Radiant Hydronic Heating Advice

[senixon]

I'm thinking of retrofitting my 1960's rancher style home heating system from electric forced air heating to hydronic radiant heat system.

I'm a bit stuck and hoping someone here can help. First dilemma: I don't have gas hooked up to my house, thinking about electric solution but don't know how efficient this will be, does anyone have any experience in this department? The system appear to be reasonable priced, but since I don't do this for a living... what do I know?! The company after a quote suggested the WFE-24-5-S-110 model with 34,500 BTUs.

There is gas at the street but not sure if all the hassle will be really worth it.

I live in Seattle area, and it doesn't really get too terrible cold (at least not lasting), the house is about 1,200 sqft with crawlspace.

Can anyone speak to the fact that these systems may have to run water at 140-160 degrees... I'm worried about the electric bill.

Any info and suggestions will be welcome, thanks in advance!

[Who]

Electric heating is extremely efficient! Pretty well every kilowatt that comes through the wire makes 3413 BTUs of heat. But if your electric rates are pricey, you may not think it is very efficient.

How much your electrical and how much your gas cost in comparison is something that a transient hobo like me wouldn't know but that you should be able to figure out.

Get your electrical price per KWH and divide by 3413 and that is your cost per BTU, or maybe 2% more.

Next take the cost of NG and divide it by the number of BTUs per unit (often 100,000 in various parts of the USA). Then add about 10% if you are getting a modcon or about 30% if you are getting a conventional boiler.

That will give you a rough idea of comparable energy costs.

While a natural gas hookup may cost you some coin, it may also cost some coin to get the wiring upgraded if your current system doesn't have 40 amps of spare capacity.

[furd]

I haven't lived in the Seattle City Light service area for over thirty years but they have traditionally had among the lowest rates in the country. I tried to access their current rates but it seems there have been several changes recently. Here is their page on rates. Seattle City Light | Rates

I only glanced at the link for the electric radiant site but I don't like what I saw. The plastic jug used for an expansion tank seems pretty "Mickey Mouse" to me. I would far prefer that you utilize a real expansion tank in your system.

Natural gas rates are a bit high in Seattle. Gas is supplied by Puget Sound Energy, a company that just recently went private. I should know the rate structure since I use gas but I don't. I suspect that you will find the gas to be slightly lower in cost. I don't know about now but many years ago PSE would run the piping from the street to your home for free. Any piping inside the home was the homeowner's responsibility. You need a permit to run any gas piping inside the home and it is available from (strangely enough) the Seattle-King County Health Department. If you hire someone to run the gas piping (recommended) then that contractor needs to be specifically licensed to run gas piping in Seattle.

[senixon]

Thanks for your suggestions guys!

The plastic jug used for an expansion tank seems pretty "Mickey Mouse" to me. I would far prefer that you utilize a real expansion tank in your system.

That was the first thing I noticed about it as well... but not knowing exactly the reasoning behind it, passed it off as odd/but not too terribly concerned about it. I liked that the system had the boiler incorporated into the manifold... they have some videos that explain the operation of the system.

Electric heating is extremely efficient! Pretty well every kilowatt that comes through the wire makes 3413 BTUs of heat. But if your electric rates are pricey, you may not think it is very efficient.

I belive the electric rates in this area are fairly reasonable (lot's of hydro-electric dams around) and have a feeling it's going to be more reasonable in the distant future due to fossil fuels rapidly increasing in cost and more/better ways of harnessing the solar/wind/natures energy in the coming years. So if the cost difference is 25% or less I'll take that hit with electric solution, since it's cheaper to implement initially I don't think it will hurt as much. Thanks for the formula, I'll do some calculating when I get home tonight.


I had a thought... currently I have a 10-15 year old tank-type electric water heater, are there any solutions out there that will let me replace it with a decent tank-less heater that will supply enough hot water for both the heating and bathing/etc needs. We have a small home 1200sqft, 1 full bath, dishwasher, washing machine and 3 people in the house.

Any recommendations are always welcome, at this point I'm weighing my options and not sold on any one solution... getting close though

[furd]

My first recommendation is that you do a heat loss calculation on your house. You can get the software for free from various places on the web, Trooper has a direct link to the Slant Fin download I think.

You may be able to do a quick and dirty by first checking the output of your present furnace (if you have one) or if you have electric baseboards add up the combined lengths of all and give me the number. Also needed is how much the heat was on during the recent cold snap when the temperatures were below freezing. Note, this is just a rough guesstimate and cannot be used for final sizing.

I just re-read your original post and you said in the Seattle area. Is Seattle City Light your serving utility or is it Puget Sound Energy? Or do you live in Snohomish county and have SnoCo PUD? Or perhaps you live in Tacoma and have Tacoma City Light?

Do you have a basement, crawl space or is your house built on a slab? What kind of finished floors do you have?

There are some homes in the greater Seattle area that have combined heating and domestic water systems but some people with them have posted here with problems. I don't recommend combined systems and I don't recommend tankless water heaters for domestic use, especially electric models. There are a few manufacturers of tankless water heaters that allow them to be used for space heating but many do not. Where I live, (Bothell) the plumbing and/or mechanical code specifically prohibits using potable water heaters for space heating.

[senixon]

@furd - thanks for all the suggestions once again... I've gotten a couple of estimates for BTU loss for my house, one was done blindly by the company that is trying to sell me the hydronic system ( I can send that if it helps ) based on limited info I was able to give them they put me just shy of 18,000 BTU/hr and per your suggestion using one of the tools I ran my own calculation (which I think is probably closer) and that put me just a hair over 22,500 BTU/hr

I'm a PSE customer and their rates for last month averaged to about 9 cents per KWh

I don't have a boiler, or baseboards... instead I have these in every room, they operate on a timed electronic thermostat and I would say for the most are very efficient, but I have very cold floors. My home has a crawl space with carpet for the flooring (looking to switch to hardwood in the near future), it's insulated, but doesn't seem to help if barefoot.

I'm also not a fan of combining systems, but you never know if advances have been made to make that possible and efficient. Know next to nothing about thankless heaters.

[furd]

The choice between gas or electric is going to be a tough one. It was about thirty years ago I tried to convince my dad to put in an electric boiler rather than the oil he had or change to gas. At that time Seattle City Light had the next to lowest rates in the country but dad didn't want a huge electric bill even if it eliminated another bill and even if the overall cost was less. Turned out he was correct but only because SCL raised their rates higher than the cost of gas.

I know that with my SnoCo PUD winter rates being just a hair over 8 cents per kWh gas is still a cheaper fuel than electricity. PSE recently raised their gas rates because of their cost of gas the previous fiscal year so right now their price structure is artificially high and I'm pretty sure the state utility commission will force them to lower the rates next year. I can pretty much guarantee that electricity costs will NOT go down in the future but will likely rise faster than natural gas, especially in our area. Of course you could install both a gas-fired and an electric boiler and use whichever was more economically prudent at any particular time.

The electric boiler has much to offer in that it works with about a 98% efficiency at all times whereas a gas-fired boiler will likely be operating at less that that figure and under some conditions much less efficiency. If your heat loss figure of 22,500 BTU/hr. is accurate you could get by with an electric boiler rated at 6.6 kW. That small a boiler would not, however, allow for much of a "load pickup" if you were to use a set back thermostat. On the other hand, you may find it rather difficult to find a gas-fired boiler that had an output that low. If you did decide on a gas-fired boiler I would suggest that you go with a "Mod/Con" (Modulating/Condensing) boiler. These have a variable firing rate and will be far more efficient over their firing range than will a single rate "standard" boiler. Other members of this board have far more information on these Mod/Cons than I.

Another item in favor of the electric boiler or a Mod/Con is your desire to have radiant floors. I do not recommend retrofitting radiant tubing under neath the subfloor although many such installations do exist and most people do like them. The retrofitted installations require hotter water running through the tubing and some pretty careful air sealing and insulation beneath the tubing installation. With you having a crawlspace this is even more important. If you are considering replacing your finish flooring then I strongly recommend using Warmboard or an equivalent. This is a plywood panel that has grooves cut in the face to accept the PEX tubing. It is applied over your existing subfloor and the tubing installed. Almost any finish floor may then be applied over the Warmboard. Using Warmboard also gives the radiant system a much faster response time, it heats up quicker (but cools off faster, too) than will a system with the tubing underneath the subfloor or one with the tubing embedded in a lightweight concrete slab.

There are a few things to consider, others may want to add to what I have written. If you have more questions, don't hesitate to ask.