back to back circs????

[mrcat]

Hi, first post here, found this site about a year ago, wow have I learned alot!
So I'm trying to push water from my boiler through 250' of 3/4" pex [2 sets] to the house with about 20 feet of fall from the highest point in my system to the top of the boiler.
I've been doing it with a grundfos ups 15-58fc for 3 seasons, but have to create a siphon to get it going. Problem is if the power goes out when I'm not around, it won't start pumping again by itself. I've got another pump of similar size and was wondering if I put them back to back would I get more "torque" so to say? Or should I just bite the bullet and buy a bigger pump......
Thanks
Paul

 

[ewdudley]

I've got another pump of similar size and was wondering if I put them back to back would I get more "torque" so to say? Or should I just bite the bullet and buy a bigger pump......
Thanks
Paul

Welcome Paul. The technical term would be 'wollop'. I believe it's standard practice in solar drain-back and similar situations to have a second pump to start a siphon. You can go back-to-back, or a have high-head pump in parallel. IIRC Taco recommends a certain length of straight pipe between the two pumps, six pipe diameters or something like that. You could have the booster pump on a timer that automatically shuts off after a certain amount of time if it's not needed once the siphon is started, the one pump will pump through the idle pump, with a certain amount head loss.

 

[mrcat]

Thanks Eliot, is there a timer that would reset when the power is interupted?

 

[ewdudley]

a timer that would reset when the power is interupted?

I've had good luck with SESTOS and ANLY.

Search ebay titles for 'digital timer', sort by price-plus-shipping, and look in the $20 to $35 range. Need to decide if you want a socket base, and note whether the power that activates them is right for what you're planning to do.

Also 3 amperes resistive is a typical relay contact rating, which would be a bit iffy even for a 700 mA circulator motor, so it might be worth it to use a separate relay to switch the motor, for better reliability, or not, for $25 it wouldn't matter too much.

http://www.ebay.com/itm/Digital-Twi...ltDomain_0&hash=item3a6c9034f7#ht_7943wt_1020

http://www.ebay.com/itm/Digital-tim...ltDomain_0&hash=item336e1a4729#ht_3907wt_1020

Not saying they're the best solution, but they're working well for me.

--ewd

 

[mrcat]

Well I finally got down to HEP and got the parts to add the other circ. Plumbed it up last night and it works great
Thanks for the help, I just have them both running all the time for now, maybe later this winter when I have more time I'll play around with the timer.....