I bought an older house (built in the 70's) and it has oil boiler forced hot water thru the usual finned baseboards.
It keeps it's heat well but there are too many baseboards for a single zone single circuit system.

But the bath and laundry rooms are always cold (in fact coldest)...
and I noticed that there are (9) baseboards all in series heating the (6) areas of the house and the bathroom and laundry are last in line...
and that is why they get no noticeable heat.

So I was thinking of having someone come in and convert the (9) drop series into a (5) and a (4) series circuit.
using a second  pump tied electrically with the original.

I am on a low budget and with little time
and that appears to be a lot of work...



But I thought I could put a small  electric water heater (on demand) in series with the last (2) baseboards to boost the water temp back up to get some heat into the laundry and bathrooms (they are both rather small areas)...

Sofar the flow rates are about the same 3-5gph and the temps are about the same 150 plus degrees F
and the on-demand heater has a flow rate switch to shut it on and off when the main pump kicks on and off from the thermostat.

Can this work?

I would be using it as a baseboard circuit reheater (near the return end) and the electric duty cycle would not be too  high
(unless of course I let the house get completely cold and try to force supplement heat it from the get go)
but I would use a shutoff/overide in such a case and switch it on when the house came up to temp normally.

Wiring this I could do and there would be money saved ...
even if I did this for just one or two seasons and converted properly when I had the time and money in the future.

Thanks For Any Feedback,


Chris

If another heater(s) is the best solution, then it is probably easier to install electric baseboard heaters (non-hydronic) in those rooms. Long term, look at an air source heat pump to handle much of your load.

You need to figure out how much the heat drops from adequate baseboards to the problem rooms, and how many kW you'd need to make up the difference. The good news is that electric tankless are inexpensive and easy to plumb (as long as you can bleed the system.) The bad news is even small ones draw lots of current. My 10kW (25k btu/hr) takes a 50 amp breaker. This isn't the cheapo approach if your wiring won't handle it. eBay has any number of offerings, along with charts that translate temp difference to kW. The second problem, control, is semi manageable. You'll need to find the tankless setting that keeps the bath & laundry mostly comfortable given the average run times of the boiler. This patch won't work if heat loss from the bath is so much higher than the house that it needs additional run time as opposed to additional heat.

Under stand that it is a patch, one that only makes sense if it will be multiple years before replacement. For a winter you're better off with electric space heaters.

I would check the aquastat settings on the boiler...if the water temp leaving the boiler is too low, or the pump gpm is falling off due to age, then that could cause this problem IMO.

If the boiler is run during the summer for domestic hot water, then a low aquastat setting is good to reduce standby consumptions during the summer. In the winter, you don't worry about standby losses (usually) and you want to deliver enough heat to the house.

Still another solution is to block off some of the radiators upstream, e.g. by closing their flaps or stuffing towels in them. This is esp helpful if any of the rooms are already running too warm. Then more heat gets downstream to the end.

Unless your boiler is undersized for the load (never heard of that) then I suspect you can get your system balanced. I had two loops that were close to 100' each. And balance was never a problem.

OT, I also had a bad aquastat once, that failed in such a way that the system could never circulate more than 50% of the time...even when the tstat was not satisfied. My point, there can always be other problems in your system than layout.

I'm with woodgeek. You gotta assume it worked for most of the house's 40 years. You should get a couple assessments if you haven't already.

I'm not sure how you're measuring the flow, but if it's accurate it should enough.  If the flow is too low the delta-T on the system is large, and the last baseboards in the loop may not be getting the design-heat.

An oil boiler running 150F output and a big delta-T is a problem, and a potentially EXPENSIVE one.  Most older oil boilers do not tolerate cold return-water temperatures.  If the water entering the return side of the boiler is below 140F there is almost certainly going to be corrosive condensation in the flue, which can ruin masonry chimneys in well under a decade by eroding the mortar from he inside out. (Stainless steel flue liners are now code many areas for ANY oil-burner for this reason.)  At anything below 135F return water there's a likelihood of condensation & corrosion on the heat exchanger plates of the boiler itself.

The first cut solution is to raise the boiler's operating temperature to something more appropriate for an oil boiler- say 160-180F out, and MEASURE the delta-T (particularly the temp of the return water piping where it enters the boiler.)

If you break it into two branches to reduce the delta-T and get more heat into the colder part of the zone, you WON'T need to add another pump.  With the strings split in two the pumping head on the whole system goes way down, and the net flow goes UP.  Installing a ball valves on each branch to be able to adjust the flow would allow you to even-up the room temperatures on each branch. Partially closing the ball valve on the branch with the warmer rooms will force more flow into the cooler zone.  Even if you had to almost close the valve to one branch to achieve this, the total flow on the system would be the same as (or higher than) what you are currently getting, assuming the total plumbing length of an individual branch is no longer than the whole loop was before you split it out.

Splitting the system into two parallel branches wouldn't be too tough on most systems, and is within the plumbing skill sets of many DIYers.

For the record, how many total running feet of baseboard, and what boiler? (If it's the original 1970s boiler which may not have much info available online, what are the input/output BTUs on the name-plate.)