Hot water cylinder coil query

[Rick B]

Hi there
I run the maintenance for a company and at the moment were having problems with a vent pipe on the roof splurging warm water at intermittent times.
Its a large building with 3 cylinders providing hot water to 6 toilets and 3 kitchen and as you can except pipework all over the place with know knowledge of what's feeding what.
There's also 3 large header tanks, Now like I said the problem is occasionally in the mornings before the staff get here the vent coming through the roof spews water out, I was presuming that it was a stat that had failed and boiling the water thus sending it through the vent, but I've changed all the stats and still it does it, I was wondering if it could be a split coil and if there was a way to test this before I get a engineer in at a cost as he'd have to trace all the pipe work (which could take a good half day if not longer)to familiarise himself with it beforehand to change the cylinder, if it is that
Cheers
Rick

 

[deg]

Don't think a split coil would make it vent through the roof as there would not be enough head in the tanks although depending on your set up it is possible. Any new mixer taps or showers fitted recently?

 

[Rick B]

Don't think a split coil would make it vent through the roof as there would not be enough head in the tanks although depending on your set up it is possible. Any new mixer taps or showers fitted recently?

Thanks,
We've got a few mixer taps but they've been in a while, no showers, what you thinking, check valves on the HW mixers? Like I said its an old building that's had god knows how many different set ups and add on which is why I would rather try and find the root of the cause than shell out 20ph+ for an engineer to spend a day just getting to know the system,Don't get me wrong I'm not penny pinching we may well have to get a contractor in the end, just hoping that I could point him in the right direction
Rick

 

[Chuck]

It's easy enough to test for a split coil if you have the right equipment (temperature probes, pressure gauge, UV dye, etc.) and know how to use it. There have been several threads discussing exactly this problem on this forum (use the search box).

A heating engineer should be able to diagnose the fault easily and you're going to need one to make the repair so my advice is just to get one in.

Not knowing where pipes go etc. is going to be a problem for any sort of repair/maintance every time anything needs doing so either track down the paperwork for the system or get the engineer to generate some as part of the job. As a minimum every boiler, cylinder, valve, etc. should have a proper id label or tag and you can then draw up a schedule of what does what.

 

[ShaunCorbs]

The most easiest way is you will have dirty hot water (as the heating water will be mixing)

 

[snowhead]

When you say Vent pipe on the roof, do you mean overflow?

If it's the overflow then the water level in the tank is set too high, leaving insufficient room for expansion.

Vent pipe would have been over the tank in the last 40 or 50 years but out throught the roof before then , although in commercial buildings now the trend is to vent to drain to prevent unneccesary warming up of the header tank.

 

[Rick B]

When you say Vent pipe on the roof, do you mean overflow?

If it's the overflow then the water level in the tank is set too high, leaving insufficient room for expansion.

Vent pipe would have been over the tank in the last 40 or 50 years but out throught the roof before then , although in commercial buildings now the trend is to vent to drain to prevent unneccesary warming up of the header tank.

No, Its definitely the vent, it looks like it did go back into the tank, but for some reason its been moved and put through the roof and about a metre up