Radiant System Help

JF3

I have a 16 year old system in Minnesota. It is a 3 zone in-floor heat system that has worked fantastic and now this winter cannot keep up with demand. Zone 1 is a 6 loop manifold wirsbo system in my 4500 sq/ft concrete basement. Zone 2 is a 3 loop wirsbo in concrete in my garage 900 sq/ft. Zone 3 is two small loops upstairs under my tile floor in the bathrooms. I suspect my boiler is the culprit and are planning a new one. It cycles every two to three minutes (two minutes on two minutes off). Supply cycles on at 140 and off at 180 at 14 PSI. No leaks and holds pressure. I would like to post my diagram as I am seeing very cold water return on my boiler like the main loop is not circulating properly. I have replaced 3 pumps the main, injection, and zone 1 which has not helped and all are operating properly. This boiler was used when we built our house and is older than the house there are rust stains on the concrete floor underneath the boiler. Is this setup a sound one or too many pumps and no way to control the return other than a lever valve? The garage is set for 50 degrees and basement at 69. To me there is no way to regulate the in coming water to the boiler and has been shocked to many times and is the boiler is rusted? Any help would be appreciated.
JF3

Solid_Fuel_Man

What are the supply and return Temps on the radiant zones? Do you know you have flow in all the loops?

Taylor

Brewbeer

The short cycling you describe seems to indicate heat is not being moved fast enough from the boiler loop, through the injection loop, and into the system loops.

The piping is curious, the injection loop should be the same diameter as the boiler loop. Check for restrictions in the injection loop. Is there anyway to backflush the injection loop?

Dave H_2

Almost sounds to me the injection pump controller is not doing its thing. If new circs were installed and nothing changed, it wasn't the circs.
The injection controller is what take the heat from the boiler loop to the radiant loops. Troubleshoot the sensors first. Start with the boiler return temp sensor.....The instruction sheet with the 370 has a troubleshooting section, here is the link
Here is the chart for the sensor testing

Doesn't sound like a boiler problem to me, its doing its thing

Dave H.

JUGHNE

Does this boiler have a pump and thermostatic valve inside the cabinet? Open the top lid and you would see it IIRC.

JF3

No pump but has a Hoffman mixing valve and started to read post on here about them and sounds very similar to my problem. Looks like it will be fun trying to open!

hot_rod

sounds like a Weil GV boiler?
It has a mixer inside, they do seize up after years of service, and yes it is a challenge to get them opened.
Two opposing hammers and tap around the casting will sometimes help loosen that big thread.

Ironman

JF3 said:

I have a 16 year old system in Minnesota. It is a 3 zone in-floor heat system that has worked fantastic and now this winter cannot keep up with demand. Zone 1 is a 6 loop manifold wirsbo system in my 4500 sq/ft concrete basement. Zone 2 is a 3 loop wirsbo in concrete in my garage 900 sq/ft. Zone 3 is two small loops upstairs under my tile floor in the bathrooms. I suspect my boiler is the culprit and are planning a new one. It cycles every two to three minutes (two minutes on two minutes off). Supply cycles on at 140 and off at 180 at 14 PSI. No leaks and holds pressure. I would like to post my diagram as I am seeing very cold water return on my boiler like the main loop is not circulating properly. I have replaced 3 pumps the main, injection, and zone 1 which has not helped and all are operating properly. This boiler was used when we built our house and is older than the house there are rust stains on the concrete floor underneath the boiler. Is this setup a sound one or too many pumps and no way to control the return other than a lever valve? The garage is set for 50 degrees and basement at 69. To me there is no way to regulate the in coming water to the boiler and has been shocked to many times and is the boiler is rusted? Any help would be appreciated.
JF3

If your description and diagram are correct, then the're several design flaws in your system:

1. 4500 sq. ft. with six loops? A slab normally has tubing spaced at 8 - 12" o.c. in a residence. A 1/2" loop should be kept at 300' or less; a 5/8" at 400' or less. The more btus needed, the tighter the spacing: 8 or 9" o.c. is more the norm. Now do the math: @ 8" o.c., 4500 sq. ft. would require 6750' of 1/2" tubing. That divided by 300' each = 22.5 loops' we'll make it 23. You've got 6?? That would mean your loops are 750 - 1125' in length. There's no way a 15-42 circulator could move enough water through that.
2. You're diagram shows no means of mixing down the water temp to the secondary loops. I don't have a single in slab floor that requires a SWT of more than 96*. How are you mixing the SWT down from 140 -180* to get it below 100* for the slab.
3. Water type of tubing was used on the floor? Is it O2 barrier?
4. The boiler definitely needs mixing/return water protection.
5. When you changed the circs, did you properly purge the air from the system?

How about posting some pics of the boiler, it's near piping, any mixing device and the manifolds?

JUGHNE

You mentioned the basement, garage and 2 bath floors. What heats the rest of the house?

JF3

Iron man you are correct. I obviously failed at math.
1. basement is 1700 sq/ft total house is 4500. Forced air heats the rest.
2. Is not the 1' piping between the return and supply tee's after the injection pump acting as mixing valve?? there is 8" of separation between the supply and return piping with a lever valve .
3, All tubing in floor is Wirsbo 1/2" hePEX SDR9 PEX-a 100 PSI 180 degree.
4. The Hoffman mixing valve inside the WM boiler I think is doing the mixing. Also no go on getting the top cap off.
5. Circ's have quick change shut off flanges and did not think I need to purge as I never lost pressure. loops seem to circulate well, when one zone is on I hear a whoosh when quickly closing the valve on the circ?

I will post some pictures later this morning. I tried to get the cap off the mixing valve but was unsuccessful and fired my unit back up the keep the garage from freezing. Using an instant read thermometer on the supply piping after the circ going to the garage reads 95 and coming back 75 right now and seems to be working. I will see if the garage heats up after some time.