injection pump control

mike terry

Thanks for the response folks.I had not considered the effect of a spring loaded check valve.As the days go past Im starting to realize that a control with out some indoor space feedback doesnt know whether the wind is blowing or not.And even though its a staple up job,it still has noticable lag.anyhow the wife is happy,says its the first time she has ever been warm in her life. ha
thanks again
Mike

mike terry

injection pump control

Having just started up my staple up job at my home,some questions have come up.controlling the injection pump. i have this thing piped in with a ball valve on the return pipe going into the primary loop.the supply and return pipes are 8 inches apart.is a flow control needed above the injection pump? I notice a certain amount of water migrating up into the radiant loop which is not a problem when its cold out,but might this cause problems in mild weather of having radiant loop staying too warm? I have looked at the tekmar control....I was wondering if anyone has used the honeywell aq775a just from looking at the catalog it looks like it doesnt start to reset until 30 degrees. Ihave worked with a honeywell T775J reset tstat that seems like it would work in this application. I realize this would not be varible speed.the T775J will hold to a 2 degree diff.I suppose that would be a lot of on and off action.....any thoughts on how to do it better...or bite the bullet and spend the cash on the tekmar361
thanks MIke

Steve Eayrs

injection pump

How much time do you have? If you manage to "make" an injection pump control, or something that will work somewhat, don't ever sell your house, without letting the new owner in on your creation.
Its possible to do, but go with the Tekmar. You can find a lot better things to do with your time, and you will never get it to work as good.
Steve

hot_rod

You may need

a check in the VS piping. A simple inexpensive solution is the Grundfos MixiMiser. It also has a small spring check built into the pupm volute.

Heat migration is a piping issue, generally not fixable with the control type or wiring.

This article will give you some good guidelines for stopping unwelcomed flow. A good one to bookmark and review from time to time.

http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,13972,00.html

hot rod

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Art Pittaway

Be careful with

the spring checks. Tekmar always shows a "thermal leg" because the pump will smoothly move a variable flow. A spring loaded check will require the pump reach a certain pressure and start to open, usually at a higher flow rate than is needed. In some cases you get cycling instead of the smooth temp adjustment you want. A swing check seems to work better where needed but the legs when done right work.
Art

bruce pirger

Does anyone have experience using the pumps with the integral check? The article seems to indicate they work well....anyone else?

hot_rod

The proper check

is important. With a spring check you need one with a "low popping pressure" spring. Most check valve manufactures offer these. I know Watts and Conbraco show these in their catalogs. Also size the check to the GPM flow, not the pipe size. Very often checks are over sized, adding to the pop open issue. Once again the manufactures specs will show you the Cv factors. Also pick a check with a soft seat, either teflon or epdm seats. This will eliminate any "chatter" Some have cone shaper plugs also. Better flow through these than the flat dics types.

Most VS injection controls start the pump at full speed for a couple of seconds, then ramp back to speed. This allows the check to pop open.

Thwe MixiMiser, by Grundfos, was developed with tekmar, and the operation of the check was considered. So far I haven't had a problem with "hunting" or other check issues with the intergral check pumps.

I have had to go back to several jobs that I used thermal drops and add a check to fix overheating problems. Sometimes they work, sometimes they don't. I've found checks work the first time, and also add some pressure drop to the injection loop, which helps the pump run it's curve better. Happy heating!

hot rod

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