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btarby15

New Member
Sep 25, 2018
11
Heatmor
I just installed a Heatmor Outdoor boiler for my home. I have an hydronic system with cast iron radiators. My oil boiler also heats my domestic hot water. I have my Heatmor and Oil boiler running through a plate exchanger. It is working great for heating my house, boiler hasn't kicked on. However, I am noticing our domestic water only gets lukewarm. Anyone else have this issue?
 

Bad LP

Minister of Fire
Nov 28, 2014
2,001
Northern Maine
What temp is your wood boiler running at?
 

maple1

Minister of Fire
Sep 15, 2011
10,924
Nova Scotia
More info.

Like, how your oil actually heats your DHW. Pics may help.

There may be a mixing valve on your DHW somewhere that was at play when heating DHW with the oil but if your oil temps are now lower than they used to be it may be mixing when it is now not needed.
 

btarby15

New Member
Sep 25, 2018
11
Heatmor
More info.

Like, how your oil actually heats your DHW. Pics may help.

There may be a mixing valve on your DHW somewhere that was at play when heating DHW with the oil but if your oil temps are now lower than they used to be it may be mixing when it is now not needed.
That is a good thought but I don't believe there is a mixing valve anywhere. I was actually thinking about installing one previously because my DHW was too hot when heating with oil boiler. DHW is heated through coil in boiler.
 

NateB

Feeling the Heat
Mar 5, 2013
294
South Central Pennsylvania
My guess would be that the HX for the DHW in your oil boiler is not designed to work at the lower water temps. You could try flushing out that HX, but I think you will still see poor performance. I would encourage you to come up with a different DHW solution, so you can shut off the oil boiler in the summer.
 
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btarby15

New Member
Sep 25, 2018
11
Heatmor
My guess would be that the HX for the DHW in your oil boiler is not designed to work at the lower water temps. You could try flushing out that HX, but I think you will still see poor performance. I would encourage you to come up with a different DHW solution, so you can shut off the oil boiler in the summer.
Yes I was thinking a similar solution. Might have to install a small electric water tank heater or something.
 

maple1

Minister of Fire
Sep 15, 2011
10,924
Nova Scotia
All setups are a bit different, but I used to have a coil in my old wood/oil unit that would still make DHW that was 'hot enough' down to a boiler temp of between 140 & 150. That's what I set the boiler down to in the summer. 'Hot enough' varies also - sometimes at that I would be having the cold tap shut off when showering, so might call it 'marginally hot enough'. Some factors at play there are size of coil, the location of the coil in the boiler, and how well the water in the boiler would convect across the coil when using DHW but the boiler temp wasn't quite low enough to make the burner cut in or boiler water wasn't otherwise flowing to heat something else. If it was really hot before but only lukewarm now, your oil settings were likely a lot hotter than what the OWB is doing now. The OWB might just not be making the oil boiler quite hot enough for the coil size/location. Reasons for that might be some sort of sub-optimum OWB install issue, or even heat loss through the underground piping. Or maybe an undersized plate HX. A good 'all-proper' OWB install should be able to keep the oil boiler warmer than 150-160 with 175-195 OWB supply temps.
 

btarby15

New Member
Sep 25, 2018
11
Heatmor
All setups are a bit different, but I used to have a coil in my old wood/oil unit that would still make DHW that was 'hot enough' down to a boiler temp of between 140 & 150. That's what I set the boiler down to in the summer. 'Hot enough' varies also - sometimes at that I would be having the cold tap shut off when showering, so might call it 'marginally hot enough'. Some factors at play there are size of coil, the location of the coil in the boiler, and how well the water in the boiler would convect across the coil when using DHW but the boiler temp wasn't quite low enough to make the burner cut in or boiler water wasn't otherwise flowing to heat something else. If it was really hot before but only lukewarm now, your oil settings were likely a lot hotter than what the OWB is doing now. The OWB might just not be making the oil boiler quite hot enough for the coil size/location. Reasons for that might be some sort of sub-optimum OWB install issue, or even heat loss through the underground piping. Or maybe an undersized plate HX. A good 'all-proper' OWB install should be able to keep the oil boiler warmer than 150-160 with 175-195 OWB supply temps.
Thanks for the detailed reply. Yeah, the showers aren't cold, but they're warm pool like water temps. The kitchen faucet is "hot" but I suspect that's because the kitchen is right above the boiler. I am new to this, so would you suggest insulting pipes and exchanger? I have insulated pipes in ground, but once they come into my house it switches to normal pex. I have a 70 plate HX, and was thinking about wrapping it with insulation, too. My Heatmor is rated for 3,000 sq ft, while my heatable space is 2200, but it's a stone farmhouse so there is minimal insulation. I haven't done temp readings on supply and return on OWB yet, but to the touch they seem similar. I have my oil boiler set to 140H, 120L, but it hasn't had to kick on because of OWB. I do suspect the temp gauge on oil boiler is off a bit, too, since when running oil boiler to 180, the temp would never read above 170. So that might also be giving me some inaccurate data.
 

maple1

Minister of Fire
Sep 15, 2011
10,924
Nova Scotia
Yes insulating all you can should help.

Your cast iron rads are great things for good even heat at lower supply temps. I suspect if you had, say, ordinary baseboards, you might not be feeling quite as warm in the current supply temp situation.
 

btarby15

New Member
Sep 25, 2018
11
Heatmor
All setups are a bit different, but I used to have a coil in my old wood/oil unit that would still make DHW that was 'hot enough' down to a boiler temp of between 140 & 150. That's what I set the boiler down to in the summer. 'Hot enough' varies also - sometimes at that I would be having the cold tap shut off when showering, so might call it 'marginally hot enough'. Some factors at play there are size of coil, the location of the coil in the boiler, and how well the water in the boiler would convect across the coil when using DHW but the boiler temp wasn't quite low enough to make the burner cut in or boiler water wasn't otherwise flowing to heat something else. If it was really hot before but only lukewarm now, your oil settings were likely a lot hotter than what the OWB is doing now. The OWB might just not be making the oil boiler quite hot enough for the coil size/location. Reasons for that might be some sort of sub-optimum OWB install issue, or even heat loss through the underground piping. Or maybe an undersized plate HX. A good 'all-proper' OWB install should be able to keep the oil boiler warmer than 150-160 with 175-195 OWB supply temps.
And as I said, the OWB is keeping the house at 72 without oil kicking on, which makes the wife and baby happy! I was a little concerned my OWB would be a tad undersized for my house considering there isn't much insulation, but I got it at a liquidated price so I couldn't say no. If I have to install a small electric water heater for domestic, I wouldn't mind that at all, still saving $$$ a month not getting a tank of oil every month!
 

salecker

Minister of Fire
Aug 22, 2010
1,767
Northern Canada
Thanks for the detailed reply. Yeah, the showers aren't cold, but they're warm pool like water temps. The kitchen faucet is "hot" but I suspect that's because the kitchen is right above the boiler. I am new to this, so would you suggest insulting pipes and exchanger? I have insulated pipes in ground, but once they come into my house it switches to normal pex. I have a 70 plate HX, and was thinking about wrapping it with insulation, too. My Heatmor is rated for 3,000 sq ft, while my heatable space is 2200, but it's a stone farmhouse so there is minimal insulation. I haven't done temp readings on supply and return on OWB yet, but to the touch they seem similar. I have my oil boiler set to 140H, 120L, but it hasn't had to kick on because of OWB. I do suspect the temp gauge on oil boiler is off a bit, too, since when running oil boiler to 180, the temp would never read above 170. So that might also be giving me some inaccurate data.
You may have a mixing valve for your shower.It is a new requirement in Canada,lived in our basement for 15 years.Then we built the house on the basement.The new plumbing for upstairs has the hot water for baths and showers going through a mixing valve set for a maximum high temp that is safe,downstairs you can cook lobsters in the bath water,no mixing valve on the old plumbing.
 

btarby15

New Member
Sep 25, 2018
11
Heatmor
You may have a mixing valve for your shower.It is a new requirement in Canada,lived in our basement for 15 years.Then we built the house on the basement.The new plumbing for upstairs has the hot water for baths and showers going through a mixing valve set for a maximum high temp that is safe,downstairs you can cook lobsters in the bath water,no mixing valve on the old plumbing.
Thanks! I will take a look at the shower plumbing tonight for mixing valves.
 

btarby15

New Member
Sep 25, 2018
11
Heatmor
Yes insulating all you can should help.

Your cast iron rads are great things for good even heat at lower supply temps. I suspect if you had, say, ordinary baseboards, you might not be feeling quite as warm in the current supply temp situation.
Oops...turns out I had both the hot and cold water on for my outdoor hydrant. I turned off the hot and have tons of really hot water.
 

Eureka

Feeling the Heat
Feb 4, 2018
349
NW Wisconsin
Oops...turns out I had both the hot and cold water on for my outdoor hydrant. I turned off the hot and have tons of really hot water.
That’s the best outcome for these situations. A smack on one’s forehead is free! :)