Grundfoss 26-99FC variable speed failing

wrooper

Hi all,

I have a Grundfoss 26-99FC that has run on Med speed for 11 years. This past spring we were travelling for 5 weeks and when I came home my indirect was calling for heat and the Grundfoss was not responding. I gave it the customary whack with a screwdriver and it has run fine until today. Assumed it just got hung up sitting at some point during our trip.

Today same indirect calling and warm,not hot second shower [mine of course] so I gave it a whack and it started again. Boiler has been under moderate use this winter.

When I switch speeds it always runs on low or high but perhaps 50% of the time when switching to medium it won't run. This makes me wonder if it is the switch failing and not the circulator? If it were a customer's unit I would replace the circulator to avoid additional service calls but since it is mine I am wondering if I can replace the switch?

Anyone else run into a multi-speed switch failure?

Can anyone describe how the switch works ? eg can I replace a resistor?

Thanks In advance Bill

GroundUp

I have never had any luck getting parts for Grundfos circs, but I do wonder what sort of piping configuration you've got that would require a 26-99 on speed 2 simply to serve an indirect. If it will run on speed 1 without trouble, why not leave it there? I'm willing to bet that speed 1 is still considerably more flow than the indirect needs

SuperTech

I'm in agreeance with GroundUp, you are over pumping your indirect. What kind of piping and heat emitters do you have? Is your boiler water full of nasty debris?

RPK

I had a smaller Grundfos wet rotor circulator that stopped running on low speed after about 1 heating season. It has run perfectly well on medium speed for two seasons. Full replacemrn would be a headache due to lack of isolation valves and glycol in the system. I was thinking of just swapping the speed selector switch out (even if I have to buy the whole pump). Never actually called looking for replacement parts, but I’ve been wondering how available they are.

wrooper

Thanks for your comments
My indirect is only a small part of my system and probably accurate to say that medium is more pump than I need when the indirect is the only thing calling however my 6 floor loops and 3 other zones of baseboard led me to the Medium speed on the 26-99. It was 11 years ago that I made the curve calculations and I can't remember them now. Suffice to say the pump has performed well in my system except now it only runs intermittently on the medium setting. High or low it runs fine.

This is why I suspect the switch/contacts/resistor but I had hoped someone else had seen this and found a fix short of replacing the whole pump

GroundUp

The same pump serves 4 heating zones AND the indirect??

wrooper

bump

GroundUp

It'd help to answer questions that have been asked

wrooper

Sorry I didn't give you a chance to lecture me about a system design that has worked well for 11 years and answer your off topic question ; )

BTW ordered a new pump today so I can run it on M for another 11 years

GroundUp

I'm glad you spent money you didn't have to ; )

Enjoy

wrooper

bump

still hoping someone found a way to repair a Grundfos 3 speed switch?

SuperTech

Bump


Why over pump for 11 years and expect failure when a properly sized pump will deliver better efficiency without having an expiration date?

Zman

wrooper said:

Sorry I didn't give you a chance to lecture me about a system design that has worked well for 11 years and answer your off topic question ; )

BTW ordered a new pump today so I can run it on M for another 11 years

There is no way to reliably repair the switch. They don't go out very often. Unless Grundfos is willing to ship an new switch, it looks like a new pump is in order.

Whether you like it or not, your present circ is oversized for your system. I am sure it "works" just fine. I am also sure that you are using more energy than needed and that your pipes will pinhole sooner and that your circ will not last as long.

If you balanced the baseboard and indirect loops, you could run a smaller circ. Sorry for the "lecture", it is just the simple facts.

wrooper

Not sure why folks seem to think I am "over pumping" or "under pumping" when both can be true depending on which zones are calling ?

I realize a more sophisticated pump could be used to gain a marginal efficency but in my experience efficiency is gained threough complexity which is the enemy of reliability.

Besides, the comments are off point. My pump has not failed but the switch seems to be. I appreciate the confirmation of what I too have found, the switch is not available for replacement.

SuperTech

You don't need a complex or sophisticated pump, just one properly sized for the load and pipe. Most likely it would be much less expensive than a 26-99. Probably a Taco 007 or Grundfos 15-58 are adequate. You could get a Grundfos Alpha and set it auto adapt and walk away with no worries. You get sophistication without complexity.

GroundUp

You'll find out when the piping starts to pinhole that you should've probably listened to those wanting to "lecture" you about your system. You came for help and it was offered, your choice to ignore it and stick with your ego will rear its ugly head. Happy new year to you and yours

Zman

You are presently over pumping all the time.
When everything is open, the lack of balance in the baseboard and indirect loops means that 2-3x the required flows are going through those loops.The radiant is flowing about right.
When just the radiant is calling, that is being over pumped as well.
The majority of buildings in the US over pump so you are not alone.
I have been trying to convince the owner of a commercial building to turn down the VFD on a 15hp pump for 3 months now. The projected savings would be $8k per year. They would have already saved $2k if they had me do it 3 months ago. The job would require no parts, just a few site visits to monitor the data loggers and verify that the flows are adequate and make minor adjustments.

They are also spending well into 5 figures annually repairing pinholes and rebuilding pumps and valves due to excess velocity.

I like this analogy: "When you hop in your car, do you put the gas pedal to the floor and manage your speed by feathering the brake? That is what you are doing with your buildings heat."

Steve Thompson (Taco)

Why speed 1 failed depends on what the switch does.

Some three speeders have three sets of windings so it could be speed one winding is burnt (the switch determines which winding gets power). Others limit the voltage going to a single winding (like a dimmer switch). Is it a switch fail or winding - and if winding, did that failure cause the switch to burn out - almost impossible to tell.

The easy part is, the lowest (worst) starting torque of a non-ECM pump is on low speed. So, these things are vulnerable to cycling during locked rotor on speed one. Sounds stupid but it's best to keep em running 24/7 if possible (hardest thing to do to a motor is turn it on).

Windings or switches are typically not available as a spare part, only the rotor/can assembly.