back to the boiler?
I just want to make sure when we call the plumber back (or get someone else in to do it) that it's clear what the problem is.
If you've made it this far thankyou and much appreciated to anyone who can help.
cheers
I'm a (somewhat, I hope...) competent DIYer and just want to get some advice if my suspicion on a problem we're having is correct. We had a Megaflo and boiler professionally installed as part of a renovation a couple of years ago. I will add all of the pipework was done by this plumber, not me! It took a couple of years for me to add the various rads on the downstairs and upstairs circuits (lockdown torpedoed progress a bit) and so we are only really noticing this issue this summer.
Basically, when the central heating is off, but the Megaflo calls for hot water, the upstairs rads begin to get warm (not hot usually, but warm). The following is a checklist of what I've done so far to narrow down the problem to what I think is reverse circulation:
1. The motorised valve for the central heating is functioning correctly - i.e. it does not let hot water through it to the flow for the central heating circuit. When the megaflo calls for hot water, the CH flow pipe is clearly cold and hot water is not entering the system this way. However the return pipe is hot;
2. Checked for crossover by isolating the hot water to the upstairs, and making sure that none of the hot water inlets had accidentally been connected to a flow for any rad (chances slim and I know the pressure differential may have exposed this earlier but just wanted to make sure). Problem still occurred which means the hot water was being introduced from either the flow/return rather than a (different) major cockup of plumbing;
3. Only the upstairs rads/circuit starts warming up when the hot water is being boosted by the system - reason this is relevant will be clear from the diagram;
4. The good old 'hands on pipes' test - I turned on the hot water boost manually, and followed the water flowing from the Megaflo return as it travelled along the pipe towards the boiler, but then started diverting up the return for the upstairs circuit (the first T point).
Here are a couple of photos of the setup in the utility room downstairs. The first shows the overall. The megaflo tank is just out of shot on the left. The second photo shows the tank.
The photo below I think is the most relevant and is a zoomed in one where I have annotated the pipes for ease and what I think is happening:
The annotations:
1=The return from the Megaflo to the boiler;
2=The return from the upstairs heating circuit;
3=Return from a single rad in adjacent room 1;
4=Return from a single rad in adjacent room 2;
5=Return from the rest of the downstairs central heating circuit;
6=Central heating flow pipe. The bit under the annotation is the downstairs element of the flow and if you track the pipe up it splits from upstairs to downstairs at the horizontal at the top of the picture (pipe with the drain cock on the end of it).
The arrows just show the 'direction' of the return pipe from the megaflo back to the boiler. Sorry for being so prescriptive but just want to make sure I'm getting everything in here.
My understanding is that ALL of the return pipes (i.e. 2,3,4,5) should fix to a common point before the return from the megaflow joins this return pipe to the boiler. And the reason the upstairs rads are heating up and not the downstairs when this problem occurs is because the T to the upstairs return is the first point at which the water on its way from the Megaflo return to the boiler is able to T off somewhere else.
Am I on the right track here? Is the solution to this to decouple the joins on 2/3/4/5 and connect them to one juncture, and then hook this in to the return on a straight back to the boiler?
I just want to make sure when we call the plumber back (or get someone else in to do it) that it's clear what the problem is.
If you've made it this far thankyou and much appreciated to anyone who can help.
cheers
