Changing a Hydronic setup for easier forced purging

mnessen

Some advice on tweaking (if prefered) my son's boiler/piping for his hydronic system.
90k Crown boiler
Mix of baseboards and radiators in a 1100 sqft two story twin.
Present setup has circulator (Taco 007) in the return without a purge station.
Water feed comes into the supply side between the boiler and Taco air scoop.

I need to replace the Taco which is presently frozen, but the system is managing to have gravity feed to keep the house warm. When I replace the Taco, I figure it would be good to add a purge station just above the circulator to more efficiently purge air (all radiators and old baseboard have manual air vents). While I have everything down to replace the circulator and add the purge (1.25 copper), I was wondering if it is better, for forced purging, to have the water feed as is in the supply side, or if I should move it to the return side just below the isolation valve in the purge station.

EdTheHeaterMan

Having radiators (the cast iron kind) and baseboard (the copper tubing with aluminum fin kind) on the same thermostat, never seems to be a balanced system. The rooms with the baseboards seem to be cooler, while the cast iron radiator room seem to be hotter. Do you find that to be the case?

While the system is drained, Now would be a good time to make all the baseboards a series loop that has one circulator one flow check valve and one thermostat to control that zone. All those new pipes can be 3/4" copper with a purging station. or you may even use PEX to connect the baseboards for that zone.

Then you can connect the original (replacement) circulator to the rest of the radiators using the existing large piping and existing thermostat. You may need to add a switching relay for the baseboard zone. Zoning with circulators requires a check valve on each zone, so the circulator on the old radiator zone may need to have a FloCheck valve added.

Just so you know, if your baseboard radiators are not in a series loop, the na fast purge station will not work. The fast purge will only fill one radiator or baseboard. That is because the water will take the branch or run of the tee that has the least resistance. All the other radiators and baseboards will not purge. they will still have air in them and will not heat the rooms they are located in.

Teemok

You didn't say where your expansion tank is. I'm guessing it's on the supply side with the feed water. Move both to a spot between the suction side of the pump and the new purge iso ball valve you want on the return. Make sure you have a good air separator, at minimum a good working vent on an CI scoop. Also, at least 6 pipe diameters of straight pipe before the old CI scoop. Get a new style micro bubble separator and it will help with air problems. How bad the imbalance the mixed emitters is depends on the piping, emitters capacities and the different spaces heat losses. Getting good flow with no air problems seem a good first goal.

hot_rod

A pic would help make some suggestions. Sometimes moving the expansion tank is easy, sometimes moving the pump location is easier.

Check out the Webstone purge ball valves for a simple purge addition.

This version is nice if you ever want to connect a purge pump, or a blast from a garden hose.

mnessen

Ed - yeah have definitely found the baseboard barely get warm, while some of the radiators are hot (not all though). Initially may main concern is that the circulator isn't functional, verified by the fact that it is pulling almost twice the running current on the tag. Once I replace it, I am curious as to how the system will operate. Additionally, almost all the valves on the radiators are not movable (either painted or packing is too tight) so my plan is to work them loose and repack once the system is drained enough not to have pressure at all. I won't push too much freeing them up as I really don't feel like doing the work to replace them at present if necessary.

Am I correct that I can use the radiator valves to throttle the flow to each radiator as desired (to adjust heating in each room)? Right now, not all radiators are heating (two on the first floor and one on the second floor are hot - actually, the one on the second floor is the warmest....lol)

One question I do have about the forced purging (and a change I can make easily when I start this project) is whether the make up water should be entering the supply side of the boiler piping or the return side (just below the purge station)?

Reworking the setup into two zones is more than I want to tackle at present, but a thought for the future.

Teemok - the scoop is a few feet past the supply exit of the boiler with the expansion tank on the bottom of it and the vent on the top. The makeup water connection is between the supply coming out of the boiler and the vent.

Hot_rod - The Webstone is the one I am choosing to install.

In general - I am avoiding working on the steel piping for now....and trying to keep the cost down for my son.

mnessen

One additional question......I am reasonably good at soldering (retired engineer and ham radio operator). Working on the 1.25 copper will be the largest I have tackled....but I figure it is just a matter of scale. Would you recommend using propane or MAP for working on the copper and new Webstone? I figure as long as I am careful, the job will go faster.

EdTheHeaterMan

PEX with an O² barrier is an easy way to connect all the baseboards in a series loop. On an 1100 SqFt home, I don't foresee that you have more than 65 lineal feet of actual aluminum fin of total baseboard. PEX is easy to run in tight places and can be fished under floors and through walls like an electrician runs wires in an existing building.

Once you have that zone completed you can address the remaining cast iron that should be already connected to the boiler. Just cap off any unused radiator take off and be sure all the old radiators are connected properly. One of the main pipes should have all the supplies to all the radiators, the other main pipe should have all the returns from the radiators connected

With all the radiator valves open, then all the radiators can be vented at the manual air valve at the top of each radiator. Then operate the zone to see how balanced the system is operating. When you find a radiator that gets hot first or gets hotter than the others, Close that radiator valve to the point where it will get hot slower. That may take several days to get this right because you will need to start from a cold system each time you make an adjustment.

Since each zone requires a check valve, I would purchase a circulator that has an internal check valve for the Cast Iron zone so you do not need to do any repiping on the large steel pipes.

EdTheHeaterMan

One question I do have about the forced purging (and a change I can make easily when I start this project) is whether the make up water should be entering the supply side of the boiler piping or the return side (just below the purge station)?

Here is a diagram of a 3 zone baseboard system that is using the Pumping Away from the expansion tank idea to eliminate air problems while the system is operating.

If you follow the diagram from the water feed (includes the pressure reducing valve and the expansion tank) as it enters the supply pipe just after a full port ball valve and before the circulator. With the full port valve closed, the feed water can only go in the direction of the circulator pump flow and around the baseboard loop where it encounters a close ball valve on each zone (or loop). The circulator pump should be off during purging. Once you build up pressure in the loop you want to purge, you can open the ball valve at the end of the loop and allow the high pressure water and air into the boiler where it will exit at the purge drain valve at the top of the supply pipe just before the full port ball valve on the supply.


If you can post a photo of your son’s boiler room, with a picture of the boiler from at least 2 different perspectives, that show all the pipes from floor to ceiling that are connected to the boiler, I could look it over to see if there is an easy way to make your son's system work better.

mnessen

Ed - Thanks for the response, this will give me a bunch to think about. Didn't think about the PEX to change the feed to the two baseboards. Capping off or plugging the feeds and returns from the 2 inch (I think) steel supply and return mains wouldn't be hard. Just have to have him save up for doing this spring of 2025.

What is interesting about the baseboards is they are different from what I have seen before. My familiarity is with aluminum finned baseboards with easily removeable front plates. These look almost unitized (nothing to remove) and when I reach in the top, I can't feel thin fins. Also, they have manual vents at the end of them (not in an elbow, but a 1/8 fitting at the top of the baseboard). I'd almost describe them as more like super low profile radiators.

Can you force purge a bank of radiators connected to one main trunk supply (all in parallel)? Would I be able to do it with fully functional valves at each radiator? (shut all off and then open each one to force purge, or is that a bad idea and it is just easier to vent air using the bleeder at the top of each radiator?)

EdTheHeaterMan

You may have Cast Iron Baseboard radiators. They can not be purger either. They need to have vents at the tops of the radiators even though they are only 9" high. Those vents are likely inside the end covers.

mnessen

Yep - that is what they must be. They look like a version of the left picture. Now these presently never get warm, but until I get a working circulator in the system, I'm not going to assume any issues I can't directly diagnose. One of my worries is that the steel mains are old, probably original from when it was an oil boiler, and all the fittings to the baseboards step down from the large 2in main runs to what looks like 3/4 or 1/2 galv. I was originally concerned about scale or rust clogging things up, but the air vents on the two low profile radiators release water, so I guess it is just a flow issue. Again, until I have a working circulator, I'm not sure what I am going to see. For now, my son has enough heat in the house, although a bit unbalanced, but livable where it counts. I just want to prepare for mid-April when I will tackle the circulator replacement and then take it from there. It almost sounds like a purge station might be useless to add at present with all these radiators in parallel.

mnessen

I should note that the frozen circ is a Taco 007 and I intend to replace with same. I am hoping that when I pull the existing one I am not met with an insane amount of scale and rust. My plan is to just pull the motor off and avoid replacing the housing unless it looks really bad inside.

EdTheHeaterMan

Can you force purge a bank of radiators connected to one main trunk supply (all in parallel)?

Force purging is not available on parallel anything. To force purge you must be in series, and it really only works on the copper tube type radiators that can be connected in series. Then all the connections must be at the top of the water chamber inside the radiator. You can not get the water at the bottom of a chamber to entrain the air at the top of a chamber. It just ain't happening

Your Quest for forced purging may be in vane. Your son probably does not have the right radiators for a force purge design. You are stuck with venting the hole at the top of each radiator.

mnessen

This is a picture of above the boiler (90k BTU Crown).
Left copper is supply and you can see where it connects to steel main.
Right copper is return, same for connection to steel main.
Circulator is just above where return goes into the boiler.

mnessen

I and he can live with that. So now my main work will be to repair circulator, get the radiator valves functioning to attempt some balancing of heat in the house.

Thanks for all the input.

If he is going to stay in this house for a while, he may have to rethink about improving the heating system, but that is a few years in the future.

Alan (California Radiant) Forbes

Can you force purge a bank of radiators connected to one main trunk supply (all in parallel)? Would I be able to do it with fully functional valves at each radiator? (shut all off and then open each one to force purge, or is that a bad idea and it is just easier to vent air using the bleeder at the top of each radiator?)

Yes, you can and that's the way I would do it. Whatever air you don't remove with the forced purge should come out when you bleed the radiators from the radiator vents.

For a proper forced purge you will have to add a purge assembly. And for a properly installed system that will effectively exclude air in the future, you will have to move the pump.

Dave H_2

Depending upon the age of the Taco 007 circ, you may need to replace the entire thing and not just the motor, the flange to flange dimension is the exact same. With that being said, if you are looking to improve the piping and going to take down the water, it would be easier to just replace the entire circ.

Here are a couple of piping diagrams and purge sequences to use, on page 2