Possible reverse circulation

[Beard06]

Hi all, we've recently moved into a property and believe there is some kind of backflow in the heating system. (I should say I am a DIYer, and not a great one).

When we have our hot water on, the rads get hot over time.

I've had floorboards up to see if there is a non-return-valve somewhere that has become faulty. Couldn't find a NRV and when reading up some more, there shouldn't be a need for NRV if plumbed correctly.

I've also checked the feeds to and from the boiler, and as far as I can tell, the hot water return is the last T in the return pipe feed back to boiler.

We had the motorised valves by the cylinder, one looked quite old, to Honeywell valves.

Next on our list is to check what side of the rads get hot when the heating is on, then switching the heating off and not water on to see if the opposite side gets hot.

The only other thing I can think of, is to look into how the bathroom towel rad has been plumbed in. This towel rad heats regardless of hot water or heating being on, which suggests it bypassed the valves and comes straight from the feed. The other odd thing is that the other rad in the bathroom gets boiling hot, even though we have turned the valve down to 0.

Could this suggest that the return for the towel rad has been T'd back somewhere it shouldn't?

Any help here would be really appreciated.

 

[Knappers]

There's allot going on here Mr Beard.
Definitely worth a visit from a heating engineer.
If you've got a specific question with pics then I could try to help but an engineer will get a much better overview in person

 

[Beard06]

There's allot going on here Mr Beard.
Definitely worth a visit from a heating engineer.
If you've got a specific question with pics then I could try to help but an engineer will get a much better overview in person

Thanks, Knappers. Agree, I went on a ramble there.

Specific questions I have are:

• Where should the towel rad return be T'd into?
• How would I tell if it hasn't been plumbed in correctly, once we still pulling up floorboards in bathroom?

Thanks

 

[Knappers]

It's possible that towel rail is connected before control valves intentionally, it could also be the trigger for a reverse flow issue.
You could try with towel rad isolated and see if issue stops.
Problem with other rad sounds like a faulty valve.

 

[Beard06]

It's possible that towel rail is connected before control valves intentionally, it could also be the trigger for a reverse flow issue.
You could try with towel rad isolated and see if issue stops.
Problem with other rad sounds like a faulty valve.

Thanks again.

Yes we tried seeing if by shutting the flow to the towel rail today, and just boosting hot water to see what happens.

The main rad in the bathroom was hot immediately. All upstairs rads got hot from the return side. The downstairs rads only had slight warmth to them after about 20mins.

 

[Knappers]

Not sure, needs a good look at the setup I think

 

[Deleted member 120897]

If you’ve turned the dial down to 0 and it’s still hot, then it’s likely the trv pin has failed.

 

[Beard06]

Hi all, done some more investigation.

In the photo, the pipe on the left is the return from the hot water cylinder. The pipe on the right is the heating feed (which is going into the bathroom).

The T in the hot water return, is the return from the rads in the bathroom. Surely this is the issue which is causing the upstairs rads to get hot when the hot water is on? As the hot water returning to the boiler is finding a way into the heating loop?

Questions:

Can we put a NRV on the return flexi pipe from the bathroom rads?

Or is it better to remove the rad return going into the hot water return pipe and T it back in closer to the boiler? (We are having some building work soon, so could tie it in with that).

One other thing I found, was that all the gate valves on the rads (across the whole house) were fully open... which I couldn't really understand why? Does this need to be the case for a pressurised system?

 

[Ric2013]

Questions:

Can we put a NRV on the return flexi pipe from the bathroom rads?

If it's the famous reverse circulation up the radiator returns that I still admit to not fully understanding, a valve should certainly prevent it. As may a simple down and up loop of pipe to prevent the hot water trying to rise?

Or is it better to remove the rad return going into the hot water return pipe and T it back in closer to the boiler? (We are having some building work soon, so could tie it in with that).

Would be 'correct', but if a non-return valve works and doesn't cause any side effects (noise or restriction of flow spring to mind), I would hesitate to say one approach is 'better' than the other.

One other thing I found, was that all the gate valves on the rads (across the whole house) were fully open... which I couldn't really understand why? Does this need to be the case for a pressurised system?

No, just they haven't bothered to balance the system.

 

[Sparkgap]

I wonder if you've got some rads which have return connections into the main between the cylinder or towel rail and the boiler? It could be return flow from the cylinder or towel rail circulating up one return connection to a rad then through the rest before rejoining the main return further down.