WHY?

MNPLUMBER

Ok I know this question may be sort of dumb but I cant' find an answer. WHY is it that on a lot of the systems I've been seeing are the zone valves installed on the return instead of the supply?

It's almost as if anything goes? Pumps on both return and supply sides,  zone valves installed on either or.



Everything I'm being taught and everything I'm reading is saying to install it all on the supply side. Expansion tank first,  then pump, then zone valves if needed. Is this correct?



Would it make a difference installing the expansion tank and pump on the supply and then installing zone valves on the return? Sorry, still confused. ;-)

billtwocase

I've never

had an issue installing zone valves on the return. Other than a mono-flow, I prefer them on the return. Seen to last longer. JMHO

Mark Eatherton

Why not....

If you hadn't heard this before, let me be the first to say it. THere is only ONE correct answer to ANY hydronic heating question, and that response is, "It Depends!"...



If it is a cylinderical (White Rodgers, Taco EBV) type of zone valve, it doesn't really matter WHERE it is set, except that the electrical components will be subjected to slightly cooler temperatures on the return, than on the supply. That lower temperature is beneficial, regardless of the type of zone valve you use.



I have personally experienced zone valve bypass when ball (Honeywell) type of zone valves are placed on the supply, with the pump also on the supply, pumping away from the PONPC. At that particular point in the system, the valve is being exposed to the greatest pressure differential and on some systems with oversized pumps, they WILL bypass. With the valve on the return, and the pump on the supply, most of the pressure potential has already been spent getting the water back to the boiler, so the pressure differential is less, and subsequently, bypass potential is less, if at all.



For me and my money, when using electric zone valves, I apply them to the return. As for the pump, on a conventional system like you are looking at, the pump ALWAYS goes on the supply, pumping away from the PONPC.



ME

billtwocase

That's exactly

it Mark. 

MNPLUMBER

I like it

Thank you very much. Makes a lot of sense to me now.



I didn't realize the heat could cause problems with the valves. I'll be installing them on the return side.

rich pickering

It depends

Had a complaint once of a convector being hot, but the stat was not calling for heat.  Zone valve on the return was off.  2" supply and return mains with 1" branch piping.

Gravity flow within the 2" was allowing the convector to get hot.

bill nye_3

I always

..put the zone valves on the return. I started working with my Dad in the early ' 70s and he always put them on the return.

 I like it better because I can put them at eye level and they are always accessible. Did you ever go on a service call at night and try to even  FIND the zone valve ?  

bill nye_3

return side

When the valves are on the supply they are often near the ceiling, above the smoke pipe, IN the finished ceiling, scattered all over the house, etc. I put them on the return near the boiler right near my purge stations. Lately I have been using zone valve relays to simplify wiring and trouble shooting (not so much the simplify for me, but for others who may hve to service the system) And what a crazy idea, I label the zones.