Ontario 20 Year Old Waterfurnace

Discussion in 'Maintenance and Troubleshooting' started by Andrew Kulin, Oct 20, 2023.

  1. Andrew Kulin

    Andrew Kulin Member

    Background:

    Been about 7 years since I have posted to this forum. We bought a cottage near Haliburton Ontario in late 2015 equipped with a Waterfurnace 2-Stage geothermal furnace (installed ~2004 when cottage was built) that was also connected to the hot water tank. But it just did not seem to be working properly (too expensive to run). So with help of the forum and likes of Doc Jenser I was able to tweak settings on the unit to at least a bearable cost to run and it has been working okay since 2016. It is a 6-ton unit. And is a lake loop. Lake level is 5.0 m (16.5 feet ) below basement floor slab elevation and coils 8 - 10 feet below surface of lake . Loop circulation is with two Grundfoss pumps which I believe I was told seven years ago not an efficient soloution

    This is a weekend home so during summer we are up most weekends and maybe a couple of weeks vacation. Maybe run it over a week or so in August if we are up and it is hot and muggy but generally we don't use it in the summer months. In heating season (generally ~mid-Oct to mid April And say needing to run throughout the day mid-Nov to end of March up here) we run it at 20C (68F) while we are up (about every second weekend, maybe a week at Christmas and a week during March Break period) but otherwise set it at 10C when we are not up (50F). I ramp up temps slowly starting a day or two in advance of weekends with our Ecobee so as not to trigger electric heat in the unit. We heat the hot water tank with it when we are not up, unless I know we are going to be away for more than two weeks (like doing Christmas out of town with my parents).

    Annual Electrical costs up here is around CDN$2,000/year (currently averaging about CDN$0.167/kWh (all-in incl. taxes)

    Issue:

    However some things have come to pass recently with the unit. In mid-September we noticed our hot water tank was not heating up the water (it was warm up here so geo not turned on, the electric heater in the tank was failing). So we had the tank replaced 3rd week of September with a larger tank and instructed plumber to connect it up as it was originally connected to the geo unit.

    A few weeks later (first week of October), when we came up we noticed water on the furnace room floor around the geo unit. At this point the geo was coming on occasionally in the evenings if it was colder out. Called my HVAC guy out to look at it and there was a leak in the copper domestic water tubing inside the furnace, just before the line entered the compressor area (?) where the tech explained to me the freon lines, loop lines and domestic water lines all did their heat transfer things. He figured corrosion will have continued inside the shroud with the domestic line at least but to fix it on a 20 year old furnace was sort of like replacing a transmission on a 20 year old car. I asked him to get the owner to give me a call early the next week to discuss.

    He actually called me Saturday afternoon as he was heading off on a 2 week vacation on Sunday. I was at a noisy event so the conversation was not too long but the gist of it was:
    • We could continue to run unit with the hot water functionality so shut of the DSW pump and the water lines to the unit (which had been done).
    • We should plan to replace the unit within the year. My wife wants to replace it before the winter season arrives as knowing our luck it dies during a -30C cold spell during Christmas and we have to run electric heat for 2 to 6 weeks for parts to arrive (or even worse for the rest of winter until a new unit can be installed)
    • I asked about Water Furnace models and he recommended a 2-stage Series 5. I asked about Series 7 but he did not think it would be worth the additional cost plus he said when things break down they are very expensive to repair. We did not get too deep into all this because I was at an event and it was not a great time to have the call. We will be speaking again in about 10 days when he is back in town.
    • Figures for Series 5, Remove and Replace around $18-$20K (Canadian)
    Questions:

    I have attached some photos of the unit and the set-up for background

    1. Would going with a Series 5 vs. Series 7 make sense? Current electric rates up here at on average CDN$0.167/kWh based on my 2023 YTD bills.
    2. What size unit do I need for the place? I had some calculations (Manual J?) done for the place in 2017 (attached) though I have no understanding how to interpret this report. I had also had a guy come in and test the place for air leakage independently and he came up with 2.2 ACH (the attached report has an ACH of 3.6 used), Air movement @1210 CFM at 50 Pa, Equivalent Leakage Area of 130 sq. in. at 10 Pa. Don't know if any of this is relevant.
    3. I would like to, if possible set this furnace up for two zones (basement and ground floor). Current system is a single zone. But if I need to rip apart walls and ceilings, or spend a lot of money to do this then we'd likely pass on this. We would reconnect to the hot water tank as well.
    4. Also would it be possible to come up with a single loop pump solution? One-way distance from furnace to where in-lake coils start is about 50 m (165 feet) (1.25 inch SDR 13.5)
    5. Last question, any ideas why there is corrosion of the copper piping of the domestic water line, inside the furnace as seen in the photo? If it happened with this unit, and it something that can be addressed I would want to do so before installing a new furnace. Looks like there is some aqua blue corrosion on the freon line too?
    Lots of questions. Thanks in advance.
     

    Attached Files:

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