Need advice on Spirovent location- Spirovent or Combi or DirtMag?

dardo

Since I will be adding a new zone to this system, it seems like a good opportunity to make some upgrades to our hot water system. We have old cast iron radiators without a dirt/ magnetic trap. Also it seems we are still having issues with air in the line even with the air scoop installed. We just installed a chimney cap to lessen the amount of moisture coming in, which was hopefully the cause of the white residue on the boiler and condensation in the temp/pressure gauge? I had originally planned on using the spirovent on the supply side (the air scoop with expansion tank is on the return) and a DirtMag on the return. I now realize there is not enough space for the DirtMag and wondered if the Spirocombi would be a good choice in my application. If so, would I leave the scoop and expansion tank as is? Thank you for your input.

Mad Dog_2

Spirovent. Mad Dog 🐕 

Intplm.

This is a Spirovent micro air bubble separator with dirt mag combo.

I would install this exactly where the current air scoop is.

Intplm.

You have two tees just after the ball valve isolation valves on the feed and return, with a nipple combining the feed and return. What purpose is that serving?

hot_rod

Plenty of room to add two separate components a A DiscalAir and a DirtMag. Using two separate allows you to put them in the best locations. Add them between the ball valves and unions.

DiscalAir at the boiler outlet, DirtMag at the return.

Looks like you are pumping at the expansion tank? Is so move the tank to the return of the boiler. Is the pump flowing out or into the boiler?

Also that bypass is not helping. It is possibly the path of least resistance and getting a good portion of the flow. A temperature type bypass valve would be best..

hot_rod

This drawing would clear up some issues. Looks like you have a bunch of high head circs as zone pumps? And a high head circ on the boiler? I would not consider that primary secondary exactly, so the pumps are sort of in series. I suspect some high velocities in the system?

Your best bet may be a hydraulic separator to assure that boiler gets adequate flow. Add a thermostatic return protection valve. Now you have dirt, air, and magnetic separation in the correct locations.

Also assure you have the correct zone pumps sizes?

This pic shows mix down on the secondary side, your zone pumps would be in place of those. If you are adding a low temperature radiant loop, pipe a mix valve as shown.

You have some repipe work ahead of you to get this to a better position. Although you still may have some micro-zoning issues causing that boiler to short cycle, when just one zone calls, on that fixed output boiler?

Nice piping work, however.

dardo

Thank you for the replies. This was an old gravity system before we replaced the boiler. My boiler installer said we needed a primary-secondary system thus the Tee's connected the supply and return. I assume this is to insure water entering the boiler on the return is not too cold? Perhaps this is not needed and not helping as HotRod suggested? Yes, I agree about using both to place in the optimal locations. I already purchased the DirtMag- it is an impressive device! Thanks for the drawing- Can you clarify or suggest the temperature type bypass valve I should install? The expansion tank is tied to the air scoop which is on the return side. The pump is flowing into the boiler.

hot_rod

Here are the best practice suggestions for P/S piping. The distances are fairly important.

This is an example of a boiler protection valve. Basically it allows the boiler to reach a safe operating temperature then slowly allows flow to the system.
This pic shows it attached to a buffer tank to demonstrate a high mass load. Same applies to a number of large cast radiators as the high mass

dardo

Bob- Your second response must have come in as I was typing which answered my question. Yes, we are experiencing some short cycling when just one zone is calling for heat. I have 2 zones left to complete which I suppose will lesson the chance of this occurring. There will not be any low temp radiant loops. I see the Thermoprotect mixing valve "automatically controls the return water temperature, preventing condensation of the water vapor contained in the flue gas". Perhaps this is why I am seeing condensation in the temp gauge and the white powder on boiler?
What should my return differential be? Now it is usually 135-140 going out and 115-120 coming back. We are using the outdoor reset as well. For zones 3-5 I am using the Grundfos UPS15-58FC, 3-Speed Circulator Pump set on the lowest setting. I am more interested in efficiency than comfort (glad my wife is not reading this) and wish there was a way to either only fire the boiler if more than 1 zone is calling for heat, or, just allow it to only fire x amount of times per hour.
Thanks again for your time. I really appreciate it.

dko

It is currently pumping away from the expansion tank.
On the raypack, the pump above the boiler is pumping towards the boiler.

Diagram in that boiler's manual

hot_rod

You would like to see the boiler return rise up to 130f within 10 minutes of run. At the very least before it shuts down.
When you have a zoned system like that and one or two zones call on a low load heating day, that is when you will most likely see cold run cycles.

It could show up in the boiler combustion area or also in the flue piping, white dust, rust, corrosion. What type of flue? With metal flux, some times the cap on top will indicate condensing temperature operation.

Any idea what the btu/ hr of the smallest zone is? What size is the boiler.
It may be wise to consider a buffer tank, or mod con boiler

dardo

We have the Raytherm H-0180 148,000 btu. Zone 1- 25,000btu, Zone 2- 55,420 btu Zone 3- 13,600btu, Zone 4 16,000 btu. So 13,600 is the smallest zone.

For what it is worth, I log the hours of each zone and total boiler run time per month. Percentages represent % of total possible run time (768 hours for 32 days)
Zone 1- 162 hours - 21%
Zone 2- 56 hours- 7%
Zone 3- 72 hours- 9%
Zone 4- not installed yet.
Boiler run time- 187 hours- 24%

Zone 1 received an unusually high load which will be lowered when zone 4 is complete.
Unfortunately, I am not technically savvy enough to install a more sophisticated monitoring system that would log first and second stage firing times for each zone and which are running concurrently. Do you think a boiler that runs 25% of the time is normal?

hot_rod

So your load at design day is 110,020, and net boiler output is 148,000btu/hr?
So first off you have way too much boiler.
Keep in mind design load may only be 5% of the heating season!

Another option that could solve a few issues is a buffer tank.

Here is the math as your system stands.

148,000- 13,600 (smallest load) X 15 minute boiler run cycle
Tank running a 20∆

2,016,000 ÷ 10,000= a 200 gallon buffer tank. To assure a 15 minute run time.

Some other options, combine any two zones if you can reduce that 148,000 vs the smallest load(s) equation.
Down size the boiler. How old is it?
Replace with a modulating condensing boiler.

IF you combine the two smallest zones, 29,600 and run the tank at a 30°∆ at 120 buffer, a common size, would get a 15 minute run.

Even if you are not seeing condensing damage, those short cycles really drive down boiler efficiency, fuel cost go up. Plus the excessive on off cycling of components.

You do have some thermal mass in the piping and radiators, but as you see that zone 3 at 9% is not a good look.

I'd bet you could run those radiators well below 180 for most of the heating season. If they keep up now, as your %s indicate.

With a mod con you get the modulation plus a % of the year running condensing mode, 90% plus efficiencies. A 150K boiler would modulate down to 15,000 btu/hr, getting close to that smallest zone.

dardo

I guess my initial heading should have been What to do with an Oversized Boiler....... Thank you for providing my options. Unfortunately, the boiler is only 3 years old so I need to do what I can to increase those run times until I can afford a mod con boiler. Combining zones would not be too difficult. I assume the heating cycle rate on thermostats would not have an effect even set to 1 per hour? Just grasping at straws here......

hot_rod

It kind of depends what zones 1-4 are. Certainly would not want a garage zone with a master bedroom for example.

Unfortunately copper tube boilers are the worse for short cycling when micro-zoned. Very low mass low water content.

Good news, with the unions above the boiler adding an air and dirt sep will be fairly easy. Shut off the two large ball valves and break the unions. Get a couple 3" nipples and add the air and dirt seps right against the ball valves. Make that bottom ell a reducing tee, move the expansion tank there so you are pumping away. Cap off the old ramp air purger 1/8 vent connection.up

Both the DiscalAir and DirtMag come apart easily if that helps spin them in.

Maybe call a knowledgable RayPak rep, maybe you can down fire that boiler a bit. They use to offer some model with a two stage, hi-lo fire gas valve which was handy for zoned systems

dardo

Yes, I am looking forward to adding those upgrades asap. The boiler is in fact a two stage hi-lo fire gas valve. As I mentioned earlier, it would be nice to log what percent of time it is running on hi. Then again, as my wife points out, why does it matter? Just because.....
You have been very generous with your time on this issue which I greatly appreciate.