New Boiler: What to do about Pump Overrun when there aren't enough wires?

[jweaver]

I need a new boiler and have been quoted for various makes, but I had pretty much settled on a Worcester Bosch just because of reliability. But then the subject of "Pump Overrun" came to light.

It seems that my system is currently fed by 3 wires (L, Neutral and Switched Live) and I am missing the necessary for Pump Overrun..

I now have a number of options and I just wondered if anyone has any thoughts.
1. Get a Baxi instead - I understand they do not need Pump Overrun
2. Get a Vaillant - I believe they need Pump Overrun, but have the option to disable it.
3. Stick a cable in - Almost impossible inside, and messy if I went up the outside to the loft and then back down into the airing cupboard
4. Look at Wireless options - The "Mainslink" seems to be built for this application.
5. Look at 'delay' timers.

The last of these is interesting, as surely you could wire the Pump via some kind of timer, which would allow the pump to stay running after the valve closes, cutting power to the pump..

It seems that the best option is either going to be a downgrade to the Baxi, or some kind of Wireless solution. But I am not sure whether I like the idea of a cheaper Baxi.. But then again, will a wireless pump solution be problematic/unreliable.

Any thoughts?

 

[Razor900]

Mainslink were always quite expensive and I never found them much good tbh. Fitted a few of the Salus version, (GGPC1 RF) and they have all been spot on.

A delay timer would invalidate the WB warranty. The boiler has to control the pump itself.

Can you get a cable across to the boiler maybe up into the loft and down the soil pipe boxing?

Or is the programmer currently next to the boiler in which case you could move it upstairs and have more than enough cables

Lastly you really should be thinking about priority hot water so you can run a low temp for space heating and ramp it up for hot water

 

[jweaver]

Can you get a cable across to the boiler maybe up into the loft and down the soil pipe boxing?

Or is the programmer currently next to the boiler in which case you could move it upstairs and have more than enough cables

thanks for the reply.. The programmer/timer is in the airing cupboard, so there is nothing downstairs with the boiler.

There is boxing for what I believe is a soil pipe close by, so this is an option and I am going to get up in the loft this weekend to see if it goes all the way from top to bottom.. But its on the other side of a brick wall to the boiler, and drilling a hole for the cable, without damaging the pipe could be tricky/risky.. But I am look at that as an option.

 

[CountryFan]

Maybe go for the Baxi to save any additional issues?

 

[jweaver]

Maybe go for the Baxi to save any additional issues?

I am swaying towards that to be honest.. I have seen mixed reviews of them and really wanted to go for the best in class, but considering the only real options are to run a cable, which might not be easy, or live with a premium boiler but the added complexity of wireless pump control which could be its Achilles heel... The Baxi just seems like the logical choice..

Cheers

 

[gas112]

The last of these is interesting, as surely you could wire the Pump via some kind of timer, which would allow the pump to stay running after the valve closes, cutting power to the pump..

The live used to run the pump afterwards is also sometimes used to keep the boiler fan on for a period of time to dissipate heat as well

 

[Johntheo5]

On the fairly large (53MW) Gas fired steam Boilers that I was very familiar with, a post purge, (fan overrun) always occured, but to clear any unburnt gases from the furnace after a normal shut down. The Baxi MIs should show if it has a permanent live to do a post purge for whatever reason, and if so, maybe advisable to ask them if its actually required and ensure that the burner doesn't lock out after every shut down if it isn't.

 

[gas112]

On the fairly large (53MW) Gas fired steam Boilers that I was very familiar with, a post purge, (fan overrun) always occured, but to clear any unburnt gases from the furnace after a normal shut down. The Baxi MIs should show if it has a permanent live to do a post purge for whatever reason, and if so, maybe advisable to ask them if its actually required and ensure that the burner doesn't lock out after every shut down if it isn't.

baxi same as all 3 wire boilers does not have a permanent live for pre or post fan purge it is purely a switched live / neutral and earth to bring boiler on when ch or hw demand

 

[Razor900]

On the fairly large (53MW) Gas fired steam Boilers that I was very familiar with, a post purge, (fan overrun) always occured, but to clear any unburnt gases from the furnace after a normal shut down. The Baxi MIs should show if it has a permanent live to do a post purge for whatever reason, and if so, maybe advisable to ask them if its actually required and ensure that the burner doesn't lock out after every shut down if it isn't.

I agree. The pre and post purge is used to make sure there is no unburnt gas in the combustion chamber in case the gas valve is letting by

 

[CountryFan]

I am swaying towards that to be honest.. I have seen mixed reviews of them and really wanted to go for the best in class,

@gas112 has fitted hundreds of them, so would be best place to answer any queries you have with them. Main is a cheaper boiler, still under the Baxi umbrella, but shorter warranty.

 

[trojanhawrs]

If there's a socket near the boiler I would think it'd be quite straightforward for an electrician to repurpose the existing power cable to a volt free contact.

 

[OvertonPlumber]

Seen loads of glowworm energys and vailants wired on switch live only.
Surprise razor didnt mention the intergas doesnt need pumo overrun.

 

[CountryFan]

Surprise razor didnt mention the intergas doesnt need pumo overrun.

Because OP wants a decent boiler....

 

[Razor900]

Because OP wants a decent boiler....

Yes the older Intergas boilers can run without pump overrun but that doesnt mean they should.

You end up with the front panel clicking much quicker.

Almost all modern boilers should have pump overrun even the ones that say they dont need it. As much as the boiler heats the water the water flowing through it also cools the boiler and when you have something thats getting on for 700 degrees at the top of the hex and 50 at the bottom the thermal difference is enough to cause longterm issues.

Of course the OP could always go for a system boiler with the pump built in and avoid the issue entirely...

 

[gas112]

Of course the OP could always go for a system boiler with the pump built in and avoid the issue entirely...

is there any 3 wire system boilers ? would still need 4th wire for perm live to power pump afterdemand