Baxi Bermuda Back Boiler Being Bonkers. Possibly.

[DavidB5]

Hello All.

Noob here with a question about a Baxi Bermuda back boiler. I've had a search, and can't find that this has been asked before.

I don't completely understand this boiler. Unlike 99% of other boilers I've worked on/ looked at, it has 5 water pipes going into it rather than 2. One pair are labeled HW flow and HW return, (which makes sense) but the remainder are unlabled. One pair are quite clearly for the CH, and there's a domestic circulator one of them, but the 5th pipe is a bit of a mystery. It's not the gas line (that's a 6th line..) so I'm not sure maybe a line to a water tank?. There is no three-way valve anywhere to be found. There is a room thermostat, a dual timer, but no cylinder-stat.

That's the system.. Here's the problem:

When the CH is activated, the HW seems to come on regardless, and cannot be switched off. While the HW is operating, the HW tank seems to get very near to boiling before the boiler turns off, but it then comes back on again fairly soon and cycles every few minutes keeping the HW tank remarkably hot.

My suspicion is that the HW is cycling on an overheat detector rather than controlling properly, and it has been wired incorrectly meaning the HW operates all the time. The system has been "serviced" recently, but I suspect the blokey who did so hadn't really got much of an idea what he's doing.

Any thoughts?

Other than "tear that inefficient heap of crap out and install a 90% condensing unit" I plan to do that anyway, but right now it would be nice if the damn unit wasn't howling it's way through gas like it's going out of fashion. A pilot light indeed! How quaint!

 

[thefloosyonthebeach]

is this a serious post????

wheres Kevplumb when you need him?

 

[Terrywookfit]

I've never seen one with five tappings.

My guess is.
Primary flow
Primary return
Htg flow
Htg return
Open vent or cold feed.

 

[nogoodatfaultfinding]

Look up Gravity system and you might find your answer there.
Im to frightened to give you any more advise.

 

[sambotc]

As above, gravity hot water circ's with pumped heating. Sounds like it's working as it was designed

 

[thefloosyonthebeach]

wheres the 5th tapping on a bbu? the c/f & o/v enter the h/w flow & return respectively.

i cant belive this is a serious question by the op.

 

[nogoodatfaultfinding]

As above, gravity hot water circ's with pumped heating. Sounds like it's working as it was designed

Im not a know it all by any means but its frightning how much some guys dont know.
It will be a one pipe system as well from just the sound of it so expect another post!

 

[nogoodatfaultfinding]

Hello All.

Noob here with a question about a Baxi Bermuda back boiler. I've had a search, and can't find that this has been asked before.

I don't completely understand this boiler. Unlike 99% of other boilers I've worked on/ looked at, it has 5 water pipes going into it rather than 2. One pair are labeled HW flow and HW return, (which makes sense) but the remainder are unlabled. One pair are quite clearly for the CH, and there's a domestic circulator one of them, but the 5th pipe is a bit of a mystery. It's not the gas line (that's a 6th line..) so I'm not sure maybe a line to a water tank?. There is no three-way valve anywhere to be found. There is a room thermostat, a dual timer, but no cylinder-stat.

That's the system.. Here's the problem:

When the CH is activated, the HW seems to come on regardless, and cannot be switched off. While the HW is operating, the HW tank seems to get very near to boiling before the boiler turns off, but it then comes back on again fairly soon and cycles every few minutes keeping the HW tank remarkably hot.

My suspicion is that the HW is cycling on an overheat detector rather than controlling properly, and it has been wired incorrectly meaning the HW operates all the time. The system has been "serviced" recently, but I suspect the blokey who did so hadn't really got much of an idea what he's doing.

Any thoughts?

Other than "tear that inefficient heap of crap out and install a 90% condensing unit" I plan to do that anyway, but right now it would be nice if the damn unit wasn't howling it's way through gas like it's going out of fashion. A pilot light indeed! How quaint!

The system is one of the best ever invented, maybe not economic by todays standards but id love it in my house.

What you have is a gravity fed system which sounds like its operating properly.

 

[sambotc]

As above, gravity hot water circ's with pumped heating. Sounds like it's working as it was designed

Im not a know it all by any means but its frightning how much some guys dont know.
It will be a one pipe system as well from just the sound of it so expect another post!

I'm confused, was this directed at me, as you've just agreed with me on your next post?

5 pipes, injector tee on the return's with vent on the 4th tapping?

 

[nogoodatfaultfinding]

As above, gravity hot water circ's with pumped heating. Sounds like it's working as it was designed

Im not a know it all by any means but its frightning how much some guys dont know.
It will be a one pipe system as well from just the sound of it so expect another post!

I'm confused, was this directed at me, as you've just agreed with me on your next post?

No directed to the OP mate sorry if thats how it came accross

 

[sambotc]

no worries

 

[DavidB5]

Look up Gravity system and you might find your answer there.
Im to frightened to give you any more advise.

Whyso?

I completely understand gravity systems, and I also completely understand pumped systems. It's fairly obvious that this is gravity HW with pumped CH, but I lack experience of this specific system as have only ever worked with fully pumped systems with three-way valves.

I assume that temperature control of the HW cylinder is done within the back boiler unit... Is this a standard setup? If so, surely it should be adjustable, and it shouldn't be cycling in and out every 5 minutes.

Also, should the HW always come on with the CH? I would have expected the ability to operate CH independently of HW, or is that "just how these ones work"?

And yes, I was being a bit sarcastic about the pilot light issue, it's just I haven't seen a pilot light for over 20 years.

 

[nogoodatfaultfinding]

Look up Gravity system and you might find your answer there.
Im to frightened to give you any more advise.

Whyso?

I completely understand gravity systems, and I also completely understand pumped systems. It's fairly obvious that this is gravity HW with pumped CH, but I lack experience of this specific system as have only ever worked with fully pumped systems with three-way valves.

I assume that temperature control of the HW cylinder is done within the back boiler unit... Is this a standard setup? If so, surely it should be adjustable, and it shouldn't be cycling in and out every 5 minutes.

Also, should the HW always come on with the CH? I would have expected the ability to operate CH independently of HW, or is that "just how these ones work"?

And yes, I was being a bit sarcastic about the pilot light issue, it's just I haven't seen a pilot light for over 20 years.

Right im not having a dig but have you honestly not seen a Classic, a 240 a Solo in the last 20 years, cmon you must have seen a boiler with apilot in that time!
Ive only been doing it 10 years and 75% + of boilers i come accross are pilots

 

[sambotc]

Look up Gravity system and you might find your answer there.
Im to frightened to give you any more advise.

Whyso?

I completely understand gravity systems, and I also completely understand pumped systems. It's fairly obvious that this is gravity HW with pumped CH, but I lack experience of this specific system as have only ever worked with fully pumped systems with three-way valves.

I assume that temperature control of the HW cylinder is done within the back boiler unit... Is this a standard setup? If so, surely it should be adjustable, and it shouldn't be cycling in and out every 5 minutes.

Also, should the HW always come on with the CH? I would have expected the ability to operate CH independently of HW, or is that "just how these ones work"?

And yes, I was being a bit sarcastic about the pilot light issue, it's just I haven't seen a pilot light for over 20 years.

Can't operate the HW independantly as there is nothing to stop it coming on when the C/H is on.

If you haven't seen a pilot light in twenty years you obviously have not been looking very hard

Sounds like the set up you have is very basic. It is possible to put a cylinder stat in, and a zone valve (c plan) if you like.

Sam

 

[DavidB5]

Right im not having a dig but have you honestly not seen a Classic, a 240 a Solo in the last 20 years, cmon you must have seen a boiler with apilot in that time!
Ive only been doing it 10 years and 75% + of boilers i come accross are pilots

I don't do this commercially! I've installed a couple of central heating systems, but they have been in my own home (more than one house!). Other than that, I've only ever worked with non-pilot-light boilers (eg when a friend/relative has asked me to "have a look" at their boiler)

I genuinely had no idea so many homes still had pilot lights merrily wasting gas all hours of the day and night!

Anyway... I can see the issue with the HW always working with the CH, but that still doesn't explain why when the CH has achieved temperature (room stat has turned off) the boiler still fires up once every 5 minutes for about 15-20 seconds, running the hot water circuit. It's definitely the HW circuit, as if the CH is turned completely off (programmer off) the boiler still does this. The water in the cylinder is absurdley hot (I'd guess well over 80deg) and desperately needs turning down, which is a bit difficult with no cylinder stat. I'd also much rather the boiler did NOT try to keep the HW tank up to temperature all the time, but if it has to run the HW all the time the CH is on, then so be it (and what an irritating and wasteful design that is!)