Grundfos Mq3-45 Pump...

[kbvicar]

Everything I've read here seems to suggest the MQ3-45 is a good pump. I called some dealers today and two of them commented they had complaints regarding the electronics with this model and suggested I buy a different model Grundfos.

My question...have any of the members here had problems or know others who've had problems with the electronics on the MQ3-45???

[longball53098]

I have this pump in operation now for almost 6 months as our main water supply pump. No issues to date with plenty of push for showers, sinks and other stuff. I ran it dry once and as advertised it shut down and then allowed a safe recovery after I put more water in the tank.

My only issue is this pump has a very small pressure tank and this causes the pump to cycle on even if you just open a tap to rinse a glass out. The pump then runs about 45 seconds to re-pressurize the system. So if the wife is opening and closing a sink faucet to wash out a plate and cup or you are brushing you're teeth the pump can cycle on/off a lot. Because of this I will install a bladder pressure tank in the not too distant future. Something in the order of 100 liters or more.

[bkkbill]

That is the best way to go longball I think cycling the pump continuously is the main cause of failure.

[lopburi3]

I have used for about three years and had one starting cap failure. I suspect that pump may not have been new as major store that sold it had no paperwork or package for it and was the only one they had.

[Crossy]

Anyone running one of these (or any other pump) with an extra external pressure tank (so there are two pressure tanks in the system)?

Are you using the original pressure switch (on the built-in tank)?

Any issues with the pump cycling with pressure bouncing between the tanks?

[powderpuff]

Can anyone tell me how to adjust the start & stop pressure on this model? Thanks

[longball53098]

The MQ 3 45 is factory adjusted and cannot be changed. This model was not designed to be installed with an outside pressure tank. The starting pressure is 28 psi for this pump and the flow switch shuts it down at .3 liters per minute. The tank only holds a very small amount of water and is only designed to keep the pump off in event of very small leaks.

I am talking with the shop that sold me this pump to see what issues I might have by installing a bladder tank but using the pumps settings. The first answer from them and a Grundfos rep was not to do this. I pressed them to do some research and get back to me. I am waiting for more information.

[stgrhe]

The MQ 3 45 is factory adjusted and cannot be changed. This model was not designed to be installed with an outside pressure tank. The starting pressure is 28 psi for this pump and the flow switch shuts it down at .3 liters per minute. The tank only holds a very small amount of water and is only designed to keep the pump off in event of very small leaks.

I am talking with the shop that sold me this pump to see what issues I might have by installing a bladder tank but using the pumps settings. The first answer from them and a Grundfos rep was not to do this. I pressed them to do some research and get back to me. I am waiting for more information.

I have been in contact with Grundfos in both Sweden and Denmark and they say the same, 'do not fit an extra bladder tank on this pump'! I will therefore select the Grundfos CH4-series that has a built-in 25 litres tank for my house.

[powderpuff]

Ok so the start pressure is 28 PSI. What is the cutoff pressure?

[lopburi3]

End of water usage and pipe pressure of 65psi.

[longball53098]

2. What causes the MQ to stop?

Answer: Other than the manual on/off button,

only the flow switch is authorized to automatically

stop the MQ during normal operation when

flow drops below 0.3 gpm. The pump will shut off

in 12-15 seconds after flow stops.

Additionally, the MQ will be turned off in the

event of a dry-run or over temperature alarm.

This quote comes directly out of the user manual.

Edited December 24, 2009 by longball53098

[powderpuff]

IIRC the spec sheet says it's capable of 7.5 bar or 7.5 kg/cm2. Sp lopburi that souds pretty good. I wanted 4 bar or 60 psi which it seems it will achieve. Thanks again.

Would you say it's perfect for a 2 storey house?

[lopburi3]

We use at ground level (actually inside kitchen) from above ground tanks for a two story house and it works fine - have five bathrooms and three kitchen sinks and never have a problem taking shower - it will slow a bit with other taps open but still stronger than than the normal Mitsubishi large 405 model pumps we had previously.

[powderpuff]

I emailed to Grundfos Thailand. Told them my specs. They suggested CH2-50PT. I went to look at them at HomePro. You can adjust trhe pressure on them. Think I'll buy CH4-50 PT to be safe.

[axeman686]

is it possible to use an existing pump in a well to a pressure tank, and after the pressure tank on the outlet to the house install the mq3-45 to increase the pressure ?

The MQ 3 45 is factory adjusted and cannot be changed. This model was not designed to be installed with an outside pressure tank. The starting pressure is 28 psi for this pump and the flow switch shuts it down at .3 liters per minute. The tank only holds a very small amount of water and is only designed to keep the pump off in event of very small leaks.

I am talking with the shop that sold me this pump to see what issues I might have by installing a bladder tank but using the pumps settings. The first answer from them and a Grundfos rep was not to do this. I pressed them to do some research and get back to me. I am waiting for more information.

I have been in contact with Grundfos in both Sweden and Denmark and they say the same, 'do not fit an extra bladder tank on this pump'! I will therefore select the Grundfos CH4-series that has a built-in 25 litres tank for my house.

[longball53098]

An update to this info,,,I contacted Grundfos in the USA and got a perspective from them on this. Their support took my question to the engineering guys and he came back with this reply: The MQ series is not designed to be used with any external pressure tanks. It is designed to be a stand alone pressure boosting pump. The fixed settings for the on/off cycles is set in the control system of this pump.

He told me that if I still insisted and added a pressure tank that he would say any tank larger than 18 liters in size may be a problem for the pump. He went on further and said a larger tank may take too long to re-fill and this could cause the MQ pump to falsely think that it has a low flow condition and shut down with a low flow alarm

I took his advice and installed a 18 liter tank and it definitely helps my situation of reducing the on/off cycles of the MQ pump. I get about 1 minute of strong water pressure now before the pump starts and this allows say rinsing glasses or flushing one toilet without running the pump. I would say the pump now starts and stops about half as often as it did before and I'm sure this will extend the life of the pump.

I am more happy now than before. The MQ is a great pump and with the added 18 liter tank it's even better for our system.

[Pib]

Kinda sounds like your modification has basically created a water pump with booster tank similar to the Mitsubishi WP series pump which have the motor/pump, manifold, pressure switch, air recharger valve setting on top of a booster pressure tank in the 15-20 liters range, like my Mitsubishi WP-255Q. Probably the most popular pump design sold in Thailand and sold at many places like HomePro, Global, HomeWorks, Lotus, Carrefour, many small outlets, etc., and usually made by Mitsubishi, Hitachi, Fujitsu, etc. Nothing against Gundfos, just saying increasing the pressure tank size to 18 liters just mirrors the design/manufacturers mentioned above. Cheers and Happy New Year.

[longball53098]

I was only pointing out what I did to cure the constant start cycles of the Grundfos. If a person needs a good strong pump I highly recommend the Grundfos line of equipment. I already owned the MQ and I I could not live with the pump starting just to rinse a glass or open the tap for some small use.

Very true I now have a setup that would be similar to a Mitsu or many other makes. If I had researched a bit more about the MQ series I may have concluded one of the other types they sell would be a better fit for me. I am a fan of Grundfos and this pump setup works for me. It would have also worked just using the pump and no added tank but I chose to add the tank to reduce the starts of the pump. Grundfos support actually suggested not to do this as the MQ is capable and designed not to use a pressure tank .

Happy New Year!

Edited January 1, 2011 by longball53098

[Pib]

Yea, no doubt the Grundfos is a very good, and strong, pump. They have a very good reputation and customer service. Before I retired to Thailand I knew particularly nothing about water pumps since I had always lived in locations that had good water pressure from the main lines (excluding some of my overseas PCS/deployed locations). When we bought our new home here in Bangkok the builder had already installed my current water pump system with storage tank, check valves, etc, etc., etc. Being a newbie to water pump setup, I initially thought the whole setup was some type of brainless design, but as I got smarter on the subject, I now know they definitely knew what they were doing for a good and reliable system, whether the pump was operating or not due to no electricity/pump breakdown, when the street water main flow may stop for a day, ensuring no back flows in case of situation X, Y, or Z, etc. I switched my opinion that it was really me that was pretty much brainless on water pumps and it was enjoyable doing to self study on them. Water pump designs are basically simple "after the light bulb" comes on in your head about how it works....but getting that bulb to initially light up can sometimes take a lot research/study...or at least it did in my case.

Cheers and Welcome to 2011.

PS: I've been thinking months about adding a 20-100 liter supplemental/2nd pressure tank to my Mitsubishi WP-255 setup. I see this type of setup at a few house in my moobaan and the folks living there say the setup works fine. I'm keeping my eyes open for a diaphragm or bladder type tank versus a basic steel tank at a low price....as soon as I stumble across one I'll probably install that additive pressure tank just to keep the WP pump from kicking on and off every 5 seconds or so when the water is running full blast....my calculations indicate an additive 100 liter tank should get me up to around a 60 second pump on/off cycle or an additive 20 liter tanks would get me up to about a 11 second on/off cycle. I've got the setup all mapped out in my head, but that will be a gee-whiz project more than anything else, if I can find a new or used tank at a good price.