Riding Under the Thermostat

flat_twin

The coldest morning so far this season put a smile on my face when I checked various rooms in the house and found all were at 71 degrees. The thermostat is set at 72 and the boiler runs non stop below 37 outdoors. Shortest observed cycle at higher outdoor temps is 9 minutes on to off. A minor tweak to the ODR settings in October is working well. Several days of windy weather last month pushed the indoor temps down to 69 at times but it recovered within a day once the winds calmed down. Perfect!
Can't wait to hit zero!

NY_Rob

Wow.... that is awesome!
You are condensing no matter what the outdoor temp.


I only wish I could go so low. I'd have to do some serious and $$$ radiator work to get those temps.

nibs

Wish my boiler would give me a complete readout like that.
Congrats on your set up.

Le John

What make model boiler is that?

flat_twin

It's a WM Eco110 tied to a single zone 80 year old hot water system with 10 cast iron rads, it's also making DHW. An Eco70 would have likely allowed continuous running below 45 or 50 degrees outside but it's not bad as is. The continuous running is interrupted two or three times a day for the DHW anyway.

Design day around here is 5 and we do see some below zero temps most winters so I should be covered without changing anything.

Eastman

How does it handle DHW? Does it have to shut-down to switch back and forth between DHW and space heating?

flat_twin

Yes it's a complete shut down for switching to either function. When the dhw calls comes, the space heating circulator stops and the dhw circulator starts immediately. The display still shows blue for heating while the post purge is going on. As soon as that's done the display goes pink to indicate dhw mode, the burner pre purges and fires again. The indirect is set at 140 and the boiler is at 155 for dhw.
When the indirect is satisfied and there's still a call for heat, the circulators change over immediately while the dhw post purge is going on. Once the boiler supply temp falls 5 degrees below the heating target the boiler pre purges and fires.

Eastman

Why do they have to shut down? Isn't there a better way?

flat_twin

Good question for WM engineers I guess. How does Lochinvar , TT or HTP do it? I will say I like the way the Eco ramps up and down to maintain the target temperature.

Eastman

I'm not sure what the Loch or TT does, but Rob said his HTP does the same thing.

Brewbeer

I have a Loch WHN055. It ramps up or down when switching between space heat and DHW modes, but does not go through post or pre-purge cycles. What does do which is annoying is that it will re-start the ramp delay program from step one, instead of just resuming the previous ramp step it was on when the DHW call began.

NY_Rob

flat_twin said:

It's a WM Eco110 tied to a single zone 80 year old hot water system with 10 cast iron rads

You can stop at "10 cast iron rads"... that's the answer right there to your long run time and super low SWT temps.

Mod cons love loads of cast iron!

I have one zone with 19ft of cast iron baseboard, it's the most comfortable room in the house and gives me great runtimes and excellent DT's.

NY_Rob

Eastman said:

Why do they have to shut down? Isn't there a better way?

Unfortunately HTP is just as clumsy when transitioning from spaceheating to DHW and back... it shuts down/restarts/shuts down and restarts on a SH-DHW-SH cycle. It's completely stupid, and wasteful and adds extra cycles to the equipment.

Eastman

@Brewbeer

Are you using the Loch multi loop temperature control?

Solid_Fuel_Man

The ECO is my favorite line of boiler. I think if more guys used them, more would love them. The control is very easy to navigate and can throttle either the heat or DHW modulation rates. I just with it gave a % modulation on the home screen.

I think the clumsy switch between heat and DHW is to cover their butts when its summertime and the boiler only runs for DHW. A simple bit of programming could easily eliminate that though. I'd also like to be able to adjust the pre and post purge combustion blower settings, keep a minimum (which is what is there now) buy allow the installer to lengthen it if needed.

Mod/cons are the best suited to high mass: slabs, cast iron etc. I have yet to get anyone to buy panel radiators sized for low temps.

Eastman

@Solid_Fuel_Man
You could say the same thing about bang-bang boilers.

Solid_Fuel_Man

The same what?

Eastman

That bang-bang boilers are best suited for high mass emitters.

Gordy

Why????

Gordy

Actually mod/cons are.

What makes them persnickety is small zones, and low mass emitters. In other works lack of mass.

Strap it to radiant, or comverted gravity iron with ample zones. Now you got something. With out worry of return boiler protection.

NY_Rob

^ 100% agree with Solid Fuel Man and Gordy!

After living with a mod-con for one winter with all fin-tube and last winter with fin-tube and cast iron baseboard I can unequivocally state that the cast iron zone makes the boiler run longer, cycle less and it gives lower return temps till setpoint is met. It also retains xxx times latent heat compared to fintube so even after setpoint is met you're still adding heat to the room which leads to increased comfort and considerably fewer boiler cycles.

An ideal setup IMO would be a mod-con and all cast iron baseboard throughout the whole house. You would never worry about short cycling and the heat level would be very even. Throw in a mini-split system with heat capability as a backup system and you're golden!

mikeg2015

All boilers prefer high mass. You can rarely have too much storage capacity.

As a bonus, cast iron radiators are often installed on older homes with a lot more mass as well. It allows you to undersize slightly and get long runs times and great effecincy, lower installed cost.

What’s easily forgotten isn’t just the mass of the iron, it’s the water volume. lb for lb water stores a lot more heat.

I have 10 big cast iron and 2 small radiators. It’s steam but one of my largest radiators is too long and short to work well on steam so I might convert it to hot water. Not sure.

tim smith

Love cast iron and modcons. Btw Lochinvar control has been really solid for us. All mfrs controls have there pluses and negatives. As long as semi easy setup with options, also like boost feature for morning pickup.

flat_twin

I haven't touched the boost function but I can see your point about quicker recovery from night time setbacks if a customer insisted on setbacks. I'm happy to leave the thermostat at the same temperature. The fancy pants Honeywell 8000 Vision Pro the contractor installed is complete overkill for us. I was told it's wired to indicate a lockout condition by showing a red warning lamp. That red warning was lit a couple weeks ago to tell me the backup batteries needed replaced. Haven't seen it come on otherwise.

Solid_Fuel_Man

I like to wire a two stage heat thermostat to mod/cons. Then you can wire the W1 (first stage heat) to a nice reset curve, but if it cannot keep up, or there was a setback, then W2 (2nd stage heat) runs the boiler to a slightly hotter curve and allows for good recovery. Better than a boost timer, but essentially the same thing, just with real world input from the t-stat.

Solid_Fuel_Man

For whatit's worth, 4 conductors is the minimum thermostat wire I ever run for a heat only system.

The boost feature is to get around just having 2 wires and a single stage t-stat, which is what most installers ever run.

mikeg2015

flat_twin said:

I haven't touched the boost function but I can see your point about quicker recovery from night time setbacks if a customer insisted on setbacks. I'm happy to leave the thermostat at the same temperature. The fancy pants Honeywell 8000 Vision Pro the contractor installed is complete overkill for us. I was told it's wired to indicate a lockout condition by showing a red warning lamp. That red warning was lit a couple weeks ago to tell me the backup batteries needed replaced. Haven't seen it come on otherwise.

flat_twin said:

I haven't touched the boost function but I can see your point about quicker recovery from night time setbacks if a customer insisted on setbacks. I'm happy to leave the thermostat at the same temperature. The fancy pants Honeywell 8000 Vision Pro the contractor installed is complete overkill for us. I was told it's wired to indicate a lockout condition by showing a red warning lamp. That red warning was lit a couple weeks ago to tell me the backup batteries needed replaced. Haven't seen it come on otherwise.

flat_twin said:

I haven't touched the boost function but I can see your point about quicker recovery from night time setbacks if a customer insisted on setbacks. I'm happy to leave the thermostat at the same temperature. The fancy pants Honeywell 8000 Vision Pro the contractor installed is complete overkill for us. I was told it's wired to indicate a lockout condition by showing a red warning lamp. That red warning was lit a couple weeks ago to tell me the backup batteries needed replaced. Haven't seen it come on otherwise.

8000 aren’t that much more than a cheaper thermostat. The advantage is it uses PI control with cycles per hour setting. SOme models can also average multiple remote wireless temperature sensors. Pretty universal. can use outdoor reset for dual fuel control on a heat pump as well.

flat_twin

I did change the cycles per hr setting to minimum but there's no setback at all. Being able to access the boost from the tstat is interesting. Just in case the mrs could even use it if it were ever necessary. It would be extremely easy to pull a four conductor thru and replace the existing wire. I think it's just a three conductor. Tip, ring, and a 24v wire.

Brewbeer

@Eastman my system is sized for running the same temps to each of the three zones. I have two of the zones disabled so that all three heat at the same time. The ODR curve is set up as low as it will go to maintain 69F, so that the boiler runs continuously.

NY_Rob

If you use any setback at all Boost would probably be needed on a really dialed-in boiler. I have it enabled on my system because I do use -2deg nite setback for my upstairs zone.

FWIW- the former member who gave me lots of good ideas when setting up my boiler had me wire a "I'm cold" switch into the ODR sensor circuit. It's a simple cabinet mounted $2 SPST switch that runs in series with one of the ODR sensor leads. When it's in the open position presents a situation to the boiler that the ODR sensor has failed so the boiler defaults to 180F max SWT.
It's there in case we get a really cold (below our 15F DD temp) windy day here and the 136F SWT just isn't hot enough. Haven't needed it yet... but nice to know it's there just in case.

NY_Rob

I also combine zones during the day to keep cycling to a minimum using this $12 timer. After 7pm each zone is on it's own because of setback.

flat_twin

NY_Rob That's an interesting way to have a manual boost. I'm not sure what the Eco would default to. I'll look into that. Easy enough to try. Today I dialed back the max fan speed settings so it's high fire is limited to 70%. I also turned on the boost to see how that works. All I can do is go from Boost off to Boost on @ 1 thru 240 minutes. A timer starts with the call for heat. If when the set minutes elapse and there's still a call for heat, the boiler will change the target to the max temp setting which is 126 currently. It did exactly that and I watched it ramp up to 70% per my new max fan speed settings. Opening one side of the ODR sensor wiring and sending a leg upstairs to a switch by the thermostat would be a great work around.

Le John

@NY_Rob do you have a wiring diagram of how you wired the timer. I’d like to try the same approach!

Gordy

NY_Rob said:

If you use any setback at all Boost would probably be needed on a really dialed-in boiler. I have it enabled on my system because I do use -2deg nite setback for my upstairs zone.

FWIW- the former member who gave me lots of good ideas when setting up my boiler had me wire a "I'm cold" switch into the ODR sensor circuit. It's a simple cabinet mounted $2 SPST switch that runs in series with one of the ODR sensor leads. When it's in the open position presents a situation to the boiler that the ODR sensor has failed so the boiler defaults to 180F max SWT.
It's there in case we get a really cold (below our 15F DD temp) windy day here and the 136F SWT just isn't hot enough. Haven't needed it yet... but nice to know it's there just in case.

I like the I’m cold switch idea. Quick, and easy instead of fumbling through a reset curve adjustment for temporary periods. That could even mount next to the tstat.

I also like the @Solid_Fuel_Man two stage approach.

Gordy

However one would have to watch what type of emitters were used in conjunction with the I’m cold switch.

Eastman

This is why I like the idea of indoor feedback. There should be some way for the ODR curve to dynamically adapt as required.

Gordy

I think it’s completely possible to make ODR more adaptive. The outdoor sensor is in place and can detect if the temp drops below the curve, and make adjustments.

Eastman

What do you mean? The temp never drops below the curve.

Eastman

Furthermore...
It would be nice if the control system could receive temperature forecasts. That would be helpful for high mass systems.

Gordy

The outdoor sensor detects the outdoor temperature right?

Eastman

Yeah, it detects the outdoor temperature and computes a target water temperature using the ODR curve.