Grundfos Condensate Pump

[Phillay]

Hi chaps,


Having to install acondensate pump below my new boiler and I'm a bit unsure of how towire this in. Boiler is a Worcester Bosch 28kW Compact and I have aHoneywell CM900 RF stat wired into the set up for heating control.


Purchased a GrundfosConlift1 to pump away the condensate. There's the twin core &earth power supply cable and a two core safety overflow switch cable(0.5mm).


The boiler is currentlypowered by a 3amp protected double pole FCU and 0.75mm heat resistantflex cable.


The receiver for the RFstat requires a link from 'L' to terminal 'A' ('B' then wires to 'LR'on the boiler). I believe I'm right in thinking I can remove thislink and replace this with the safety overflow switch cable from thepump. Brown (COM1) to 'L' and Blue (NO4) to 'A'. This will then actas the link, and break it should the pump fail, stopping the heatingdemand.


Regards the pump powersupply, is it acceptable to wire the power cable into the same 3ampFCU as the boiler? ...The manual does state “check that theinstallation has a 10amp slow blowing fuse on the mains side”.


Cheers for anyinput/advice


P.S. Sales literatureindicates the pump runs at 0.65amps.

 

[gasmanrob]

Unless you are gas registered you can't do it as it means removing the case which is a seal on those boilers.

And cue croppie

 

[Ermintrude]

Who installed the boiler? U aswell?

 

[Phillay]

Nope, I didn't install the boiler or the thermostat receiver into the boiler electric points. That was all done by someone I paid who is Gas Safe registered. No chance I would touch.

The stat is already wired in and is external to the boiler casing controls. Neither touching this, nor opening the FCU requires me to touch any part of the boiler... the whole circuit would be isolated when I turn it off at the mains.

 

[Dotty]

As long as you don't take the boiler case off.

Keeping an eye on this one.

 

[Phillay]

Before the question is asked, the condensate is currently terminated into the stack, but this pipe is run surface mounted through my hall into the bathroom (the only way the gas engineer could get a fall).

He suggested a condensate pump for permanent replacement (so the hose could go under the floorboards) but had never wired one in himself.

 

[gasmanrob]

All the safety wire does is interrupt the supply on the switch live boiler on in the event the pump fails. make it part of that loop jobs a fish

 

[Phillay]

Yeah, I'm lead to believe by the installer instructions it can either break the live switch between the stat and the boiler.... or can be wired to break the live power between the FCU and the boiler.

I wasn't sure which was the best way, but thought that if it was wired between the stat switch and the boiler, it would only kill the demand for heat (thus stop condensing) and not completely switch the boiler off.

 

[Ermintrude]

Ok. So to do it without touching the boiler.

Mains lead from boiler remove from spur, connect neutral and earth to the pump and a piece of 3core 0.75mm flex. Using a suitable junction box and connector. Connect the live from new flex to live of pump and one of the two wires (high level cut out switch) the other wire from high level cut out to the live on the boiler flex. Then connect the other end of the "new 3 core flex" into fused spur.


Assumed you were competent and qualified to do electrical work. If your not you should consult an electrician

 

[Phillay]

I have consulted an electrician, but to be honest he was confused by the Grundfos instructions... and again had never had the joy of fitting a condensate pump so wasn't filling me with confidence.

I'm competent at electrics to a certain level through College, but no, not qualified. The FCU is already there to cut the supply and the boiler + electrics isn't in a restricted zone. Take your point though.

 

[Ermintrude]

I edited it as was slightly wrong

 

[Phillay]

No worries, thanks for that, mapped it out and can see what you're saying... the high level cut out would basically turn the boiler off completely. Here's where my 'concern' comes in.

The high level cut out cable is 0.5mm... so the live to the boiler would end up going from 0.75mm down to 0.5mm, then back to 0.75mm. I know the amp usage is very low, but is there the chance that would cause a problem?

Also, will it all be ok remaining on a 3amp fuse? (given the installer instructions for the pump talk about a 10amp slow blow).

 

[mountainman]

An electrician confused by condensate pump wiring?
Surely not!

 

[Phillay]

Yep... I had alot of "not really sure what they're saying there... but I think..." didn't fill me with a lot of confidence in all honesty.

I fired an email off to Grundfos pleading for a black and white diagram I could present to him!!!

 

[Ermintrude]

No won't be a problem. 3amp. Basically high level just killing boiler it it all goes Pete tong!

 

[Phillay]

Cheers for your help, much appreciated.