commercial boiler

the doctor · Jan 30, 2010

Hi All,

In my spare time I do the odd repair over at my local Royal British Legion.

The heating went off a couple of weeks ago with a loose wire. ( the plumber found that)

Anyhow it was going haywire and I took a look. It is on a Sangamo clock which was all over the show. I set the on/off time and set the clock time correctly and everything is good-ish. However they want it on at 7pm mon-fri and on at 12pm on the weekends and are fed up having to walk round to the boiler house to press the red override button on saturdays and sundaysX(

they asked me could i get another, more modern time clock and fit it. This I was at this afternoon. I have wired the new clock on a 4 core flex through to the kitchen and was ready to connect into the wiring centre and that is where the trouble started.

When i took the lid off the wiring centre a big rats nest of wiring fell out bad day explode it is that bad it will have to be ripped out and started again!

i am going back to try and tidy it up tomorrow but have a couple of questions for the forum.

It is a big old commercial boiler with 3 inch pipes coming out the back. The pipework splits into two halves with two pumps. there are no motorised valves fitted. at the moment the pumps seem to keep running when the room stat knocks off the boiler. Is this correct?

i and the steward dont have a clue how the hot water ends up at the taps. i said there must be a cylinder somewhere with a coil in it. is this a fair comment?

Thanking you in anticipation

alan

Lurch · Jan 30, 2010

It is a big old commercial boiler with 3 inch pipes coming out the back. The pipework splits into two halves with two pumps. there are no motorised valves fitted. at the moment the pumps seem to keep running when the room stat knocks off the boiler. Is this correct?i and the steward dont have a clue how the hot water ends up at the taps. i said there must be a cylinder somewhere with a coil in it. is this a fair comment?

Older boilers commonly have 2 tappings, one for the gravity water circuit and one for the pumped heating circuit. Where these are used on larger commercial installations it's not uncommon to find a pump on both circuits as the lengths and routes of pipes aren;t optimal for gravity water operation.

I'd also say there's a hot water cylinder somewhere.

As for when the pumps should run, depends how it's wired. Is it wired on an overrun from the boiler, or through a pipestat?

Without seeing it it's hard to say what the original installer had in mind, but usually it would just have the pumps running off the timer via a room\tank stat as appropriate. Run on circuits are usually optional.

kme · Jan 30, 2010

The pipework splits into two halves with two pumps. there are no motorised valves fitted. at the moment the pumps seem to keep running when the room stat knocks off the boiler. Is this correct?

For the heating; yes.

i and the steward dont have a clue how the hot water ends up at the taps. i said there must be a cylinder somewhere with a coil in it. is this a fair comment?

Thanking you in anticipation

alan

Ermmmm - probably; unless it`s a combination boiler; with instantaneous water..... Which sort of fits, as Sangamo timeclocks (which do, incidentally, come as a 5+2 day variant) are generally single channel.

What is the water pressure at the hot tap? Can you stop the flow with your finger over the end, or does it spray out all over the place? Not a definitive method (unvented cylinder possibility) ; but would verify gravity supply.

KME

the doctor · Jan 30, 2010

ta for the replies guys.....

at the wiring centre there are wires for, the two pumps, roomstat, clock and boiler so it is not wired for a pump run on from the boiler.

so from what you guys say i will wire the pumps for on while programmed with the room stat only controlling the boiler. What about when the programmer switches off while it is running, here the pumps and boiler will switch off together. this is ok i take it?

I will check that tap pressure tomorrow....

If i find the camera, i will take pics, it is horrendus:coat

Lurch · Jan 30, 2010

Well this is where the limitations and shortfalls of the single channel programmer come into play. Usually you'd have the HW channel control the boiler and the CH channel control the pump via the room stat. the programmer, if set to 10 position, will bring the hot water on whenever the heating is on. If you add a pump to the hot water circuit you would connect the hot water pump to the boiler so the boiler and hot water pump are on when the water only is on and the heating pump is on as well when the heating is on.

If you are using a single channel programmer I would put the hot water pump and boiler off of the programmer output and have the heating pump via the room stat.