Grundfos Home Booster

[oldsparky]

Hi There

I wonder if anyone can help me please? I have recently had a Grundfos Home Booster installed to supply boosted water to hot and cold services via the integral tank and a Range Tribune 250l pressure cylinder.

I have set the outlet pressure at 3.0 bar to match the existing regulating valves in the system, with the differential set at 1.0 bar.

Unfortunately the system pump continually cuts in and out instead of running continuously when an outlet is opened or shower used. Not conducive to long pump life!

The unit has 28mm outlet pipework splitting into two 22mm legs, one to the Tribune, the other to the CWDS.

Any help gratefully received!

 

[ChrisR]

Is there an existing or new pressure vessel?
What has the precharge been set to? Perhaps it's too high? Or it's full of water?! Try 2 bar.

 

[Agile]

The usual advice would be to call back the installer if its not working properly.

My guess is that the air charge pressure has not been correctly adjusted to match the pressures that you have set.

Tony

 

[oldsparky]

Thank you, gentlemen. There are two expansion vessels. One contained in the packaged Grundfos unit, the other supplied with the Tribune (in 2005). As you suggest, I suspect the installer did not check and commission the pressure in the Grundfos vessel. Both vessels 'sound' like they ar not full of water when tapped.

I will check the pressure in the HWS vessel as it was last done at service in October last year. Presumably this is checked with the Tribune at atmospheric pressure and not pressurised?

I would rather walk over burning coals than have the installation guy back, hence my desire to rectify the problem myself. I won't bore with the sordid details.

Many thanks for your advice.

 

[ChrisR]

Presumably this is checked with the Tribune at atmospheric pressure and not pressurised?

Correct.
Home Boosters will often work with NO extra vessel, so maybe a call to G would be worthwhile. I guessed there would be a reason for not badgering the installer!

 

[tonybhoy]

I would rather walk over burning coals than have the installation guy back, hence my desire to rectify the problem myself. I won't bore with the sordid details.

Many thanks for your advice.

Go on,tell us you tease

 

[Biggles..]

This unit works like an accumalator,what grundfos haven't done is updated the instructions adding that you need to fit a pressure reducing valve to the outlet of the unit. Run unit at 5 bar so unit squeeezes pressure, differential is set so when squeeze has gone by set amount it repressurises(3.8bar ish normal). set presure reducing valve you've fitted to the outlet to the required pressure you want your hot and cold to run at say 2bar.

If you do this you'll cure the hunting.

This unit is not a constant pressure pump and should not run often even with taps opening. the pump wont burn out, the contacts will and then you'll have to swap the pump wiring position.

It appears some of the other posters haven't had the pleasure of fitting one of these and then discovering the same fault as yours

Oh dont bother with grundfos on this their technical dont know how to set them, they'll book you a service call which will be subbed out and you'll get charged for your troubles.

Lee

 

[oldsparky]

Thanks Icgs. I checked the built in EV pressure (1.5 bar and obviously not commissioned as I suspected). Setting this to the correct pressure has had little effect on the problem. Real pain in the a*sr to get to the Schrader valve behind the booster pump. Checked the EV on the Tribune and that's spot on.

Interesting comment on Grundfos tech support; without going into too much detail (sorry tonybhoy!) the unit p*ssed water from the overflow when initially installed. There is no way of getting to the float valve to adjust the factory preset levels without ripping off the top fly screen.

My 'installer' called Gfos about this and all they could offer was "you don't need to get access to the valve". Wow! a completely maintenance free ball valve! Must get a patent on that! Needless to say he removed the sealed fly screen and did the necessary - nicely stuck back down with some Aly duct tape now!

I'll get around to fitting the prv when I get back from hols in a couple of weeks time.

Once again, Gentlemen (all), thank you for your sound contributions.

BTW - I'm having an ICOS 18 installed this week to replace my old Envoy 60............. Yes I know....................

 

[Agile]

BTW - I'm having an ICOS 18 installed this week to replace my old Envoy 60............. Yes I know....................

Well, the Envoy was not very good.

The question is whether the Icos 18 is any better or perhaps even worse!

Tony

 

[Biggles..]

To get to the ball valve you remove the large 6 screws, take off front panel and a large hole appears at the top where you can then stick your arm through and adjust the level.there should have been no need to even touch the fly screen.

 

[oldsparky]

Sorry Icgs but they have changed the construction of the tank. The only access, having removed the cover as you say 6 crosshead screws, is via the hole you describe in the top of the unit - which is now covered with a mesh fly screen mastic sealed to the tank top! Cracking bit of design but Gfos 'say' it's to meet the water regs and " you shouldn't need access to the ball valve! I'll send you a pic if you want because I couldn't believe it either!

Anyway I've just checked the pipe work and there is a prv in the cwds downstream of the unit set at 3 bar. This is a legacy of the original installation of two ST KB-6 pumps (one on hot one on cold) which proved far too noisy. With the built in 3 bar prv on the Tribune your suggestion of upping the pressure should work without yet another prv mod. I'm going to try it shortly.

Agile

The Envoy 60 was a wonderful boiler Installed in 1997 broke down after 6 months and then all the usual hot surface ignitor, power supply/pcb problems and O ring failures. Having said that the Heat Exchanger has lasted 11 years. Time to quit whilst I'm ahead! I have a load of new spares (for obvious reasons!) soon to appear on eBay. I'll let you know how I get on with its younger brother the Icos.

 

[Biggles..]

My apolagies ,you've go the mark 1 the design has changed with the breather hole now situated at the back with the above mentioned fly screen.

Up the charge pressure of the unit, lower the differential to that above the PRV and set the prv to about 2 bar(cant think why you'd need more than that.)

Lee

 

[oldsparky]

All done! I've left the prvs at their preset 3 Bar (I'm lazy) as they aren't easy to get to and I'm packing today. Set booster to 5.5 Bar and cut out at 3.5 Bar. Thing now works perfectly!

Why on earth Gfos don't include this info is beyond me. Good job you know your stuff, Lee - many thanks.

PS The Icos is now alive. Let's hope it lasts................

 

[Agile]

Ideally once the system has been set up with suitable pressures the expansion vessel pre charge pressures should be set accordingly.

Tony

 

[Biggles..]

Glad its all sorted.