Mysterious Heat Flow (Logamatic 2107) in warm weather.

D107

Buderus G115-3, Riello 40F3, Logamatic 2107 with indoor sensor and indirect hwh. I was at family house yesterday--very humid day, AC on, I feel radiators are hot. Outside temp on Logamatic registers 75, Warm-Weather-Shutdown set at 65. System with indoor sensor set at constant circulation, but as far as I know constant circulation should not be on with the WWSD symbol on. Yet zone circ was hot and a few rads were hot.

I did see on the indoor sensor that it was somehow set to 'daytime' rather than auto but that should not have caused the boiler to put out heat. I wondered if this was perhaps a migration of heat from the DHW--we had been using some HW and so when I heard the boiler go on three times during the day I thought that was the reason. Then I recalled that Zone 1 was placed first in the supply piping, followed by the HW, then zone 2, so I'm thinking could this be ghost flow? Note that five minutes after I set indoor sensor to auto circulator stopped--not sure if it won't start again or if that setting had anything to do with it.

But that wouldn't answer the question as to why circulator was on at 75º outside temperature. See attached photo. Zone 1 is a split loop; most supply flows right except for the big living room rad (flows left) on the other part of the loop. Zone 1 circ is farthest right, then going left, 'HW', then Zone2. I have never noticed this before--possibly since I don't live there and might have missed it. Or else the home inspection engineer for the buyers changed some setting when he turned on the boiler in my absence while inspecting.

HVACNUT

Constant circulation is just a prompt.

It seems theres a gravity heat rise through zone 1. With constant circ, the zone will heat throughout with a domestic call and residual heat in the boiler.
When the circ was turned off, only a few rads get warm?

You can try to open the flo valve, bounce the circ on and off numerous times to try and clear any debris on the plunger and seat, then tighten the valve back down. Put the circ back on constant and see what happens.

If that doesn't work, and if you feel confident, you can drop the pressure, wrench open the top of the flo valve and clean the plunger and brass seat, or you can install a Shark Bite spring check on the return for zone 1.

I dont know why IFC circs weren't used with isolation valves.

mercedes

Good morning

I have the same Logamatic 2107 and during the summer my panel radiator will get warm. I think this is normal. The "Operating Instructions" booklet this is one of the features to exercise the circulars during period of not being used.
See page 1 The R2107 can be equipped with the following features: "Periodic operation of pumps during the summer/vacation to prevent pump seizures."

HVACNUT

Good call @mercedes

D107

@HVACNUT and @mercedes Yes, thanks. I'd forgotten all about that. Page 36 User Manual:
USER NOTE
In all modes (WWSD ON or OFF), all zone pumps are activated for approximately 30 seconds every Wednesday at 12.00pm in order to avoid pump seizing up during the extended off cycle. The actuator is then run for approximately 3 minutes (known as pump kick).

Well that might explain it, though I was there on a Thursday and it wasn't noon--2107 calendar/clock is accurate. Not sure what the 'actuator' is.

@HVAC to answer your question about lower radiators only getting hot after circulator stopped, can't say I stuck around long enough for the next DHW cycle to test that, but I assume your point would be that even with the circulation off, the lower rads could still get the gravity heat rise during DHW cycle--seems like a waste of fuel in summer. At the time this was installed twelve years ago IFC circs were much debated here on the Wall. Perhaps now they're used all the time and save alot of labor and money compared to the free-standing units.

All this comes in the middle of our plan to remove the indoor sensor/constant circulation and put it back to T-stat control for Zone 1. (Zone 2 is already T-stat.) Zone 1 is the larger and warmer of the zones, and with the Indoor sensor favoring Zone 1 in all its compensation, Zone 2 can't reach target temp.

With T-stat/Taco relay control I can either set a 2107 target temp that's a little higher than the T-stat --used as a high limit--so there's always headroom to provide enough heat to both zones' requirements OR set the T-stat temp a little higher than 2107 can reach so thereby get defacto constant circulation. I think I'll opt for the former.

Also have to find the right 'cool spot' to locate the T-stat which it admittedly is not in right now ten feet from a radiator. One might argue first move the indoor sensor to cooler location, lower 2107 compensation from 15 to 1 and see if that can cover Zone 2 before switching to T-stat.