DIY Chatroom Home Improvement Forum

DIY Chatroom Home Improvement Forum (
-   HVAC (
-   -   Mystery heating behaviour (

tls1 12-23-2012 09:27 AM

Mystery heating behaviour
Hi all,

We live in Montreal in a split level house. The house is not well insulated in the walls. The roof is well insulated. And the basement is not insulated at all (cement walls and floors exposed). We have a 1989 Lincoln oil furnace and a 2 year old heat pump. This is our first winter in the house.

We have an Aube TH146-N-U thermostat and the external thermometer. The system is set to switch to oil at -10C.

I have noticed some weird behaviour in recent days....

1) Yesterday it was -3C and medium winds. The HP & fan turned on for 30 second, then off. After a couple of minutes it went on again for 30 seconds, then off. After another couple of minutes it turned on again (and started burning oil -I could hear the burner). Turned off after about a minute. Then after another couple of minutes the HP turned on again and ran for quite a while (normal). Any ideas?

2) The thermostat is set to burn oil at -10C. Sometimes when it's around -9/-9C the heat pump can run for hours at a time, trying to maintain a steady temperature. It will not go up half a point above the set point (to turn off), nor down (to maybe switch to oil). So it keeps running. The thermostat has an interstage delay set to 30 minutes, for which I thought it would switch to oil if the HP cycle was not finished after 30 min. We go thru furnace filters like crazy...they're black after 1 month (maybe related to burning oil?).

3) I understand that the oil can be used to heat the system to speed up the HP defrost cycle. So far we have used about 200-250 liters of oil (approx 60 US gallons). Seems reasonable? We may have had a couple of colder days when oil was used exclusively.

4) I think the location of the thermostat might be involved in the problem. It's on the main floor in the stair well. I think there is a small "wind" in there which affects the thermostat. I covered the vent holes with masking tape. Seems to help a bit... I would like to change the thermostat for a more accurate one. This one communicates thru the old 2 wire system to a control box near the furnace. I would like to replace it with a traditional system that has multiple wires between the thermostat and furnace/HP. Also most importantly, we also have a 3 speed fan which is hard wired on high speed. It would be nice to have it on low speed when there is no demand, med speed for heat, high speed for AC. What do you recommend?

Any advice is welcome!
Happy Holidays to everyone!

beenthere 12-23-2012 12:05 PM

Relocate the new thermostat to a better location. Then use a Honeywell stat that is dual fuel capable. You would have to install relays to have blower speed control. or something like an ICM 750 to control blower speed.

tls1 12-23-2012 12:15 PM


Do they have wireless thermostat? Might have some trial and error to find the best spot... weird house!


beenthere 12-23-2012 12:44 PM

Yes they do.

tls1 12-24-2012 05:00 AM

While that is a cool thermostat, it's not exactly what I meant...

I wanted a battery operated thermostat that I could move around the house and test until I found the optimal location. Like a wireless phone...

This one simply has wifi that allows lazy man to see the screen and manipulate the setting from afar :laughing:

Any thoughts on the amount of oil we have used so far? Or the long running heat pump ?


beenthere 12-24-2012 12:51 PM

Honeywell has models that use a portable thermostat that you can move from room to room if you want.

60 Gallons sounds about right for my area, can't say for sure about your area. Might be excellent.

All times are GMT -5. The time now is 06:40 PM.

vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

Search Engine Friendly URLs by vBSEO 3.6.1