series-loop design question

hws

The series loop is the simplest piping design but after (during?) a major problem with direct-return piping (see my other thread "possible blocked radiator") I'm second guessing everything I do.

I'm pricing a re-pipe job that involves a 15-year old 5/8"Kitec series-loop system. Guy is selling the house, home inspector wants the Kitec removed. I'm going to price re-piping it in 3/4" heating pex with crimped fittings. I want the system to perform as good as it ever did before re-piping. It's 4 zones, zone valves pumped with a Grundfos UP15-58 (equivalent to a Taco 007).

I'm going to keep this job simple. Run the zones in series-loop just like it already is, substituting 3/4" heating Pex for the existing 5/8" Kitec. Sounds simple enough.

My question is: Will the friction caused by the pex crimp fittings (insert) be "too much", leading to a need to upsize the circulator? Should I recalculate the head, adding an extra pick-up factor to allow for the internal crimp fittings that I will be using with the heating Pex?

Thanks.

SWEI

first, check the design

Were the series-piped emitters properly sized?



To minimize friction losses in PEX, use radius bends wherever possible and choose a cold expansion fitting system like ASTM F1960 (Uponor ProPEX) or F2080 (Rehau Everloc.)

hws

haven't done a heatloss yet

Just came by to measure up existing pipe & heater lengths.. Homeowner is sending me all the info I need room dimensions, window sizes etc. They have expressed that they are sufficiently warmed without costing too much though, so my guess is that what I come up with will be close to what the original installers came up with.

Mostly what I'm worried about is friction loss from pex fittings. Not really set up for Uponor, it'll most likely be a crimp job. The only fittings are at the boiler and at each heater.

Zman

I would..

Look at the approximate lengths of the runs and footage of baseboard. Unless you have an extremely long run or have way to many emitters, the pex should would great.

Adding a few crimp fittings to a run will not have a serious impact. I would have to look it up, I don't think the fitting will add more than an "equivalent foot" of resistance.

Carl

Ironman

The Inspector...

Doesn't know what he's talking about. The problem with Kitec, or any other pex-al-pex, was with using it on potable water. There are no issues with it on hydronics, that's what it's made for.



I don't want to see you lose work, but if you want to be honest, you'll tell your customer so and let him decide what he wants to do.

hws

Appreciate the input Ironman,

and I agree with you.

I told him first that the issues were usually found on potable systems and at fittings; explaining that his was a heating system with very few fittings, and that I didn't see any corrosion. I first offered to pressure test his system and document the results to put his mind and the inspectors mind at ease. However, there is no stronger force than public opinion, however wrong it may be...he's had some potential buyers walk away because of the Kitec, and home inspectors armed with only half the information aren't helping, so he wants to remove it to get the ball rolling.

Too bad about Kitec though, the idea behind it was right on. I'm interested in the Pex-Al-Pex with stainless compression fittings that Ipex makes for pneumatic air piping. Looking forward to using it on my next commercial job.

Ironman

If Ignorance is Bliss...

Then a lot of these home inspectors would be blisters!



There's not enough time or space to relate all the experiences I've had with these guys. And the crazy thing is that the homeowners will believe what one these 30 day wonders tells them over someone with 40 years experience and a masters license in five trades.

Ironman

Fittings

Why not just replace the brass fittings with the new stainless ones?



Honestly, I've literally run miles and miles of Kitec and other pex-al-pex over the last ten years and never had a problem with any of it. We still use it quite a bit and will continue to do so. And I do maintenance and repair on almost all of these installs, so I would know if there was an issue and there's not.



But, I understand that you have to make your customer happy also. Quite often, perception is what drives things, not facts.