Shoulder season discomfort

[larrybgood]

Dear Heating Experts,

Our building is a 4-story walk-up circa 1955, with a partially underground basement and 21 units in total, located in Toronto Canada.

Heating is very good during the long winter though can be uncomfortably warm during the shoulder seasons. Baseboard heating, rather long taking up the full length of 1-2 walls. Probably cast iron but not certain. A few typical height radiators in the stairwells.

There are 2 natural gas atmospheric 250MTH Hydrotherm boilers about 15 years old, Cast Iron HEs I'm told. A Tekmar 261 control with outdoor reset of 4F and WWSD of 58F currently. WWSD was 65F however I lowered it because of the complaints, and this has helped to a degree. This is the only control for the boilers for the building, there are no internal thermostatic controls in units.

I've been told that there are two heating loops however there is no bypass or mixing valve to adjust the temperature of the heated water. So it leaves the boilers and enters the heating loop at HW boiler temperature.

My understanding is that for atmospheric boilers the minimum temperature should be 140 degrees to avoid corrosive condensation.

I've informed residents that they can reduce the flow through the radiators using the shutoff valve at the entry point into the radiator. Some do this but it's not easy to adjust and a very rough method.

I've lowered the room temperature setting to around 60F but it doesn't have any noticeable impact compared to when it's 70F, at least when the minimum water temperature is 140F.

I've lowered the WWSD temperature to 58F as mentioned. We wouldn't want units to be this temperature, however the building holds heat well. I suppose the worst case would be temperature stays at 58F for days on end however typically it drops below this at night so the heat kicks in. This has helped. It could be raised if there were too many complaints that units were too cold.

So my main question is, is it safe to lower the minimum water temperature to 120-125 degrees during the shoulder season, or would it result in corrosive condensation even in the warmer and typically wetter weather at this time of year? We'd like to extend the life of the boilers for another 10 years if possible.

Is the ideal solution (short of upgrading to condensing boilers which is another topic) setting up a bypass and mixing valve to help deal with this time of the year? I'm sure how large and expensive of a job this is. Would this be the preferred approaching your opinions, or what would be?

Thanks much,

LBG

[Poodle Head Mikey]

Didn't you ask this exact same question last year?

PHM
---------

Dear Heating Experts,

Our building is a 4-story walk-up circa 1955, with a partially underground basement and 21 units in total, located in Toronto Canada.

Heating is very good during the long winter though can be uncomfortably warm during the shoulder seasons. Baseboard heating, rather long taking up the full length of 1-2 walls. Probably cast iron but not certain. A few typical height radiators in the stairwells.

There are 2 natural gas atmospheric 250MTH Hydrotherm boilers about 15 years old, Cast Iron HEs I'm told. A Tekmar 261 control with outdoor reset of 4F and WWSD of 58F currently. WWSD was 65F however I lowered it because of the complaints, and this has helped to a degree. This is the only control for the boilers for the building, there are no internal thermostatic controls in units.

I've been told that there are two heating loops however there is no bypass or mixing valve to adjust the temperature of the heated water. So it leaves the boilers and enters the heating loop at HW boiler temperature.

My understanding is that for atmospheric boilers the minimum temperature should be 140 degrees to avoid corrosive condensation.

I've informed residents that they can reduce the flow through the radiators using the shutoff valve at the entry point into the radiator. Some do this but it's not easy to adjust and a very rough method.

I've lowered the room temperature setting to around 60F but it doesn't have any noticeable impact compared to when it's 70F, at least when the minimum water temperature is 140F.

I've lowered the WWSD temperature to 58F as mentioned. We wouldn't want units to be this temperature, however the building holds heat well. I suppose the worst case would be temperature stays at 58F for days on end however typically it drops below this at night so the heat kicks in. This has helped. It could be raised if there were too many complaints that units were too cold.

So my main question is, is it safe to lower the minimum water temperature to 120-125 degrees during the shoulder season, or would it result in corrosive condensation even in the warmer and typically wetter weather at this time of year? We'd like to extend the life of the boilers for another 10 years if possible.

Is the ideal solution (short of upgrading to condensing boilers which is another topic) setting up a bypass and mixing valve to help deal with this time of the year? I'm sure how large and expensive of a job this is. Would this be the preferred approaching your opinions, or what would be?

Thanks much,

LBG

[larrybgood]

Didn't you ask this exact same question last year?

PHM
---------

Not that I recall but it's not impossible. Certainly not with to this degree of detail.

Did you answer then?

[Poodle Head Mikey]

The described circumstance and desires just seemed to parallel a question from some time last year. That's why I asked.

I see that your post count is only 2 - so this question had to be Post-One. Were you here last year using another screen-name?

The details about the project were discussed at what seemed like some length (at least in my memory <g>) by several members here. Reset controls, minimum boiler water temps, condensation issues, etc.

I wish I could remember more about last year's Q&A - it would be a nice reference for you. Maybe somebody who was involved (and CANRS <g>) will chime in soon.

PHM
----------

Not that I recall but it's not impossible. Certainly not with to this degree of detail.

Did you answer then?