Newbie..... well kinda.

I like this puzzle, but I think we could really use 1 detailed schematic to help.

I can't quite tell from the pictures, but I see the oil "return' is tied to the pellet "supply". The pellet "supply" is T-ed to the pellet "return" (is this for return water protection? it looks like there is a valve and it is "off").

It looks like they tried to put the boilers in series on a loop. Kinda primary/secondary style. I see an aquastat on the loop, what does that control?

The more I look at it, the more I think it is plumbed "fine". I think you have a control issue...or you just have a bad component. Are you SURE your circulator pump is good? Since you only notice a problem when it is really cold I get the idea that the zone valves might be opening, but your only flow might be convection.

ac

Chris, I am close enough I could swing by to look at it. PM me if you want to contact me for that. I can already guarantee you may not like what I have to say about it.

First call is to the gas company to see if natural gas is available in the street or will be in the future. If so, I would be planning on a NG conversion and taking everything else out.

I've looked at the Harmon PB 105 manual online for other poster's reported troubles and what I saw I did not like. My next step in that process would be to call the Harmon factory and beat on them a bit.

I saw several flaws in the Harmon design that were untouchable for me.

On/off is a manual switch. It will sit there maintaining itself hot indefinitely as long as fuel is available even with no load demand from the house. This short cycling of burning just to keep itself hot is a recipe for creosote, higher maintenance/cleaning issues, and higher fuel consumption/efficiency loss.

From memory the manual showed the PB 105 plumbed in series with the oil boiler. If so, you would be effectively depending on the hot PB105 to keep the oil boiler aquastat off. I would score that as totally non professional hack scrap. The oil boiler in series is an additional load and efficiency loss of heat to where you don't want it. The plumbing and controls to do independent parallel heat sources is more complex and expensive, which would put Harmon into competition with better equipment at a higher price.

The PB 105 modulating burn rate was also a fixed manual adjustment. There was no matching of modulating firing rate to demand. Again, a recipe for short cycling, creosote, and efficiency loss.

State of the art pellet boilers come from Europe at this time. IMO they are suitable for primary heat with no backup source, so the oil boiler is not needed, and imo would be coming out to save money and footprint.

A state of the art pellet boiler is able to modulate the firing rate with a 3 to 1 turndown ratio to match demand automatically. It is off and cool when there is no call for heat and fires longer at a lower firing rate to match demand when the heat call is on.

This is mated to a heat distribution system that also modulates output to demand. For your example I would be looking to put in an outdoor air reset controller and mix down the hot water supply temp to the baseboard radiators. The loads would stay on longer at a lower temp and the boiler must be able to modulate down the firing rate to match demand and stay on longer at a lower output. This is a recipe for higher efficiency, cleaner burning, no creosote, less fuel consumed, greater overall user satisfaction.

If it were me the only way I would see forward of getting from there to here is saving my money for new equipment. I feel strongly that saving from the fuel and maintenance costs of what you have now compared to what the state of the art is would pay for new equipment over the life of the install.

PM me if you want me to look at it.

You will need to do more trouble shooting & diagnosing - tracing hot water flows, verification of pumps running, check aquastat settings, seeing how changing settings affects things, etc. etc.. Or find some who can do it. You could need simple stat adjustment, or some rewiring, or some replumbing, a combination of all, or who knows what. We're still light on details.

For example - we see where the zone valve ends of your zones hook into the pellet boiler. But where do the other ends of the zones hook into? Does the water go up or down thru the zone valves? You say zones don't get hot - does that mean the zone pump doesn't pump, or the oil boiler doesn't start? Or the valves don't open? Or?

ct97fd said:

Thank you all for the info. Unfortunately I can't afford to replace the system I have. I'm going to have to make it work.

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Have you tried shutting the by-pass ball valve (looks to be partially closed in the pic) if you are sending 3-4GPM through there @20 Delta thats 40MBH short cycling into your pellet boiler. Brian

ct97fd said:

Thank you all for the info. Unfortunately I can't afford to replace the system I have. I'm going to have to make it work.

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Yes, that's understandable. That's where the majority of the market is. I expected an answer in that range. My point was that for myself as a contractor, I would expect trouble if I tried to install that for customers. I would get the blame.

Any system will have a learning curve to it. As long as you are advised the PB 105 may have higher maintenance and fuel consumption, I am certain it can be made to run. Once you learn the maintenance requirements like cleaning or creosote, you can adjust your burning to make things easier for yourself. I would foresee the PB 105 will require more user, owner, intervention.

There are PB 105 owners on the thread who have direct experience and people with wood hydronic experience. If you continue to post, or try to put PB 105 in the title, I'm sure you will get replies. Ask your questions.