Cylinder set up

[SmokeyJ]

Hi all, first thread on the forum.
Have this set up in a boarding house at a school I'm working at. Never seen anything like it before and will be servicing water heater soon.
The inlet/outlet of the small cylinder seems to be connected to a heating flow and return. The coil is connected to the hot water outlet and hot secondary return. Is the cylinder acting as a heat exchanger and possibly serving a form of 'towell rail' circuit to the bathrooms and shower rads? The building (old listed ) has a central boiler house and only one heating circuit. Feel I'm on the right path and was wondering if anyone else has come across this kind of set up before?
Thanks in advance
Jason
*Apologies couldn't get pics to go the right way up

 

[ShaunCorbs]

the andrews got a few faults needs sorting asap

 

[SmokeyJ]

I'll explain a bit further.
I'm replacing a gas water heater (vented) that sprung a leak in another part of the building. When isolating turned everything off on cwsc's to drain cold feed to relocate valve and kept getting hot water back down the cold feed. Lead me to find this cylinder back feeding to my cylinder, found they share same supply from cwsc - old 3" galv. Isolated cylinder to stop back feed. I am working the weekend to complete the replacement for when the kids go back so the system is currently off until sunday.
The cylinder is vented and can appriciate the t+p, prv discharge and vent issues (ducting is high level vent) which I can deal with. Its the small cylinder that i'm not familiar with.
I am g3 and gas safe

 

[ShaunCorbs]

I'll explain a bit further.
I'm replacing a gas water heater (vented) that sprung a leak in another part of the building. When isolating turned everything off on cwsc's to drain cold feed to relocate valve and kept getting hot water back down the cold feed. Lead me to find this cylinder back feeding to my cylinder, found they share same supply from cwsc - old 3" galv. Isolated cylinder to stop back feed. I am working the weekend to complete the replacement for when the kids go back so the system is currently off until sunday.
The cylinder is vented and can appriciate the t+p, prv discharge and vent issues (ducting is high level vent) which I can deal with. Its the small cylinder that i'm not familiar with.
I am g3 and gas safe

seen one or two (normally when ripping out and starting again) and normally there were in for a buffer, but yours slightly different to the ones im thinking of (pipework wise)

 

[SmokeyJ]

Its only 49% efficient, not ideal for a boarding house, timer probably on 24/7 so imagine it gets a lot of use. I'm installing a A O Smith bfc cyclone as a replacement for the leaking one and see they do this -

Same principal I think

 

[snowhead]

Looking at the Andrews, I'd say that's been put in not that long ago as a replacement for an older less efficient unit.

I doubt there is much gain from that additional small cylinder, the coil won't have much capacity.
They'll be more gain from lagging the pipework.

Rip it out, it's a liability.

 

[SmokeyJ]

My bad its 79% Efficient. Its an A O Smith (don't get me started on andrews/baxi group 😀) Think its pretty old, its permanent pilot and have seen a few hsi ignition ones that are 15 years old. Would assume the hsi ones superseded the permanent pilot. May be wrong and they might still make permanent pilot ones.
The small cylinder is piped up backwards and seems to be acting as a heat exchanger connected to a sealed heating circuit and piped up backwards. My concern was, if I was to price to replace the A O Smith what would i do with the small cylinder. The above diagram I found has kinda cleared it up for me. A way of getting hot water and heating from a gas fired water heater

 

[ShaunCorbs]

My bad its 79% Efficient. Its an A O Smith (don't get me started on andrews/baxi group 😀) Think its pretty old, its permanent pilot and have seen a few hsi ignition ones that are 15 years old. Would assume the hsi ones superseded the permanent pilot. May be wrong and they might still make permanent pilot ones.
The small cylinder is piped up backwards and seems to be acting as a heat exchanger connected to a sealed heating circuit and piped up backwards. My concern was, if I was to price to replace the A O Smith what would i do with the small cylinder. The above diagram I found has kinda cleared it up for me. A way of getting hot water and heating from a gas fired water heater

dont they have a boiler for heating?

 

[SmokeyJ]

dont they have a boiler for heating?

Yes, as I said in 1st post central boiler house with one heating circuit. Only explanation I could see was small cylinder is supplying a form of 'towel rail'' circuit. It would involve massive works to install a separate 'towel rail' circuit so it seems like a cheap alternative I suppose