146 therms per month, is my Prestige Solo boiler broken?

alex2022

This is our first winter in the house, we looked at the bills for November today and were shocked. We have original radiant heating in the 1960 Eichler home (1800 sqft), powered by a new Triangle Tube Prestige Solo 110. We run it for about 3 hours a day (the history in the Nest app matches the schedule we configured and our own observations). According to the bill, total gas usage in November was 146 therms! It seems insanely high, taking into account we run it for just a few hours and we'd love to make things much warmer than it is right now.

Any chance something is misconfigured or broken? The boiler is advertised to be highly efficient.

Jersey2

Three hours a day? That's about 90 hours and if you are using about 140K btu, would be about 130 therms, no? If there were more days in the billing cycle 140 might be right.

kcopp

Radiant floor heating and Nest thermostats are not a good mix.
I would be inclined to think its the homes insulation and air tightness (or lack thereof) that is contributing to the higher gas bill...
How many sq feet? is there lots of glass?

Ironman

Your house is like a bucket with holes in it. If the bucket has a lot of large holes, don’t blame the faucet because it has to provide more water to keep the bucket full.

The Nest is the worst stat that could be used with a modulating boiler or a radiant floor. Get rid of it and use a simple stat that’s designed for radiant and leave it set at one temperature.

Hot_water_fan

As noted, a Nest is not the thermostat you want. Do you have baseboard? Radiators? Radiant floor? 

EBEBRATT-Ed

you can't turn radiant heat on and off and on. it has to warm the floors and stay on to work properly

hot_rod

It is the house that dictates the fuel bill most often. I wonder that there is any slab insulation, below or around the slab?

SteamBoiler

alex2022 said:

This is our first winter in the house, we looked at the bills for November today and were shocked. We have original radiant heating in the 1960 Eichler home (1800 sqft), powered by a new Triangle Tube Prestige Solo 110. We run it for about 3 hours a day (the history in the Nest app matches the schedule we configured and our own observations). According to the bill, total gas usage in November was 146 therms! It seems insanely high, taking into account we run it for just a few hours and we'd love to make things much warmer than it is right now.

Any chance something is misconfigured or broken? The boiler is advertised to be highly efficient.

We live in a similar size house in NJ, have a Weil McLain steam boiler with radiators controlled with a Nest learning thermostat that I put in myself, and used approx 150 therms in November (approx 80 hours of boiler run time plus gas range dryer etc), 30% lower than the previous November when the boiler was controlled off a "set and forget" mercury Honeywell Chronotherm thermostat with appropriately set anticipator. The mercury thermostat was short-running my boiler and the early radiators were always barely hot and the late ones never came on. The basement and utility room were always warm (since the boiler was frequently running but not long enough each time) and the house always cold. I had no idea what the average heat call duration was with the old thermostat, obviously.

With the Nest the heat calls are approx 20 minutes long once every 2 hours (more frequent if below freezing or cloudy). Home is set to 68F from 7am to 10pm, backed off to 64F at 10. Recovers in 1F steps from 3am to 6am so boiler doesn't pressure cycle. The home is warm and the basement comfortable. Most radiators now come on, there is one stubborn late one that is intermittent. Energy is obviously expensive so I am considering backing off to 67F during the day from 8am to 3pm.

I love the Nest because the heat call duration is a great proxy for steam system health and I look at my heat calls every day. Early this season I had an extra long heat call since the boiler was short on water and the low water cut off unit was intermittently firing the boiler (pressure surges early meant I had removed a bit too much water). I saw that call and went in and added water and the calls were back to normal.

For your particular situation, I don't know what to say. Make sure all your windows are caulked on the inside around the trim to prevent cold air coming in and on the outside around the sill. Check your heat call duration. How often does the Nest call for heat, and what is the duration, for a temperature "maintenance" call. Turn off all Nest auto-schedule features, go into the schedule and make sure only your particular settings are there (it looks like you have already done that). It is not clear what type of radiant heat you have, if it is a steam boiler make sure your pressuretrol is set to low pressures so you aren't running the boiler just to build pressure.

pecmsg

1 Yea

1000 Nay

alex2022

SteamBoiler said:

alex2022 said:

For your particular situation, I don't know what to say. Make sure all your windows are caulked on the inside around the trim to prevent cold air coming in and on the outside around the sill. Check your heat call duration. How often does the Nest call for heat, and what is the duration, for a temperature "maintenance" call. Turn off all Nest auto-schedule features, go into the schedule and make sure only your particular settings are there (it looks like you have already done that). It is not clear what type of radiant heat you have, if it is a steam boiler make sure your pressuretrol is set to low pressures so you aren't running the boiler just to build pressure.

Thank you, that is very helpful! Well half of the walls in the house are glass, single-paned glass from 60s. Replacing them will cost a small fortune so we are not going to do that very soon. You are right, I disabled all smart Nest features and it just works by schedule - 67F between 6 and 9 AM, 62F the rest of the day. It usually does not achieve 67F till 9AM (probably because of the heat loss), so the boiler is constantly working during that time.

So if ~100h is ~140 therms for this boiler, I think we'll just get an oil-filled electric heater instead and use it until we replace the windows. It should cost way less 100$/month and likely be enough for our small office rooms (it's not too cold during the day in Northern CA).

fentonc

Those 140 therms at, say, 80% efficiency, would be 11.2 million BTUs. To get the same amount of heat from an electric resistance heater would be 3,282 kilowatt-hours - it should be cheaper if you pay less than $0.03/kwh all-in.

Hot_water_fan

Extremely unlikely the windows will ever pay off. The way to efficiently use that kind of boiler is to use the lowest temperature water you can and actually keep it at a more consistent temp. It’s surprising, but “low and slow” is how these work. It’s like driving 55 mph for 2 hours vs driving 110 mph for one. 

Alan (California Radiant) Forbes

14,600,00 BTU divided by 100,000 BTU (the output of your boiler) = 146 hours of run time at full modulation. That's almost 5 hours of run time per day. Maybe you do a lot of cooking, too?

Ironman

SteamBoiler said:

This is our first winter in the house, we looked at the bills for November today and were shocked. We have original radiant heating in the 1960 Eichler home (1800 sqft), powered by a new Triangle Tube Prestige Solo 110. We run it for about 3 hours a day (the history in the Nest app matches the schedule we configured and our own observations). According to the bill, total gas usage in November was 146 therms! It seems insanely high, taking into account we run it for just a few hours and we'd love to make things much warmer than it is right now. Any chance something is misconfigured or broken? The boiler is advertised to be highly efficient.

We live in a similar size house in NJ, have a Weil McLain steam boiler with radiators controlled with a Nest learning thermostat that I put in myself, and used approx 150 therms in November (approx 80 hours of boiler run time plus gas range dryer etc), 30% lower than the previous November when the boiler was controlled off a "set and forget" mercury Honeywell Chronotherm thermostat with appropriately set anticipator. The mercury thermostat was short-running my boiler and the early radiators were always barely hot and the late ones never came on. The basement and utility room were always warm (since the boiler was frequently running but not long enough each time) and the house always cold. I had no idea what the average heat call duration was with the old thermostat, obviously. With the Nest the heat calls are approx 20 minutes long once every 2 hours (more frequent if below freezing or cloudy). Home is set to 68F from 7am to 10pm, backed off to 64F at 10. Recovers in 1F steps from 3am to 6am so boiler doesn't pressure cycle. The home is warm and the basement comfortable. Most radiators now come on, there is one stubborn late one that is intermittent. Energy is obviously expensive so I am considering backing off to 67F during the day from 8am to 3pm. I love the Nest because the heat call duration is a great proxy for steam system health and I look at my heat calls every day. Early this season I had an extra long heat call since the boiler was short on water and the low water cut off unit was intermittently firing the boiler (pressure surges early meant I had removed a bit too much water). I saw that call and went in and added water and the calls were back to normal. For your particular situation, I don't know what to say. Make sure all your windows are caulked on the inside around the trim to prevent cold air coming in and on the outside around the sill. Check your heat call duration. How often does the Nest call for heat, and what is the duration, for a temperature "maintenance" call. Turn off all Nest auto-schedule features, go into the schedule and make sure only your particular settings are there (it looks like you have already done that). It is not clear what type of radiant heat you have, if it is a steam boiler make sure your pressuretrol is set to low pressures so you aren't running the boiler just to build pressure.

Your comparing apples to oranges. Your steam boiler runs at 100% on then 100% off. The Prestige is a modulating hot water boiler which seeks to run at its lowest modulation for the longest time needed to maintain an even temperature in the house. Using a Nest which tries to turn the boiler off for as long as possible is counter productive to what the boiler is attempting to.

A Nest should not be used with any modulating equipment. The manufacturers teach this in their training class.

I don’t mean to be unkind, but your recommendation for the Nest is misleading in this scenario.

bburd

If this is the original radiant floor heating system in an Eichler house, the reported gas usage sounds low, even in California. There is probably no insulation around the edges or beneath the floor slab, as well as a general lack of insulation in the structure.

Other posters are correct that it is best to keep this type of system at a steady temperature unless the house is vacant for days or more. That will get the most efficiency from the condensing function of the triangle tube boiler.

SteamBoiler

Ironman said:

SteamBoiler said:

This is our first winter in the house, we looked at the bills for November today and were shocked. We have original radiant heating in the 1960 Eichler home (1800 sqft), powered by a new Triangle Tube Prestige Solo 110. We run it for about 3 hours a day (the history in the Nest app matches the schedule we configured and our own observations). According to the bill, total gas usage in November was 146 therms! It seems insanely high, taking into account we run it for just a few hours and we'd love to make things much warmer than it is right now. Any chance something is misconfigured or broken? The boiler is advertised to be highly efficient.

Your comparing apples to oranges. Your steam boiler runs a 100% then 100% off. The Prestige is a modulating hot water boiler which seeks to run at its lowest modulation for the longest time needed to maintain an even temperature in the house. Using a Nest which tries to turn the boiler off for as long as possible is counter productive to what the boiler is attempting to.

A Nest should not be used with any modulating equipment. The manufacturers teach this in their training class.

I don’t mean to be unkind, but your recommendation for the Nest is misleading in this scenario.

Thanks for the clarification re the Peerless which I wasn't aware of. I wasn't recommending the Nest, just stating my experience with it, especially since OP already has a Nest. Nest is well capable of maintaining one temperature set and forget. Instead of addressing your post to me you would have done well to address OP and telling him your recommendation. 

SteamBoiler

alex2022 said:

Thank you, that is very helpful! Well half of the walls in the house are glass, single-paned glass from 60s. Replacing them will cost a small fortune so we are not going to do that very soon. You are right, I disabled all smart Nest features and it just works by schedule - 67F between 6 and 9 AM, 62F the rest of the day. It usually does not achieve 67F till 9AM (probably because of the heat loss), so the boiler is constantly working during that time.

So if ~100h is ~140 therms for this boiler, I think we'll just get an oil-filled electric heater instead and use it until we replace the windows. It should cost way less 100$/month and likely be enough for our small office rooms (it's not too cold during the day in Northern CA).

You have an incredibly simple heat schedule. Based on the remarks in this thread around the modulation of your boiler - it isn't a catch up type of boiler - you should just run a simple experiment, leave the Nest on 65F the whole day for a couple days and check the boiler run time and compare to the run time with your current schedule. The one issue with that approach though is that run times may not necessarily equal therms (you should research this for modulating boilers) so you may want to try this for a billing cycle. I suggest curtains as another layer of insulation at the windows.