Pump run on / bypass valve on oil boiler

DublinDilbert

Hi all,

Was looking at an oil burner for a family member, the odd time it has hit the hi limit stat shutdown. The system is zoned (myson valves) no by pass fitted. There is also no timer or stat to allow the pump run on.

The boiler is a good 20m fro the house and is only fed by a 3 core cable, so no perminant live supply so can't fit a stat for the pump.

Most oil burners I see have some way of getting the pump to run on, I'd imagine it's important if the boiler is very hot and firing at the end of the timer cycle.

Is there any clever solution for situations like this?

jimf

sometimes it can as simple as turning the stat down from 70 to maybe 65

is boiler in garage or a heatpac /module

DublinDilbert

jimf wrote: »

sometimes it can as simple as turning the stat down from 70 to maybe 65

is boiler in garage or a heatpac /module

Thanks for the response.

Yep I knocked back the main control stat closer to 65/66 it was around 70/72. It's in an outdoor enclosure at the end of the garden.

Wearb

DublinDilbert wrote: »

Thanks for the response.

Yep I knocked back the main control stat closer to 65/66 it was around 70/72. It's in an outdoor enclosure at the end of the garden.

If pump is beside boiler, you could put an overrun wired to the incoming live. It would work some of the time and cut down on a lot of the hi limit faults.

Jim's suggestion is simplest and worth a try first. All these old guys know their stuff LMHO.

John.G

I think Grant suggested a pump overrun "where the pipes turned down" like in the heatpacs but even if the pipes are angled upwards if all zone valves close then no where for the hot water to go.
I have a heatpac Firebird 90S and I did test the o/temp stat operation a few years ago by running the boiler with the pump off, it cut out at my normal set temp of 75C but did not subsequently trip the o/temp stat, I measured the boiler outlet temp just on the elbow where it exits the boiler and it read ~ 95C. Also if my boiler has been running (normally) on the HW coil only when the cylinder is nearly up to temp and after the boiler has cycled off then the temperature does again seem to rise to 95/100C but again no trip. The only time I can recall the o/temp tripping was after a system drain down and refill where I had forgotten the vent the boiler via its PRV.
I should also add that even though my pipes turn down (heatpac) there is always a path for some little movement of the hot water through 8 of my rads which are on TRVs only, the other (master) two are on zoned/roomstat control.

DublinDilbert

Wearb wrote: »

If pump is beside boiler, you could put an overrun wired to the incoming live. It would work some of the time and cut down on a lot of the hi limit faults.

Jim's suggestion is simplest and worth a try first. All these old guys know their stuff LMHO.

Yea i would fit one but Ive no permanent live at the boiler, and it would be a pain to run one. I could make the live to the boiler permanent, but then I'd need to use some other method of controlling power to the burner (rf etc...)

The owner is elderly, so looking to do anything to make it more reliable. The burmer is serviced and otherwise working fine. I migh knock the temp a couple of degrees lower, which would increase the headroom on turn off.

John.G

Don't know what the boiler make is but I would be a bit surprised at tripping at 70/72C setpoint, maybe control stat/o/temp stat faulty?
I think o/temp stat is ~ 110/113C.

Wearb

With reference to John's second last post and reason his tripped once, does boiler have a working auto air vent?

Btw you misunderstood my suggestion which doesn't need a permanent live.

Calahonda52

Is there no rad that does not have TRV?
maybe take off the TRV in the bath room?

John.G

No manual or auto vents anywhere on my system (open vented).

I have seen a normally open motorised valve installed as a bypass on systems, so when all the zone valves are de energised the shut bypass springs open and re closes when any zone valve opens but how does a circ pump run without power?.

Wearb

John.G wrote: »

No manual or auto vents anywhere on my system (open vented).

I have seen a normally open motorised valve installed as a bypass on systems, so when all the zone valves are de energised the shut bypass springs open and re closes when any zone valve opens but how does a circ pump run without power?.

You stated that only time yours tripped was when there was air at top of boiler. That's why I suggested AAV might help.

're circulating pump, it will have power when boiler cycles on boiler stat.

John.G

The only time I get air is after a drain down/refill that is so infrequent that the PRV
does the job, I know its said that PRVs can leak when used for this purpose but mine is as old as the 15 year old boiler.

If the o/temp stat is tripping during normal operation then some other problem IMO as the pump runs continuously once there is a switched live, the burner cycles on/off. I was under the impression that the problem is arising when the burner and the circ pump shuts down.

DublinDilbert

Wearb wrote: »

With reference to John's second last post and reason his tripped once, does boiler have a working auto air vent?

Btw you misunderstood my suggestion which doesn't need a permanent live.

Sorry i'm not sure i do get you. My incoming live to the boiler is switched via a time clock, so once the time clock turns off I lose all power at the boiler.

If there's no stat / permanent live what will keep the pump going?

Wearb

DublinDilbert wrote: »

Sorry i'm not sure i do get you. My incoming live to the boiler is switched via a time clock, so once the time clock turns off I lose all power at the boiler.

If there's no stat / permanent live what will keep the pump going?

While the timer is on, the burner will turn on and off several times on the boiler stat. During those off periods, there will still be a live to the boiler.

John.G

And the pump will still be running so no problem regarding this??

John.G

DublinDilbert wrote: »

Sorry i'm not sure i do get you. My incoming live to the boiler is switched via a time clock, so once the time clock turns off I lose all power at the boiler.

If there's no stat / permanent live what will keep the pump going?

To clarify for everyone, is the problem arising after the boiler and circ pump stop?? ie when the timer or whatever switches every thing off.

Wearb

John.G wrote: »

To clarify for everyone, is the problem arising after the boiler and circ pump stop?? ie when the timer or whatever switches every thing off.

Of course you're correct John. When the boiler cycles on the boiler stat the pump will still be running.


@DublinDilbert, ignore my suggestion. I wasn't thinking it through properly.

wilser

DublinDilbert wrote: »

Sorry i'm not sure i do get you. My incoming live to the boiler is switched via a time clock, so once the time clock turns off I lose all power at the boiler.

If there's no stat / permanent live what will keep the pump going?

One solution would be to move the timeclock out to the boiler house and then you would have permanent live out there. Only problem is the timeclock is at the end of the garden.
You could put a rf timeclock on the system c/w an Internet gateway, then the heating could be controlled via an app.

jimf

i think the problem been so intermittent only happens when the boiler is near or at its max set temp on the stat and the clock turns off

static water then in the boiler continues to rise in temp

95% of the time just turning the stat down as iittle as 5dg can solve the problem

for some reason this problem is more of an issue with firebird boilers probably to do with pipe set up

so much so that fb issued a pipestat as part of the boiler package to be wired as part of the boiler install

always a good idea to run 4 core for any boiler permanent needed or not

are you at the gin already wearb at boolavogue as the sun was setting up limerick

Wearb

jimf wrote: »

are you at the gin already wearb at boolavogue as the sun was setting up limerick

Congrats on the win Jim.
I'm a teatotaller at the min. Couldn't be bothered having a few at home. The kids gave gotten draught beer dispensers, so I'll give that a try soon.