Weil-McLain GV90+: Not keeping up below 20 degrees :(

Lois

HI folks. Looking for some answers before experts arrive, informed advice welcome!

Below 20 degrees, my heating system cannot keep up with Tstats. Single digits and I'm dealing with 55 degree zones caused by lukewarm baseboards and very warm cast iron radiators.


What is the cause, where do i start looking?

Three year old gas boiler. Fires right up, LED status lights on main board all correct.
Temp dial to 200 (max) and efficiency (min).
Z1 = two story 1850s house, six cast iron radiators
Z2 = one story 900 sq foot kitchen/family room, baseboard + kick
Z3 = water heater set to 160 deg and NO priority

Tstats both set to 70. Might was well be set to 100, doesn't make any difference.
Tstats ARE calling for heat at the boiler.
Boiler running for 5 and shutting down for 5. ish. Boiler temp gauge seems to be fluct between 160 and 190, I don't recall i need to go back down there and look,
Plenty of (160) deg hot water.
Tacos on two zones, both are spinning as they should. Zone 2 Taco is 2 years old.

I have bled all radiators and kick heater (let at least half quart of water out of each). Cast iron radiators are same temp top and bottom. No air / spit came out of any of the bleeds.

I cannot find where to bleed baseboards? I bled kick which is either last or first in line, in any event, on the same level/floor as all the baseboards.

Baseboards are LUKEWARM, at best.
Cast iron radiators are very WARM but far from scalding hot - on floors one and two.

Downstairs, at the boiler:
SUPPLY pipe at boiler/beyond to all zones - warm
RETURN pipe at boiler - scalding hot !
Insulation on much of, but not all of the pipes under the house.

In short, heat is fine when above 25 degrees or so but below that I'm in the situation above.

Where should I be looking next?

Jamie Hall

For some reason you are not getting enough water circulation through your zones -- particularly the baseboard zone. Baseboards are hard to bleed. Both zones probably would benefit from being really purged. Then the other question is -- are the pumps correctly sized? And are there any valves on the zones which might be partly closed?

And how are the zones connected to the primary circulation?

Lois

Thanks for the quick reply.

How do I measure flow and calculate/verify correct size pumps?

The thermometer on the output side of the burner is showing only 120 degrees with 40 Psi. The output pipes are very warm, feels like 120.

The return pipe back into the burner is super hot, scalding. Feels like closer to 200.

The first zone pump appears to be pulling from the end of the return, not pushing the hot wayer.

The second zone appears to be drawing from the return of the first zone and therefore is even colder...

I can draw a diagram of the pipe configuration/zone flow if that helps others (help me).

DZoro

Picture of the system would help. I believe that boiler has a internal pump, it could possibly either plugged and or failed.

Gordy

^yes there was another gv90 poster 3 years old with issues. Haven't heard back.

Lois

Read that post before I posted.... Little chance of finding a professional this week with temps in single digits through the weekend, take a number

I'm not afraid to read the manual/diagnose myself. Thanks for the help.

lchmb

just curious..if it's piped properly you should have a system circulator supplying the zone valves. Is it getting power and working? Or extremely hot to the touch...post either pics or a drawing.. (pics would be better)..

Ironman

The boiler has an outdoor reset feature to save energy. The ODR curves varies water temp as the outdoor temp changes. The colder outside, the warmer the water and vise versa.

It sounds like your ODR curve needs to be adjusted to supply warmer water to your baseboards.

Lois

Thanks Bob. I see no sensor or wiring from the boiler to the outdoors. How does the boiler measure outside temps; Is there somewhere I can check for this?

I will post pics/zone diagram tomorrow morning.

Thanks again all

Ironman

Lois said:

Thanks Bob. I see no sensor or wiring from the boiler to the outdoors. How does the boiler measure outside temps; Is there somewhere I can check for this?

I will post pics/zone diagram tomorrow morning.

Thanks again all

I should have said: "if the boiler has outdoor reset". It's optional with that boiler.

The other thing to look for would be how it's piped. The boiler has an internal circulator that's controlled so as not to allow the RWT to the heat exchanger to drop below 140*. It does this by bypass supply water back into the boiler to protect itself. That's means the system gets bypassed of hot water until the heat exchanger is hot enough.

If the system is not piped correctly, that can cause the boiler to bypass too much.

If you could post pics of the boiler and its near piping, that would help/

unclejohn

Need pictures. There should be a shut off valve and a drain valve right close to each other. Thats where you bleed the baseboards.

Lois

Lois

I believe these pics should answer most everyone's questions.

Why is the last leg of the return line at the boiler SCALDING hot, all other supply lines and the supply temperature gauge only 120 deg / very warm?

Please let me know if you need more info and thanks again for all the help.

Ironman

If your arrows are correct, then the boiler's piped in backwards at the closely spaced Tees. That will cause the supply from the boiler to short circuit back into its return.

Lois

@ ironman - i updated my arrows in third pic to better represent what I believe correct flow to be. Thanks again.

Lois

Plus

DougS

Lois, what was the solution to your problem, I have the exact same conditions happening with my system?

psb75

Maybe also give a little history as to: when the system was last working well. Who has been there in the mean time and what have they added or subtracted from the system? Without a proper schematic drawn out, it is difficult to diagnose just looking at the picture.

DougS

The boiler was installed approximately 5 years ago and it never worked properly but I was unaware because the renter at the time did not report an issue. The house is 1000sq ft, one loop, there is no zone circulator only the ones that are in the boiler. We have a separate gas hot water heater. The water temp returning from the radiators is always around 110-120F. I turned the boiler temp to 191F and it made no difference, seems like its in bypass mode. I am not sure the submodel of the boiler so not sure if the plumber installed incorrectly and it should have am external circulator. Its a simple install with the supply going to the radiator loop and the return back to the boiler. Since the other forum question I referenced has circulators and is doing the same thing I think it must be some internal issue with the boiler like the return sensor is not taking the boiler out of bypass mode.

neilc

Doug,
you might want to start your own thread,
post pictures showing your boiler and the piping around it,
floor to ceiling

rick in Alaska

I would almost bet one of the pumps in the boiler is not working. The pipe coming out of the boiler and then going back in should be at boiler temp. I am betting on the internal system pump to be out.
Rick

Tom_133

I agree with rick, I have run into that several times where one of the pumps in the boiler was stuck and not spinning. That would cause your issues.

DougS

After further diagnostics, and speaking with Weil-McClain tech support, the system circulator (one furthest to the back) shows no voltage reading when connected to the control module, boiler over 140F and calling for heat. Once I disconnect the wires I get a voltage reading from the control module, Tech is saying that indicates a bad relay on the control module, so replacement is in order. I am going to hard wire the circulator as instructed by tech to verify the circulator is good before replacing with part# 381-330-025 for my GV90+4 boiler.