Oil Boiler Setup Questions

[jb1390]

We have been heating exclusively with wood for the past number of years, we have not used the hydronic system at all. I am working to revamp it a bit - and I'm replacing the original (General Motors) boiler, with a Liberty Slant Fin (LD-30P I believe) I bought secondhand. I have some questions about how to set up zone and boiler controls. House is 1150 sf, poorly insulated with single pane windows.

1. We heat Domestic Hot Water with an electric water heater. There is not a DHW coil on this boiler, and I'm not planning to add one. If we end up tying in a wood boiler someday, we may connect DHW to that, but I'm not currently planning to alter the DHW system.

2. I would like to zone with separate pumps. The pumps are relatively cheap, and contain check valves. It seems this is the easier way to go - and will allow appropriate flow for each zone. Otherwise it's a bigger pump with zone valves - and chances are only one zone will ever run due to continued heating with the wood stove. Using separate smaller pumps seems more appropriate and simpler for this application. The pumps would be controlled via relays and thermostats.

3. For ease of control, I was planning on controlling the boiler purely off an aquastat - and the thermostats would tie in only to the pumps. So the boiler would run independently, maintain hot water, and the pumps would move it as required. From what I've read, it seems some systems will increase the boiler temp when it calls for heat, but allow the temp to relax when there is no call for heat, but maintain a lower temp for DHW. Since I am not doing DHW, I was going to get an adjustable aquastat, and adjust the range as required so the boiler doesn't short-cycle excessively. Is this approach ok?

4. We would like 3 zones - one that will be shut off most of the time. This space is not typically used during the winter due to very poor windows and insulation. I was planning on including glycol for this zone - and it will have a heat exchanger and separate pump. I did not want to include glycol throughout the entire system - but would not be strongly opposed if that's the better way to go. It seems the drawbacks outweigh the slight increase in cost and equipment to isolate that particular zone.

Am I missing anything major? Any suggestions on a different approach?

 

[nybirdman]

I think you are missing the boat by not using the domestic water circuit on your boiler(add one if you don't have it) ;basically your domestic is free during the heating season.And expensive with electric.
Control the boiler with an aquastat and run the circulators off the thermostats is the way to go.
I would recommend putting glycol in the whole system.

 

[quicksandfarmer]

There's no way you can put glycol in one zone and not the whole system, when the circulator runs it will mix it all up. I put glycol in the whole system. I also normally keep the makeup water off, if my system is leaking I want to know about it and fix it. I had expensive damage to a system once that I thought was protected by glycol, but it was leaking and the glycol had been mostly replaced by makeup water.

Hot water from the boiler isn't free, it still takes fuel to make, but it is cheaper than electric. Your boiler will also produce a lot more hot water than any electric water heater. The preference now seems to be for indirect loops in tanks rather than tankless loops, the water temperature is more stable.

 

[aczlan]

I would run glycol in the whole system as that will help keep you from having damage if you have power issues in the winter.
I have an indirect HW heater and its nice, but it can get spendy in the summer.

Aaron Z

 

[jb1390]

There's no way you can put glycol in one zone and not the whole system, when the circulator runs it will mix it all up. I put glycol in the whole system. I also normally keep the makeup water off, if my system is leaking I want to know about it and fix it. I had expensive damage to a system once that I thought was protected by glycol, but it was leaking and the glycol had been mostly replaced by makeup water.

Hot water from the boiler isn't free, it still takes fuel to make, but it is cheaper than electric. Your boiler will also produce a lot more hot water than any electric water heater. The preference now seems to be for indirect loops in tanks rather than tankless loops, the water temperature is more stable.

If I had that zone separate, it would require a heat exchanger, and 2 circulator pumps to make it work. Just not sure if the cost of glycol would offset the cost of the extra parts, or if there are other issues that arise by using glycol in everything.

I agree that the DHW through oil would save a little in the winter but probably cost more money in the summer - not sure we use enough of it to make it worth the effort for slight winter savings. Someday we will tie in a wood boiler with this system - I was planning on preheating the DHW with the wood boiler if we get it hooked up, and leaving the DHW alone for now.

 

[coolreinfarm]

Be sure the pumps you select are glycol compatible, the seals in some pumps are not. Use glycol like Dow sr-1 designed for boilers and hot water systems, do not, repeat do not use automotive antifreeze in a hydronic heating system too many additives, stop leak, corrosion protection etc. I would use 1 pump and multiple zone valves, depends on how much money you want to spend.

 

[aczlan]

If I had that zone separate, it would require a heat exchanger, and 2 circulator pumps to make it work. Just not sure if the cost of glycol would offset the cost of the extra parts, or if there are other issues that arise by using glycol in everything.

I agree that the DHW through oil would save a little in the winter but probably cost more money in the summer - not sure we use enough of it to make it worth the effort for slight winter savings. Someday we will tie in a wood boiler with this system - I was planning on preheating the DHW with the wood boiler if we get it hooked up, and leaving the DHW alone for now.

We go through almost a full tank of oil each summer. Planning on adding an electric HW heater to use in the summer to help with that. It should pay for itself fairly quickly.

Aaron Z

 

[jb1390]

Be sure the pumps you select are glycol compatible, the seals in some pumps are not. Use glycol like Dow sr-1 designed for boilers and hot water systems, do not, repeat do not use automotive antifreeze in a hydronic heating system too many additives, stop leak, corrosion protection etc. I would use 1 pump and multiple zone valves, depends on how much money you want to spend.

I'm looking at using Grundfos UPS15-58FC pumps, they are less than $100 each. Based on literature I have seen, they are glycol compatible.

 

[dadster4]

Most of your plan sounds good. Isolating the little-used zone with a separate heat exchanger seems to be overkill and expensive, is the piping and fin tube subject to possible freezing? It may be better to set the thermostat in that area to a lower temp so that zone cycles often, but will not run for long. You can control the boiler in a way that it will only fire if one or more zones call for heat, keeping the boiler hot(weather full or reduced temp) is wasteful. When piping in the pumps, plan on your possible future DHW needs with stubs for another pump, for an indirect heat exchanger. It would be great if an electric HW heater was available with a heat exchanger...does anyone know of one? Adding glycol to the whole system gets expensive and also reduces efficiency. FYI-30 years HVAC

 

[jb1390]

Most of your plan sounds good. Isolating the little-used zone with a separate heat exchanger seems to be overkill and expensive, is the piping and fin tube subject to possible freezing? It may be better to set the thermostat in that area to a lower temp so that zone cycles often, but will not run for long. You can control the boiler in a way that it will only fire if one or more zones call for heat, keeping the boiler hot(weather full or reduced temp) is wasteful. When piping in the pumps, plan on your possible future DHW needs with stubs for another pump, for an indirect heat exchanger. It would be great if an electric HW heater was available with a heat exchanger...does anyone know of one? Adding glycol to the whole system gets expensive and also reduces efficiency. FYI-30 years HVAC

The room we are isolating is really a 3 season room - the windows are very drafty, the floor is not insulated, and the pipes run underneath that room in a crawl space. Typically we close the door to that room, and it is common in the winter for the snow to stay frozen on the floor in there. We are not looking to change that with the boiler install - but we would like to use the space occasionally. I would be concerned with pipes freezing if we left the heat shut off in there for days over the coldest part of the winter. I don't think the cost is excessive to isolate - I'm looking at $90 for an extra circulator, 80 or so for a heat exchanger, and 25 for an expansion tank, plus the glycol. It seems that the cost of that would be saved in oil pretty quickly.

I had read about the boiler cycling only when called for heat - I thought from what I had read that this was primarily for DHW purposes - so that the boiler would not sit at too high of temperature over the summer, without having to touch the aquastat - but then would increase temp to keep up with heat load. I was thinking of just adjusting the aquastat depending on season - so leave the water temp low for spring/fall, and increase it some in the winter as required to meet heat demand. I was also thinking a programmable aquastat would be a neat feature - if one exists. I'm not too concerned about standby losses - I think most of that loss would be radiated to the basement, which we would like to keep semi-heated anyway. Also would be simpler to wire and control for a first cut. Would this be difficult to modify if I changed my mind later?